Wiggerswug archive of wind power industry articles

Farm-wide interface fatigue loads estimation: A data-driven approach based on accelerometers

Francisco de N Santos, Nymfa Noppe, Wout Weijtjens, Christof Devriendt, OWI-Lab, Vrije Universiteit Brussel, Brussels, Belgium

One key challenge faced by the different stakeholders relates to the fatigue lifetime of offshore wind turbines. Increasingly, a greater focus has been given to sustainable asset management: If wind energy is to realize its potential in supplying sustainable and cheap energy, one is required to know more precisely the current lifetime consumption of each turbine within a farm. This is because operation and maintenance (O&M) amounts to nearly a third of global costs ...

Wind Energy, February 15, 2024

Discontinuous Jump Behavior of the Energy Conversion in Wind Energy Systems

Daan van der Hoek, Bert Van den Abbeele, Carlos Simao Ferreira, Jan-Willem van Wingerden, Delft Center for Systems and Control, Faculty of Mechanical Engineering, and Department of Flow Physics and Technology, Faculty of Aerospace Engineering, Delft University of Technology, The Netherlands

Wakes generated by upstream turbines can negatively impact the performance of downstream turbines and the wind farm as a whole. They contribute to significant losses in energy and increased loading of structural components.

Wind Energy, February 8, 2024

Discontinuous Jump Behavior of the Energy Conversion in Wind Energy Systems

Pyei Phyo Lin, Matthias Wächter, M. Reza Rahimi Tabar, and Joachim Peinke, ForWind, Institute of Physics, University of Oldenburg, Germany, and Department of Physics, Sharif University of Technology, Tehran, Iran

[W]hen examining time series of a wind turbine’s power output, rapid fluctuations can occur, exceeding 50% of the rated power. These short-term power fluctuations in the megawatt range impose additional stress on the turbine’s drive train and the power grid, as they may accumulate within a wind farm rather than being averaged out.

PRX Energy, August 16, 2023

Erosion modelling on reconstructed rough surfaces of wind turbine blades

Antonios Tempelis, Leon Mishnaevsky Jr., Department of Wind Energy, Technical University of Denmark, Roskilde, Denmark

Wind turbine blades suffer from many forms of damage. One of them is leading edge erosion that causes roughness forming on the surface of the blade. The main mechanisms and parameters that govern leading edge erosion are stated in the work by Mishnaevsky Jr. et al. Leading edge roughness influences the aerodynamic performance of the blade, causing energy production losses. In a study by Maniaci et al., the estimated annual energy production (AEP) loss due to severe erosion is calculated as high as 5%. An increase in maintenance costs is another negative effect of leading edge erosion.

Wind Energy, August 28, 2023

Model-free closed-loop wind farm control using reinforcement learning with recursive least squares

Jaime Liew, Tuhfe Göçmen, Wai Hou Lio, Gunner Chr. Larsen, Department of Wind Energy, Technical University of Denmark, Roskilde, Denmark

Wind farms experience significant power losses due to wake interactions between turbines.

Wind Energy, July 7, 2023

A Bayesian reliability analysis exploring the effect of scheduled maintenance on wind turbine time to failure

Fraser Anderson, Rafael Dawid, David McMillan, David García-Cava, Institute for Energy & Infrastructure, University of Edinburgh, Edinburgh, and Electronic and Electrical Engineering, Strathclyde University, Glasgow

Significant turbine frailties were observed.

Wind Energy, July 6, 2023

Data-driven modelling of turbine wake interactions and flow resistance in large wind farms

Andrew Kirby, François-Xavier Briol, Thomas D. Dunstan, Takafumi Nishino, Department of Engineering Science, University of Oxford, and Department of Statistical Science, University College London

Turbine wake and local blockage effects are known to alter wind farm power production in two different ways: (1) by changing the wind speed locally in front of each turbine and (2) by changing the overall flow resistance in the farm and thus the so-called farm blockage effect.

Wind Energy, July 3, 2023

Mitigation of transient torque reversals in indirect drive wind turbine drive trains

Saptarshi Sarkar, Håkan Johansson, Viktor Berbyuk, Department of Mechanics and Maritime Sciences, Chalmers University of Technology, Gothenburg, Sweden

Bearing failure in wind turbine gearboxes is one of the significant sources of down-time. While it is well-known that bearing failures cause the largest downtime, the fail-ure cause(s) is often elusive. The bearings are designed to satisfy their rolling contactfatigue (RCF) life. However, they often undergo sudden and rapid failure within a fewyears of operation. It is well-known that these premature failures are attributed tosurface damages such as white surface flaking (WSF), white etching cracks (WECs)and axial cracks. In that regard, transient torque reversals (TTRs) in the drivetrain have emerged as one of the primary triggers of surface damage, as explained in this paper.

Wind Energy, June 4, 2023

Wind turbine main-bearing loading and wind field characteristics

Edward Hart, Alan Turnbull, Julian Feuchtwang, David McMillan, Evgenia Golysheva, Robin Elliott, Wind and Marine Energy Systems Centre for Doctoral Training, University of Strathclyde, Glasgow, ONYX InSight, Nottingham, UK

The rate of wind turbine main-bearing failures is high, with most not reaching their design lives of roughly 20 years and in some cases, failing in less than 6 years.

Wind Energy, August 30, 2019

Improving wind turbine drivetrain designs to minimize the impacts of non-torque loads

Yi Guo, Roger Bergua, Jeroen van Dam, National Renewable Energy Laboratory, Golden, Colorado, USA, Alstom Wind, Barcelona, Spain, and Richmond, Virginia, USA

Non-torque loads induced by the wind turbine rotor overhang weight and aerodynamic forces can greatly affect drivetrain loads and responses. If not addressed properly, these loads can result in a decrease in gearbox component life. ... On average, gearboxes in wind turbine drivetrains have not been achieving their expected design life. Premature gearbox failures have a significant impact on the cost of wind farm operations. A large number of damaged gearboxes require repairs or complete overhauls during the service.

Wind Energy, November 10, 2014

Offshore wind turbine scaling is creating unsustainable market risks: GCube

Saumya Jain, Reinsurance News

8MW+ machines suffer component failures within the first two years of operation, while 55% of all turbine claims now come from 8MW+ component failures during construction. This is juxtaposed against the significantly shorter timeframe of 5 years for component failures during operation in the 4-8MW category of turbines.

Assessment of low-frequency aeroacoustic emissions of a wind turbine under rapidly changing wind conditions based on an aero-servo-elastic CFD simulation

Florian Wenz, Oliver Maas, Matthias Arnold, Thorsten Lutz, Ewald Krämer, Institute of Aerodynamics and Gas Dynamics, University of Stuttgart, Institute of Meteorology and Climatology, Leibniz University Hannover, and Wobben Research and Development, Aurich, Germany

Low-frequency noise of wind turbines

A good overview of the noise emissions of wind turbines and the underlying mechanisms as well as approaches for calculation can be found in the book by Wagner et al [doi:10.1007/978-3-642-88710-9]. The flow-induced noise mechanisms, called aeroacoustics, generate sound over a wide frequency range. The acoustic equations are derived from the more general flow equations, and the flow fields are the basis for aeroacoustic phenomena. For comprehensive information on, the general concepts and equations, please refer to literature. While the sources of acoustic emissions from wind turbines in the audible range have been extensively researched and various methods are used to reduce aerodynamic and mechanical noise, much less is known about low-frequency sound emissions from wind turbines. Low-frequency noise has a smaller dissipation factor in air and can travel farther than high-frequency noise. This was found in measurements on the infrasound propagation for distance up to 10 km, especially for stable atmospheric conditions [doi:10.1121/1.5051331; doi:10.3390/acoustics2020020]. Hence, the extent to which such low-frequency emissions can be perceived by humans living in the vicinity of the WT is the subject of intensive research and is sometimes controversially discussed. This paper does not deal with this topic, but focuses on the mechanisms for the generation of low-frequency emissions from wind turbines.

The main noise mechanism on which the low-frequency sound emissions of WTs are based is the temporal change in the amplitude and direction of the force acting on the air from a surface. The frequency of the load fluctuations corresponds to that of the emitted sound and the amplitude determines the sound power. Therefore, it is crucial for the evaluation of low-frequency aeroacoustics to take into account all features that influence the aerodynamics, which also includes the controller. Besides the dominant loading noise, the thickness noise due to the moving blades and fluctuating Reynolds stresses in the turbulent flow of the blade wake are sources of low-frequency acoustic emissions. Various aerodynamic phenomena cause load variations on WTs, including above all the blade-tower interaction (BTI), the interaction of the blades with inflow turbulence (IT) and the periodic vortex shedding (VS) at the tower in the form of a von Kármán vortex street. Hansen and Hansen [doi:10.3390/acoustics2010013] provide a detailed literature review of the current state of research on noise emissions from WTs. Among other things, they conclude that better methods are needed to predict the effects of different topography and different meteorological conditions on the sound power levels of WTs. Only one study has been found that allows a prediction of the generation of infrasound based on atmospheric inflow parameters. In D'Amico et al [doi:10.1016/j.jweia.2022.105021], a detailed long-term measurement campaign is presented that combines infrasound measurements in the vicinity of WTs with meteorological measurements to investigate the noise emitted by WTs as a function of meteorological parameters. A distinction was made between tonal BTI-noise and broadband IT-noise. An artificial neural network was used to derive physical relationships between the meteorological situation and the emitted low-frequency sound. With this, they found that mean wind speed, turbulence intensity and turbulent vertical heat flux are the most important factors for infrasound emission.

BTI as the main cause of low-frequency emissions from WTs has not only been investigated experimentally by measurements, as in the study mentioned above, but has also been proven by numerical simulations. The aeroacoustic emissions can only be predicted correctly if the underlying aerodynamics are captured with a high degree of accuracy. CFD simulations of fully resolved WTs represent the approach of highest quality. Based on Lighthill's acoustic analogy, the Ffowcs Williams–Hawkings (FW-H) equation allows to calculate the generation of sound from aerodynamic results by means of elementary sources, namely monopoles (moving volume), dipoles (forces acting onto the fluid) and quadrupoles (fluctuating Reynolds stresses). Yauwenas et al and Klein et al are among the few to realize this and also consider the entire surface of the WT, i.e. blades and tower, as a source of sound emissions. The first study focuses on BTI-noise, while the second study also considers IT-noise and VS-noise (ƒ < 20Hz). In order to extend the frequency range with this numerical approach, the spatial and temporal resolution of the CFD simulation must be refined accordingly. This is computationally unfeasible for complex flow situations [doi:10.1088/1742-6596/2265/3/032060]. Therefore, semiempirical models for the noise sources based on flow parameters can be used to estimate the noise emissions, as presented in Cheng et al in a state-of-the-art framework.

Wind Energy, May 1, 2023

Non-destructive and contactless defect detection inside leading edge coatings for wind turbine blades using mid-infrared optical coherence tomography

Christian Rosenberg Petersen, Søren Fæster, Jakob Ilsted Bech, Kristine Munk Jespersen, Niels Møller Israelsen, Ole Bang, Department of Electrical and Photonics Engineering, Technical University of Denmark, Kongens Lyngby, NORBLIS, Virum, and Department of Wind Energy, Technical University of Denmark, Roskilde, Denmark

One major challenge is reducing downtime occurring from the failure of different parts of the turbine, where gearbox failures typically result in the longest turbine downtime. At the same time, the drivetrain module (gearbox, main shaft, mechanical brake etc.) is only second behind the power module (frequency converter, generator assembly, Low Voltage Switchgear, Medium Voltage Switchgear, transformer etc.) in contribution to the total downtime. It is also important to note that drivetrain module repair costs are typically more expensive due to crane costs. The main contributor to gearbox failures are bearings (~70%) followed by gears (~26%), and other failures constitute the rest (~4%). 48% of all failures are attributed to high-speed shaft bearings, followed by 13% to the intermediate shaft bearings and 7% to the planetary bearings. All other component failures (gears and others) account for the other 32%. Therefore, it is clear that bearing failures contribute greatly to wind turbine gearboxes' unpredictable and premature failure. Surface damages on high-speed shaft bearings, planetary bearings and intermediate-speed shaft bearings substantially limit the service life. ... It has been observed repeatedly that despite proper user practices by the manufacturer and the end-user, the bearing lives are often limited by wear and damage.

Two prevalent failure modes in multi-megawatt wind turbine gearbox bearings are identified in this paper as smearing/scuffing and white structure flaking (WSF). Bearings are designed to satisfy minimum rolling contact fatigue (RFC) life. However, failures within a few years of operation are observed because smearing/scuffing, white etching cracks (WECs) and axial cracking failure modes are different from the classical RCF failure mode. Slip is often considered as being essential to the formation of white etching areas (WEAs), and smearing damage. Slip can independently lead to either smearing/scuffing damage and WSF or severely promote WEA formation. Once an event initiates subsurface WEA formations, normal rolling action of the bearing can initiate cracks at the junction of the inclusion-like areas. The crack inevitably propagates to the surface and becomes a WEC, which grows axially across the raceway and causes premature bearing failures. The slip and impact loading during TTRs is suggested to be a leading candidate in causing stress-induced subsurface WEA damage in Sharpley.

Smearing is defined as the change of the surface area of a metallic roller sliding contact under relative motion due to the beginning of adhesive wear. Cylindrical and spherical roller bearings with large dimensions are especially susceptible to smearing/scuffing due to the sliding and slip conditions within the bearing. According to Scherb and Zech, smearing is connected to the following:

... The second dominant mode of failure often observed in wind turbine bearings is often described as WECs and axial cracks and is associated with WSF. Axial cracks and WECs associated with the microstructural change in small areas called WEAs can occur in as little as 6–24 months of operation. They are decorated by WEAs on the steel surface. White etching refers to the white appearance of the altered microstructure of a polished and etched steel sample. WEAs around cracks are 10%–50% harder than the surrounding unaffected microstructure. Similar to the phenomenon of smearing, the drivers and mechanisms of their formation are still highly contested. Evans presents an extensive review of operational modes, drivers and mechanics that lead to three types of WECs and axial cracks: (a) hydrogen-induced, (b) electro-thermal stress-induced and (c) mechanical stress-induced. Some of the drivers identified by researchers are hydrogen embrittlement, sliding kinematics, water contamination, low Hertzian contact pressure, electrical potential, lubricant additives and tensile hoop stress. It is clear from the available literature that hydrogen plays a significant role in the embrittlement of the surface, leading to WECs. It has been noted by Ruellan et al that WEC initialization often corresponds to tribological hydrogen generation, and its mechanism is enhanced by sliding kinematics. The authors have also noted that WECs tend to occur at low Hertzian stresses for which high sliding velocities can be reached without prompting quasi-instantaneous damage such as smearing and scuffing. Torrance and Cameron noted that white etching layers were formed in the surface material beneath scuffing damage marks, and Stadler et al6 noted that one of the reasons for steel reaustenization that lead to WEA is smearing/scuffing, thus connecting the mechanism of smearing/scuffing and WECs.

... Based on the above literature review, the two parameters that mostly dominate smearing/scuffing and WEAs are identified as the bearing loads and raceway speed. A schematic diagram of the risk of cage/roller slip is plotted against bearing loads and raceway speed in Figure 2 to summarize the information available in the literature. It can be observed that the risk of slip increases drastically with decreasing bearing loads and increasing raceway speeds. The load cases that lead to these situations lie outside the range of normal operation. Available industrial reports and academic literature point to the fact that transient events such as emergency shutdown and electrical faults, such as grid voltage dips and power converter faults, in DFIG-based wind turbines, leading to rapid variation in electromagnetic torque that can then lead to TTRs in the drivetrain shafts.

Region of expected slipping and smearing

Wind Energy, April 26, 2023

Non-destructive and contactless defect detection inside leading edge coatings for wind turbine blades using mid-infrared optical coherence tomography

Christian Rosenberg Petersen, Søren Fæster, Jakob Ilsted Bech, Kristine Munk Jespersen, Niels Møller Israelsen, Ole Bang, Department of Electrical and Photonics Engineering, Technical University of Denmark, Kongens Lyngby, NORBLIS, Virum, and Department of Wind Energy, Technical University of Denmark, Roskilde, Denmark

Leading edge erosion of wind turbine blades is one of the most critical issues in wind energy production, resulting in lower efficiency, as well as increased maintenance costs and downtime. Erosion is initiated by impacts from rain droplets and other atmospheric particles, so to protect the blades, special protective coatings are applied to increase their lifetime without adding significantly to the weight or friction of the blade. These coatings should ideally absorb and distribute the force away from the point of impact; however, microscopic defects, such as bubbles, reduce the mechanical performance of the coating, leading to cracks and eventually erosion.

Wind Energy, March 9, 2023

Wind Turbines and Fire: Why Take the Risk?

By Ross Paznokas

Despite being the second leading cause of reported incidents in wind turbines, the wind industry is still largely overlooking fire risk.

Even light icing can produce enough surface roughness on wind turbine blades to reduce their aerodynamic efficiency, which reduces the amount of power they can produce.

Few sights are more dramatic than that of a wind turbine on fire. Though rare, the spectacle of rotating flames and falling debris live long in the memory.

Even light icing can produce enough surface roughness on wind turbine blades to reduce their aerodynamic efficiency, which reduces the amount of power they can produce.

Even so, despite the high-profile nature of these events, there is little in the way of accurate records detailing the number of turbine fires and the extent of the financial damage they cause. Indeed, these facts tend to be known only by insurers and project owner operators.

North American Windpower, March 9, 2023

The science behind frozen wind turbines

Hui Hu, Aerospace Engineering, Iowa State University

Winter is supposed to be the best season for wind power – the winds are stronger, and since air density increases as the temperature drops, more force is pushing on the blades. But winter also comes with a problem: freezing weather.

Even light icing can produce enough surface roughness on wind turbine blades to reduce their aerodynamic efficiency, which reduces the amount of power they can produce.

Frequent severe icing can cut a wind farm’s annual energy production by over 20%, costing the industry hundreds of millions of dollars. Power loss isn’t the only problem from icing, either. The uneven way ice forms on blades can create imbalances, causing a turbine’s parts to wear out more quickly. It can also induce vibrations that cause the turbines to shut down. In the case of extreme icing, restarting turbines may not be possible for hours and potentially days.

The solution is obvious: de-ice the blades, or find a way to keep ice from forming in the first place. So far, however, most of the strategies for keeping ice off wind turbines blades come from aviation. And airplane wings and wind turbines are built differently and operate under very different conditions. ...

Not all ice is the same

Ice isn’t the same everywhere. It may come from precipitation, clouds or frost. It also freezes in different ways in different climates.

For example, rime icing, formed when tiny, supercooled water droplets hit the surface, usually occurs in regions with relative dry air and colder temperatures, under 20°F. That’s what we typically see in Iowa and other Midwest states in the winter.

Glaze icing is associated with much wetter air and warmer temperatures and is commonly seen on the Northeast coast. This is the worst type of ice for wind turbine blades. It forms complicated ice shapes because of its wet nature, which results in more power loss. It’s also likely what formed in Texas in February 2021 when the cold air from the north collided with the moist air from the Gulf Coast. While the majority of the power shut down by the storm was from natural gas, coal or nuclear, wind turbines also struggled. ...

While ice can form over the entire span of the blade, much more ice is found near the tips. After one 30-hour icing event, we found ice as much as a foot thick. Despite the high wind, the ice-heavy turbines rotated much slower and even shut down. The turbines produced only 20% of their normal power over that period.

Keeping ice off blades

There are a few reasons the strategies that effectively keep ice off aircraft wings aren’t as effective for wind turbine blades.

One is the materials they are made of. While aircraft wings are typically made of metals like aluminum alloy, utility-scale wind turbines are made of polymer-based composites. Metal conducts heat more effectively, so thermal-based systems that circulate heat are more effective in airplane wings. Polymer-based turbine blades are also more likely to get covered by dust and insect collisions, which can change the smoothness of the blade surface and slow water running off the blade, promoting ice formation.

Wind turbines are also more prone to encounters with freezing rain and other low-altitude, high-water-content environments, such as ocean spray for offshore wind turbines.

Most current wind turbine anti-icing and de-icing methods remove ice buildup through electric heating or blowing hot air inside. Heating these massive areas, which are many times larger than airplane wings, adds to the cost of the turbine and is inefficient and energy-consuming. Composite-based turbine blades can also be easily damaged by overheating. And there’s another problem: Water from melting ice may simply run back and refreeze elsewhere.

Another strategy in cold-weather regions is to use surface coatings that repel water or prevent ice from sticking. However, none of the coatings has been able to eliminate ice completely, especially in critical regions near the blades’ leading edges. ...

The Conversation, March 4, 2021, updated February 25, 2023

Adding wind power to a wind-rich grid: Evaluating secondary suitability metrics

Nathaniel S. Pearre, Lukas G. Swan, Renewable Energy Storage Laboratory, Mechanical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada

As the quantity of renewable electricity generation from wind farms increases in a region, the costs associated with integrating it into the broader electricity system also grow. This is primarily due to the need for dispatchable generators that vary power output to compensate for wind farm power variations. Such “balancing services” are an economic cost to the system that is typically not passed on to wind farms.

Wind Energy, published online January 17, 2023

Field-data-based reliability analysis of power converters in wind turbines: Assessing the effect of explanatory variables

Karoline Pelka, Katharina Fischer, Fraunhofer Institute for Wind Energy Systems, Hannover, Germany

Power converters are part of virtually all modern wind turbines (WT). Located between the generator and the main transformer, they allow decoupling the rotational speed of the drive train from the grid frequency. At the same time, the main power-converter systems are among the most frequently failing subsystems of wind turbines. These failures cause unscheduled downtime as well as maintenance costs, compromise the turbine availability, and consequently increase the levelized cost of energy (LCOE).

Wind Energy, published online December 17, 2022

Quantification of wind turbine energy loss due to leading-edge erosion through infrared-camera imaging, numerical simulations, and assessment against SCADA and meteorological data

By Keshav Panthi and Giacomo Valerio Iungo, Wind Fluids and Experiments (WindFluX) Laboratory, Mechanical Engineering Department, University of Texas at Dallas, Richardson

[W]ind turbines experience soiling and erosion at their leading edge (LE hereinafter) as they operate in harsh environmental conditions entailing exposure to rain, snow, hailstones, seawater aerosols, sand, dust, or insects. The aerodynamic efficiency of wind turbine blades has been observed to decline with time due to the deterioration of the blade surface and, in turn, wind turbine performance as well. The enhanced LE roughness causes an anticipated laminar-to-turbulent transition (LTT hereinafter) of the boundary layer evolving over an airfoil and, thus, reduced lift and increased drag force. Field experiments and numerical simulations showed that the LTT position is significantly affected by the incoming turbulence intensity, TI, specifically moving the LTT position closer to the LE for increased TI, mainly on the pressure side of the airfoils. The reduced aerodynamic efficiency of the turbine blades leads to lower annual energy production (AEP hereinafter). Even the application of protective tapes on LE to repair the erosion is found to reduce the AEP of turbines by up to 2%.

Wind Energy, published online December 7, 2022

A passively self-adjusting floating wind farm layout to increase the annual energy production

By Mohammad Youssef Mahfouz and Po-Wen Cheng, Stuttgart Wind Energy, University of Stuttgart, Germany

As a wind turbine extracts energy from the free flow wind field, the wind speed behind the turbine decreases and the turbulence increases. When this lower energy and more turbulent wind field hits a downwind turbine, wake losses occur as the downwind turbine extracts less energy than the upwind one. Moreover, as the downwind flow is more turbulent, the fatigue loads on the downwind turbine are higher. These energy losses increase the levelized cost of energy (LCOE) of the wind farm.

Wind Energy, published online December 7, 2022

Assessment of an actuator disk-based approach for the prediction of fatigue loads in a perspective of wind farm-scale application

By Maud Moens, Matthieu Duponcheel, and Philippe Chatelain, Institute of Mechanics, Materials and Civil Engineering, Université Catholique de Louvain, Louvain-la-Neuve, Belgium

Fatigue is a critical factor in the lifetime of a wind turbine and is one of the causes of failure of the machine components. The actual loads that contribute to fatigue of a wind turbine originate from a variety of sources: high winds, wind shear, gravity and/or potential yaw errors, turbulent fluctuations, ambient gusts, starts and stops of the machine, and so on. Moreover, in a wind farm arrangement, fatigue phenomenon is exacerbated by the presence of other rotors: The wind turbines impacted by the wake of the upstream machines see their cumulated fatigue damage rise due to the increase level of ambient turbulence and the wake meandering phenomenon. The variety of these load sources and the complexity of some of them increase the uncertainties in the predicted fatigue damage, leading to unexpected failures for some wind turbine components. For some wind turbine subassemblies, the downtime associated with repair may be significant, mainly in the offshore environment: This decreases the wind turbine reliability, directly impacting the Levelized Cost of Energy, as demonstrated in Dao et al.

Wind Energy, published online August 2, 2022

New device to reduce noise and increase efficiency

By European Research Media Center

Wind power technology engineers today have to face a number of challenges: discontinuity of supply due to weather conditions, difficulty of energy storage, impact on the environment, high costs of energy generation and maintenance of equipment. ... Noise pollution is one of the main public concerns associated with operating wind turbines.

published on Youtube August 1, 2022

Mechanical and interfacial characterisation of leading-edge protection materials for wind turbine blade applications

By Ioannis Katsivalis, Angeliki Chanteli, William Finnegan, and Trevor M. Young, University of Limerick and MaREI Research Centre, School of Engineering, National University of Ireland, Galway, Ireland

Modern wind turbine blades experience tip speeds that can exceed 110 m/s. At such speeds, water droplet impacts can cause erosion of the leading edge, which can have a detrimental effect on the performance of the wind turbine blade. More specifically, rain erosion is leading to both reduced efficiency and increased repair costs.

Wind Energy, published online July 13, 2022

National-scale impacts on wind energy production under curtailment scenarios to reduce bat fatalities

By Galen Maclaurin, Cris Hein, Travis Williams, Owen Roberts, Eric Lantz, Grant Buster, and Anthony Lopez, National Renewable Energy Laboratory, Golden, Colorado, USA

Future scenarios for decarbonizing the United States energy system frequently envision broad-scale deployment and geographic expansion of wind energy, which could potentially impact certain wildlife populations. Particularly, estimates of bat fatalities at operational wind plants are in the hundreds of thousands per year across the United States and Canada. Mortality searches at wind plants have reported fatalities of at least 22 of the 45 species that occur in the United States. Several of these species, including the Indiana bat (Myotis sodalis), are federally listed as threatened or endangered under the Endangered Species Act (ESA), and additional species are undergoing species status assessments1 for potential listing by the United States Fish and Wildlife Service (USFWS). One approach that has consistently resulted in significantly reducing bat fatalities is to curtail wind turbines. Curtailment involves slowing or stopping the rotation of the turbine blades during periods of high risk for bat collisions (e.g., during low wind speed conditions). Implementation can be voluntary or required by state permitting authorities or under the ESA. Curtailment to reduce bat-turbine collisions is an evolving practice predominantly founded on a relationship between low wind speed and high bat mortality during late summer and early autumn. ...

Bats face numerous threats that can result in population level declines, including White-nose Syndrome (WNS), habitat loss, reduced prey base, climate change, and wind energy development. Hibernating, cave-roosting bats are most vulnerable to WNS, which has caused population declines in numerous North American species. Estimates suggest that populations of northern long-eared bats (M. septentrionalis), little brown bats (M. lucifugus), and tri-colored bats (Perimyotis subflavus) have declined by more than 90% since WNS was first reported in 2006. Species status assessments for these three bat species are currently being conducted for ESA listing or up-listing from threatened to endangered. Migratory tree-roosting species have not demonstrated vulnerability to WNS but are impacted by wind turbines and account for nearly 80% of bat fatalities at wind plants across the United States and Canada. The three species most often reported at wind turbines are hoary bats (Lasiurus cinereus), eastern red bats (Lasiurus borealis), and silver-haired bats (Lasionycteris noctivagans). In the United States, hoary bat fatalities account for 30.8% of estimated fatalities, which could represent a population-level risk for the species. These three unlisted species appear to be particularly at risk because of their low reproductive rate, broad geographic habitat ranges, and migratory routes that span across North America. ...

Our results suggest that high levels of curtailment (both blanket and smart) could substantially reduce the future footprint of financially viable wind energy. Our modeling approach considered spatial exclusions including setbacks from infrastructure (e.g., from buildings, roads, and radar stations), urban areas, steep terrain, and protected areas. Consideration of additional siting and operational constraints could further reduce the geographic footprint of viable wind energy deployment. These encompass a broad range of considerations including social acceptance (e.g., turbine noise, shadow flicker, and viewshed), transmission constraints and costs (e.g., available transmission capacity and transmission congestion), airspace concerns (e.g., radar line-of-sight and civilian and military airspace), and wildlife other than bats (e.g., sage-grouse and eagles).

Wind Energy, published online May 24, 2022

Effect of drop-size parameterization and rain amount on blade-lifetime calculations considering leading-edge erosion

By Anna-Maria Tilg, Witold R. Skrzypiński, Ásta Hannesdóttir, and Charlotte Bay Hasager, Department of Wind Energy, Technical University of Denmark, Roskilde, Denmark

Leading-edge erosion (LEE) of wind turbine blades is caused by the impact of particles, for example, raindrops, and leads to a loss in the power production and high maintenance cost.

Wind Energy, published online February 2, 2022

Failure mechanisms of wind turbine blades in India: Climatic, regional, and seasonal variability

Wind turbines require repair quite often, and this can be rather expensive. Carol et al. observed that 6.2 minor repairs, 1.1 major repair and 0.43 major replacements are required in average per turbine per year.

Failure mechanisms of wind turbines depend on the local climatic conditions, types of loading, and environmental effects. Low temperatures increase brittleness of components whereas temperature variations could cause thermal fatigue. Lightning, icing, and high winds can drastically increase the failure rate of wind turbines. ...

Wind turbine blades are one of the main contributors to the wind turbine failure statistics. The typical observed damage mechanisms of wind turbine blades include skin/adhesive debonding, adhesive joint failure, sandwich debonding, delamination, splitting along fibers, and cracks in the gelcoat. In Robinson et al., the blade failures are classified into root connection failure, catastrophic structural buckling or separation, leading edge, trailing edge, or other bond separation, lightning damage, erosion, and failure at outboard aerodynamic device. The wind turbine blades consist of laminates, foams, coatings, sandwich structures, and adhesive layers. With view on these elements, damage mechanisms of wind turbine blades can be classified as (a) surface damage (coating degradation), (b) polymer resin and/or interface damage, and (c) structural element damage (with broken structural fibers). The surface damage can be caused by erosion (rain erosion, sand, and hail), or small object impacts. It reduces the aerodynamic performance of blades and energy generation. It does not prevent the wind turbine from functioning, but the defects grow, develop, and lead to the structural damage.

Figure 1 shows the frequency of observing of various wind turbine blade failure mechanisms, depending on the age of wind turbines, in Europe (a) and India (b).

blade failure mechanisms

... It is interesting to see the variety of challenges reported: grease leakage issues, local skill availability, servicing turbines at remote locations, grid reactor replacement, delayed spare parts, issues with blade root pitch bearing connection, issues with service completion, damages to the transmission network, generator replacement issues, customer not interested in after sales service, delayed blade inspections, budget constraints for repair and maintenance, issues with SCADA connectivity, issues with crane accessibility and availability, and ageing impacts on wind turbine degradation. The systems and components that have caused big troubles for the respondents are shown in Table 1.

System name   Component name   Typical downtime for the component failure (hours)
DrivetrainGrease leakage48
BladesPitch controller5
GeneratorStator overheating10
ConverterGrid reactor360
Control systemPitch, yaw8
GearboxLow speed shaft bearing300

Figure 2 shows the frequency of different manufacturing defects, observed by service companies. ... Other types of blade issues reported from the field include loosening of blade root studs, bolt crack, and issues with blade root pitch bearing connection. Components causing major turbine downtime in India include erosion, stator winding, grid reactor, cooling system, yaw and pitch control system, and stator overheating.

blade defects

Figure 9 shows photos of heavily eroded wind turbine blades. The erosion of blades can reduce the energy production of wind turbines by 5%–20%, and ultimately, lead to the cracking in laminates.

eroded wind turbine blades

Figure 10 shows wind turbine blade, damaged by lightning strike. It is worth to note that after a blade repair has been carried out, the same kind of repair can be needed again in only 2–5 years, depending on the site conditions.

lightning damage

... Comparing the often observed damage mechanisms in Europe and in India, it was observed hat leading edge erosion plays a critical role in both regions, starting from the installation and growing over 5 years. In India, also operational errors and manufacturing defects are among main failure mechanism of recently installed wind turbines, even after installation or 1–3 years old, leading to structural failure even in recently installed wind turbines. In Europe, manufacturing defects, fire and even operational errors determine the failure of wind turbines, reaching 5–10 years and more. Lightning strikes are registered relatively often, every 1–2 years, depending on climate and are especially often observed in monsoon regions of India.

Wind Energy, published online December 15, 2021

The significance of bypass transition on the annual energy production of an offshore wind turbine

By Aidan Duffy, Grant Ingram, and Simon Hogg, Department of Engineering, Durham University, Durham, UK

Awareness of leading-edge erosion (LEE) on wind turbine blades, and the impacts it can have on annual energy production (AEP) have increased significantly over recent years. This is especially important in offshore environments, where a combination of more extreme weather and higher tip speeds result in higher rates of erosion.

Wind Energy, published online November 25, 2021

Development of a passive-adaptive slat for a wind turbine airfoil

By Florian N. Schmidt and Jochen Wild, Institute of Aerodynamics and Flow Technology, DLR—German Aerospace Center, Braunschweig, Germany

The root sections of commercial wind turbines often operate with separation on the upper blade surface due to stalled flow caused by their nonaerodynamic design. The separated flow in combination with a fluctuating wind field induces fluctuating loads on the rotor blade, which cause a reduction of the blade's lifetime and efficiency.

Wind Energy, published online December 1, 2021

Operation and maintenance costs of offshore wind farms and potential multi-use platforms in the Dutch North Sea

By Christine Röckmann, Sander Lagerveld, and John Stavenuiter, Wageningen University and Research–Wageningen Marine Research, and Asset Management Control Centre, Den Helder, The Netherlands

Large wind farms farther off the coast pose high expectations because of higher average wind speeds and hence greater wind energy yield (in terms of megawatts per capital). These conditions entail additional challenges in logistics, though. One of the main hurdles that hinders use of offshore wind energy is the high cost for O&M. Operation and maintenance costs make up 25–30% of the total costs of an offshore wind farm. This is almost as much as the cost of the wind turbines and about as much as the costs of construction and installation. Individual offshore wind turbines currently require about five site visits per year: one regular annual maintenance visit, and three to four visits in case of malfunction).

Aquaculture Perspective of Multi-use Sites in the Open Ocean, doi:10.1007/978-3-319-51159-7_4

A probabilistic long‐term framework for site‐specific erosion analysis of wind turbine blades: A case study of 31 Dutch sites

By Amrit Shankar Verma, Zhiyu Jiang, Zhengru Ren, Marco Caboni, Hans Verhoef, Harald van der Mijle‐Meijer, Saullo G.P. Castro, and Julie J.E. Teuwen, Faculty of Aerospace Engineering, Delft University of Technology, The Netherlands, Department of Ships and Ocean Structures, SINTEF Ocean, Trondheim, Norway, Department of Engineering Sciences, University of Agder, Grimstad, Norway, Department of Marine Technology, Norwegian University of Science and Technology, Trondheim, Norway, and TNO Energy Transition, Petten, The Netherlands

Rain‐induced leading‐edge erosion (LEE) of wind turbine blades (WTBs) is associated with high repair and maintenance costs. The effects of LEE can be triggered in less than 1 to 2 years for some wind turbine sites, whereas it may take several years for others.


Wind Energy, published online March 26, 2021

Mesoscale modeling of a “Dunkelflaute” event

By Bowen Li, Sukanta Basu, Simon J. Watson, and Herman W. J. Russchenberg, Faculty of Civil Engineering and Geosciences and Faculty of Aerospace Engineering, Delft University of Technology, The Netherlands

The word Dunkelflaute was coined by combining two German words “Dunkelheit” (darkness) and “Windflaute” (little wind) to describe heavy overcast skies and weak wind conditions. These meteorological events can last from a few hours to a few consecutive days. It is needless to say that under the influence of such a meteorological condition, little or no wind and solar energy can be produced. On the 30th April 2018, an unexpected Dunkelflaute event occurred over the southern part of the North Sea and caused a large imbalance in renewable power generation and overall consumption. Given the acuteness of the situation, TenneT—the main transmission system operator for Germany and the Netherlands—had to issue an emergency alert in the Netherlands. The crisis could not be avoided by simple load management or by making use of reserve power; instead, a substantial amount of electricity had to be imported from neighboring countries at high market price.

This Dunkelflaute event was not an isolated episode. As a matter of fact, over the past few years, several Dunkelflaute events occurred in Belgium, Germany, and other neighboring countries. Some of them caused significant impacts on the power grids and electricity markets. There is no reason to believe that the occurrences of Dunkelflaute will subside in the future. Instead, with the ever increasing penetration of renewables in the power grid, the (negative) impacts of Dunkelflaute events will likely become more and more detrimental.

Wind Energy, January 2021

Characterization of offshore vertical wind shear conditions in Southern New England

By Dager Borvarán, Alfredo Peña, and Rémi Gandoin, C2Wind, Videnparken, Fredericia, and DTU Wind Energy, Technical University of Denmark, Roskilde

Vertical wind shears could have a significant effect on the energy produced by a wind turbine and on its loads. ...

Along with the analysis of the wind speed, the study of the turbulence intensity, atmospheric stability, and vertical wind shears plays an important role for the net energy and loads estimation of a wind farm. Atmospheric stability affects the wake recovery of the wind farm, and in the case of turbulence intensity and vertical wind shear, both have an influence on the rotor fatigue loads. Additionally, the vertical wind shear has a significant influence on the energy produced by a wind turbine.

Wind Energy, published online October 27, 2020

Optimal preventive maintenance for wind turbines considering the effects of wind speed

By Rui Zheng, Yifan Zhou, and Yingzhi Zhang, School of Mechanical Engineering, Southeast University, Nanjing, and School of Mechanical and Aerospace Engineering, Jilin University, Changchun, China

[T]he high operation and maintenance (O&M) cost of wind turbines has limited the development of the wind industry. Over 20-year operating life, maintenance and spare partscosts are estimated to be 10%–15% of total income for an onshore wind turbine, and 20–25% for an offshore wind turbine. ...

Many previous studies have illustrated that the correlation between wind speed and hazard rate is positive and obvious for both onshore wind turbines8-11 and offshore wind turbines.

Wind Energy, published online June 10, 2020

UK wind capacity could grow 5% this winter

By Cornwall Insight

The lack of inertia arising from a larger proportion of asynchronous technologies, including wind, on the system is one such issue. Lower levels of inertia become problematic due to the increased rate of change of frequency (RoCoF), meaning system frequency can deviate more rapidly. As a result, National Grid ESO requires more actions from generators to balance the system, leading to higher balancing costs and BSUoS [balancing services use of system] charges.

Another variable affected by the greater wind capacity available on the system is wholesale power prices. A larger share of intermittent generation unsurprisingly brings about increased price volatility, demonstrated by periods of high wind output last winter, resulting in wholesale power prices for day-ahead delivery falling negative for the first time.

Press Release, October 21, 2020

Costs of repair of wind turbine blades: Influence of technology aspects

By Leon Mishnaevsky Jr. and Kenneth Thomsen, Department of Wind Energy, Technical University of Denmark, Roskilde

O&M costs make up 20–25% of the total levelized cost per kilowatt hour produced over the lifetime of the turbine, growing from 10–15% for new to 20–35% by the end of the turbine's lifetime. WTs lose 1.6% of their output per year, with average load factors declining from 28.5% at the beginning to 21% at age 19,8 increasing the levelized cost of electricity (LCOE) by 9%. ... Among the main causes of WT blade damage, one can list the manufacturing defects, transportation damage, assembly damage, installation damage, lightning strikes, environmental wear, rain, sand, and contaminants caused erosion, bird impacts, thermal cycling, leading and trailing edge erosion, fatigue, moisture intrusion and foreign object impact, egress of moisture through the laminate skin structure, as a result of the surface damage, and mechanical failure. With an estimated 700 000 blades in operation globally, there are, on average, 3800 incidents of blade failure each year.

According to Carrol et al., average failure rate of an offshore WT is 8.3 failures per turbine per year. That includes 6.2 minor repair (costs below 1000 EUR), 1.1 major repair (10³–10⁴ EUR), and 0.43 major replacement and 0.7 failures where no cost data can be categorized. The blades are the fifth biggest contributor to overall failure, with 6.2% (after pitch and hydraulic system, auxiliary components, generator, and gearbox). Blades show 0.456 minor repairs, 0.010 major, and 0.001 major replacement per turbine per year. The minor repair can mean protection tapes or shields, filling and injection, while a major repair is typically a structural repair.

Also, Dao et al. showed that the failure rate per turbine per year is 4 times higher for offshore than for onshore WTs, for blades and hub. There are various data on annual failure rate of rotors and average downtimes pro failure: 0.11 annual failures with average downtime per failure of 3.2 days based on WMEP database (corresponds to an average downtime of 9 h per year per turbine and probability 0.10% for each turbine), 0.23 annual failure rate with an average downtime per failure of 11.4 days based on LWK (corresponds to average downtime of 62 h per year per turbine and to a probability of 0.71% for each turbine). In Stenberg and Holttinen (VTT database), downtime of a WT due to blade failure is shown to be 7% of the total technical downtime, that is, 18 h per year per turbine and 0.21% probability for each turbine. Two percent of turbines per year require blade replacements, mainly because of lightning strikes. The failure rate is rather high in the second year and then again in the 15th and 16th operational years, with spike at year 15. Einarsson, referring to Tavner and Branner and Ghadirian, noted that 75% of failures cause only 5% of downtimes and 25% of failure cause 95% of down times.

A specific question is the estimation of bird impacts. With estimatedly 140,000–328,000 bird impacts in North America, and of the order of 100 thousands WTs in North America (57,000 WTs across the United States, ~50 wind power plants in Mexico, and ~300 farms in Canada), it means roughly one hit per year.

Wind Energy, published online July 26, 2020

Leading edge erosion of wind turbines: Effect of solid airborne particles and rain on operational wind farms

By Hamish Law and Vasileios Koutsos, School of Engineering, Institute for Materials and Processes, University of Edinburgh

Leading edge erosion (LEE) describes the phenomena of the erosion of a wind turbine blade's leading edge by rain, hail, UV, sand, dust, insects and other airborne particulates. This erosion has a deleterious effect on the blade's aerodynamic efficiency, reducing the turbine's annual energy production (AEP) and hence lifetime profitability. Almost all wind turbines will be affected by LEE due to the ubiquity of its causal factors. EDP Renewables inspected 201 rotor blades on a wind farm after 14 years of operation and discovered that 174 blades (87%) had visible signs of erosion, with 100 blades (50%) showing severe levels of LEE.

Wind Energy, published online July 24, 2020

Assessing the blockage effect of wind turbines and wind farms using an analytical vortex model

Emmanuel Branlard and Alexander R. Meyer Forsting, Wind Energy Department, National Renewable Energy Laboratory, Golden, Colorado; and DTU Wind Energy, Technical University of Denmark, Roskilde

The energy extraction from a wind turbine or wind farm induces a reduction of the upstream wind speed. This effect is referred to as “wind farm blockage,” and the area that is affected is called the induction zone. Wind farm developers and owners have turned their attention to this phenomenon because the current wind energy prediction procedures neglect wind farm blockage effects, resulting in an overprediction of the wind farm production (see, e.g., Meyer Forsting et al.), and biases in power curve measurements.

Wind Energy, published online July 16, 2020

Structural reliability assessment of offshore wind turbine support structures subjected to pitting corrosion‐fatigue: A damage tolerance modelling approach

Abdulhakim Adeoye Shittu, Ali Mehmanparast, Mahmood Shafiee, Athanasios Kolios, Phil Hart, and Karl Pilario, Department of Energy and Power, Cranfield University, U.K.; Department of Mathematics and Statistics, Federal University Wukari, Wukari, Taraba, Nigeria; School of Engineering and Digital Arts, University of Kent, Canterbury, U.K.; Department of Naval Architecture, Ocean and Marine Engineering, University of Strathclyde, Glasgow; and Department of Chemical Engineering, University of the Philippines Diliman, Quezon City

The majority of wind energy is harnessed by onshore wind farms, despite regular local opposition due to visual and sound impacts. A solution is to deploy wind turbines at sea thus minimizing sound and visual impact, with additional capacity factor benefits obtained from the improved wind domain due to unobstructed fetch.

Most of the existing offshore wind turbines (OWTs) use monopile foundations and are installed in water depths less than 50 m. However, for larger turbines in deeper waters, monopiles become very large and increasingly uneconomical due to the difficulty of fabricating and installing such systems, as well as the consideration of modal requirements. ... To address these issues, space frame structures such as jackets are used, which have lighter weight and are stiffer than monopiles. ... However, designing these structures effectively is resource-intensive, especially when designing to withstand the wide set of dynamic loading mechanisms.

OWTs are subject to more significant dynamic structural responses than conventional jacket platforms utilized on the oil and gas industry as a result of the effects of wind load and turbine behaviours. The fatigue load levels as well as the number of cycles to be accounted for are especially of note. The fatigue damage contribution for the multiplanar welded tubular joint from wind load effects can be high (exceeding 60% of the total), and the number of hot spot stress cycles associated with wind and wave loads in a year can exceed 7 × 10⁷.

Wind Energy, published online July 12, 2020

Optimal preventive maintenance for wind turbines considering the effects of wind speed

By Rui Zheng, Yifan Zhou, and Yingzhi Zhang, School of Mechanical Engineering, Southeast University, Nanjing, and School of Mechanical and Aerospace Engineering, Jilin University, Changchun, China

Over the last decade, wind power generation has experienced extensive and worldwide growth. However, the high operation and maintenance (O&M) cost of wind turbines has limited the development of the wind industry. Over 20-year operating life, maintenance and spare parts costs are estimated to be 10%–15% of total income for an onshore wind turbine, and 20–25% for an offshore wind turbine.

Wind Energy, published online June 10, 2020

Numerical study of a concept for major repair and replacement of offshore wind turbine blades

By Wilson Guachamin-Acero, Zhiyu Jiang, and Lin Li, Departamento de Ingeniería Mecánica, Escuela Politécnica Nacional, Quito, Ecuador, Department of Engineering Sciences, University of Agder, Grimstad, Norway, and Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, Stavanger, Norway

Despite maintenance plans and improved designs of OWTs, major OWT components such as blades, gearboxes, and generators still have relatively high failure rates. Recently, wind turbine blades of the Anholt offshore wind farms off Denmark were brought ashore for repair of leading-edge erosion damage less than 5 years after the wind farm was commissioned in 2013. As the longest announced wind turbine blade has a length close to 200 m, challenges arise when major OWT components such as blades need to be removed and replaced, as these components cannot be easily handled offshore. Major repair and replacement of these OWT components are often conducted using specialized jack-up crane vessels and by following a reverse procedure of installation. For major repair activities, huge and expensive crane vessels need to be mobilized to the offshore sites. Take the Teesside offshore wind farm for example. In a recent effort to replace the gearbox of an OWT, the marine operation was scheduled for 5 to 6 days, and the Wind Server jack-up crane vessel was employed. Even without considering the time for mobilizing and installing the jack-up vessel, the installation of a single 7-MW OWT blade can take between 4 to 8 h.

Wind Energy, published online April 22, 2020

Wind turbine asymmetrical load reduction with pitch sensor fault compensation

By Yanhua Liu, Ron J. Patton, and Shuo Shi, Department of Engineering, University of Hull, U.K.

[T]here are two major challenges that the offshore WTs [wind turbines] industry must face for Region 3 operation (above rated wind speed):

1. Unexpected malfunction and failures of WT components will result in expensive repairs and typically months of machine unavailability, thus increasing the operation and maintenance (O&M) costs and threatening to increase the LCoE. However, offshore WT O&M are also challenged by the fact that wind farms are sometimes located 100 km offshore.

2. The use of large rotors and towers with composite structures has led to a very significant increase in unbalanced or asymmetrical loading due to complex air flow, wind shear, gravity, yaw misalignment, tower shadow,1 and so forth. The structures bend very significantly particularly at high wind velocity.

Wind Energy, published online March 11, 2020

Bearing monitoring in the wind turbine drivetrain: A comparative study of the FFT and wavelet transforms

By Daniel Strömbergsson, Pär Marklund, Kim Berglund, and Per-Erik Larsson, Division of Machine Elements, Luleå University of Technology, and SKF (Sweden), Luleå, Sweden

Wind turbines are often plagued by premature component failures, with drivetrain bearings being particularly subjected to these failures. ... [W]ind turbines designed for a 20-year lifetime still experience premature failures with the root cause not yet fully understood. When compiling failures occurring in all the subsystems within the wind turbine, gearbox failures have been shown to cause the longest downtime and are thereby also associated with the highest cost per failure.2,3 Out of the two main component types, the bearings experience most failures, around 76% of the time and with the gearbox output and generator shaft bearings being most represented, while the gears fail 17% of the time and other sources 7%.

Wind Energy, published online February 18, 2020

Maximizing the returns of LIDAR systems in wind farms for yaw error correction applications

By Roozbeh Bakhshi and Peter Sandborn, Center for Advanced Life Cycle Engineering, Department of Mechanical Engineering, University of Maryland, College Park

One of the major hurdles in the widespread use of wind energy is the cost of energy production. ... One of the contributors to high costs of electricity production for wind turbines is yaw error. Yaw error is the angle between the wind turbine's central axis and the wind flow. Yaw error reduces the energy production of a wind turbine, hence reducing the revenue it produces. At the same time, yaw error puts extra cyclic loads on the turbine components, which results in more failures and consequently increased maintenance costs.

Wind Energy, published online February 18, 2020

A review on ice detection technology and ice elimination technology for wind turbine

By Kexiang Wei, Yue Yang, Hongyan Zuo, and Dingqing Zhong, School of Mechanical Engineering, Institute of Engineering, Xiangtan, Hunan, China

Blade icing can affect wind turbines to generate electricity. In severe cases, 30% of power generation is lost in a year, and safety problems in the vicinity of wind power plants are also caused. ... Figure 3 shown the icing blades, and the surface icing on the blades can seriously affect the power generation efficiency of the wind turbine. For example, North America and China often install wind farms in the mountains of the cold regions but the wind turbine blades freeze causes a large amount of power loss. As shown in Figure 4, Tammslin et al. estimate that 20% of wind farms will be installed in ice-prone areas. ... Icing changes the aerodynamic capability of the blade in turn c through affecting the surface roughness of the blade. In particular, a small amount of icing at the front end of the blade greatly affects blade performance. The power loss due to icing is 0.005 to 50% per year and the degree of loss is related to the duration of icing. ... The main cause of wind turbine generator power loss is ice on blades .... It can be seen that the loss of power generated by ice on blades to wind turbines is much higher than other adverse environmental factors. Ice accretion increases the total mass of the blade and increases the load on the blade. Inhomogeneities caused by ice accretion can also cause blade instability and can lead to wind turbine blades to be damaged by excessive vibration. Low temperatures can cause oil failure at the joints of the fan components with increasing friction between the components results in excessive component temperatures and a significant reduction in service life. Falling ice or snow in the cabin of a wind turbine can cause condensation of electronic components. Ice on the blades can result in serious safety problems when separated from the blades due to centrifugal forces, especially when there are roads, houses, wires and transportation routes nearby.



Wind Energy, published online December 23, 2019

Probabilistic risk assessment on wind turbine towers subjectedto cyclone‐induced wind loads

By Miguel A. Jaimes, A. David García‐Soto, J. Osvaldo Martín del Campo, and Adrián Pozos‐Estrada, Universidad Nacional Autónoma de México and Universidad de Guanajuato

International experience has shown that high winds generated by tropical cyclones can cause severe damage and important economic losses towind turbine towers in coastal regions. Wind turbines are vulnerable to hurricanes when the generated wind speeds exceed the design limitsof such structures. Common failure modes include loss of blades and buckling of the supporting tower. There are several examples of wind turbinefailures reported in the literature. For instance, a wind farm was destroyed by the typhoon Maemi in Okinawa, Japan in 2003; several turbines were damaged by the typhoon Dujuan in China; the typhoon Jangmi that struck Taiwan, on September 28, 2008, caused the collapse of windturbines on the shore in Taichung Harbor.

Potential wind turbine failures in Mexico are always feasible, since it is a very hurricane‐prone region. The first wind turbine farm in this country dates back to 1994 with the pioneering project the “Venta I,”when seven wind turbines started operating with a capacity of 1.575 MW. This enterprise was followed by a couple of similar projects,“Venta II” and “Venta III,”inaugurated in 2006 and 2008, respectively; many other farms have been developed afterward. There are several wind turbine failures reported in the media and other sources, for example, the collapse of a nonprofit wind turbine because of gusty winds and oil spills attributed to strong winds; a fatality during the construction stage of a wind farm is also reported in the news. Although there are not reported failures because of cyclone‐generated wind loads, yet the time window is relativelyshort (25 y from 1994), and therefore, failures are expected in the future, especially considering that the last 8 years major wind turbine farms have been developed. Other nonhurricane‐related failures are reported in the literature. For instance, lighting struck, this problem may be associated to certain atmospheric conditions together with the shape of the blades that seems to make them work as lighting rods during electric storms.

Wind Energy, published online December 6, 2019

Wind power forecast using neural networks: Tuning with optimization techniques and error analysis

By Gonçalo Nazaré, Rui Castro, and Luís R.A. Gabriel Filho, University of Lisbon and São Paulo State University

Since the wind power has a cubic relationship with wind speed, any error in the wind speed forecast leads to a larger error in wind power production. This dependency in the stochastic nature of wind speed also causes uncertainty in wind power production, and unexpected variations of wind power output may increase the operating costs for the overall power system.

Wind Energy, published online December 4, 2019

A prediction approach using ensemble empirical mode decomposition‐permutation entropy and regularized extreme learning machine for short‐term wind speed

By Zhongda Tian, Shujiang Li, and Yanhong Wang, Shenyang University of Technology

[I]t is found that the randomness of wind speed has a serious impact on the stability of power system.

Wind Energy, published online December 4, 2019

An engineering condition indicator for condition monitoring of wind turbine bearings

By Aijun Hu, Ling Xiang, and Lijia Zhu, North China Electric Power University

[T]he industry still experiences premature component failures, which increase operation and maintenance (O&M) costs. For example, for a 20‐year life turbine, the O&M costs of 750-kW turbines may constitute about 25% to 30% of the total generation cost or 75% to 90% of the vestment costs. And the O&M costs for 2‐MW‐type turbine might be 12% less than an equivalent project of 750‐kW machines. At the same time, as turbines are installed offshore, these failures will become even more costly. General Electric Energy quoted that a $5000 bearing replacement task can easily turn into a $250 000 project involving cranes, servicecrew, gearbox replacements, and generator rewinds without mentioning the downtime loss of power generation.

Wind Energy, published online December 3, 2019

Analysis of low-frequency noise from wind turbines using a temporal noise code

With the deployment of increasingly larger wind turbines in rural area, but still relatively close to dwellings, wind turbine noise is one of the major environmental concerns associated to wind energy. In this respect, low-frequency noise (LFN) is pointed out as a possible threat to human health.

Franck Bertagnolio, Helge Aa. Madsen, and Andreas Fischer, DTU Wind Energy, Denmark, presented at 23rd International Congress on Acoustics, 9–13 September 2019, Aachen, Germany

Trading wind power through physically settled options and short‐term electricity markets

Wind power producers participating in today's electricity markets face significant variability in revenue streams, with potential high losses mostly due to wind's limited predictability and the intermittent nature of the generated electricity.

Wind Energy, published online August 14, 2019

Mother wavelet selection in the discrete wavelet transform for condition monitoring of wind turbine drivetrain bearings

Ribrant and Bertling report from a statistical analysis of two Swedish sources that wind turbines are expected to experience a failure within three years of operation instead of the 20-year designed lifetime. These failures lead to high operations and maintenance costs, which can be up to 20% of the wind energy generation costs. The largest contributor to the downtime of a turbine, and thereby costs associated with failures, has been shown to be the drivetrain gearbox. The costs of a gearbox failure originate in the production loss during the long downtime of the turbine as well as unplanned and difficult maintenance. Therefore, the gearbox is seen as the most critical subsystem to focus on for maintenance cost purposes. The cost of the gearbox itself is another large cost to be accounted for, according to Crowther et al, up to 400 k€ for a 2 MW gearbox. Furthermore, turbines with a capacity rating over 1 MW are more susceptible to component failures compared to smaller turbines.

Wind Energy, published online August 7, 2019

Prediction of wind turbine generator failure using two-stage cluster-classification methodology

Costs associated with the operation and maintenance (O&M) of a wind farm makes up a significant proportion of total lifetime costs. In fact, up to 30% of the total energy cost can be spent on O&M for some large offshore developments.1 With wind farms moving into harsher environments further offshore, this value is only expected to increase in the future. ... Generator faults can contribute significantly to the overall downtime experienced by a wind farm because of component failure, with around one failure per year in state-of-the-art offshore wind turbines

Wind Energy, published online August 7, 2019

Wind turbine gearbox failure and remaining useful lifeprediction using machine learning techniques

The cost of energy for offshore wind is currently too high to make it truly competitive with traditional fossil fuel energy generationtechniques. Past analysis has shown that costs for offshore wind energy are roughly 40% higher than gas turbine generation and 30% higher than onshore wind. ... The gearbox has one of the highest downtimes and replacement costs out of all wind turbine components. ... The gearbox planet bearing issue is located on the low speed planetary stage of the gearbox. The bearing issue eventually results in complete fail-ure of the bearing and subsequently the gearbox. When this occurs, the turbine is shut down and only restarted once a complete gearboxexchange occurs. ... The gearbox tooth issue is located on the pinion of the intermediate stage of the gearbox. The tooth issue eventually results in complete failure ofthe intermediate stage of the gearbox. When this occurs, the turbine is shut down and only restarted once an exchange of the intermediate gearbox stage occurs.

Wind Energy, March 2019

Quantitative detection method for icing of horizontal‐axis wind turbines

Icing seriously endangers the operational safety of wind turbines

Wind Energy, published online December 28, 2018

By Luis Bartolomé and Julie Teuwen, Department of Aerospace Structures and Materials, Faculty of Aerospace Engineering, Delft University of Technology, The Netherlands

A variety of environmental effects, eg, hailstorms, snow, rain showers, wind gusts, icing, extreme temperatures, lightning, sea water, ultraviolet light, and sandy winds, degrade the blades of wind turbines over their working lifetimes. This degradation leads to reduction in aerodynamic efficiency and power production, eg, the degradation caused by erosion on the leading edge affects the drag and the lift. Depending on the drag increase and lift decrease, the loss of the annual energy production of wind turbines can range from 2% to 25%.

Wind Energy, published online September 17, 2018

By Bjarne Havsteen, Svendborg Brakes

Yaw noise is a significant contributor to the noise produced by wind turbines. It is the result of contact between the yaw brake pads and the disc when nacelle adjustments are made to optimize wind generation. The brakes are released to let the yaw motors turn the nacelle sufficiently into the optimal wind direction, and then reapplied to the hold position.

Windpower Engineering & Development, October 4, 2018

In “Modelling the effects of environmental conditions on wind turbine failures” (Wind Energy 2018) Maik Reder and Julio Melero summarize wind farm (WF) characteristics and failure data. The observation period is 3 years (January 2013 to December 2015), resulting in 1149 operational wind turbine (WT) years for 11 WFs and, in total, 383 turbines. All farms are located on-shore in different areas of Spain and operate 3 bladed, geared-drive and pitch-regulated turbines. The turbine sizes range from 300 kW to 2 MW, and their age from 4 to 16 years. Over the 3-year observation period, there were 541 failures, 155 of them gearbox failures.

wind turbine failure data

Wind Energy, published online August 1, 2018

Assessment of frequency performance by wind integration in a large‐scale power system

Large‐scale wind energy integration has affected available transfer capability and imposed additional uncertainty on power system operation and reliability. Integrating large amounts of wind energy into the system is challenging due to the variability in power flow patterns, low local demand, and a more complex active and reactive power dispatch. ...

Several issues, in particular, make the integration of wind power difficult:

  1. Wind power spatial distribution. A large amount of wind power is concentrated on a small geographical region.
  2. Wind variability. Wind power fluctuations ranging from 0 to approximately 100 MW within an hour are not uncommon, especially early in the morning (during off‐peak hours). Further, wind generation is out of phase with load demand thus adding to system variability.
  3. Relative size. The ratio of wind power relative to hydro generation in the southeastern system is high (approximately 50%). As a result, the AGC must compensate fluctuations in wind power and load variations.
  4. Point of interconnection. Wind parks are connected in a radial fashion to the 400‐kV transmission system. A ±300‐MVar SVC is used to support local voltage. As a result, loss of SVC voltage support or loss of major transmission lines may result in the loss of a large amount of wind generation. ...

Large‐scale wind energy integration into the southeastern system of the MIS [Mexican interconnected system] has affected available transfer capability and imposed additional uncertainty on power system operation and reliability. ...

High levels of wind integration introduce major frequency deviations in the electrical grid. Simulation results indicate that a very high concentration of wind farms in one point of the electrical grid produces more frequency deviations than a similar value of wind farms distributed on several places of the electrical grid. Also, the injection of real power may be implemented as an emergency action to improve the frequency response of the power system.

Wind Energy, published online August 1, 2018

Improving the efficiency of wind farms via wake manipulation

The power available in the wind is proportional to the cube of its speed. A small increase/decrease in the speed of the wind can increase/decrease the power associated with it by a large amount. ... Modern day wind farms often consist of a large number of individual turbines arranged in a group or cluster with an interturbine spacing of 6 to 10 rotor diameters. The leading (or upstream) turbine in an array is the one to receive the fastest air. After it extracts a part of the energy from the incoming wind stream, it creates a wind shade in the region behind it, which is referred to as the wake. As a result, the wind behind the leading wind turbine is energy deficient and more turbulent than the wind flowing into the turbine. Hence, in large wind farms consisting of many rows of turbines, the wakes generated by upstream turbines are often incident upon the downstream turbines. The interaction of the wakes with the downstream turbines reduce the power output of the downstream turbine significantly. The average power loss due to wind turbine wakes is 10% to 20% of the total power output in large offshore wind farms.

Wind Energy, published online July 30, 2018

Gearbox high‐speed‐stage bearing slip induced by electric excitation in a test facility

Wind turbine systems are excited by the dynamics of the turbulence in wind conditions, changes in stable operation of the electricity grid, and wave excitations for offshore machines. Wind turbine reliability has a significant influence on the cost of electricity. Costs are a combination of downtime and repairs. According to public databases, gearbox failures result in significant downtime per failure, and the need for cranes can make a bearing replacement costly. Bearings tend to be the components that are the most susceptible to failure in wind turbine gearboxes. The National Renewable Energy Laboratory (NREL) gearbox failure database documents more than 1000 gearbox failure cases. High‐speed‐stage (HSS) and intermediate‐speed‐stage bearings are among the most frequently failing gearbox parts together with the associated helical gears.

Wind Energy, published online July 19, 2018

Conceptual study of a gearbox fault detection method applied on a 5-MW spar-type floating wind turbine

Experiences show that faults or damages in the drivetrain contribute significantly to the wind turbine's downtime and nonavailability. The maintenance and repair are particularly too costly for the offshore wind turbines where special vessel and crane barge are needed to replace the faulty drivetrain. In addition, the harsh offshore weather reduces the repair period only to few months often in summers.

Wind Energy, published online July 2, 2018

Field investigation on the influence of yaw misalignment on the propagation of wind turbine wakes

Wind turbines in a wind farm are typically subjected to mutual aerodynamic interactions due to their wakes. Depending on the farm layout and inflow direction, this can lead to unfavourable structural loading and a substantial reduction in the power yield over extended periods of time

Wind Energy, published online June 28, 2018

Wind turbine blade coating leading edge rain erosion model: Development and validation

Leading edge erosion on wind turbine blades is an industry wide problem as it may reduce the aerodynamic efficiency of wind turbines and is an unsightly defect.

Wind Energy, published online June 19, 2018

On the tails of the wind ramp distributions

One of the major challenges facing the wind energy industry is the accurate prediction of sudden and sharp fluctuations in the wind field (aka wind ramps) near the lower part of the atmospheric boundary layer. These not-so-rare and inauspicious events can drastically modulate deficiencies (ramp-down) and/or surpluses (ramp-up) in wind power production causing disruptions in operations and energy supply balance.

Wind Energy, published online April 18, 2018

Modelling the effects of environmental conditions on wind turbine failures

The following observations were made for non-environmental covariates:

The coefficients of the meteorological covariates show the following behaviour:

Failure mode

Wind turbine gearboxes can fail in a variety of different ways. However, according to the National Renewable Energy Laboratory gearbox failure database, more than 60% of all gearbox failures are directly related to the gear bearings. The principal reasons forWT gearbox bearing failures are oil degradation and contamination. Additionally, temperature-related changes in oil viscosity can affect the gearbox.Oil contamination is caused by moisture, particles, and entrained air (foam), which can result in high vibrations and wear. These contaminations can enter the gearboxes in a variety of ways. They could be introduced during manufacturing or maintenance or generated internally. Additionally, they can be ingested through air exchange with the ambient air. The latter occurs often during warmer months or because of diurnal temperature variations, which cause air to be sucked into the gearbox through the seals and “breathers.” The typical breather systems in WT gearbox housings are usually not sufficiently preventing the contaminants from entering the system. The model suggests that the gearbox failures occur in the presence of these temperature variations, as discussed in the next 2 paragraphs.

The month before failure

The model indicates that the month before the failure is characterized by lower RH and thus higher temperatures, lower mean wind speeds, and less PWR. Although the RH might be lower at higher temperature, the increased air exchange contributes to a higher risk of contamination inside the gearbox. As the effect of these contaminations usually occurs time delayed, the component might only fail after a certain period or when the operational conditions change because of higher wind speeds and/or increased operational time.

The month of failure

The month of failure is defined by lower temperatures. This is consistent with earlier studies conducted by the authors. As the previous month was rather characterized by higher temperatures, this is likely to indicate a transition month from warmer to colder seasons. In particular, the daily temperature swings during these months can cause wear due to oil viscosity changes, which are resulting in less oil flow. Additionally, temperature variations due to heavy rain facilitate further air exchange between the ambient air and the interior of the gearboxes through the breathers. Along with lower temperatures, usually higher mean wind speeds are registered, causing more WT shutdown and start-up events and higher times in operation. Under these conditions, the gearboxes are mechanically challenged, and possible damages due to previously entered oil contaminations can lead to a component breakdown. So a combination of degraded and contaminated lubricant due to previous air exchange with the surroundings and problems with oil viscosity and higher loads during the failure month are affecting the gearbox lifetime behaviour negatively.

Wind Energy, March 6, 2014

Why integrated bearing designs reduce wind-turbine gearbox failures

[O]ne of the challenges still facing the wind industry is premature component failures that lead to increased operation and maintenance costs, which increase the cost of wind energy. To make wind power more competitive, the reliability and availability of turbines have to be improved, especially as turbines increase in size and are installed offshore. Various historical statistics have shown that the largest downtime driver and the most costly component to maintain throughout a turbine's 20 year design life is the gearbox. It is an industry-wide challenge that needs to be addressed by all parties along the gearbox supply chain.

Wind Energy, published online May 2, 2018

Why integrated bearing designs reduce wind-turbine gearbox failures

By Michelle Froese

A bearing typically has three pieces: the rollers, an inner race that is pressed onto a shaft, and an outer race that is pressed into the gear bore. Exceptional engineering and quality components are important if the gearbox is to endure the harsh and variable conditions inside an operating wind turbine. A gearbox bearing will also require proper lubrication and regular condition monitoring to ensure optimal performance.

However, even with a top-notch O&M strategy, bearing failure rates typically occur every 5 to 10 years depending on the type and position — which eats into most turbine’s 20-year life expectancy. High-speed bearing failures occur more frequently, but planet-carrier and low-speed bearing failures are more costly.

Windpower Engineering & Development

Limpieza de aerogeneradores con helicóptero [Washing of wind turbines by helicopter]

Es conocido que existen muchos factores que provocan la “rotura” del perfil aerodinámico de las palas: nieve, hielo, contaminación, humedad, polvo en suspensión, insectos, etc., lo que motiva la “caída” del rendimiento del aerogenerador. Estas pérdidas suponen aproximadamente entre un 2% y un 20% en la generación de energía eléctrica o de un 100% en caso de hielo o nieve sobre las palas.

[It is known that many factors can “break” the aerodynamic profile of the blades: snow, ice, pollution, humidity, dust, insects, etc., causing decreased performance of the turbine. These losses represent from 2% to 20% off the generation of electrical energy, or up to 100% in case of frost or snow on the blades.]


Report: The O&M Costs Of North America’s Aging Wind Fleet

By Betsy Lillian

The aging North American wind energy market is costing the industry $3 billion to $4 billion annually in operations and maintenance (O&M) expenses, claims a new benchmarking study from IHS Markit.

IHS Markit estimates total O&M spending for the wind energy sector will exceed $40 billion, cumulatively, from 2015 to 2025. The firm notes that the U.S. Bureau of Labor and Statistics is also keen on the potential for employment in the sector; it estimates wind energy technicians will be the fastest-growing occupation and will more than double in demand during the next seven years.

“The average age of the North American wind fleet will rise from 5.5 years in 2015 to seven years in 2020 and to 14 years in 2030,” says Maxwell Cohen, senior research analyst at IHS Markit.

Cohen and Ryan Siavelis, senior research analyst at IHS Markit are co-authors of the “2017 IHS Markit Wind O&M Benchmarking in North America: Summary of Key Findings.”

The report comprises data from nearly 300 wind projects, representing 30 GW of capacity and nearly 20,000 turbines installed in North America (about one-third of the market). Project start dates range from 1994 to 2016. The data represents more than 115,000 turbine-years of operational history and includes information on wind turbines manufactured by more than 15 OEMs.

“Though it may seem counterintuitive, first-year start-up costs are quite expensive as problems with new equipment are addressed; then, as projects age, we see a spike in costs for equipment maintenance at about the five-year mark through to 10 years of operation,” Cohen says. “Some wind installations in California date back to the 1980s, so you have a wide variety of equipment and installations, and there is a real need for some comparative analysis to help the industry assess and manage operations and maintenance costs.”

Currently, according to the report, more than 50,000 utility-scale wind turbines comprising nearly 100 GW of generating capacity are installed in 42 U.S. states and 12 Canadian provinces and territories, and they have an average age of six years. By the year 2030, IHS Markit expects those numbers to increase significantly: More than 70,000 wind turbines will generate more than 150 GW of power in the U.S. and Canada.

“The age of that capacity in 2030 will make the O&M business very lucrative, which is why so many players are expanding into this sector of the business,” says Siavelis. “We see new entrants from across the value chain competing for wind O&M service agreements. Original equipment manufacturers (OEMs) including Suzlon, Siemens Gamesa, MHI and Vestas are becoming more active in offering to service turbines manufactured by other OEMs, for example.”

Suzlon and MHI, which have both shuttered U.S. manufacturing, says IHS Market, are re-focusing in the U.S. as service companies for their respective installed wind turbines, as well as for other OEMs. In 2015, E.ON Climate & Renewables, a wind independent power producer (IPP), launched a business serving turbines owned by others, following in the footsteps of EDF RE and Duke.

“These IPPs are tapping project administration and balance of plant (BOP) experience to capture new deals,” Siavelis says.

O&M costs are lowest in the first year of operation, but only slightly, the report says. During the first 10 years of a wind turbine’s operations, costs average between $42,000 and $48,000 per megawatt, IHS Markit says. There is, however, a great range of costs from project to project; age, location, and O&M strategy are all important factors.

As projects continue to age, direct O&M costs (the direct cost of actually maintaining the turbines) increase while indirect costs (e.g., general site administration and other business services) remain steady or even decline – leading to mostly stable total costs on net, according to the report. However, Cohen says a wide variation in costs exists for wind projects depending on size of the installation; equipment used; and whether maintenance costs are managed by the OEMs, independent service providers (ISPs) or operators themselves.

The median O&M cost for a project with a full-wrap warranty was slightly more than $48,000 per MW per year in 2016, according to the study. After the warranty period, the median costs for projects maintained by OEMs and ISPs were nearly the same, while the median cost for projects moved in-house was 19% lower.

IHS Markit says the study indicates that substantial cost-savings can typically be obtained by switching to self-performance, but the authors caution that the data used in this study is weighted toward large owners that are experienced in self-performance of maintenance.

“Performing their own O&M can be risky for owners who do not have a track record of conducting maintenance,” Cohen says. “These turbines are massive, complicated machines, containing thousands of parts perched 25 stories or higher above ground. Our study found that one-quarter of all turbines’ gearboxes need replacement during just the first decade of operations. Owners that perform their own O&M need to coordinate labor, spare parts and cranes for this sort of complicated turbine maintenance, all while minimizing turbine downtime. These owners may have projects using turbines built in different years by different OEMs that are spread all across North America in remote locations, so doing their own O&M is a major undertaking.”

Contracting with an ISP can provide greater flexibility, but the report finds that ISPs have a mixed record when it comes to cost-savings. ISPs, IHS Markit says, have a long tail of projects in the bottom quartile in terms of cost-savings, and owners should note that savings may not be as great as expected in low-performing projects.

“The key here is that there is no one-size-fits-all strategy for wind operators,” Cohen concludes. “Our goal was to provide a comprehensive assessment of the entire O&M market so wind asset owners can select the O&M strategy that best balances cost, convenience and risk profile for their particular portfolios of wind projects.”

Windpower Monthly, November 8, 2016

"The power-curve warranties OEMs give are worthless"

Earlier this year, Jan Nikolaisen, co-CEO of technology and service provider Romo Wind, issued a short open statement to the wind industry, in which he decried the lack of trust between operators and original equipment manufacturers (OEMs). He attributed part of that mistrust to a general failure to accurately measure and monitor turbine performance.

"When performance is not as expected, the operators tend to think the turbines are not performing well, while the manufacturers blame the wind," he said. "The industry standard of using a met mast is too expensive, too impractical, and too imprecise to give us the transparency we need to defuse the unnecessary tension we have in our industry." ...

Can you tell us more about the mistrust you have noted between wind-farm operators and turbine makers? What, more precisely are the operators complaining about? How are the OEMs responding to these complaints?

When I commented to the chief technology officer of a sizeable independent power producer that I was surprised about the seemingly little trust between operators and OEMs he looked angrily at me and said: "What do you mean? Little trust? There is no trust". That might be an extreme view, but I have yet to meet an operator who says he fully trusts the OEM.

The main complaints I hear are about ownership, availability and comparability of data. In short, a lack of transparency.

As operators have become larger and more sophisticated, they want more control over their assets, and to control your assets you need data and transparency. So they want data they can trust and work with. If they see a problem they want to be able to find the root cause themselves.

This pro-active mentality of operators is relatively recent in the industry. It has partly been driven by the utilities entering the wind sector. They come from a world where, if you own the asset you own the data the asset is producing, and they have found it difficult to adjust to the realities of the wind industry. Another driver has been disappointment over performance and service quality, which has led non-utility operators to think differently. ...

You say that "part of the lack of trust comes from the fact that we have not been able to accurately measure and monitor turbine performance". Surely a fair amount of progress has been made in this area over the past, say, ten years. How inaccurate are we, do you think?

Wind turbines have certainly become much better over the past ten years, but we are still measuring their performance in the same way and with the same accuracy as we did decades ago.

The gold standard of the industry - a met mast - has an uncertainty of annual electricity production (AEP) in the 4-8% range, so we have to admit that we do not really know how well the turbines perform. That is especially true for how performance changes over time.

Only a small percentage of turbines have undergone a proper performance validation using a met mast, due to the complexity and tremendous cost of met-mast power-curve campaigns.

The lack of accurate performance measurements makes optimisation difficult. If you can't prove a small but meaningful improvement — say a 1-2% increase in AEP — no one is going to pay for it, so optimisation measures are not going to happen.

Also, it is close to impossible to intervene when performance is declining more than it should. In the long run, this must have an effect on the levelised cost of energy (LCOE), but a number I often hear referred to is 4-8% improvement potential for existing turbines.

Could you elaborate on the deficiencies of met masts – in terms of their cost, impracticality, and lack of precision? What should replace them? Who agrees?

Where should I start? The issues with met masts are both economical and practical. First, they are too expensive to be used for anything more than spot checks on nominated turbines in a wind farm.

Second, they are impractical for meeting the industry's need: continuous and comparable performance measurement on all turbines, in all terrain types and at all times.

Given that the met mast measures the wind somewhere else than where the turbine is, the measurements will generally be affected by the local terrain, and the performance measurements are consequently site specific.

In other words, the measurements are not comparable from turbine to turbine. A met mast can only be used in the free wind sector and in non-complex terrain, even though the turbine obviously operates in all wind sectors and in all terrains.

So in practical terms, it means the power curve warranties the OEMs give are worthless. This is a stone in the shoe for the operators, and if they were presented with a better alternative they would jump on it.

We need to develop reliable and accurate wind measurements on the turbine, be it our iSpin, Lidar, or other technologies. It is the wind that hits the turbine that produces the energy, not the wind several hundred metres away.

Only by making local wind measurement can we take out terrain and wake effects, and make the measurements comparable. ...

Windpower Monthly, September 1, 2016

Preventing a Flame-up

By Travis Dees

Fire prevention is a big land-management issue right now, especially after El Nino drenched most of the nation earlier this year. Weeds are at an all-time high, just as fire season kicks in. The past decade of droughts and catastrophic wildfires have left parched landscapes ill prepared. Project site assessments and maintenance practices should be carefully considered, especially given the large assets at stake on wind projects.

Time for Fire Prevention

A wet growing season was a blessing for farmers, ranchers, and watersheds; however, as the temperature warms up and new vegetation reaches maturity, it’s not exactly a blessing for wind projects.

Dry vegetation is an extreme hazard, especially around potential ignition sources. Owners and operators probably could expect more visits from fire departments this year thanks to El Nino, so make sure you’re in compliance. Most municipalities or county fire departments have vegetation management regulations to remove or mow to a prescribed height before the start of the fire season. It is also important to know inspections are conducted throughout the dry season, and the property must be maintained in order to remain in compliance. Even if property owners abate their property early in the season, there is potential for re-growth.

For some power facilities, managing vegetation around equipment where an ignition source could occur is another best management practice (BMP). Around power transformers and inverters, vegetation should be removed from the ground in a radius of not less than 15 feet.

Clearing this radius will help prevent a fire from starting if the component has a major failure that causes sparks. Inside the substations, fenced parameters should be removed to bare ground or rock. Low-growing vegetation is often encouraged as a means of mitigating dust, but it should be mowed to a height of four inches since this is an effective way to minimize fire hazards while allowing for low ground.

Most fire requirements ask for large defensible spaces for the site, but codes vary by region. Clearing around power poles, turbines, transformer pads, and junction boxes is essential, along with the other obvious places on sites such as roads and buildings. A 10-foot radius around power poles will help prevent a fire from starting if there is any arching due to a failed component. Trees and other large brush should be cleared at least eight feet below a power line.

Maintaining roads also will help as a firebreak if a brush fire starts. Most roads in high-risk fire areas need a 20-foot distance on either side after a project has been constructed, allowing for access and acting as a firebreak.

Using parameter roads and fence lines as a firebreak is a site’s best defense for the spread of fire whether the source is internal or external. Keeping the groundcover and fence line maintained may mean seasonal inspections and services to remove windblown vegetation that has accumulated. Vegetation in fence lines can become a tinderbox, so this has to be cleared throughout the season, too.

Fire safety starts with mowing as one small spark from a mower or a mower’s blade hitting a rock can result in a big fire. Given the high-dollar cost of the site owner’s assets at stake on wind fields, hiring safety-conscious licensed professionals with proven track records is recommended, especially given the chemical and mechanical weed-abatement strategies used.


One of the biggest weed challenges often faced is contending with the dreaded tumbleweeds (also known as Russian Thistle). In the Antelope Valley alone last year, World Wind & Solar (WWS) removed more than 2,000 tons of tumbleweeds — that’s 4 million pounds — from both solar and wind projects. Tumbleweeds can cause serious problems when they get caught in equipment. In order to prevent these problems, WWS tells clients it’s better to be proactive than reactive.

Each tumbleweed can produce up to 200,000 seeds if it’s not removed from the site, and it also contains oils that can be flammable. WWS will mow them while they’re still green and physically remove them from the site. WWS also uses a chemical weed abatement program that requires careful planning and permitting.

There are other professionals to turn to. A great source for assistance in identifying potential fire risk is often times the county fire department. WWS recommends inviting them on site to help with a proper proactive approach.

Reducing Damage

Preparation now will reduce potential damage later. Set up operations and maintenance vendor agreements. Look at your policies: Do they follow best practices discussed here? Can your staff effectively manage the ongoing tasks that need to be performed? Between the wet-winter season, followed by what is expected to be a dry summer season, fires are a looming danger for projects with catastrophic consequences. Given all of these potential devastating effects from improper land management, wind pros should take steps to minimize damage and protect their projects. 

Wind Systems, August 2016

Data-Driven Main Bearing Maintenance Strategies to Reduce Unplanned Maintenance Costs

By Becki Meadows and Jason Shapiro

Main bearing failures can wreak havoc on a wind farm’s operating budget. Operators are experiencing high numbers of main bearing failures resulting in unplanned operating costs. Reference data from seven sites over four years shows that annual failure rates of 3-6 percent are not unusual. As bearings age and damage accumulates, that rate of failure is expected to increase.

Although replacement costs can be as high as that of a gearbox, main bearings are usually not maintained with the same rigor.

Wind Systems, May 2016

It’s Not Just Gearboxes That Have Bearing Problems

By Rob Budny

The failures of pitch bearings – the interface between the turbine blades and the hub – have not received nearly as much attention as gearbox and main shaft bearing failures. Nonetheless, pitch bearing failures are becoming commonplace.

North American Windpower, April 2016

A Case for Wind Farm Construction

By David W. Carns

The Wild Horse project is owned by a public utility company, and it is located on approximately 9,000 acres of shrub-steppe land about 140 miles east of Seattle, Washington. The project is a 229-megawatt capacity wind-powered electrical generating facility with 127 wind turbines. The generators are connected through underground cables to a central electrical substation, which in turn delivers power to the main power grid. To provide access to each tower, over 32 miles of roads were constructed. ...

The towers and turbines were designed and manufactured by a firm from Denmark. Towers are made of steel and were constructed in three sections totaling 221 feet in height. They were manufactured in Vietnam, and each tower is topped by a 1.8-megawatt nacelle weighing 75 tons. The nacelle houses the turbine, gearbox, transformers, generator, and mechanical and control devices. Each nacelle is driven by three 129-foot long blades that can vary their pitch and are designed to produce power from wind ranging in velocity from about four mph to a cut-out speed of 25 mph. ...

Project Construction

Roads and Quarries: The 34-foot wide roadbed was designed and constructed to accommodate the width and weight of a 31-foot wide crane and included a 16-foot wide compacted crushed rock surface for vehicle travel. Because of the size of the cranes, the road design also limited vertical grade, vertical curves, and side slope of the travel surface.

To allow erection of the towers, a crane pad was constructed near each tower site using small dozers. The soil was primarily hard fractured basalt that required ripping, but there were also areas of soft compressible silt that required use of geo-textile fabric. Two on-site quarries were centrally located. Portable crushers were used to produce 1 ¼ inch minus and ¾ inch minus basalt aggregate, which was later used both to make concrete at the mobile concrete batch plant, and as a final surfacing for the roads. With the exception of a portion of the concrete sand, all of the aggregates for the project were provided by the on-site quarries.

Foundations: The towers are supported by a cast-in-place, post-tensioned, two-foot thick concrete “ring” ranging from 25 to 32 feet in length. A drill core sample was taken at the center of each foundation location to aid in the preparation of a geotechnical report. Each tower foundation was located in the field using Global Positioning System (GPS) technology. Since drilling and blasting was required for most foundation locations, a drilling crew drilled the rock to a depth of two feet beyond the design depth of the foundations. Drilling proceeded at the rate of two to three foundations per day, followed by blasting of four to five foundations per day. An excavating crew followed the blasting crew using an extended-boom excavator ranging in size from a Caterpillar (CAT) 320 to a CAT 365. Foundation excavation continued at the rate of one and one-half to two foundation holes per day.

Each tower foundation consists of a post-tensioned high-strength concrete ring formed by two Corrugated Metal Pipe (CMP) forms. The outside CMP is 14 feet in diameter, and the inside CMP is 10 feet in diameter. After excavation, a rough-terrain crane was used to lift and set the outside CMP in the hole. The CMP was then stabilized using concrete gravity blocks and cables and then backfilled on the outside with a 300 psi compressive strength cement-based slurry. Post-tensioning for each concrete foundation “ring” was provided by a “bolt cage” consisting of 120 high-strength bolts. Because the bolts serve as the post-tensioning mechanism, all but the ends of the bolts were encased in a greased sleeve. The cage was assembled in an upright position by a crew who first fitted the tops of the bolts into a steel ring template that matched the bolt pattern in the base of the towers.

The bolt cage was then lifted from the foundation hole by a crane and the bottom steel embedment ring was permanently attached, with a nut on each rod beneath the ring. Next, the inner CMP was lowered into the foundation hole, followed by the bolt cage, as shown [below]. This assembly was then centered between the two CMPs and cribbed to the proper elevation.

The center of the inside CMP was then backfilled using the foundation excavation spoils. This material served primarily as ballast for the foundation and compaction was not necessary. Next, formwork for a 12-inch thick reinforced concrete floor was constructed on top of the foundation. In a monolithic pour, the concrete foundation ring and tower floor was placed and vibrated, utilizing concrete with a 5,000 psi compressive strength. Approximately 12 of the foundations were located in areas of poor soil and required a square reinforced concrete “collar” four to five feet thick and four feet below grade, as shown [below]. Tower sections were later bolted to each foundation, with one ring of bolts on the outside and one ring on the inside. Bolts were tensioned in a specified sequence to provide the prestressing force for the concrete foundations and to permanently anchor each tower base section.

Tower, Nacelle, and Blade Erector: The erector was a U.S.-based firm that subcontracted with the tower/turbine supplier to erect the towers, nacelles, and blades, and to transport these large and heavy items from the port to the job site. The erector also prepared, installed, and pre-commissioned the internal components of each nacelle. The erector used two cranes: a 359-ton wheel-mounted crane, and a 550-ton crawler crane. Additional support equipment such as rough terrain forklifts, small wheel-mounted cranes, and maintenance vehicles were also employed. Prior to beginning work, this contractor had to plan and execute a major mobilization effort that involved 43 tractor-trailer loads of equipment. ...

Electrical Distribution: The main electrical substation for the wind farm was constructed at a location central to a majority of the towers. This substation steps up the incoming power (34,500 volts) from each tower to match voltage in the power grid and is connected to the grid through overhead high-voltage transmission lines. Each wind tower is connected through underground wires to the main substation. To reduce heat buildup due to a combination of the high voltage and high ambient temperature of the site in the summer, the underground power distribution system had to be very carefully designed and constructed. The design called for a deep trench and backfill of bedding sand to ensure heat buildup would not damage the cables or reduce their design life. Additionally, in parallel but separate trenches, fiber optic control and monitoring cables were installed between each tower and the main control building located at the entrance to the wind farm. A large chain trenching machine was used to excavate these trenches, as shown [below].

Wind Systems, September-October 2009

Wind Turbine Blade Repair

By Greg Efthimiou

Today’s wind turbine blades are large, robust structures, but they are prone to damage like any other composite component. This damage can begin to occur even as blades are being de-molded or moved around the blade factory. The blades then usually travel long distances to their end destination, often negotiating ports, roads, towns, and being manipulated with forklift trucks and cranes. Each of these handling steps creates the opportunity for further damage. Once on site the assembly process and hoisting of the completed rotor up onto the tower is a final opportunity for damage to occur before the rotor has made even one revolution. Once in operation the blades begin to see erosion from rain, dust, and other atmospheric contamination, and lightning strikes add to the amount of damage that a blade experiences. With the constant fatigue loading from rotation and wind gusts, any hidden manufacturing flaws may also start to show up in the form of cracks in the blade surface, inside the laminates, or between the blade components.

Wind Systems, April 2011

The Future of Wind Turbine Diagnostics

By Andrew Kusiak and Anoop Verma

Despite the increasing rated capacity of wind turbines, operation and maintenance (O&M) costs remain high due to failures of wind turbine components such as gearboxes and blades.

Wind Systems, April 2010

Minimising fire risk in wind turbines

By Shaun Campbell

You need three things to start a fire: fuel, ignition and oxygen. And you can find all three of them in ample quantities within the nacelle of a wind turbine.

A 1.5MW machine, on the small side by today's standards, can still contain up to 900 litres of lubricating and cooling oil. The nacelle itself, probably made with flammable fibre-reinforced plastic (FRP), will house acoustic insulation materials, which are also flammable. Ignition can be provided by faulty electrical and electronic components and connections, or overheating mechanical parts. And high winds, the reason the turbine is there in the first place, can be guaranteed to feed the spark and fan the flames.

Once a fire takes hold there is practically nothing that can be done to prevent the turbine's complete destruction. The remote location of many wind projects means that fire-fighting services are often slow to arrive the scene, while the nacelle's height rules out any meaningful action to dowse the fire. The best that can be expected is that burning debris is prevented from starting ground fires.

Windpower Monthly, 28 August 2015

How To Protect Your Assets When The Heat Is On

By Scott Starr

Incidents of fires in wind turbines are the second most common accident following blade failure. When a fire occurs, the typical action is to wait patiently for the fire to burn out. This can cause significant damage and lead to thousands of dollars in repair costs – plus revenue losses as a result of downtime. To illustrate, a single 2.5 MW-3 MW commercial-scale wind turbine is valued at approximately $3 million to $4 million, with an output averaging $2,800 per day. A minor fire can result in weeks of downtime, while a larger fire can result in a complete loss of the turbine.

There are generally three main causes of wind turbine fires: sparks caused by mechanical failure, electrical malfunction and lightning strikes. A small fire can accelerate quickly in a nacelle that contains large amounts of flammable resin fiberglass. Internal insulation in the nacelle, which can become contaminated by oil deposits, further adds to the fuel load. Lightning strikes also pose a uniquely high risk due to the turbines’ exposed and often high-altitude locations together with the height of the structure; there are turbines now being built that exceed 450 feet.

Despite the high fire risk in wind turbines, there are relatively few widely reported incidents of fire in the industry. Yet in discussions with wind farm owners, turbine manufacturers and insurers, losses from fire are far more frequent than what is publicly documented. ...

Since 2011, there have been 30 large wind turbine fire incidents reported in the mainstream media. The range of property damage on those incidents cost between $750,000 and $6 million, including loss of productivity.

One of the worst incidents recorded in recent times took place in California in 2012. More than 100 firefighters were required to put out a wildland fire that had spread across 367 acres – and it could have been far worse if not for a witness. The final report indicated equipment failure – specifically, an arc flash – was to blame for the fire. ...

Despite the availability of affordable fire-suppression methods, thousands of wind turbines are still being installed without adequate fire protection and preventable wind turbine fires continue to occur.

North American Windpower, Volume 12, Number 5, June 2015

Meet The Achilles Heel Behind Most Gearbox Failures

By Rob Budny & Ashley Crowther

It has often bene noted that wind turbine gearboxes are prone to premature failure. Published estimates on the average lifespan of wind turbine gearboxes range from several years to 13 years and vary by turbine type, gearbox manufacturer, gearbox subcomponent manufacturer, the wind regime in which the turbine operates, the quality of mainenancy practices and the date of turbine manufacture. ...

In the complex gearbox system, failure of any one of the components can result in a costly failure of the entire gearbox. Even if all of the individual components are likely to last 20 years or more, the reliability of the overal gearbox system can be substantially less than 20 years. ...

Most wind turbine gearbox failures are the result of bearing failures.

North American Windpower, Volume 12, Number 4, May 2015

Does The Wind Industry Have A Blade Problem?

By Mathew Malkin, Alex Byrne & Dayton Griffin

DNV GL has compiled blade failure rates from 10 GW of operating wind projects and found that 1% to 3% of turbines in North America require blade replacements annually in the first 10 years of operation, with the highest failure rates usually occurring in year 1 and year 5. ...

Blades fail when an applied load exceeds the blade strength. A single extreme wind event, such as a severe gust or high shear event, could lead to an applied load that exceeds the blade strength. Blade strength might be reduced int eh rpesence of manufacturing defects, damage incurred during transportation and handling, degradation over time, other minor damage that propagates over time or inadequacies int he original design.

Operational factors can also lead to excessive loads on the blades. Take the following, for example: incorrect pitch set-points, incorrect shutdown sequencing or failure to maintain yaw alignment during high winds can lead to defects. Damage from lightning strikes can also lead to blade failure.

North American Windpower, Volume 12, Number 4, May 2015

White-Etching Crack [WEC] Bearing Failures

By Rob Budny, President, RBB Engineering, USA

The WEC failure mode occurs most often in the inner ring of a bearing. The reasons for this are two fold:

There are serveral theories regarding the root cause of WEC failures ... skidding ... hydrogen embrittlement ... electrostatic discharge ... corrosion fatigue ... adiabatic shear ...

WEC failures have become a major source of wind turbine gearbox failures. WEC failures occur much earlier, and at lower stress levels than classical rolling contact fatigue failures, which is the criterion used to evaluate the suitability for wind turbine gearbox bearings.

Windtech International, April/May 2015

Transient Wind Events and Their Effect on Drive-Train Loads

By Doug Herr, General Manager, Aerotorque, USA

Wind turbines asee a broader range of dynamic loads than other rotating equipment. They experience variation fromt he grid/generator (in the form of curtailments, grid loss, voltage changes etc) and also see very frequent wind changes. Storms, gusting conditions and even a sudden wind loss can cause significant variability in drive-train loads. These common events all contribute to the reduction in the expected life of drive-train components.

Extreme wind eents have been defined for a long time. However, the transient torque reversals that these events impart in the drive system have only recently been identified, measured and recognised as a cause of increased O&M costs. Extreme wind events of relatively short duration can be caused by wind shear and turbulence resulting from topography and local weather phenomena, but the design of the wind farm itself can also cause problems due to the downwind wake effects of moving rotor blades.

... A torsional reversal is a rapid torsional unloading of the drive-train and loading up in the opposite direction. While the direction of rotation of the shafts do not change, the direction of the bearing load zone in the gearbox shifts up to 180 degrees very rapidly. One this shifting begins, the system can wind-up back and forth many times causing multiple load zone shifts until the torsional energy is dissipated. These rapid reversals can cause substantial impact loads on rollers and races in bearings. It is believed that a significant number of gearbox failures are caused by the impact loads form these reversals, evidence by the axial cracking observed in turbine gearbox bearing race analysis. these torque reversals can occur any time there is a significant transient event on either end of the system (i.e. significant turbulence or shear winds, e-stops, curtailments etc).

... At higher wind speeds, the blades are precisely pitched to safely deflect the excess wind power. Further pitching beyond the optimum feathering or stalling angle will cause the blades to try to decelrate the generator and can reverse the torque in the styem. During an emergency stop at wind speeds close to cut-out speed, rapid blade pitching can reverse the torque in the system in less than one second.

A sudden change in wind direction can result in momentary torque reversals that can cause damage ot the turbine drive system. ...

... The industry trend is towards increase blade length ... However, there can be a significant downside to this increase in blade swept area. As wind speed increases beyond rated power, more of the potential energy in the wind needs to be safely deflecte via pitching of the lbades. Even with precise pitching the risk of torque reversals caused by wind gusts as winds approach cut-out speed will increase dramatically.

Windtech International, April/May 2015

Special Report: Grinding Gearboxes – Better Call Roy

By GCube Underwriting

GCube’s claims data reveals that gearbox-related failures are the second most frequently reported form of component damage in the North American wind energy market, following blade damage. Of the estimated 175,000 geared turbines in operation in 86 countries worldwide, there are around 1,200 incidents of gearbox failure reported annually – a rate of one incident per 145 turbines per year.

The overall claims cost of an individual incident, when both component damage and associated business interruption are taken into account, commonly reaches $300,000 and has in some unique cases exceeded $500,000. In cases of serial defect, these figures can rapidly be multiplied across entire wind farms and portfolios. ...

The sheer number of recognized root causes of failure serves to illustrate the complexity of modern gearboxes, comparative to other turbine components. While GCube’s Breaking Blades report identified 12 broad categories of failure, the range of known gearbox incidents is both more extensive and more specific.

16 root causes are listed by Grinding Gearboxes. Amongst the most significant gearbox failure trends identified are issues relating to the bearings, which are responsible for more than half of gearbox failures. Breakdown and cracking of the bearings over time – particularly when black oxide coatings are not used or the system is not adequately lubricated – can cause “scuffing” and generate debris that causes wider damage to the gearbox mechanism. Likewise bearings using a 3-point suspension layout commonly demonstrate an above-average failure rate.

Abnormal loads are also a common cause of gearbox failure and loss. Blade behavior has a direct impact on the loads experienced by the gearbox, and rapid acceleration and deceleration can exact a huge amount of stress on the driveshaft, while inappropriate load sharing between bearings can also lead to high stress and strains causing cracks.

These factors, combined with manufacturing defect and human error during the operational phase, rank among the most frequent causes of gearbox-related downtime worldwide.

However, when it comes to assessing the variables affecting the length of that downtime, the impact on the balance sheet and the total cost of insurance claims, the root cause is only one part of the bigger picture. The financial impact of any technical failure is ultimately determined by a large number of interlinked factors, including the nature of the damage, the geographical location, the equipment specifications and evidence of proactive risk mitigation procedures. ...

Cutting the Cost of Blade Breakage

By GCube Underwriting

The wind power industry is undertaking a global migration. It is slowly but surely moving out of established growth centres in Europe and North America – where changing support mechanisms and subsidy regimes have contributed to stuttering new construction – into emerging sectors in Asia Pacific, Africa and Latin America. Here, ambitious manufacturers, developers and operators are hoping to carve out an early share of these new markets, eyeing long-term growth and returns.

In doing so, however, they have naturally come into contact with a variety of additional market-specific risk sources. These range from logistical hurdles – for example supporting transport infrastructure constraints hindering the export and replacement of parts and equipment – to construction challenges involving the use of local labour and theft of resources and, topically, political risk.

While the range of coverage offered by insurers continues to evolve to take into account these unique territory-specific risks, often the main discernable effect of the move into emerging markets is to exacerbate common causes of loss and business interruption. One such cause is the phenomenon of blade failure, which has posed a consistent challenge to the wind energy industry for as long as wind turbines have been rotating. ...

[R]apid supply chain expansion and project development in these new and often highly remote territories has coincided with growing pressure to deliver cost competitive energy across the board. In this climate, current trends appear to suggest that the overall integrity and performance of blades has suffered.

With an estimated 700,000 blades in operation in 85 countries around the world, there are an estimated 3,800 incidences annually of blade failure – a rate of one in 184, or, put more simply, one incident per 61 turbines in operation. ...

[G]iven that total cost incurred by a single incident and the associated business interruption can fall anywhere between $100,000 and $1,000,000 – and has been known to exceed $6,000,000 – there is a clear industry imperative to categorize historic blade incidents and seek to mitigate associated losses as far as possible. ...

While it might seem logical to pinpoint the age of the blades in question as a causal factor for failure and breakage – and the use of obsolete technology no longer in serial production has been known to heighten the cost of repair and replacement – the report [“Breaking Blades: Global Trends in Wind Turbine Downtime Events”] finds that there is no direct relationship between the age of a turbine and the likelihood of a blade incident.

Instead, the various root causes can range form technological fault to manufacturing defect, external incidents such as lightning and human error during the construction or maintenance phases. Likewise, the impact of this failure on the balance sheet and total claims costs is often governed by a number of interlinked factors.

These include the nature of the damage, the equipment specifications, the employment and evidence of risk management procedures and the location of the project in question. Given the market shift into more remote territories and more testing geographies, the latter is of particular significance to developers.

Specifically, proximity to suitable blade manufacturing or repair facilities and access to crucial resources and equipment, such as skilled labor and cranes makes a big difference to the costs of unscheduled maintenance. Delays can be compounded if site access is impeded by poor transport infrastructure or adverse weather conditions. Likewise country-specific permitting challenges and financial incentives will have an impact on the overall cost of blade repair or replacement.

This logistical risk combination continues to present a considerable challenge to those looking to build wind energy infrastructure in the African and Latin American markets in particular. ...


On Top of Turbines

By Morgan Troedsson, Product Manager, FORCE Technology, Denmark

Studies of early offshore turbines showed that the impact of the harsh conditions on the whole turbine structure was much higher than expected. External ladders and access platforms on turbine towers were often washed away, as heavy waves hit and climbed along the tower base. Gearbox failures were common. Heat dissipation and electronics cooling, as well as nacelle venting, were not as easy as expected. The internal cooling system was not functional in most cases. Corrosion effects inside the nacelle and on foundations became visible and showed the need for specific designs for offshore wind turbines.

Rotor blades were also subjected to heavy and unpredictable environmental loads. Surface gel coatings were not sufficiently resistant to the harsh offshore weather conditions. Leading edges of rotor blades started to erode much earlier than expected. The erosion rate was quite high. Lessons learnt were that offshore rotor blades require professional refurbishment after only 3 to 5 years in continuous operation. In comparison, onshore blade refurbishment is normally done after 8 to 12 years.

It came as a surprise to most people in the wind power business that offshore wind turbine blades were degraded so early in their life. Wind fatigue load is quite substantial offshore, causing premature damage and cracks to the blade structure itself. Even more obvious is the damaged aerodynamic appearance, with worn coatings and leading edges seriously eroded in only 4 years on average.

Windtech International, April/May 2014

Prognostics Extends Wind Turbine Life

By Stephen Steen, Manager, New Business Development, Sentient Science, USA

At the current time, turbines have an average gearbox life of between 5 and 13 years, depending upon the manufacturer. A key factor that wind farm operators must assess is the asset risk for their turbines. Typically, a wind turbine OEM provides a warranty covering the first two to five years of operation. Beyond that, the operator will have to fix the turbine if it breaks or purchase an extended warranty from the manufacturer or third-party provider. At the moment, the average cost for fixing a wind turbine is between US$ 200,000 and 750,000 per failure plus crane mobilisation and operational costs. This means that the wind farm operators can face millions of dollars of turbine failures within a few years.

Windtech International, January/February 2014

How To Use Insurance To Lessen Wind Farm Risk

By Alba Alessandro

Wind turbines have a life expectancy of 20 years, and mechanical breakdowns and factors such as lightning plague the machines’ operation. ...

Fire damage is usually caused by overheated bearings, a strike of lightning or sparks thrown when the turbine is slowing down.

Lightning. Lightning strikes are the most common insurance claims filed by owners and operators. A lightning strike to an unprotected blade will raise the temperature to as high as 54,000° F and result in an explosive expansion of air within the blade that can cause delamination, damage to the blade surface, melted glue and cracking on the blade's leading and trailing edges.

Lightning can destroy the control panels that include the sensors, actuators, motors for steering the equipment, rotor blades, gearbox, generator and control system.

Wind. High-velocity wind speed, gust and direction changes can damage and destroy the rotors. Risk of damage from a storm can result in a collapse of the tower and the loss of rotor blades and gearbox due to runaway spinning under extreme wind conditions.

Mechanical damage. Damage to gears and bearings often occurs because of breakdown or wear, backlash and tooth breakage; defects in material; fatigue; the use of wrong oil or wrong oil temperature; vibrations; or overloading.

North American Windpower, October 2013

Turbine Maintenance: Pay Now Or Surely Pay Later

By John Clark

Wind turbines, generally located in wide-open, stormy places where Mother Nature takes her toll, operate under tremendous stress. The unpredictable nature of weather conditions results in constantly changing loads. ...

Because half of the U.S.’ wind turbine generator fleet is behind in OEM-scheduled maintenance, wind turbine owners can expect that increased demand and limited availability for services will drive up the cost of labor and equipment. ...

Mobilization of a main lift crane onto a site to repair one turbine can exceed $200,000, and that does not include the expenses for the crew, tools and equipment. Moreover, it can take 25 truckloads to transport a big crane to a job site and two to four days to assemble the crane. The downtime is costly as well. ...

Renewable energy insurance company GCube said that blade damage and gearbox failure were responsible for the greatest number of losses according to 2012 U.S. claims data – accounting for 41.4% and 35.1% of total claims reported, respectively. Poor maintenance (24.5%) and lightning strikes (23.4%) were cited as the most frequent causees of loss.

... Gearbox claims typically cost the industry $380,000, and turbine blade claims cost an average of $240,000 each.

North American Windpower, October 2013

How To Minimize Axial Cracking Failures

By Rob Budny & Robert Errichello

The failure of bearings due to the development of cracks on the inner ring of the bearing has become a major source of wind turbine gearbox unreliability. Gearboxes at some sites have experienced failure rates as high as 70% within the first two years of operation. While failure rates this high are not typical, axial cracking is the leading cause of gearbox failure for many wind turbine gearbox original equipment manufacturers. The failures are not confined to any single gearbox or bearing manufacturer; they are systemic throughout the industry. The root cause of the failures is not known, although many theories have been proposed and are currently under investigation. ...

Although most wind turbine gearboxes meet or exceed these [Germanischer Lloyd] design criteria, axial cracking failure rates are very high and typically occur within the first or second year of operation. ...

Axial cracking failures most often occur in bearings in the high-speed and intermediate-speed stages of the gearbox, for reasons that are not well understood.

North American Windpower, June 2013

Underperformance Issues Deserve Fresh Examination

Although wind farm underperformance may have been overstated, more work needs to be done to shrink the performance gap.

By Gail Kalinoski

From North America to Europe, researchers and wind industry consul. tants are studying ways to make wind farms perform better, including more accurate wind assessments and component-design improvements. They are making progress: At least two industry consulting groups say the 10% underperformance figure that has been widely accepted as the norm may have been overstated. Much of the gap between operating statistics and preconstruction estimates can be explained by availability, grid curtailment and other issues.

GL Garrad Hassan and AWS Truepower have each done extensive research into performance and have also reviewed and revised their own methods for wind farm energy predictions. Improved forecasts will help the industry get financing for future wind projects and better return on current investments. But researchers and investors say owners and operators need to make more information available so that studies can continue.

Clint Johnson, vice president of GL Garrad Hassan's U.S. energy group, tells NAW that from data the company has analyzed, "We see actual production, on average, some eight percent below original projections and estimate that of this discrepancy, approximately five percent can be explained by a combination of availability, grid curtailment and suboptimal turbine powerperformance issues."

Albany, N.Y.-based AWS Truepower used data from 11 wind projects that had been operating for a combined total of 4S years, according to Eric White, vice president of investor and asset services. By using revised energy-estimation methods to improve accuracy, the firm found those wind farms showed an underperformance gap of about 3.5% rather than the industry average of about 10%.

Paul Veers, chief engineer at the National Renewable Energy Laboratory (NREL) says there has been a lot of effort to operate plants more efficiently to bring down all the sources that lead to underperformance.

"The real problem is the lack of good, hard data that's available in the public sector," Veers notes. "We have to create a decent structure for getting this data out to the public, to make sure it's vetted."

Investor concern

Stuart Ashton is a director at New York Life Investments who makes equity investments in the renewable markets on behalf of the firm's clients. He agrees that having more information and reliable data is crucial. He says the reliability issues have caused "some investors to step away from this market."

There is more interest in building bigger projects rather than addressing underperformance issues in existing portfolios or models, Ashton explains.

"[It] has been a substantial problem in the industry," he notes. "Let's know what the facts are and what some of the fixes are. Let's be open about it. Unfortunately, the pattern that's developed is one of promoting the industry rather than making sure the industry is keeping pace with the growth."

White disagrees that underperformance has kept investors away from wind.

"It's not a huge issue with people sitting out solely for that issue." he says. "A lot are still participating. A lot who weren't participating are participating now. Maybe some have stepped out, but others may have stepped in."

White believes the federal stimuIus package may have affected which investors are in now more than any underperformance problems at the wind farms.

"The production tax credits are not as significant; there are other financing options rather than the equity player. Debt players may be more significant than they were before," White says.

He says that tax-equity investors have in the past played a dominant role in financing wind projects, but this year, it is closer to so-so. White adds that improvements and recalibrations in energy-production assessments that companies like his are making at U.S. wind farms are resulting in more "realistic results that can be treated by the financial folks with some confidence."

According to GL Garrad Hassan's Johnson, the company also continually seeks to review and refine its energy-prediction methods and considers its current energy predictions "to be robust and reliable."

"Loss-factor assumption methods have been refined to better track observed availability, performance and grid levels, and, as a consequence, it is believed that this source of bias in the observed results has now been removed," Johnson says. "It is clearly a challenge for the whole wind industry to recoup some of the energy being lost due to wind farm downtime and suboptimal turbine performance."

Tracking wind

Although there are always going to be year-to-year variations in wind farm energy production because of the natural variability of winds, researchers continue studying ways to improve wind assessments and overall performance. Increased use of remote sensing devices - sonic detection and ranging (SODAR) and light detection and ranging (LIDAR) systems - are helping to better assess wind speeds, particularly on taller turbines.

"If a proven remote sensing device is used properly, it can greatly increase our understanding of the vertical wind profile, which is currently a large source of uncertainty in wind resource assessments," says Johnson.

The need for more research into wake losses - the energy lost in the wake of a turbine - is growing as the size of North American wind farms expand with taller turbines.

"Flow that's been disturbed by other turbines - that's downstream of other turbines - affects performance and reliability," says White. "Most of the turbines are not operating in pristine wind."

Researchers at NREL, as well as at Lawrence Livermore National Laboratory (LLNL), are working on various wind-assessment studies, including wind plant aerodynamics and wake loss, says NREL's Veers.

Julie Lundquist, an assistant professor at the University of Colorado and joint appointee at NREL, teamed up with Sonia Wharton, a post-doctorate researcher at LLNL, for an analysis of data from a West Coast wind farm run by a major wind energy developer. The pair wanted to see how power generation varied with atmospheric conditions.

"For this particular wind farm, during times when the atmosphere was stable, turbines tended to overperform," says Lundquist. "During very turbulent times, they tended to underperform."

Lundquist says the data showed there was often a 20% difference in the power curves.

"We were surprised by that," she says. "We expected six percent or 10 percent. The 20 percent figure was very dramatic."

Wharton says that, in the past, "wind power forecasts have been limited by a lack of high-quality observations of wind speed and turbulence in the rotor disk."

The wind farm had two meteorological towers, whereas most projects only use one with cup anemometers placed at a few heights. In addition, SODAR was in use at the wind farm.

"The SODAR data allows us to know exactly what the wind speed is at 10-meter height intervals in the rotor disk," Wharton notes. "You have a better operating idea of what the power production is really going to be. These observations will come in use for short-term forecasting, too."

The report, released earlier this year, says, "Our work shows promise for using remote sensing in strum en tation to observe complete profiles of wind speed, wind direction and turbulence across a nearly 80-meter diameter rotor in mildly complex terrain. Our study also shows evidence that turbulence and wind shear play a role in power production, and highresolution instruments such as SODAR are needed to quantify these parameters across the rotor diameter."

"Without correct forecasts of stability, errors in predictions of turbulent mixing or wind shear would likely undermine the performance of a wind energy forecasting model," the report also notes.

Lundquist and Wharton say more advances would be possible if more developers could offer data to researchers for analysis. Ashton agrees that it would help the industry and investors to get actual projectperformance information.

"Developers can create a database and track how well future projects perform," he says. "It would improve on their projection abilities."

Johnson notes that "there is a need for continued dialogue in the industry regarding the analysis and modeling techniques used and tracking the trends in the performance of the technology and the grid interfaces."

White says curtailment has become an "increasingly significant issue" at North American wind farms, particularly in West Texas, and can playa big role in some plants' underperformance.

"By and large, our energy assessments assume no curtailment," he notes.

A survey of wind farm availability released in mid-September at the American Wind Energy Association's Wind Resource & Project Energy Assessment Workshop noted that, although the overall impact on total survey fleet is relatively small, the impact on affected projects can be significant.

The survey, which included 2005 and 2009 results, stated that curtailment is being seen at "an increasing number of projects." The report analyzed data from 79 projects with a total of approximately 5,300 MW in service - about 25% of the U.S. fleet as of the 2009 fourth quarter. There was an average plant operation of two years per project - with 20 projects having over three years of service - and a maximum operating time of over nine years. The wind farms were located across the U.S., with Texas representing 30% of the dataset and the Northeast 18%. Wind farms from the Northwest and Plains states represented 14% each, while the Midwest had 15% and the Southwest 8%.

Component concerns

One of the components often criticized for causing underperformance problems is the gearbox. Ashton says not enough attention has been paid to gearbox malfunctions.

"For reasons that I don't fully comprehend, they have not been made robust enough as the physical demands and forces grow on turbines," he says.

NREL is collaborating with leading industry experts to improve gearbox performance. The Gearbox Reliability Collaborative is running dynamometer and field tests on two extensively instrumented gearboxes.

"We're doing a fairly comprehensive [study of] gearboxes and the loads and how modeling can predict what turbulence will do to a gearbox," Veers says. "They continue to be built with decent capability and continue to have problems."

He says NREL findings so far point to problems occurring when gearboxes are overloaded.

"We find that the loads are not always evenly distributed," Veers says.

Another issue involves bearings. According to Brent Reardon, GL Garrad Hassan's head of its turbine assessment group in North America, "There are very few failures in the gearing now due to design issues. Most of the problems seen are related to quality issues, in particular of the steel being used to produce the gears and bearings.

"Some of the issues are due to the type and size of bearing used," he explains. "Bearings that have performed well in other applications have not always been reliable in wind turbine designs."

A joint committee between the International Organization for Standardization and the International Electrotechnical Commission is updating the gearbox reliability standard for wind turbines, according to Reardon. A consortium of European Union companies, working together as the Reliawind Project, is studying improved reliability of wind turbines. Reardon notes that papers already published by the Reliawind Project "seem to contradict the commonly held belief that gearboxes are a major factor in underperformance."

North American Windpower, November 2010

Assessing Insurance And Risk For Offshore Wind Projects


But how do offshore wind projects differ from onshore projects? The answer is in just about every way imaginable. For starters, there is a significant amount of risk in offshore wind projects, of which developers need to be aware.

An offshore project will cost three to four times what it costs to build an identical onshore project.

There are many reasons for this. The equipment required to construct or perform major component replacement on an offshore project is vastly different from onshore - and much more expensive.

Jack-up ships or barges with cranes having up to 600-ton capacities are required. During construction, these vessels sail to a project site, lower four legs to the sea bottom and "jack-up" the ship above the water level, then pile drive the foundations' erect the three section towers and install the nacelle and rotor.

Such vessels cost $1 million to mobilize, $1 million to demobilize and up to $50,000 per day to lease. During operations, a ship with similar capabilities may be required to replace a damaged blade, gearbox or generator, or to remove a nacelle to repair yaw drives. By comparison, a 600-ton land-based crawler crane costs about $50,000 to mobilize and demobilize and at least $1,500 per hour to operate.

During operations, it may take weeks, or even months, to locate and schedule a jack-up ship or barge to perform major component replacement, resulting in significant lost revenue. Onshore cranes that perform such replacements are commonly available within days.

Work on offshore projects can also be held hostage by the weather. Simply getting technicians to a turbine to investigate a malfunction or perform routine maintenance can take days at a time due to bad weather. Jack-up ships might be required to sit and wait out bad weather for long periods of time until conditions permit then1 to sail and set up near a turbine that needs repair. Again, revenue losses due to these delays can be extensive. Onshore, a technician with a service truck can be up in a turbine nacelle within minutes of a problem being identified, even in inclement weather.

Expensive dedicated-service boats and - with some projects - helicopters are used to transport technicians and small replacement parts at significantly higher cost. Onshore, a service truck can usually be driven at any time to each turbine.

Solar photovoltaic on the grid: All's well ... for now

Most distribution systems are equipped to operate efficiently in tandem with grid tied PV, but caution is warranted.

By Michael Bates, Renew Grid, July 2010, page 7

Although any energy company should be aware of how distributed generation systems affect their grids, utilities operating in states with aggressive renewable portfolio standards and generous solar photovoltaic (PV) incentive programs must be on alert as PV penetration rates rise within their service territories. Experts agree that a fine line exists between a distribution system that can handle high levels of solar generation and one that cannot.

States such as New Jersey, Oregon, Colorado, Nevada, Arizona and, in particular, California have all prioritized increasing the share of solar power in their overall energy portfolios. Unfortunately, accommodating solar on a large scale is not an easy feat.

"PV is your classic 'disruptive' technology," says Michael DeAngelis, supervisor of the advanced renewable and distributed generation technologies department at the Sacramento Municipal Utility District (SMUD) in California. "It doesn't fit, and it cuts across a lot of parts of an organization. It's hard for parties to wrap their arms around."

SMUD is in the enviable position of having nearly three decades of experience integrating solar power onto its grid. In fact, the utility still operates a 1 MW PV system that was installed 25 years ago. And in the early 1990s, SMUD established its PV Pioneer program, which helped usher in the statewide California Solar Initiative a few years later. California investor-owned utilities, such as Pacific Gas and Electric Co. (PG&E), were also solar forerunners.

To date, utilities generally have not encountered significant service disruptions associated with grid-tied solar PV installations, whether residential or commercial. Quite simply, solar power's contribution to the grid's mix - even in California - is a relative speck, so electric-system planners have been able to effectively work around the voltage oddities and reverse power flow that PV creates.

In SMUD's case, so far, the solution has been low-tech. Engineers have mapped the utility's distribution service territory and identified which feeders can handle the two-way power flow - a sort of "X marks the spot" approach. Those are the circuits into which SMUD has tied higher concentrations of PV power. Today, there are about 2,000 PV systems, representing approximately 13 MW, installed in the utility's service area.

Further north, Portland General Electric (PGE) is operating in a state that is working diligently to establish itself as a solar hotbed, with a robust net-metering paradigm in place and a feed-in tariff being planned. Approximately 600 PV installations - residential, commercial and PGE-owned - totaling more than 12 MW reside on the utility's system, and utility engineers continually monitor what is coming online.

"We actually have a 'feeder queue,' as we call it," explains PGE's Mark Osborn. "As customers sign up, we keep track of all the systems on a given feeder." The idea, he adds, is to remain vigilant as the concentration of PV increases.

PG&E has a much wider footprint than both SMUD and PGE, so its share of PV is substantially larger - more than 38,000 systems contributing in excess of 330 MW to the grid. And like SMUD and PGE, PG&E has not experienced problems. The PV systems are sufficiently dispersed across the utility's service territory so as to not wreak havoc on grid stability.

"We haven't seen a lot of concentration in specific geographic areas," explains David Rubin, director of service analysis for PG&E. "It's something that we're very much focused on, because we want to make sure that the amount of solar generation on our system grows. But we're mindful of what the impacts could be as we steer toward relatively high concentrations."

Boning up

Preparing for high PV concentrations is the name of the game, the experts suggest. Because most distribution systems are tolerant of relatively low levels of solar generation, the time is now to ascertain how PV systems behave, how they affect the grid and how to best manage them.

For instance, SMUD is beginning a major study with Hawaiian Electric Co. to look specifically at the relationship between PV arrays and the distribution grid. The utility intends to focus on pieces of its territory that contain high numbers of solar systems, monitor system conditions and then model that data to engage in predictive analysis. Doing so will require SMUD to gather more - and better - information about the solar resource itself.

"We're going to deploy a network of 72 solar irradiance monitors, collecting one-minute-interval data," DeAngelis says. "This will help to ascertain when and to what degree PV output fluctuates."

DeAngelis is interested in seeing that historical data put to use to help SMUD create hour- and day-ahead forecasts. In turn, the utility will be able to plan for seemingly mundane events - such as cloud cover - that can dramatically alter system conditions almost instantaneously.

"Solar [forecasting] has the potential to be more precise," he says. "I think that for the overall systems, in terms of meeting peak loads, it should be very predictable downstream. We're going to have the tools to manage this very well."

Rubin notes that because so many factors can influence how PV affects the grid - such as the characteristics of a circuit, the load on that circuit and the characteristics of the PV on that circuit - information equates to empowerment: The more a utility knows about the solar installations on its system, the better it can adjust its operations to account for them.

"We need to know, as the penetration increases, what these systems are producing - independent from what the homeowner or business owner is consuming," he says. "This would allow us to collect data and use it to have the kind of visibility we need to effectively monitor and manage the grid."


Both Rubin and Osborn point out that this area - data collection - is a perfect domain for both advanced inverter technology and smart meters. These devices, coupled with a communications backbone, could play an important role in rounding out utilities' understanding of the PV installations on their systems.

PGE is taking steps toward a high degree of transparency without full-bore smart meter integration. For instance, the solar projects PGE owns and operates are all metered separately, and they can be connected and disconnected as needed. Moreover, these projects are completely visible to utility engineers and operators.

"On our larger solar projects, we have continuous monitoring and control;' he says. "It's a distributed resources control system that we developed that allows us to monitor the inverter status at the site,"

The monitoring system, backed by Ethernet radio, collects live meter data, aggregates it and sends it to PGE's control center. At the center, the projects' aggregated power output appears in unison, just like any other generating asset.

Feed-In-Tariff Applications Flood Ontario Grid

By Uwe Roeper, North American Windpower, May 2010

Adding thousands of megawatts of renewable generation to the distribution side of the grid, as many feed-in-tariff program (FIT) projects will do, is leading to increasingly complex and unanticipated technical challenges.

Because the FIT launch applications were submitted in November 2009, Hydro One, the regional transmitter and largest distributor in Ontario, began to reduce the stated amount of available capacity on the distribution side of transformer stations and on distribution feeder lines.

At some Hydro One distribution system locations, there have been reductions by as much as 80% of the previously stated connection capacity. In total, the available transformer ratings as posted on the list of allocated capacity on Hydro One's Web site (hydroone.com) was reduced from 12,202 MW in August 2009 to 7,840 MW in January, suggesting that many FIT applications could potentially be affected. ...

On March 24, Hydro One provided a detailed 32-slide update to clarify three technical issues that constrain generation connection to the distribution system: feeder-distance limitations, transformer-station limitations and short-circuit considerations.

Hydro One indicated in the report that it is still learning how the connection of generation projects is impacting its distribution systems. Apparently — and depending on the size and type of generator — connecting to feeder lines far from the transformer station can result in voltage fluctuations that are unacceptably large for load customers.

Lightly loaded feeders, intermittent generation and weak electrical systems further impact the connection capacity. It was clarified by the utility that the list of allocated capacity refers to the capacity that is available if the generator connection point is "ideally located," meaning that projects are situated very close to the transformer location. ...

Because the grid was originally designed to carry power from the higher-voltage transmission system to the lower-voltage distribution system, technical issues arise when generation is connected at the distribution end and result in the reversal of power flow.

To manage short-circuit levels, Hydro One decided to limit reverse power flow to 60% of transformer capacity. In addition, short-circuit levels at the low-voltage side must be within Ontario's Transmission System Code limits.

Of particular concern are dual-wound transformers (i.e., twin windings on the secondary winding side), because they are at risk of overheating if flow reversal occurs on one of the twin windings. A number of these transformers are shown in the list of allocated capacities and have seen the largest reductions in stated connection capacity.

Hydro One noted that information about known short-circuit limitations has now been added to the list of allocated capacity to make FIT participants aware of these constraints. Sources of short-circuit contributions arise from the transmission connection, previously connected generators and large motor loads.

The "amount of additional short-circuit contribution from new generation depends on the type of generation technology (such as inverter-based or rotating machines) and the distance from the transformer station. In this case, the farther a project is situated from a transformer, the better.

Hydro One concluded that recent analysis of the following three factors has led to, the noted reductions on the allocated capacity list:

• dual-wound transformers do not allow for reverse power flow;

• there has been a reduction in minimum system loads on some lines; and

• short-circuit levels at some stations are already high.

Making Wind Power Work: Utility Integration Concerns

By Sandy Smith, North American Windpower, May 2010

To electric power system operators, wind and other forms of energy that have variable output generation present unique challenges. Unlike traditional fossil-fuel generation, wind and solar plants cannot be dispatched on demand. ...

The U.S. Department of Energy's 2008 report "20% Wind Energy by 2030" concluded that there are no fundamental technical barriers preventing the U.S. from obtaining 20% of its electricity supply from wind, but noted that a great deal must happen, including a change in the way the electric power industry handles the uncertainty and variability created by wind generation's output.

The North American Electric Reliability Corp.'s Integration of Variable Generation Tas Force Phase I report, released in April 2009, identified a number of specific issues that must be further investigated to ensure the reliability of the bulk power system under high renewable energy penetration scenarios in the future.

Key challenges

Transmission. North American grid operators view transmission expansion and reinforcement as priorities in ensuring system reliability. Couple that with the locational constraints posed by the best wind resources (the best resources are typically located far from power demand), and transmission emerges as the number-one challenge to integrating more wind.

Considering that the Electric Reliability Council of Texas frequently has to curtail wind plants in the western part of the state due to transmission congestion affecting load centers in the east, it is easy to understand why system operators and plant operators see transmission as a priority. ...

Understanding wind output. Wind power output is variable by nature, and in most cases, the wind blows best when demand for electricity is low. ...

Dispatching wind intervals. Many system operators currently dispatch generation resources for hourly intervals using high-price, fast-response regulation reserves to accommodate variable output during that hour. Because wind energy output can change within that hour, it becomes more cost-effective to design and implement sub-hourly energy markets, which can access the flexibility of the generation fleet at no additional cost. ...

Understanding availability. As with any other generation resource, system operators need to know about the operational status of a wind plant and its ability to fulfill its supply commitments. Improvements in plant supervisory control and data acquisition systems and enhanced communication networks within the grid will facility this process.

Digging Deep to Complete Horizon's Blue Canyon V

By Angela Beniwal, North American Windpower, May 2010

"The topography was primarily rock," says John Stone, Horizon Wind Energy's director of construction for the Blue Canyon V project in the Slick Hills region of southwestern Oklahoma. "There was a lot drilling and blasting of nearly every turbine site to install the foundation. ...

The project is also located in a rural ridgeline area, which means there were no roads to transport heavy equipment. ...

Wind Generators Find Wyoming Laws Taxing

By Nora Caley, North American Windpower, June 2010

In Wyoming — which, according to the American Wind Energy Association, is seventh in the U.S. in terms of potential wind capacity — Gov. Dave Freudenthal [Dem.] recently signed into law several bills that are not exactly wind-friendly. The bills covered siting, permitting, eminent domain and — in the case of H.B.101 — a tax on wind power.

H.B.101, which becomes effective in January 2012, imposes "an excise tax upon the privilege of producing electricity from wind from wind resources." The tax is $1/MWh on projects that have been producing electricity for at least three years. Future developments will be taxed starting three years after the turbine first produces electricity. ...

"The intent was to come up with a mechanism for local communities to offset socioeconomic impacts from wind development," says Aaron Clark, special adviser to Freudenthal. "For example, the county may have to spend money to upgrade roads to transport the turbines." ...

Freudenthal also signed H.B.79, which places a moratorium, through June 30, 2011, on using eminent domain to build collector systems for wind energy projects. The law affects merchant lines only, and public utilities that have been granted a certificate of public convenience and necessity are exempt from the moratorium.

"Transmission in the state of Wyoming is very unpopular," Clark explains. "You can find people in Wyoming excited about having turbines [on] their land, but I haven't found landowners who want their land to be used for transmission."

Ryan Lance, deputy chief of staff for Freudenthal, agrees, adding that landowners are especially unwilling to have their land used for transmission lines that will export power to other states.

"The real concern came when we realized that 1,500 miles of lines and 27,000 acres of land would be required to construct our collector system," he says. "Private landowners were saying, 'Wait a minute — you're going to condemn our land to send power to California?'" Other estimates predict 1,000 to 1,800 miles of lines will be needed. ...

There are also two new permitting bills. The first is H.B.72, which requires wind power facilities that generate more than 0.5 MW of electricity to obtain a permit from whichever county in which the facility is located. ...

Senate File 66, "Industrial Siting Amendments," expands the Industrial Siting Council's jurisdiction over facilities to include wind energy facilities — including their collector systems — which consist of 30 or more towers.

Blade Inspection Deserves Closer U.S. Scrutiny

By Mark del Franco, North American Windpower, June 2010

Blade shortcomings have become increasingly common in the North American marketplace. ...

A major issue has surfaced regarding the quality-control methods for manufacturers that have established U.S. operations. Some, such as Matt Crompton, national sales manager at Dantec Dynamics, a test and measurement services provider, contend that quality control has been sacrificed in North American production facilities. ...

As the North American marketplace grows, more blades will be needed — stretching production resources even thinner. Concurrently, blades are becoming longer and heavier, carrying increased loads. Taken together, it is likely that the industry will see more blade failures. ...

"In the U.S. market, the emphasis is on fulfilling orders and not on producing quality components," Crompton says.

The Challenges of Developing Projects in Rugged Environments

By Patrick Graham, North American Windpower, June 2010

Steep slopes, rocky soil, wetlands and the unpredictable New England weather combine to create unique deign and construction challenges. This is especially noticeable in the building of access-road infrastructure and crane paths, which typically transport 390,000-pound turbine components and 440-ton cranes with 330 feet of boom. ...

Kibby Wind Power Project, Maine

Each turbine required 10 truckloads in order to be transported. The heaviest part was the 77-ton nacelle, which required a truck with 19 axles.

To accommodate the navigation of this equipment from port to site, numerous narrow roads and intersections required temporary upgrades, which were all permitted and constructed in compliance with Maine Department of Transportation and local community regulation. ...

The team recognized at the outset that constructing roads to meet the stringent grade and curvature specifications of the turbine component transport vehicles would require blasting to excavate rock.

Generally speaking, such stringent requirements come from the limitations of the trailers that are used to carry the turbine components — such as tower sections, nacelles, transformers and blades — to the project site. Because these are low-riding trailers, sharp changes in grade can result in the vehicles' bottoming out and getting stuck.

In addition, the nacelle and transformer components are quite heavy, so the roads cannot be too steep, or the trucks will not be able to make it up the hill without assistance — which would typically be in the form of a bulldozer helping to pull the truck up the hill.

Eurus Wind Farm Propels Development in Mexico

By Laura Dimugno

"It is a region of Oaxaca with more social groups involved int he development — political and economic — which makes [the project] an especially delicate matter," Acciona's Miguel Ångel Alonso Rubio, project manager for the wind farm, explains. ...

Fortunately, the Eurus project was spared from regulatory hurdles, as the Federal Electricity Commission (CFE) worded in direct cooperation with Acciona and cement giant CEMEX in developing the project.

"We did not have an problems with governmental or municipal permits," Rubio notes. "The corresponding applications were realized, and in the cases in which the law stipulated, the corresponding payments were made."

[more: http://kirbymtn.blogspot.com/search?q=oaxaca]

Protecting Man and Machine in Cold-Weather Projects

By Angela Beniwal

"You [can] have large icing events come through where the airfoil — the blades — are actually iced up," says Bernie Lacoste, vice president of operations at First Wind. "If the machines ice up on us, the only thing we can do is turn them off and wait until it warms up again."

States and the Supply Chain: More than a Trivial Pursuit

By Mark Del Franco

When it comes to landing a turbine supplier or component manufacturer, states are offering big bucks and steep tax breaks to win the business.

... emblematic of the fierce competition developing among states to attract turbine manufacturers and component suppliers. ...

To date, manufacturers and suppliers have been the main beneficiaries of states' largesse.

For example, among the incentives Arkansas used to woo turbine supplier Nordex USA last June were a corporate tax exemption for 25 years, a cash rebate for 10 years at 5% of total payroll, a sales tax refund, $8 million in cash from the state's Economic Infrastructure Fund and $6.9 million in cash from the governor's Quick Action Closing Fund.


By Mark Del Franco

If wind is ever to become mainstream, a renewed focus must be made to cut the capital costs of turbine components, such as by making less expensive rotor blades and improving gearbox reliability.

The Department of Energy's "20% Wind Energy by 2030" report assumes that to meet the stated goal, capital costs must be reduced by 10%, while the capacity factor must increase by 15%.

How Suzlon Identified, Solved Blade-Cracking Problems

By Ole Gunneskov, chief engineer, Suzlon Wind Energy

In September 2007, our U.S.-based subsidiary, Suzlon Wind Energy Corp., received the first report of a crack in one of the blades on our S88-V2 2.1 MW turbine. ...

On-site and in the laboratory, blade inspections showed damage of the foam core that, in turn, caused the fiberglass skin to fail near the leading edge of the blade. ... Adding to the concern was that the S88-V2 blades met all industry-standard certification guidelines.

The question we needed to answer was how a blade designed for a calculated lifetime of 20 years and built in accordance with strict design standards and testing methodologies could develop such a discrepancy relatively early in its service life. ...

The blade itself

Turbine blades are complex composite structures that incorporate advanced aerodynamics. When in operation, they are subjected to extreme loads, as well as variable fatigue loads. ...

Our production switched to the new design in November 2007, and we replaced or upgraded the V2 blades on all affected S88 machines worldwide.

Curtailment Crimps Texas Wind Output

While everyone was working to get more transmission built in Texas, few thought about the near-term consequences for wind farms already in operation. As a result, because of the lack of transmission, some wind farm operators have had their output curtailed.

According to the Electric Reliability Council of Texas (ERCOT), more than 1,600 MW of wind was curtailed on July 9. Two weeks later, more than 700 MW of wind was curtailed. The July events are not one-time events. Curtailments of wind projects have become a daily occurrence in West Texas, as generation is growing faster than the transmission infrastructure.

The curtailment of wind farms is directly tied to the construction of transmission to support the competitive renewable energy zones (CREZs) that are now being built around the state to address transmission needs. Additional transmission associated with the CREZ effort will alleviate some — but not all — of the grid constraints.

"Curtailment in West Texas has become a significant issue," says Heather Otten, vice president of development for Chicago-based developer Invenergy. "There's an approximate transfer capacity from West Texas to load of 4,500 MW, and we have around 8,000 MW of wind power installed. So naturally, there are going to be some issues."

Gearbox Lubricants Deserve Attention

By Christie Longhurst

With the significant investments being made in wind turbine equipment, companies need to exercise due diligence when it comes to the type of lubricants and fluids that are used.

Over the past several years, wind turbine operators have experienced a number of equipment issues. Many of the mechanical failures observed in the field were bearing-related.

Distortion and bearing failures due to weight are among the most prevalent of these issues. A 10% increase in peak load can reduce bearing life by up to 50%. Corrosion is another problem, especially in offshore wind farms.

Another factor that could contribute to equipment failure is filter blocking caused by sludge formation that results from thermal or oxidative decomposition. Precipitate formation could also cause equipment failures, possibly due to poor additive solubility or interaction with water contaminants.

In addition, mechanical failures in the field can be caused by micropitting or surface fatigue resulting from cyclic contact stresses. All gears are susceptible to micropitting, which can also be referred to as fatigue scoring. ...

Bigger turbines, more wear

... The move toward higher-capacity turbines requires slower rotational speeds and higher gear ratios. However, this also makes equipment more vulnerable to wear-related problems. Furthermore, offshore turbines are more susceptible to corrosion, and many sites are inaccessible for maintenance for up to 30% of the year because of harsh weather. The growing interest in offshore turbines is also creating a greater need for environmentally friendly products.

Mitigating Wildlife Impacts During Pre-Construction

By Robin Dornfest

[W]hile wind turbines themselves garner much of the focus, the access roads leading to the site can also be problematic when it comes to environmental impacts. The habitats of nearby animals, wetlands, surrounding waterways and stormwater drainage are all at risk. ...

Common impacts

The environmental impacts of wind developments include bird or bat kills, noise emissions, wetland and waterway disturbances, and encroachments on endangered species' habitat.

Because many wind farms are located in rural locations and on topographic highs, developers must build construction and maintenance roads. ...

Wildlife. One of the largest risks to a wind energy project is its potential to impact animal and plant habitat — either directly or indirectly. The U.S. Endangered Species Act (ESA), as well as specific state endangered species laws, spell out how to protect endangered and threatened animals. For example, in the Rocky Mountain West, protect species include the Preble's jumping mouse, the Ute ladies'-tresses orchid and the black-footed ferret.

Administered by the Fish and Wildlife Service (FWS), the federal ESA aims to protect, and recover and restore to ecological health[,] imperiled species and their ecosystems. As of 2008, more than 1,350 U.S. species were endangered, and two-thirds of them have at least some habitat on private land.

Under the ESA, it is illegal to take, harass, kill or harm and endangered or threatened animal without a permit. Wind farms run into problems with the act primarily as it relates to the definition of the term "harm," which includes modifying the animal's habitat and impairing its ability to breed, feed or gain shelter. ,,,

Migratory birds. Migratory birds have become one of the biggest challenges for wind farm developers.

Several years ago, the iconic Altamont Pass wind farm was forced to stop producing power after environmentalists threatened a lawsuit over the death of thousands of birds, including Golden Eagles.

Lesser known than the ESA, the Migratory Bird Treaty Act makes it illegal to kill migratory birds without a permit. A similar law, the Golden Eagle Protection Act, makes it illegal to kill Golden Eagles[] as well. ...

Wetlands and waterways. Aside from wildlife and birds, developers should also be cautious if their project is sited near or around bodies of water, including lakes, ponds, streams or wetlands. ...

Stormwater. Federal and state environmental regulators are becoming increasingly strict about how construction sites and new developments handle and dispose of stormwater.

Stormwater is rain or snowmelt that normally, in small amounts, flows over soil into waterways. Construction can alter the land's natural hydrology, increasing the volume, velocity and temperature of runoff. That in turn, can lead to high volumes of water eroding stream banks and flooding streams which carry sediment, oil, garbage and chemicals into surrounding waterways, disturbing fish and aquatic life.

The Clean Water Act says that all developers involved in clearing more than one acre of land should obtain a National Pollutant Discharge Elimination System permit for their stormwater discharges.

Ailing California Works To Solve Wind Slowdown

Amidst siting delays and permitting controversies, California has lost its way when it comes to wind energy development.

By Kristen T. Castaños & Allison D. Cook

Sadly, one of the casualties of the California budget compromise reached in July was funding for the Williamson Act, but the result may create an opportunity for wind developers. The Williamson Act provides a tax break to highly productive agricultural land in the state that remains in agricultural use, allowing many California farms to remain financially viable. Farmers could turn to wind energy leases, while still maintaining their agricultural activity, to gain another revenue stream ...

Developers Tell Tales Of Lofty Towers

By Deston Nokes

As wind turbine generators increase in size, some tower manufacturers are gearing up to accommodate developers' requests for towers that rise above 100 meters [328 feet] in height. ...

Today, with so many of the "lower" level resources being harvested, companies are seeking ways to maximize domestic wind generation. WindKraft Nord (WKN) USA was the first in the U.S. to vault higher to take advantage of wind resources at higher altitudes. However, all signs indicate that more developments will include taller towers. ...

"The challenges of hauling the new towers are obvious," Jess Collins, group president at Broadwind Energy, says. "Most 80-meter towers already are 14 feet in diameter at the base, and increasing it will be an even bigger challenge when it comes to bridge clearance. A larger-diameter structure means a taller load once it becomes horizontal on a truck. Finding routes through many states already is a challenge, and it will continue to get tougher.

Collins notes that trains have been helpful in transporting components to wind sites but that any increase in tower diameter will limit rail['s] ability to serve the wind industry.

As turbines and rotor diameters grow, the physical demands on the towers will continue to increase.

"To build 105-meter towers, the foundation has to be redesigned larger," Florian Zerhusen, president of WKN USA, says. "Plus, it also depends on the soil condition."

According to Peder Hansen, executive vice president of Northstar Wind Towers in Nebraska, there are two options for managing the loads of these massive turbines: The first is to increase the structure's wall thickness, and the second is to increase the bottom diameter of the tower, thus enabling a continuous or increasing taper towards the foundation.

"Thicker walls are the number-one option today, because transportation restrictions dictate the maximum diameter allowed," Hansen says.

New York Updates Wind Code

The Wind Industry Ethics Code prohibits conflicts of interest between municipal officials and wind companies and establishes public disclosure requirements.

In addition, provisions of the code include the following:

• bans wind companies from hiring municipal employees or their relatives, giving gifts of more than $10 during a one-year period or providing any other form of compensation that is contingent on any action before a municipal agency;

• prevent wind companies from soliciting, using or knowingly receiving confidential information acquired by a municipal officer in the course of official duties; and

• requires wind companies to establish and maintain a public Web site to disclose the names of all municipal officers or their relatives who have have a financial stake in wind farm development.

—Mark Del Franco

EPA's Cement Plan May Add Costs, Delays

The Environmental Protection Agency wants to rid hazardous pollutants from cement, which could cause project delays and increased costs for developers.

By Nora Caley

If the U.S. environmental Protection Agency (EPA) has its way, wind developers can expect project delays and increased cement costs in the near future. That's because the EPA is proposing amendments to the current National Emission Standards for Hazardous Air Pollutants (NESHAP) for portland cement.

The rules would add or revise emissions limits for mercury, total hydrocarbons and particulate matter from cement kilns.

Mercury and other gases are released during the heating process in manufacturing cement, which is made from gypsum, limestone and silica. The NESHAP rules, if adopted, would take effect in 2013.

While environmental groups say the rules are important and overdue, Skokie, Ill.-based Portland Cement Association (PCA) says the proposed rules would burden the domestic cement industry and endanger thousands of jobs.

Because a typical wind turbine foundation comprises about 400 cubic yards of concrete, rules affecting its manufacturing could dramatically affect costs, project timelines and the wind development itself. ...

The EPA performed cost-analysis models and estimated that changes to NESHAP will cause the average national price of portland cement to increase about 4% and production to decrease by 8%. Imports are expected to increase by approximately 2%. The costs of compliance could be $240 million or more. The models also predict that nationwide, the rules would save $4.4 billion to $11 billion in healthcare costs.

Wise Developers Heed Plight Of Sage Grouse

By Rob Bouta

Citing the declining populations of all prairie grouse species, the U.S. Fish and Wildlife Service advocated for a five-mile buffer from prairie grouse leks. ...

Wildlife agencies lack the data to say precisely how wind energy will affect prairie grouse, and project developers lack the data to demonstrate that impacts will not be significant. What both parties know is that wind turbines and related infrastructure are poised to invade relatively intact prairie grouse habitats in an unprecedented way.

Proposed Setback Rules May Hinder Ontario Wind

If enacted, new setback rules concerning wind turbines could dramatically alter more than three-quarters of Ontario's wind projects.

By Crystal Luxmore

Under the proposed regulations, turbines must be set back 550 meters (about 1,800 feet) from the nearest residence. Noise levels would also need to fall to 40 decibels at receptors such as dwellings or businesses. Setback distances would rise with the number of turbines or the sound power — so, for instance, eight turbines with a sound power level of 105 decibels would need to meet a setback of 1,000 meters. Additionally, any turbines registering more than 107 decibels would require a noise study.

The new regulations also propose a safety setback, equivalent to the distance-of-tower plus blade-length measurement, away from roadways, property lines, railways and other rights of way. ...

The combination of the 550-meter minimum setback and the safety setback would stop most of the proposed new wind farms currently in the development pipeline from ever seeing the light of day, says Sean Whittaker, vice president of policy for the Canadian Wind Energy Association. "Together, these two requirements would eliminate many of the turbines in the planning process in Ontario," he says, adding that three-quarters of the projects would be rendered "non-viable" or would need to be complete[ly] redesigned.

As an example, Whittaker evokes AIM Power Generation's 99 MW Erie Shores project, which was installed three years ago near Port Burwell, Ontario. ... "That project has 66 turbines," Whittaker says. "But under the proposed setbacks, only seven turbines would be considered compliant." ...

The setback proposals are part of the Ontario government's promise under its Green Energy and Green Economy Act, proposed in May, to streamline approval processes. The proposals are also a response to health concerns often expressed by citizens living or working close to wind farms.

Ontario Wind Comes Under The Microscope

By Mark Del Franco

A big gamble

By eliminating a major power source — the province uses coal-fired generation during times of peak demand — Ontario is taking the gamble that renewable energy can replace coal.

However, renewable energy has not been battle-tested to show it can handle such a shortfall. In 2008, coal accounted for 14% of Ontario's total generation, says Jack Gibbons, chair of the Ontario Clean Air Alliance, adding that 8% was used domestically, with the remainder exported to the U.S.

Currently, renewable energy accounts for 25% of Ontario's electricity. However, when hydro is excluded, the percentage becomes very small. "Wind energy alone accounts for less than 1%," Gibbons says.

To hedge its renewable energy bet, the Ontario government is building natural-gas facilities as insurance. Just the same, the province is gambling on a cleaner future by retiring its dirty past, specifically the Nanticoke Generating Station, the largest coal-fired plant in North America, which sits on the Ontario side of Lake Erie. The province, however, has promised to close Nanticoke in the past, but has yet to do so.

Wetland Areas Heighten Project Concern

By Phil Hall

In his ongoing research for a doctoral dissertation, Rick Walker, an instructor at Texas Tech University and a 15-year veteran of wind development, is studying the effects of wind turbine turbulence on wetland evapotranspiration.

BPA Institutes Wind Integration Rate

The Bonneville Power Administration (BPA) has instituted a wind integration rate of $1.29/kWH per month — a reduction from the initially proposed rate of $2.72/kWH per month. This is due primarily to actions taken by wind generators to reduce their use of BPA generation for reliability when wind power ramps up or down unexpectedly.

"There's been an explosion of wind power on the BPA system, especially since 2005," says BPA Administrator Steve Wright. "We're proud of this accomplishment, but it has led to operational challenges, including risks to reliability and substantial costs. ...

In addition, rates for customers that buy power and transmission will increase by an average of 6%. Transmission rates will stay the same. Power rates will increase by an average of 7%.

Minnesota Power Files Rate Case

To meet the future energy needs of its customers and state-mandated environmental and renewable goals, Minnesota Power has announced its intention to file a request with the Minnesota Public Utilities Commission (MPUC) before the end of the year to increase base electric retail rates.

Minnesota Power, an ALLETE company, previously filed for a rate increase in May 2008. Final rates for the 2008 rate request are expected to take effect in the fall.

Ongoing investments to build the company's renewable energy portfolio to satisfy Minnesota's 25% by 2025 mandate include the acquisition of an approximately $80 million direct current (DC) transmission line that will deliver wind energy from the company's growing number of wind generation facilities in North Dakota to the company's customers in Minnesota.

"Wind generation facilities are being built all around the country, but it will take thousands of miles of new transmission lines to bring this renewable energy to customers who need it," says Don Shippar, CEO of ALETTE.

UWM researchers get grant to help make wind power flow continuously

Researchers at the University of Wisconsin-Milwaukee are trying to figure out ways to make power from wind keep flowing even when the wind isn't blowing.

One phase of that research received a $422,266 grant Thursday from the U.S. Department of Energy for a project that could boost the efficiency of wind turbines by relieving some of the wear and tear on turbine gear boxes.

The engineering school research is taking place in phases — with the final leg studying the use of batteries to capture wind power generated when demand for electricity is low, storing it and then sending it to the grid when demand for power rises.

"What happens is that the wind speed is very high and we have very good wind speed after midnight, and very early morning when there is not much load (demand) on the grid," said Adel Nasiri, an assistant professor in the electrical engineering department. "In the afternoon when there is high demand, there is no wind." ...

At UWM, Nasiri is leading a team of three researchers looking at the implications of a massive expansion of wind power that could be in the offing for the state and the country. Nasiri is director of the power electronics and electric motor drives laboratory.

The UWM team is studying ways to make wind turbines work better and improve the stability of power sent to the grid by wind turbines, which produce power at varying levels depending on how fast the wind is blowing.

"We're looking to find ways to mechanically support the wind turbine systems so the drivetrain doesn't wear out very quickly. Currently the gear boxes are under huge stress and wear out and have to be changed after five years," Nasiri said.

The researchers are also seeking funding from the National Science Foundation for a project that would research energy storage for wind turbines — testing the use of batteries to store power from periods when wind speeds are high and send it out to the grid when power demand is high.

Among renewable energy sources, solar power is much better suited to the afternoon spikes in power demand on hot summer days. UWM has installed solar panels on a campus building.

Prevailing against anti-wind sentiment

Turning anti-wind sentiment into permits requires organization, strategy and plain ol’ grassroots politics.

By Ben Kelahan, North American Windpower, July 2009

Community relations may be the road to reputation, but understanding practical local politics paves the way to permits. Opposition groups are sophisticated, organized and well funded. They have borrowed the highest-priced tactics from corporate public relations and masterfully use the Web to circulate misinformation about the impacts of wind farms.

Understanding how the opposition plans to stop your wind farm may be the first step toward planning for its approval. The truth is that planned wind developments run into local trouble every day. Let’s begin by examining some customary tactics used by the opposition.

Opportunistic opposition

Energy developers, particularly wind developers, expect to face opposition from individual landowners and other residents based on the typical siting concerns, such as shadow flicker, noise impacts and property value arguments, that pop up across the country. However, in some cases the opposition takes on some special interest from known characters. Thus, it also takes special care in managing their impact.

Local politicians are accustomed to the usual suspects showing up at public hearings and in letters to the editor of weekly papers on controversial development projects.

Now, wind companies are beginning to notice a pattern to the cast of opponents appearing before zoning hearing boards, road commissioners and alderman, who oppose wind farms using the locality’s zoning codes and planning restrictions as tools to defeat developments town to town.

In Illinois alone, developers such as Horizon Wind Energy, NextEra Energy Resources and Iberdrola Renewables have been the targets of vociferous anti-wind sentiment.

Turning to the Web

Need talking points for the public hearing tonight? Look no further than the growing number of Web sites that circulate their own “myth versus fact” sheets about wind farms and their impact on local communities. Many of these sites have organized talking points by issue, including public safety concerns, such as wind turbine syndrome, or counter-arguments to wind energy’s effectiveness, such as like intermittency.

There are plenty of anti-wind Web sites online. These sites provide a quick primer should you be motivated to oppose the local wind farm proposed down the road. Further they provide best practices borrowed from wind energy site fights from around the globe, complete with per sonal testimonials of those that have opposed wind turbines and won.

The effectiveness of these online anti-wind sites is not necessarily their basis, because impactful opposition doesn’t necessarily need sound science or experience to be effective with local politicians. All it takes is an emotional trigger on a critical local issue to start the flames of opposition to motivate a vocal minority.

If the anti-wind sentiment goe unchecked by a majority of people in the project area who make known their support based on equally passionate arguments that activate locals to take political action on you behalf, you could be in trouble come the day of the permit vote.

Democracy in action

Wind developers are keen on establishing strong relationships within their communities. Community meetings are a popular method of introducing your project to the most people at one time.

An efficient and productive use of time and resources, community meetings provide an educational one-stop shop for answering questions and informing the public about your plans. Although these meetings can allay the concerns of locals, perceptions can change if you let the opposition speak at the gatherings.

So, that raises the question: Why have these meetings if they are not required? Some developers, mindful of being new to the community, do so as a courtesy. But is it helpful?

“It’s one thing if an agency requires a public session – you have to do those,” says Robert Kahn, a 25-year veteran public relations consultant working in wind power, “But it’s rarely a good idea to volunteer to host your own,” he says. “Too often, a public meeting simply provides opponents a chance to identify one another and get better organized. There are much better ways to get the word out.”

When the format for a community forum plays to the positions of opponents, beware.

Here’s how it typically occurs: In an effort to demonstrate transparency and a willingness to consider resident concerns about a wind development plan, the developer begins with a 10-minute presentation of the proposed plan, with specific sound bites reviewing the merits of constructing the wind farm in town. Some of the positives include green jobs, tax revenue, road improvements and donations to local schools. All of those benefits accruing to the community sound wonderful.

After your presentation, undecided residents are satisfied, even though they know it’s in your financial best interest to say so. So even after hearing the pitch, they may not trust you. Then, the outspoken opposition speaks about public safety and health issues. For those attending the hearing, it is a question of taking sides.

If you are fortunate, the undecided members will leave undecided. However, those who have decided may be recruited to speak against you at the next hearing on your special-use permit.

At some point in the approval process, holding an open house allows local residents to see visual simulations, maps and descriptions of construction plans and schedules, along with displays of planned environmental mitigations. An open house is far more relaxed than a community meeting.

Thinking like your opponents may mean acting like them. Several wind power developers have encouraged local citizens to organize support groups around which to rally environmental and property rights activists, business interests and other pro-wind constituencies. Think of these groups as an anti-not-in-my-backyard (NIMBY) antidote.

“There’s no substitute for supporters standing up and speaking out on behalf of proposed projects,” Kahn says. “They can say things which a developer, who has one hand tied behind his back, can’t.’

What you can do

However, until such counter-NIMBY organizations expand, developers must n-lake a concerted effort to outnumber the vocal minority and special interest groups that desire a political victory for their own constituencies and members. It can be done, starting with the following basic steps:

Research. Understand the political climate surrounding your project before you go public with your proposal. First, make a list of likely supporters and opponents. Then, do some research. Has this site been the subject of previous controversies? Some sites are considered too troublesome and will never succeed in obtaining change-of-use permits. Knowing the history of the site could impact your decision making.

Time and target your outreach. Never let the news media be the first to describe the impact of your wind project nor be considered the best source of facts about your plans for the site. Inform the politicians and neighbors before they read it in the press.

Persuade. Go door to door informing landowners and residents. Explain the proposal, and attempt to determine who will support it, who will stay neutral and who will oppose. Shortcuts, such as hosting public meetings, will not do the trick in inoculating public opinion over a wind power project.

Get started by scheduling small meetings with key constituencies and community leaders. “These are the people who shape local opinion,” says Kahn. “Their support will be indispensable in countering the opposition.”

Political process. You need to attack this as if you were a local politician running for office, which means identifying, recruiting and organizing. Organize supporters, and then get them to attend meetings, sign petitions and write letters to the editor. Above all, you need to demonstrate public support equal to or greater than that of your opponents.

Negotiate when possible. In some cases, you can offer mitigation, or negotiate in some other way to get opponents to drop their positions. In other cases, the opponents or their backers have an economic interest in defeating your project that will never be overcome by an attempt at compromise.

In those cases, you must marshal sufficient political support to overcome the opposition and be prepared to educate your supporters in the community about what you know about your opposition – where they come from and why you feel they’re involved. Let them be the judge.

Ben Kelahan is senior vice president, energy, at Vienna, Va.-based Saint Consulting Group, a community outreach consultancy. He can be reached at (703) 531-8274 or kelahan@tscg.biz.


A Better Read On Gauging Fleet Underperformance

Despite record growth over the past several years, the wind industry in North America still faces numerous challenges. Among these challenges, wind plant underperformance versus preconstruction estimates has been cited as one of the top issues. In fact, it is generally believed that North American wind plants, on average, perform about 10% below their preconstruction forecast levels.

Foundation Support From The Ground Up

By Daniel Harpstead, William Gates, Ronald Gibson & Keith Yamatani

It is well known that wind tower are subject to considerable stress because of the sizes of the turbines mounted atop them and the forces created by wind pushing against turbine blades. In turn, these stresses introduce cyclic and constant torque, tension and compression stresses on the pads and foundation systems. ...

Turbine structures encounter large horizontal wind loads. In turn, these loads create stress on the foundation by inducing tension on the leading edge of the foundation and compression on the trailing edge of the foundation. These stresses move as the wind shifts direction. ...

While geologic behavior is critical to turbine design and operation, owners and design teams should also consider access roads, lay-down areas and crane support during the subsurface investigation phase of a wind turbine project.

Access roads are used for component delivery of the turbines, blades and other construction equipment typically delivered by truck. Some turbine components (blades, specifically) are more than 100 feet in length and heavy, thus requiring special trucks with multiple axles. Often, there are limitations to the grades at which these trucks can traverse and turn while carrying these blades to the wind farm site. Because wind turbines are often placed on ridge tops, construction costs may rise significantly if large quantities of retaining walls are required to facilitate truck access during construction.

Lay-down areas for construction equipment should also be considered during the subsurface investigation. Large trucks with heavy loads will need to access lay-down areas in addition to turbine locations.

Finally, large cranes are generally required to erect wind turbines. The crane type and loading conditions should be evaluated by the geotechnical and structural engineers to establish what subgrade improvement or, in some cases, foundation is required to support the cranes used for construction.

Climate Form Forecast Calls For Change

By Mark Del Franco

The site Washington's Windy Point project, developed by Cannon Power Corp., is among the windiest locations in the state. The area features an upper and lower plateau with more than 1,000 feet of elevation difference between them, which caused the project's turbine vendor some trepidation about the potential negative effects wind veer (i.e., the change of wind direction at different heights) could have on its turbines. ...

"Nowadays, the turbines are so large and so costly, the failures are more spectacular — and, of curse, more costly," Ron Nierenber, a Camas, Wash.-based meteorologist, says.

The meteorological data reported on climate forms represent the basis under which turbine warranties are created. That climate forms are becoming mandatory is evidence that today's wind turbines — with their carbon fiber blades and wingspans exceeding that of a 747 jet — are highly engineered and delicate. ...

It is also notable that as the forms required by the vendors become more complex, some warranties are evaporating. "It used be that warranties were good for five years," Rolf Miller, technical consulting services manager for St. Paul, Minn.-based consultancy WindLogics, says. "Now, you're lucky to get two."

Take Eight Steps To Cover Your Assets

By Phil Hall

"I'm seeing a lot of blade and gearbox failures," Rick Koebbe, president of PowerWorks Inc., Tracy Calif., adds. ...

"We get a lot of rain in wintertime, and that causes a lot of failure in turbines," he continues.

Wind Farm Cabling Has Its Own Challenges

By Nora Caley

"When you look at a wind farm, 30 percent to 50 percent of the construction dollars are going toward the electrical infrastructure," says Larry Sevy, president of Tetra Tech Electric Inc. In Pasadena, Calif. "That involves a lot of cabling."

Sevy, whose company provides services such as engineer-procure-construct and balance-of-plant construction services for wind farms, adds that cabling wind farms is a complex endeavor. The cables can be three inches in diameter, and the spools can weight up to 10,000 pounds. That presents logistical challenges, particularly for wind farms located in remote areas.

"You have limited rights of way, and access between towers is usually limited to brand-new gravel roads," he says. ...

Tom Lenaghan, [Madison, Wis.-based] RMT Inc.'s director of project development, notes that wind projects tend to have more underground cabling than other utility generators.

"It's not like one power plant feeding one system," he remarks. "The generation is distributed over a large area, and that causes you to have to put more electrical collection system lines in."

Lenaghan says a 100 MW wind project could have up to 150,000 feet of trenches containing underground cables.

"There are three cables in each trench, so that's 450,000 feet of cable," he explains.

Keeping A Wind Farm Running At Its Peak

Managing wind energy

Although free to harness, wind energy lacks the predictability of hydroelectric power or steam turbines, and many of the problems associated with extracting energy from wind result from unforeseen downtimes, due to both mechanical and electrical component failures.

The issue regarding wind lies in its variability in terms of both speed and direction. These might not be issues if the changes occurred uniformly, but this is not the case. At a tower height of 200-plus feet, energy density doubles for every wind speed increase of 2 mph. With gusts, the torque across the plane of the blades vary from one minute to the next.

Unlike generators that rest on solid, stable footers, wind generators are in almost constant motion. All generators flex from changing electrical loads - this is true of wind generators as well - but wind generators shake from external mechanical loads caused by changing wind currents. Like an airplane in turbulent air, the generating package encounters torques that are random in magnitude and direction. These torques produce a vibration that is in addition to the cyclic loads caused by blade imbalance.

Wind fluctuations cause electrical fluctuations, too. Blade-feathering mechanisms react to changes in wind speed to maintain blade speed, but because these corrections lag wind speed changes, output from generators rises and falls. Additional stress on wind generators comes from temperatures that can range from -30 degrees F to 100 degrees F. On offshore towers, corrosion accelerates wear.

Because of these environmental factors, the components in wind turbines wear out quickly. For example, wind generator bearings require close monitoring because mean-time-before-failure (MTBF) is shortened. Bearings that last for 30 years in a conventional ground-based application typically last five to 10 years in a wind generator.

Wind turbine gearboxes experience similar wear rates. In a conventional gearbox application, such as a speed reducer for an extruder, a gearbox may last a generation before bearings are replaced. However, in a wind turbine, the gearbox not only acts as a speed increaser, but is also subject to variable external forces and vibrations. These factors necessitate bearing replacement much sooner.

VRB Power Curtails Operations

Richmond, British Columbia-based VRB Power Systems Inc., an energy storage technology developer, says it has been unsuccessful in its efforts to seek offers for the merger, sale, refinancing or other strategic alternative for the company. It has decided that it will not proceed with its previously announced rights offering.

As a result, VRB has substantially curtailed its manufacturing, research and development operations and has laid off or given notice of termination to most of its employees. Given its current financial and operational status, the company has ceased accepting new orders.

In order to meet its liabilities, VRB intends to dispose of its remaining inventory and other redundant assets. The company plans to continue to seek offers for the possible sale or license of its core technology and patents or the reactivation of its commercialization efforts.

In the event that VRB is unable to make adequate arrangements to discharge its outstanding liabilities, it may consider seeking other remedies under applicable corporate or insolvency legislation.

Protecting Ecology While Promoting Wind Energy

"At [the American Wind Wildlife Institute (AWWI)], we don't propose shutting down and not building wind farms while we study impacts, but we do need to have a better understanding of where these impacts occur the most." [Julia Levin, director, National Audubon Society, and chair, AWWI)

AWWI was created last year with support from the American Wind Energy Association (AWEA) board of directors and the AWEA siting committee to address regional — rather than site-specific — issues related to wind development, and wildlife and habitat protection. ...

Levin stresses the importance of education in the organization's initiatives. "We need to separate the [not-in-my-backyard] concerns from the legitimate concerns," he [ sic ] says. "We can't say 'no' to all energy development." ...

"This isn't esoteric," agrees Levin. "We don't know what spoke in the wheel we can pull out without the wheel collapsing. That's why this is such important work.

How To Maintain Bearings To Extend Generator Life

Electrical damage

High-frequency currents induced on the shafts of wind turbine generators can reach levels of 60 A and 1,200 V or greater. Once these voltages reach a level sufficient to overcome the dielectric properties of the grease in the generator bearings (which are designed to operate with a thin layer of oil between the rotating ball and the bearing race), they discharge along the path of least resistance typically the bearings - to the generator housing.

Voltage discharges from the generator shaft to the frame via the bearings, leaving a small fusion crater in the bearing race. These discharges are so frequent that, before long, the entire bearing race becomes marked with countless pits, known as frosting. As damage continues, the frosting increases - eventually leading to noisy bearings and, ultimately, bearing failure.

A phenomenon known as fluting may also occur, producing washboard-like ridges across the frosted bearing race. Fluting can cause excessive noise and vibration, which also leads to bearing failure.

Most of today's wind turbine generators have insulated bearing housings and shaft grounding brushes. However, without proper maintenance, these components can fail and rapidly lead to bearing failure.

For instance, the insulation in the bearing housing can become contaminated with carbon and other conductive material, leaving a path for shaft voltages to travel. Regular maintenance of the grounding brush and ground ring is important to keep a low resistance path to ground. The grounding brushes must be inspected often.

Also, using the improper grade of brush can cause excessive wear to the ground ring or corrosive buildup on the ring. This will result in poor contact between the brush and ring.


Improper lubrication of bearings is also a leading cause of failure. Not enough grease or too much grease will lead to premature failure. Because of the remote locations of most wind generators, a lack of grease is more common. ...

Grease compatibility (or incompatibility) is a huge issue in the wind industry. For example, incompatible additives used in bearing grease can cause deterioration and subsequent failure of the bearing bronze cage, resulting in a catastrophic generator failure. ...


It is generally agreed that proper alignment is critical to the life of a machine. Coupling wear or failure, bearing failure and bearing housing damage are all common results of poor alignment.

20% By 2030: Overcoming Four Key Challenges


"This is a huge challenge and has to be addressed at a national level," Susan Giordano, general manager at Second Wind Inc. in Sommerville, Mass., says. "Part of the solution in developing renewables has to begin with transmissions, and the willingness to accept transmissions through your community is part of the renewables mission."

Power distribution

If you build it ...

The wider world

Hurdles Remain For Kansas To Become Major Player

"We went from no transmission at all to having a terrible fight over transmission," Horizon Wind Energy's Mark Lawlor says. "Both movements had the same result: no wind connectivity."

Combating Fugitive Dust On Wind Farms

By Bob Vitale, CEO, Midwestern Industrial Supply, Inc.

During construction at the site of a wind farm, massive amounts of dust are kicked up into the atmosphere or are lost via erosion. This continues during wind farm operations, as unpaved roads are the norm. What is considered state-of-the-art dust control in many areas is merely the use of water. However, this method can be expensive or ineffective and can contribute to severe soil erosion.

Possible solutions to the problem posed by dust and erosion include vehicle restrictions, paving and surface treatment. It is important that the right approach is taken to safeguard the environment. Further, plants that neglect dust problems are likely to either face permitting barriers or create ill will within the local population. ...

Fugitive dust can have a serious effect on day-to-day operations of a wind farm, leading to diminished visibility, congested breathing, increased vehicle maintenance and storm water runoff problems. These issues can adversely affect the safety and morale of personnel and hamper the efficiency of operations. ...

As a result of runoff or windblown particles deposited into drains, ditches or lakes, sediment can seriously endanger plant and aquatic life. Each phase of a construction project has the potential to create significant volumes of sediment runoff. ...

Storm water permits, for example, are becoming more and more a factor as water quality remains a core concern of regulatory agencies. Without proper planning to protect the soil surface, erosion can have a negative impact on the environment, and an inability to control it exposes the developer to fines and legal liabilities on top of the high cost.

But more importantly, permitting failures can effectively end a project. If residents find greater quantities of dust accumulating on their coffee tables, or a greater incidence of allergies and asthma, there will be local repercussions.

With a National RPS Likely, Utilities Must Adapt

Transmission costs will inevitably factor heavily into the price equation. "There's no doubt that to continue to meet renewable portfolio standards, we're going to have to build transmission, and it's going to cost money," says Elliott Mainzer, executive vice president of corporate strategy at Bonneville Power Administration

Other, less immediately obvious costs for certain generation sources — particularly renewables — will include the compensation measures necessary to overcome any intermittency issues. ...

"The problem with [wind energy] is that the capacity factor is about 25 percent — simply because wind is such an intermittent resource," Dan Riedinger, a spokesman for the Edison Electric Institute, notes. Thus, regulators often require backup generation in the form of natural gas turbines, which are more expensive to run than a coal plant or a combined-cycle natural gas plant. ...

Mainzer warns that this rapid influx of such a variable resource has begun to tax the integration capabilities of the hydroelectric systems typically used in the region as rapidly dispatchable backup generation.

"As you put more and more wind n the system, you are undeniably going to need more flexibility to ramp other resources up and down to deal with the fluctuations in the wind," he says. For now, BPA will likely bring gas plants and other additional sources to market to cope with these demands, but energy storage may play an important role in future years.

Hawaii Targets 70% By 2030

According to Ted Peck, administrator for Hawaii's energy office, grid stability is one of the biggest concerns about incorporating more wind power into Hawaii's energy portfolio. Lack of transmission is another concern.

Saskatchewan: Where Oil And Wind Mix

By Crystal Luxmore

But ramping up from 22 MW to 172 MW of wind in just one project made it tough for SaskPower to integrate such a large block of intermittent power into its existing 3,034 MW electric capacity from conventional coal-fired, hydroelectric and natural gas stations.

This challenge forced SaskPower to put a hiatus on new wind projects in the fall of 2007 to undertake a wind power resource study.

Getting Bolts Ready For North America

By Wayne Wallace

Currently, it appears that the wind industry as a whole is experiencing bolting problems. Anecdotal evidence from several wind generator manufacturers and maintenance crews tells us that nearly everyone is running into trouble in areas related to bolting.

It is understandably difficult, however, to get a full description of these bolting problems from the field crews and quality assurance officials. In March 2008, Vestas, one of the largest wind generator companies in the world, admitted that two failures resulted from insufficiently tightened bolts.

If you look on the Internet, you will see hundreds of situations that are called bolting failures — many of these in tower splices — and many that are conceivably influenced by the load capacity of the bolted splices.

These tower splices are a steel designer's nightmare. The design loads are, to a large extent, predictable, but each bolt is loaded in service by what we call very high prying loads as the wind pushes on the tower.

Furthermore, the service loads are non-conservative — i.e., if one bolt is unable to resist the applied prying load, that load is transferred to the adjacent bolt, which may cause more distress. There is also a certain dynamic component to the service loads that must be resisted by the splice bolts.

How To Hedge Against Congestion Cost Risks

By Nora Caley

Scott Harvey a director for global consulting firm LECG, explains that financial transmission rights (FTRs) could be important for wind.

"In regions that don't have FTRs, in order to get access to the transmission grid, power providers have to buy firm transmission service on a daily basis for the whole day, and they can't predict precisely in advance whether wind conditions will be favorable."

Building An Accurate Supply-Demand Picture

By Ron Bianchi

Forty-eight is a "magic number" for many wind power producers. That is the number of hours ahead that they would like to be able to forecast their ability to generate power.

Predicting wind speed and other meteorological factors is important for power producers because of the inherent variability of the wind resource. As wind power generation capacity grows, it becomes a bigger wild-card destabilizing factor in the supply for more utilities.

Unlike wind resources, hydro, [other renewable,] gas, coal, oil and nuclear generation capacities are predictable. ... While hydro, gas and oil can usually increase generation quickly, other sources — such as coal and nuclear — require long lead times.

OG&E Renewable Program Approved

The Oklahoma Corporation Commission voted 3-0 to approve OGE Energy Corp. subsidiary OG&E's comprehensive renewable energy program, which includes construction of [a] 115-mile, 345 kV transmission line between Woodward and Oklahoma.

Utilities Cooperate On Transmission

ITC Great Plains will build two sections of the Kansas V-Plan, which will further wind energy development, according to the company. The first sectionis a transmission line from Spearville, Kan., to Comanche County, Kan., and the second section is a transmission line from Commanche County to Medicine Lodge, Kan. The V-Plan will be constructed at 765 kV, if deemed appropriate by Southwest Power Pool Inc.

AEP, Duke To Form Transmission J.V.

Through the 50-50 partnership, Columbus, Ohio-based American Electric Powr and Duke Energy are proposing to build 240 miles of extra-high-voltage 765 kV transmission lines and related facilities in Indiana. The project would link the Greentown Station with the Rockport Station.

Estimated costs for the project are approximately $1 billion ...

"The need to build additional transmission provides the opportunity to invest in a long-term transmission solution that will facilitate development of additional generation — including renewables — and support the reliable transport of electricity to fuel future economic growth," says Susan Tomasky, president of AEP Transmission. "For example, more than 3,000 MW of wind power has been proposed in central India, but additional transmission is necessary to bring it online."

MATL Awaits U.S. Approvals

In August, the Alberta Energy and Utilities Board granted Montana Alberta Tie Ltd., a subsidiary of Tonbridge Power, a permit to construct and license to operate a proposed 346-kilometer, 230 kV alternating-current international power line from Lethbridge County, Alberta, to Great Falls, Mont.

Why Utilities Blame Rate Hikes On RE

By Jeff Siegel

Otter Tail Power, the utility subsidiary of publicly owned Otter Tail Corp., asked North Dakota state regulators for a renewable resource cost recovery rider earlier this year and expects to do the same thing in its Minnesota service area. Meanwhile, Xcel Energy's Texas utility, Southwestern Public Service, asked for a rate increase this summer, citing — among other factors — costs associated with "a burgeoning wind power industry."

These are only two U.S. rate cases among thousands, but their significance could be far-reaching. That is because the rate increases are not just about whether the cost of wind-generated electricity is going up. There is no question that the cost is increasing — due largely to higher construction costs, transmission constraints and increased demand for blades, nacelles, and other parts and equipment. ...

According to the second annual energy department report "U.S. Wind Power Installation, Cost and performance Trends" by [Mark Bolinger, one of the leading researchers in the field and principal research associate in the Electricity Markets and Policy Group at the Lawrence Berkeley National Laboratory] and Ryan Wiser, prices for wind power have "risen significantly" over the last five years. While the researchers admit that analysis of national trends in wind power prices is complicated by variability of prices across projects, their report finds that prices from 2008 installations, at least, "may be higher still."

Market Uncertainty Swirls In Newfoundland/Labrador

By Crystal Luxmore

The provincially owned energy utility, Newfoundland and Labrador (NL) Hydro, put an 80 MW capon wind development in Newfoundland, of which 54 MW ar set to come online by the end of this year.

However, a closer look at the province reveals this slow start could be the beginning of a big future. For now at least, the 80 MW cap is simply a case of too much of a good thing. Newfoundland, an island in the Gulf of St. Lawrence, is not connected to the North American grid. Sixty five percent of its 1,919 MW grid is fueled by hydroelectricity, which has to be kept working at a certain minimum level to prevent overflow.

"If we add too much wind to our system, we run the risk of generating wind power and spilling hydroelectricity," says Greg Jones, business development manager at NL Hydro.

Understanding U.S. Wind Fleet Underperformance

By Jennifer Delony

There is growing concern within the wind industry about underperformance of the U.S. wind farm fleet in actual operations as compared to preconstruction estimates. A poor performance trend across the board is not good news for the financial community if investors do not receive a high enough return from their wind project investments. ...

Director of engineering for Albany, N.Y.-based meteorological consulting firm AWS Truewind Eric White's comments on underperformance in the U.S. set the stage for a two-part discussion at the American Wind Energy Association's annual conference about the realities of actual wind farm energy production compared to preconstruction forecasts. He reported an average 10% underperformance for the U.S. overall versus expected wind farm performance values ...

Motor Oversizing Wastes Energy

Atlanta-based WEG Electric Motors Corp. Product Manager Andrew Glover explains that energy efficiency losses through oversizing of pump electric motors by engineers are commonplace, and if motor specification far exceeds the application, it could be costing the industry billions of dollars in wasted energy.

New High-Capacity Transmission Needed to Industrialize Rural and Wild America

Grid Enhancements Needed In Maine

Despite slow development progress to date, plans for new transmission in Maine could open capacity for more than $1 billion in wind energy projects.

By Jeff Siegel

Equally as important, the state is located near the high-use ISO New England (ISO-NE) market, where peak demand can hit 30,000 MW. But the state does not use much electricity itself, with peak demand in northern Maine at just 140 MW ... Hence, it would seem to make good sense to build wind in Maine to sell to the New England grid. Traditionally, there has been a number of obstacles to this strategy.

First, part of Maine is not on the New England grid ...

Second, low peak demand means inadequate transmission capacity for adding enough wind to sell to the New England grid. ...

Another obstacle to this strategy is the state's pride in its unspoiled rural areas. The new legislation has made it easier to permit and build wind farms ...

Finally, Maine's sense of political and cultural independence could deter utility-scale development. It is one thing to build wind facilities to generate electricity in Maine, with the attendant environmental concerns that have caused controversy. But it is another issue entirely to site a turbine in a forest, disturbing wildlife and driving away tourists so that people in Boston will have electricity. These issues also could hinder the development of new transmission.

Maine Could Get New Transmission

The Maine Public Service Co. (MPS), a subsidiary of Maine & Maritime Corp., and Central Maine Power Co. (CMP) have announced plans to construct a 345 kV transmission line from central Maine to northern Aroostook County.

... a 200-mile, 345 kV transmission line and related substations from the Detroit area to northern Aroostook County ...

NorthWestern Energy Files [Major Facility Siting Application]

NorthWestern Energy proposes to construct, operate and maintain the approximately 400-mile, 500 kV transmission line ... The new transmission line is expected to run from a new substation near Townsend, Mont., to a substation near Midpoint, Idaho.

New Transmission Company Formed

Topeka, Kan.-based Westar Energy Inc. and Electric Transmission America (ETA) have formed Prairie Wind Transmission LLC, a joint venture company that plans to construct ultra-high-capacity transmission facilities.

International Finance Corp. Updates Lender Guidelines

The guidelines reflect rising pressure being placed on companies worldwide to protect the environment and the health and safety of workers as well as people living near wind energy projects.

U.S. Slow To Engage Condition Monitoring

The authors of an Electric Power Research Institute report titled "Condition Monitoring of Wind Turbines" note the following: "Enough examples of premature failures exist to shed considerable doubt on the likelihood of a turbine reaching the 20-year design life without replacing one or more of the drivetrain components; estimates of 15% of the initial turbine capital cost for replacement parts over the life of the project are not unreasonable. Continuing premature failure of planetary/helical gearboxes indicates a mean time between failures may be as low as four to five years, on the average across all manufacturers."

Relocating the wind: New strategies for moving wind generation from high-wind areas to high-loa

By Marcus A. Wood and Jennifer H. Martin

The western U.S. has excellent wind-generation resources stretching over a vast expanse of the West and the Great Plains. The U.S. also has great pent-up demand for wind generation, particularly up and down the West Coast and in the Midwest. Exploitation of this vast wind-generation resource, available where the wind blows hardest and most steadily, is greatly hampered by a lack of economic long-distance transmission facilities and by multiple east-to-west and north-to-south firm transmission constraints found on existing transmission paths.

Any long-distance transmission of large amounts of electric generation presents electrical engineering challenges. Utility engineers routinely surmount such challenges in the construction of long-distance transmission systems for conventional electric generation systems. However, transportation of wind by wire must also accommodate special characteristics of wind generation. Briefly, these key special characteristics are:

1. Low capacity factor. Even in the most energetic wind areas, sites with generation capacity factors of 40 to 45 percent are considered premium sites. By comparison, large thermal generation units can achieve capacity factors in the 85 to 95 percent range. Long high-voltage transmission lines are very expensive, and the reduced capacity factors for wind generation translate to a roughly 2-to-1 cost transmission disadvantage for long hauls of wind-generation megawatt-hours.

2. Hourly forecasting difficulty. Despite continuing improvements in wind forecasting techniques, actual wind generation in each hour can vary substantially from forecast levels. Generally, the geographic areas with the best wind potential are not part of any organized regional transmission organization with centralized dispatch. Instead, each transmitting utility schedules out-of-region deliveries of wind generation based on forecasts and may impose substantial charges for deviations between forecast and actual generation.

3. Intra-hour swings in generation. Wind generation, even if produced over an hour on average in the amount forecast, may vary greatly within the hour. The within-hour output swings can be particularly noticeable as weather fronts pass through. Although the Federal Energy Regulatory Commission's (FERC) Open Access Transmission Tariff does not address the cost of such intra-hour variations, transmission providers are beginning to assess sometimes substantial new transmission ancillary service charges to cover the supposed cost of such generation swings.

As a result of these aspects of wind generation intermittency, the cost per megawatt-hour of relocating wind generation to other regions can be much higher than the cost of similarly relocating thermal generation. An even greater problem arises when control area operators maintain that they lack the generation flexibility required to provide the necessary hour-to-hour and within-hour shaping of the wind generation required for interregional deliveries. ...

Evaluating Project Risks With Monte Carlo Analysis

By Ralph E. Evans

Local concerns

Quantifiable issues of local consequence frequently include acoustic noise (both construction and operational), visual impact, setbacks, bird and bat collisions, future decommissioning requirements and effects upon archeological, recreational and historical districts. ,,,

State concerns

At the state level, permits may be required from the public utility commission and, in some states, from an energy or environmental agency. Some states have monitoring requirements to ensure expected parameters are observed, such as noise, bird kill and icefall as represented in the local conditional use permit.

Federal concerns

The third level of permitting is represented by the federal agencies of primary jurisdiction, such as the EPA (wetland protection), the Federal Aviation Administration (FAA) (aircraft hazard), the U.S. military (interference to long-range radar) and the FCC (telecommunications interference to microwave, two-way, public safety and broadcast facilities). Telecom interference can be caused by aperture blockage (turbines turning through a microwave beam), by re-radiation from turbine support towers, or by unintentional radio frequency radiation from generators or electrical combining equipment.

Understanding Turbine Sound Impact Studies

By Kenneth H. Kalinski

Turbine sound levels

The two most important parameters related to noise impacts from wind turbines are sound power and tonality. Sound power, which has units of watts, is a measure of the acoustical energy emitted by a source. Sound power is distinct from sound pressure. Sound pressure is the perceived level of fluctuation of air pressure at a point in space. Sound pressure is measured in Pascals. Because of the large range of sound power and pressure, both are usually reported in decibels, and therefore, are often confused. And although sound power cannot be directly measured, it can be calculated using several methods, including the measurement of the sound pressure at a given distance. ...

Wind turbines['] ... sound level is highly dependent on meteorological conditions. In addition, wind turbines generate some low-frequency sound, which tends to propagate better than higher-frequency sound. ...

Note that although winds may be blowing where turbines are located, there may be little or no wind at ground level near the project neighbors. This is because the "roughness" of ground cover slows surface winds. This effect is amplified in more mountainous areas, where hills further reduce valley winds.

... Wind shear is the difference in wind speeds by elevation, and temperature lapse rate is the temperature gradient by elevation. Under conditions with high wind shear (large gradient), sound levels upwind from the source tend to decrease and sound levels downwind tend to increase. With temperature lapse, when ground surface temperatures are higher than those aloft, sound levels on the ground will decrease. The opposite is true when ground temperatures are lower than those aloft - an inversion condition. ...

Infrasound is sound pressure fluctuations at frequencies below about 20 Hz - sound below this frequency is generally not audible. At very high sound levels, infrasound can cause health effects and rattle lightweight building partitions. ...

Low-frequency sound is in the audible range of human hearing that is, above 20 Hz but below 100 Hz to 200 Hz, depending on the definition. As with infrasound, high levels of low-frequency sound (e.g., above 70 dB at 31.5 Hz) can rattle lightweight partitions in buildings. In addition, low-frequency sound that is well above background sound levels at higher volumes can be annoying.

Wind turbines generate low-frequency sound, primarily from the generator and mechanical components. ... Low-frequency sound can also be generated at higher wind speeds when the inflow air is very turbulent. ...

Low-frequency sound propagates better than higher-frequency sound and tends to diffract more in the atmosphere under inversion conditions. ...

Electric power substation noise should also be considered, especially if transformers are located near residences.

Industry Defends Billion-Dollar CREZ Estimates

By Jennifer Delony

Costs for CREZ transmission have raised concerns about the high price to introduce more wind energy to the ERCOT system.

The scenarios for wind energy integration outlined in ERCOT's report "CREZ Transmission Optimization Study" are provided in megawatts, making extrapolation of cost savings dependent on establishing the average MWh output for every 1 MW in a scenario. The report does not provide an assumption for this figure or estimate annual fuel-cost savings.

NY Releases Study Guidelines

In January 2008, the New York State Department of Environmental Conservation (NYSDEC) released its "Draft Guidelines for Conducting Bird and Bat Studies at Commercial Wind Energy Projects." The draft guidelines outline the NYSDEC-proposed protocols for conducting pre-construction and post-construction studies at onshore wind energy projects in New York. The purpose of the protocols is to formalize the methods by which bird and bat resources are characterized, and the impacts resulting from construction and operation of wind projects in New York are estimated and documented. ...

Based on a number of factors, NYSDEC would recommend either "standard" or "expanded" protocols to assess potential impacts. ... Sites specifically identified as requiring an expanded protocol include the following:

• sites with habitat for listed bird or bat species,

• sites within five mites of the Atlantic coastline or the shoreline of one of the Great Lakes,

• sites located within a concentration area of raptors, waterfowl, or other vulnerable species or within two miles of such a concentration area, or within 10 miles of a major bat hibernaculum, and

• sites on which there is a specifically identified habitat or landscape feature (e.g., ridgeline) that functions to funnel or concentrate birds/bats during migration or for feeding, breeding, wintering or roosting activities.

Pre-construction studies for a standard site include breeding bird surveys, habitat surveys, raptor and songbird migration studies, and acoustical monitoring for bats. Radar studies are not currently included in the standard pre-construction protocol despite NYSDEC'S insistence that these studies be conducted at nearly all proposed sites over the past few years.

Pre-construction monitoring for a site requiring expanded studies could include:

• radar studies, waterfowl or wintering bird surveys,

• additional raptor migration or breeding bird studies, and

• studies specifically for the Indiana bat (Myotis somalia, a federally endangered species) or other migratory bats, in addition to the studies associated with a standard site.

Standard protocol post-construction studies include ground searches, searcher efficiency and carcass removal trials, bird habituation and avoidance studies, raptor migration surveys, acoustical monitoring for bats and bat specimen collection. Expanded post-construction protocols also could include radar studies and additional raptor migration surveys. For all projects, NYSDEC would require that samples of bat carcasses be provided for a nationwide genetic isotope analysis project. ...

The standard protocol requires one year of pre-construction monitoring. If an expanded protocol is deemed necessary, pre-construction monitoring would be lengthened to two or three years, significantly lengthening the period between the start of fieldwork and project permitting. Post-construction monitoring would be conducted for three years under both the standard and the expanded protocol.

— Christine Sousa & Mike Morgante

Research Pushes EES Tech For Wind

By Deston Nokes & Jennifer Delony

Wind's performance shortcomings have dampened discussions about its suitability as a reliable resource. Wind is intermittent, it tends to blow when less energy is needed and the high cost of transmission capacity can outweigh the value of delivered wind energy.

The Aerial Angle on Fatal Flaw Analysis

By Terry J. VenDeWalle & Elizabeth A. Day

... construction and operation of wind energy projects have the potential to impact bird and bat populations through habitat alteration and fragmentation, habitat loss, displacement, electrocution and collision mortalities. ...

... little is known about the migratory pathways of bats. ...

The USFWS has recommended several measures that can be taken to minimize potential impacts to bird and bat species during wind project site development. Such recommendations should be acknowledged and incorporated early in the project planning stages. Examples of these measures include but are not limited


• avoiding turbine siting in areas known to have special status or rare bird or bat species occurrences,

• avoiding turbine siting in areas known to concentrate birds (e.g., important bird areas, refuges, migration corridors, wetlands, staging areas, rookeries and landfills) or bats (e.g., woodlands and water features),

• siting wind turbines on cultivated agricultural lands (i.e., avoid woodlands and wetlands),

• using an existing transmission line as opposed to constructing a new line,

• constructing underground electrical collection systems,

• minimizing safety lighting as allowable by the Federal Aviation Administration, and

• arranging and configuring turbines parallel, rather than perpendicular to, nearby migration and river corridors.

Green Foundations Matter In A Green Industry

By Brendan Fitzpatrick & Michael Pckoski

Massive earthwork operations for wind tower foundations utilize naturally occurring, local materials to construct the engineered fill, a process that eliminates the use of man-mad materials from non-renewable sources. However, fossil fuel consumption by earthmoving equipment and by trucks transporting unsuitable soils to landfills results in a significantly larger carbon footprint compared to towers supported on natural competent soil. ...

Steel pile foundations incorporate energy- and resource-depleting manufactured materials, such as steel or concrete. Typically, piles use material that is manufactured or fabricated at locations hundreds or thousands of miles away from the construction site. Concrete production, while local, is also energy-intensive and ozone-depleting. The combination of the energy-intensive manufacturing process and the significant transportation efforts required for deep foundations to arrive at the site increases the carbon footprint of the foundation solution.

PSC Determines Wind Rate

"Unlike other sources, wind is intermittent," says Montana Public Service Commission (PSC) Chairman Greg Jergeson. "Using it in a power grid requires the addition of other sources. How much does this additional step cost — and who should pay for it — are the questions the PSC answered today for Northwestern Energy and Two Dot Wind."

Study Highlights RPS Impact

Existing state RPS policies, if fully achieved, would require roughly 60 GW of new renewable capacity by 2025, equivalent to 15% of projected electricity demand growth from 2000 through 2025.

Predicting Turbine Noise With Test And Simulation

By Marc Marroquin, director of marketing, LMS North America

Optimizing turbine acoustics

The noise that wind turbines generate is influenced by many factors, including blade size and design, drivetrain operation, and the orientation, force and turbulence of the wind. Typically, a megawatt-scale wind turbine generates a relatively flat 45 decibels (dBA) to 55 dBA broadband noise spectrum at a distance of 130 m to 150 m. At average wind speed, wind turbine noise only drowns out wind turbulence, vegetation and traffic noises that are present in the background by approximately 10 dBA to 15 dBA [ i.e., the wind turbine increases the noise level 2-3 times ].

Specific tonal noise components occur as a result of dynamic forces that come into play inside the gearbox (e.g., teeth meshing), the generator (e.g., electro-mechanical poles interacting) and system hydraulics equipment. These dynamic forces cause local housing surface vibrations, which distribute the noise to the surrounding area through radiation. The noise generated by drivetrain rotating machinery also propagates directly through structural noise paths.

Report Paves Way For Municipal Wind Bylaws

By Kate Rowland

Within the report [on wind turbine bylaws and best practices released by the Union of Nova Scotia Municipalities at the beginning of February], 15 different wind turbine impacts are discussed, including aviation safety, birds and bats, blade throw, erosion, fire, ice throw, noise, oil spills, property value, shadow flicker, structural failure, telecommunications and electro-magnetic interference, traffic and roads, vegetation and habitat, and visual impact. ...

And public concern in certain areas of the province is palpable. The report notes: "Citizens are concerned about the effects these projects may have on the community and its residents; specifically, noise, shadow flicker, ‘viewscape alterations,’ as well as concern for community identity and resulting property values. Concern has also been expressed that communities are expected to accept all of the potential downsides while the profits often flow out of the community to developers."

New Regulations Create Permitting Backlog

By Jon Gumtow, Natural Resources Consulting

At a minimum, wind farm construction requires Wisconsin Administrative Code NR 216 compliance from the Wisconsin Department of Natural Resources (WDNR) to address erosion control and stormwater management standards. Compliance with NR 216 is generally well understood and accepted in the construction industry, and the approval process can be completed in a couple of weeks.

However, more often than not, wind projects involve crossing wetlands or waterways that are regulated by the WDNR and usually by the U.S. Army Corps of Engineers (USACE) as well. Depending on the project type and complexity, permit approval from these agencies can take up to 12 months to receive. These permit actions also trigger compliance with other rules, including the Endangered Species Act and Section 106, which regulates historical and archaeological resource impacts.

Wind farms and other utility projects in Wisconsin are regulated by WDNR staff, who routinely manage between 20 and 35 ongoing projects, ranging from small telecommunication lines to large transmission corridors and wind farms. Traditional utility projects have temporary impacts to wetlands and waterways during construction, followed by restoration. In addition to temporary impacts, wind projects also have permanent impacts associated with access roads that are required for long-term turbine maintenance.

Another difference is associated with the type of temporary waterway crossings used for equipment access during construction. Vehicles and equipment used in transmission line construction typically use temporary bridges to cross small waterways. However, the cranes and equipment needed to install structures for wind turbines often require temporary culverts and engineered access roads of considerable width, leading to more disturbances to waterways. This in-stream disturbance can trigger time-of-year construction restrictions to minimize impacts to fish and other aquatic life.

The USACE regulates activities within U.S. waters under Section 10 of the Rivers and Harbors Act — work in waterways considered navigable for interstate commerce — and Section 404 of the Clean Water Act — fill within hydrologically connected waterways or wetlands. Recent changes resulting from the 2006 U.S. Supreme Court decision in the consolidated Rapanos and Carabell cases have led to new guidelines that the USACE must follow to make jurisdictional determinations related to whether or not a wetland has a "significant nexus" or hydraulic connection to regulated waterways and wetlands.

Utilities Brave New World Of Power Planning

By Jeff Siegel

Basic portfolio planning

In the old days, says Janice Hager, managing director of integrated resource planning for Duke Energy, portfolio planning was straightforward — utilities used what was available and what cost the least. These days, it is much more complicated than that. ...

So why do utilities want to include renewables? ... Some reasons include:

• existing or potential RPS requirements, including a possible federal RPS,

• regulatory settlements that require construction and ownership of wind,

• wind as a hedge against volatile fuel prices, including natural gas (also, some utilities want to build the cost of wind into their portfolios now as a hedge against future RPSs and possible carbon legislation),

• taking advantage of the production tax credit (PTC) while it is available, and

• improved public relations (consumers view utilities that use renewables or offer renewable options as being greener than other utilities).

Including renewables presents several difficulties for utilities, whether investor-owned of municipally owned. Foremost is the cost. Renewables are not only more expensive, but they are capital and not incremental costs. ...

In fact, says [Doug Pedrigo, an attorney with Thompson & Knight in Houston who handles energy- and renewable-related issues], take away the PTC and RECs, and it is very difficult to justify the added cost of renewables.

In addition, finding renewables to include in a power portfolio can be challenging. ... [R]enewable procurement is sometimes hampered by shortages in sites, contractors and turbines, as well as the regular uncertainty over the PTC. ...

Additional options

This is where RECs, building renewable costs into the system as a hedge against future carbon legislation, and even conservation-based efforts, fit into the mix. ...

Duke, says [Janice Hager, managing director of integrated resource planning for Duke Energy], sees RECs as a way to add wind power to its portfolio even though its service area does not have nay wind power facilities in it.

Wind And Transmission: Ontario’s Challenge

By Valerie Helbronner, Charles Keizer & Jennifer Tuer, Ogilvy Renault LLP

Transmission is fundamental to bringing new wind projects online. In many jurisdictions, the development of new wind projects is adversely impacted by limited transmission capacity either because transmission is not available in proximity to the resources, or because of congestion.

In Ontario, specifically, vast amounts of money must be invested in transmission assets to permit the development of renewable generation in remote areas of the province, where viable wind resources exist. ...

In the years following 2015, the integrated power system plant of the Ontario Power Authority recognizes that it will be necessary to plan for more substantial transmission reinforcements in order to access and deliver the renewable generation resources that are stranded in remote areas of Ontario. The currently proposed near-term upgrades of the north-south transmission tie would allow for 1,000 MW of new renewable generation to come online in northern Ontario. Without those reinforcements, many of the potential northern renewable resources would not be developed.

Conference For Marketers Forecasts More Wind

By Jennifer Delony

... American Wind Energy Association’s Jeff Anthony noted that U.S. independent system operators and regional transmission organizations currently report 300,00 MW of new generation in their interconnection queues — 140,000 MW of which is renewable energy.

"A vast majority of that is wind," Anthony added. "If all of those projects were to come online that are in the interconnection queues — and not all will — but it would be 10 times as much wind power than is currently on the grid today." ...

"Every structure has different risk-reward profiles," [Iberdrola’s director of REC origination, Peter Toomey] warned. "Depending on the developer and depending on where the capital is coming from, some of these structures may or may not work."

He emphasized, however, that RECs are critical to project finance, "period."

"There’s no question they always find a way into a deal," he said. "There are few companies that have not needed the RECs to get their project financed, but with the dramatic increase in wind turbine prices over the last few years, every wind project now sees RECs as an important element."

Alberta Says Farewell To Its Wind Generation Cap

By Jennifer Delony

"In order to offset the variability of wind when it ramps up very quickly, conventional generation can be dispatched down through the energy market merit order, and if it happens faster than that, then we have these regulating reserves, which are like cruise control for moving the generators down faster or up faster."

Ultimately, the amount of dispatch range available on the system and the region's intertie capability with other jurisdictions limit the operator's ability to integrate variable power resources, such as wind. ...

The Market and Operational Framework [proposal] also requires wind power facilities to help mitigate their own variable nature through power limiting and ramp-rate limiting capabilities. For example, says Frost, wind power operators can [pitch] the wind turbine blades into the wind to reduce the output of the generator. ...

"The province needs more gas-fired generation in the souther part of the province relative to the loads from wind farms," says Peter Hunt, vice president of public affairs for Enmax Corp., "and Enmax is building a 1,200 MW natural gas plant in or around Calgary, which will be online by about 2011. That's going to play a contributory role in balancing out supply when the wind doesn't blow.

Soderglen Plays Alberta’s Spot Market

By Kate Rowland

The Alberta government's new climate change regulations, which came into effect on July 1, require Alberta facilities that emit more than 100,000 tonnes of GHG emissions per year to reduce emissions intensity by 12% between 2007 and 2014. In Alberta, companies have three ways to meet their reductions: They can make operating improvements, buy Alberta-based offset credits or contribute to the province's Climate Change and Emissions Management Fund. Similar federal regulations are expected to come into effect by 2010.


By Jennifer Delony

Of the 14 U.S. Projects [out of 16 commissionings in North America from Jan. 1 to Nov. 1, 2007], six were built in Texas. Legislative support for renewable energy has been a clear driver for wind power development in 2007. Eight of the nine states in which these wind farms were commissioned have passed an RPS. ...

Together, the Texas projects represent about 890 MW of installed capacity ... The Texas market, which already is home to the 736 MW Horse Hollow project, is poised to support ever-larger developments, with 3,000 MW and 4,000 MW wind farm proposals announced in 2007. ...

Project completion dates tracked by NAW place a possible 2,369 MW online by the end of the year in North America in addition the previously commissioned 1,929 MW. ...

On record since January are announcements from seven wind turbine manufacturers for delivery of wind turbines with approximately 4,200 MW of capacity for North American projects in 2008.

RIS Establishes Safe Harbor Tax Guidelines

By William Ewing

The flip structure is common in the wind power industry and allows project developers to obtain the value for Section (§) 45 production tax credits (PTCs) and depreciation tax benefits that the developers would not otherwise be able to utilize.

In the typical partnership flip situation, a project developer and one or more equity investors will generally enter a partnership that will own one or more wind farms. The equity investor receives 95% to 99% of the tax credits and other allocations during the 10-year PTC period until the investor realizes a predetermined rate of return. After such return is achieved, the investor's interest in the partnership is reduced to as low as 1%, and the developer, in turn, receives 99% of the economic returns going forward. ...


Revenue Procedure 2007-65 provide welcomed guidance on partnership flip structures in the wind power sector. The safe harbor requirements are very favorable in allowing investors to receive up to 99% of the tax credits and other allocations during the 10-year tax credit period and then flip down to a 5% interest. Moreover, this revenue procedure clearly allows the investor to invest in a wind partnership for the primary purpose of benefiting from the § 45 tax credits, albeit the investor must have a reasonable expectation of deriving part of its return through participation in operating cashflow. Conversely, this revenue procedure mandates that the investor bear real economic risk ...

Seeking Standards For U.S. Siting And Approvals

By Lewis T. Putman

The height, motion and often remote location of wind turbines create potential natural resource and environmental impacts that are not normally presented by non-renewable power projects. ...

Most state guidelines for windproject siting make specific reference to post-construction monitoring to insure that no threatened or endangered species or their habitats are affected by the development of wind energy. In most cases, state guidelines call for projects to consult with agencies charged with implementing the federal Endangered Species Act and other habitat protection requirements. Other state guidelines mandate consideration of non-wildlife environmental issues, such as visual, noise, safety and construction-related effects. ...

["It's the law: Migratory bird treaty act of 1918, Bald eagle protection act of 1940, Endangered species act of 1973" — Bob Anderson, West Wind Wires, November 14, 2007, NARUC Annual Convention, Anaheim, California]

The goal of the USFWS interim guidelines is to protect wildlife and their habitats ...

A Coordinated Approach To Wind Farm Construction

By Diane Reinebach

Completion of roads is the most important first step in wind farm construction.

Quebec City Hosts CanWEA

Joshua Magee, an analyst with Cambridge-Mass.-based Emerging Energy Research, noted that off-the-shelf turbine prices increased by 50% from 2004 to 2007 and likely will continue to increase through the end of the decade. ...

["2009 installed costs likely to be double of 2004" — Mike O'Sullivan, Senior V.P., FPL Energy, November 14, 2007, NARUC Annual Convention, Anaheim, California]

... wind turbine manufacturing represents about 65% of the economic value in a wind power project ... tower and blade manufacturing can represent 40% of the economic value in a wind turbine ...

With limits set on wind power development in Canada by utility requests for proposals, some of the country's developers, such as TransCanada and SkyPower, are prospecting in the U.S.

A Wind-Side Look At U.S. Power Deregulation

By Jennifer Delony

"Wind does have a big foothold in states that have a very good [renewable portfolio standard along with] the federal tax credit, says Tyson Slocum of Public Citizen. "Take them away, and it will not kill the wind industry, but that is a big reason why there is so much investment going into it."

Deregulated States With Renewable Portfolio Standards

California: 20% by 2020

Connecticut:23% by 2020

Delaware: 20% by 2019

Illinois: 25% by 2025

Massachusetts: 4% by 2009

Maryland: 9.5% by 2022

Maine: 30% by 2000?

Montana: 15% by 2015

New Hampshire: 23% by 2025

New Jersey: 22% by 2021

New York: 24% by 2013

Rhode Island: 16% by 2019

Texas: 5,880 MW by 2015

District of Columbia: 11% by 2022

... Greater amounts of intermittent wind power on the grid require a method, such as demand response, to organize wind power when it is available and compensate when it is not.

The American Wind Energy Association (AWEA) submitted comments to the Federal Energy Regulatory Commission under its June advance notice of proposed rulemaking in support of further development of demand response, noting that "AWEA has not reached positions as an association on which vehicles best advance demand response."

Council Suggests Project Revisions

[The Washington Energy Facility Site Evaluation Council]'s new order recommends modification of the project to include a provision that, when considering final siting of wind turbines within 2,500 feet of a nonparticipating landowner's residence, the project developer shall give "highest priority" to increasing the distance of the turbine from the residence, even beyond the minimum four-time-height setback.

IPPs Present Untapped Investment Opportunities

By Charles Morand

While onshore European development is slowly, but surely, reaching capacity, the U.S. and Canada are only beginning their foray into wind. ...


In March 2007, the market research firm Emerging Energy Research (EER) released a report discussing growth prospects for Canadian wind. The report noted that after more than doubling its capacity in 2006 to 1,468 MW, the Canadian wind power market was slated to grow nearly tenfold to 14,100 MW by 2015 ... supported by strong programs in Ontario, Quebec and British Columbia.


In May 2007, EER released a sister study to the Canadian one, this time assessing the U.S. industry's prospects. ... The U.S. wind power market is expected to reach installed wind capacity of 49,000 MW by 2015, ... with Texas, California, Minnesota, New York, Colorado and Washington together accounting for around 53% of market growth between 2007 and 2015. ...

[L]arge U.S. incumbents, such as FPL, and international renewable heavyweights, such as Iberdrola, will increasingly be the ones battling for North American wind market share, likely at the expense of smaller independent power producers.

Innovation Characterizes Expanding Wind Industry

By Drew Robb

Nordic Windpower is one of many European firms casting a greedy eye on the burgeoning North American wind market. ...

Do you want ice with that?

"Ice causes the loss of a blade's aerodynamic profile and the increase of vibrations, leading to stress generation on the rotor, fatigue and premature wear," says Redouane Megateli, scientific director of the CORUS Centre [of Cegep de la Gaspesie et des Iles, Quebec]. "The consequence of these induced effects is production loss and the increase of the operating and maintenance costs."

Knight & Carver Expands Workforce

Knight & Carver Wind Group, a National City, Calif.-headquartered wind turbine blade manufacturer and repairer, has hired nearly 100 employees and dispatched blade-repair crews to over a dozen U.S. sites, including wind farms in Southern California, Missouri, Kansas, Pennsylvania, Oklahoma, Vermont, Oregon, Texas, Iowa, South Dakota, North Dakota, New York and Minnesota.

Canada’s Wind Generates More Than Electricity

By Kate Rowland

Spanish wind giant Acciona SA has been in Canada for several years as a development partner with Suncor Energy Inc. and Enbridge Inc. in a number of wind projects. But in the past two years, international investment has become even more prominent, as evidenced by Toronto wind developer Gale Force Energy Ltd.'s purchase by Irish multinational Airtricity Inc., and the acquisition of Ontario's AIM PowerGen Corp. by U.K.-based Renewable Generation Ltd. in 2006. As well, this summer brought the announcement that a SUEZ Energy North America affiliate had signed an agreement to purchase Toronto-based Ventus Energy Inc. SUEZ SA, the parent company, is an energy and natural gas giant based in France.

In the meantime, HSH Nordbank AG acquired a minority interest in Ontario's SkyPower Corp. in 2006, and mid-2007 brought the announcement that the private equity arm of New York-based Lehman Brothers had taken a significant equity stake in the company. ...

Permits, too, are an issue fr large developments, [Glen Estill, president of Ontario-based Sky Generation Inc.,] says, noting that it needs some public support. "It is far easier to bash a 'big, bad business' than an independent player or a community group," he adds. Consequently, the best of both worlds would allow small projects the advantage of a multinational's balance sheet, such as that of Airtricity or SUEZ North America, along with the on-the-ground, small-project expertise of Airtricity Canada or Ventus Energy.

North America Plans For Green-Collar Jobs

By Chanda Kapande

According to the American Wind Energy Association, the wind power industry provides approximately one skilled operations and maintenance job for every 10 turbines installed.

Steps To Successfully Securing Equity Agreements

By Jessica Lillian

Turbine complications

One common snag of late in the sequence from a project's planning to completion of financing has been a lack of wind turbine availability. All of te projects Midwest Wind Finance is currently assisting are "still waiting to be finalized with supply orders," according to [Ken Valley, president]. ...

"Obviously, the production tax credit has been very important to the development of the wind business in the U.S.," [John M. Eber, managing director and head of energy principal investments at JPMorgan,] states, though he points to cashflow from a wind farm's power sale and depreciation-related tax benefits as other important components of "a whole stream of benefits that is available to the owner of a wind farm."

New Policies Needed To Assess BC Project Impacts

By Charlie Palmer


Provincial and federal regulatory agencies in B.C. are demanding more detailed studies of potential wind energy impacts, particularly those relating to noise and the bird, bat and caribou populations. This requirement is leading to increased costs and challenges for project schedules, as it calls for studying multiple years of data. The move toward more stringent provisions is being driven by the increased knowledge of impacts associated with wind energy projects as well as proposals in new and more sensitive areas, such as northeast B.C.'s caribou habitat.

Quebec Seeks Economic Prosperity Through Exports

By Kate Rowland

In Quebec, a frustrating combination of delays in municipal approvals, loss f the federal wind power production incentive program and a global wind turbine supply shortage have set back at least one Quebec project currently under development. ...

[Sean Whittaker, policy director and technical affairs for the Canadian Wind Energy Association,] cautions that there are risks involved in wind development. "There's no doubt that the cooperative model can be very viable, and from an investment perspective, it can include many more participants than would a standard project," he says. "But the key issue here is risk. Wind projects require a great deal of analysis, and slight changes in terms of cost or capacity factor can have a significant impact on the project rate of return. So, it is critical that the cooperatives are aware of these risks and that they have the expertise on hand and solid analysis to ensure that these risks are minimized."

Environmental Monitoring Mitigates Construction Impacts

By Marjolaine Castonguay

... For power from an energy system to be considered as green energy, the entire process associated with project construction, operation and decommissioning must be analyzed in order to assess all related impacts upstream and downstream of the project. ...

Activities to monitor

The construction phase of a wind farm includes a multitude of activities that can impact the environment in different ways and to various degrees. Clearing, road building, improvement, and the transportation and installation of project components are the activities most likely to modify the quality of the environment when a wind farm is located in a forested context. ...

The environmental monitor must make sure all transportation activities are planned so as to reduce the impact on people living in the area and on road traffic.

The dust raised by traffic on logging roads at the wind farm site during dry periods is another environmental impact that lowers ambient air quality and increases the risk of traffic accidents. ...

In addition to air quality concerns, construction of a wind farm can impact the acoustical climate. ...

Tower Technologies Reach New Heights

... "The reality is, the towers are getting taller and heavier and they're more challenging and expensive to transport, says Lars Moller, president of DMI Industries, based in West Fargo, N.D.

Bigger towers

Two years ago, the tallest wind towers measure 50 meters to 60 meters at hub height. Today, manufacturers say they are building towers measuring 80 meters or more, and according to Kerry Cole, president of Trinity Structural Towers, it is necessary to reinforce the towers.

"You try to get them to the right height where the wind is blowing in a particular field, and you also need them to be heavier to support larger turbines," he says. "You have to maintain the same diameter of the tower for transportation purposes. To transport them you can't go wider, but you can get thicker in the material."

As manufacturers make wind tower bigger, meteorological towers are built larger as well. ...

Tower cleaning is cosmetic, but blade cleaning is for efficiency.

"I've seen bugs on the leading edge a quarter inch thick, and the thicker it is, the less efficient," says Alvin Cargill, president of Turbine & Tower Enviro-Cleaning in Cache, Okla.

DOE Report Tracks Maturation Of U.S. Wind Industry

Wind power prices

... Based on a limited sample of seven projects built in 1998 or 1999 and totaling 450 MW, the weighted average price of wind in 1999 was just under $61 per MWh (expressed in 2006 dollars). ...

Following a general decline since 1998, prices bottomed out for projects built in 2002 and 2003 and have since risen. Specifically, the capacity-weighted average 2006 sales price for projects in the sample built in 2006 was roughly $49 per MWh, up from an average of around $35 per MWh for the sample of projects built in 2004 and 2005, and $31 per MWh for projects built in 2002 and 2003.

Moreover, because recent turbine price increases are not fully reflected in 2006[,] wind project prices from projects being built in 2007 and 2008 my well be higher still. ...

Installed project costs

... Among the sample of projects built in 2006, reported installed costs averaged $1,480 per kW — up $220 per kW (18%) from earlier years.

Though most of this project cost increase is attributable to rising turbine costs, there is reason to believe that recent increases in turbine costs had not fully worked their way into installed project costs in 2006. First, the average cost estimate for projects under development but not completed in 2006 was $1,680 per kW, or $200 per kW higher than for projects completed in 2006.

Second, based on data from 32 U.S. wind turbine transactions totaling 8,986 MW from 1997 to 2006, it is clear that turbine prices have risen by more than $400 per kW (60%) on average. Because the sample of installed costs has risen, on average, by just over $200 per kW, further increases in project costs should be expected in the near future as the increase in turbine prices fully flows through to project costs.

Wind Farm Infrastructure: A Primer

By Brian Sedgwick

Access roads

Turbine access roads are permanent roads used during construction for the transport of equipment and material, and thereafter for operation and maintenance vehicle access. Although use of the access road during construction is temporary, the road must be designed for the extreme loads and turning requirements of the material and equipment transporter trucks. ...

Typically, the maximum truck load realized during construction is for the nacelle or base tower section delivery, which can have an individual vehicle gross weight of 250,000 pounds or more.

Individual axle loading used for design is approximately 10 tons per axle for transporters and up to 15 tons per axle for concrete delivery trucks. In addition to allowing for loading, access roads must be designed to accommodate the requirements for overall length (up to 180 feet), turn (up to 150-foot inside turn radius, crest/dip (limited to six inches per 50-foot road length), inside and tail "swing" distance, and slope (typically a maximum of 10% to 12%) of the loaded transporters. ...

Turbine foundations

Various foundation types can be used for turbine support. In the U.S., these types include gravity/spread (most common), drilled shaft and deep pile. ...

Paths and pads

Crane walk paths are temporary routes for the main lift/erection crane (typically a 500- to 600-ton crane) to travel from one turbine location to another for turbine erection. Breaking down a crane and rebuilding it at another turbine location can be quite expensive. It is more cost-effective to construct an improved path for the fully erect crane for transportation between turbines.

Crane walk path design presents specific engineering challenges because of the size and the high center of gravity of the cranes used for turbine erection, which often are 3000 feet tall when fully assembled. The design must allow for the extreme loading and associated bearing capacity requirements of the crane, while ensuring minimal cross-path elevation differences to avoid crane tipping. These crane paths can be between 32 feet and 36 feet wide, and can be independent of the access roads discussed above or they can run along the access road route.

Where the crane walk path follows the access roads, the crane would straddle the access road, and two improved crane walk shoulders would be designed and constructed on either side of the aggregate access road. ...

Crane pads are improved surface areas designed and constructed primarily for the main lift crane and any support cranes during turbine erection. This area will experience extreme loading during the lifting and placement of turbine components during erection. This loading can approach 6,000 pounds per square foot during nacelle and tower section lifting. ...

An additional, important component related to crane pads is the turbine assembly or construction area. This is a specially constructed ground surface of approximately 1 acre to 2 acres around the turbine location where the tower sections and nacelle are staged and the rotor assembly components are stored and assembled for subsequent crane pick and placement during turbine erection.

"Clean Development Mechanisms" In Oaxaca Benefit Mexico And Spain

By Shelley Paventy

Mexico, because it is a developing country, does not have an emissions standard under Kyoto, and Spain's allowable amount of emissions under Kyoto is -8%, which means the country must reduce the amount of emissions it produces by 8% by 2012.

Consequently, Iberdrola and Gamesa can use the traded emissions from their Mexico wind farms to help Spain meet its required emission reduction set by Kyoto. ...

The Global Wind Energy Council reports that Mexico is one of the most promising areas for developing wind energy. In 2002, the U.S. Agency for International Development, a Washington, D.C.-based organization that assists developing countries, and the U.S. Department of Energy (DOE) invested nearly $200,000 in assessing the wind resource in Mexico. As part of DOE's investment, the National Renewable Energy Lab (NREL) analyzed the wind potential in Oaxaca.

The following year, NREL released its "Wind Energy Resource Atlas of Oaxaca" report, which revealed that the best area for developing wind in Mexico is in the southern region of the Isthmus of Tehuantepec, Oaxaca.

According to the report, there are Class 5 wind resources in the Isthmus of Tehuantepec and Class 7 — the highest class — near the foothills.

"Using a conservative assumption of 5 MW per square kilometer, this wind land could support approximately 33,000 MW of potential installed capacity," the report states.

Though the La Venta II wind farm represents Mexico's first large-scale wind project, it is not the only wind farm planned for Oaxaca. The Comisión Federal de Electricidad (CFE) hired Iberdrola Ingeniería y Construcción to build the La Venta II substation and interconnection grid, which, according to a representative of CFE, connects to La Venta II and will connect to the proposed La Venta III wind farm. This third phase, which will have a capacity of 101 MW, is being funded by World Bank's Large-Scale Renewable Energy Development program.

"Additional projects will be connected to a new substation operating at 400 kV, where the energy secretariat has planned to connect 2,300 MW by 2010," CFE's representative added. "The 2,300 MW is composed of 1,900 MW self-generation and 400 MW undefined scheme (probably independent power producer). Other 550 MW wind farms self-generation projects will be constructed in the same La Venta II/III wind farms regions."

Additional development in the region includes Parques Ecológicos de Mexico's 102 MW La Ventosa wind farm in the municipalities of Juchitan de Zaragoza and Asunción Ixtaltepec, in the vicinity of the town of La Ventosa, Oaxaca.

Industrial Wind Energy Tidbits

Lifting Equipment Now Available

According to Bigge Crane and Rigging of Sand Leandro, Calif., nine Liebherr LR 1200sx crawler cranes, which can lift up to 485,000 pounds; 12 Liebherr LR 1300 crawler cranes, which can lift up to 660,000 pound and include a short 23-foot jib for placing turbines on wind towers; and six Manitowoc 2250 crawler cranes, which can lift up to 600,000 pounds, are now available to contractors nationwide.

Nordex Installs N0/2500 Turbine

The turbine includes safety features such as ice sensors and an automatic fire-extinguishing system.

3M Introduces Wind Tapes

According to the company, its wind tapes provide protection from damage caused by sand, rain, moisture ingression, insects, airborne particles and ultraviolet rays.

Project Financing Evolves In Canadian Power Market

By Kate Rowland

In the U.S. and Canada, provincial, state and federal governments are looking at another important, long-neglected investment necessary for the addition of new wind energy to the electrical mix — new transmission infrastructure. In the U.S., the Department of Energy authorized a National Electric Transmission Study — completed in August 2006 — that identified areas requiring new transmission investment to deliver wind power.

In fact, delivering wind power to the grid is the most significant challenge facing the wind industry today, says GE Energy president and CEO John Krenicki. In written testimony in March 2007, Krenicki told the U.S. Senate Committee on Finance: "Many of the nation's most promising wind resources are located in relatively remote areas where there is little or not transmission access. In other areas, congestion on the existing grid also may limit opportunities to delver wind-generated electricity to the areas where electricity is consumed.

"Further investment in transmission lines is essential for large-scale wind installations to be built," he continued. ...

To stimulate investment in the U.S. transmission infrastructure, [John] van't Hof [CEO of Tonbridge Power Inc., a publicly traded transmission development company building a 210-mile, 240 kV merchant power line between Lethbridge, Alberta, and Great Falls, Mont.] says, "I believe that the tax incentives granted to renewable energy projects should be extended also, on a pro-rata basis, to the investment in the transmission systems the renewable energy projects require."

Canadian wind projects are also feeling the pinch in terms of transmission capability. Newfoundland has a great wind resource, but insufficient transmission infrastructure to send it to nearby Labrador. Albertan developers are awaiting both the Southwest Alberta and Southeast Alberta transmission reinforcement lines, without which many potential projects in transmission-congested areas are sitting on hold.

Ontario, too, has both large wind projects and smaller community wind projects waiting in the pre-development stage due to transmission constraints in the Bruce region. Incidentally, Bruce has some of souther Ontario's best wind resources, but it needs the transmission capability for the area's nuclear power plant. In late March, Ontario's Hydro One announced it would begin the process of seeking approvals for a new transmission line from the Bruce region. The Ontario Power Authority indicated the new investment in transmission infrastructure in the Bruce region would allow for approximately 1,700 MW of new renewable electricity generation — primarily from wind power.

Gulf Winds Carry PEI's Eastern Kings

By Jennifer Delony

"With 15% intermittent wind power, the utility feels that, for its size, that's essentially all it can handle for the time being until some fo the issues surrounding the intermittent nature of wind have been resolved" [Wayne MacQuarrie, chief executive officer of PEI Energy Corp., a Crown corporation].

Consequently, wind power from any new developments in PEI will have to be sent off the island for now. According to MacQuarrie, the exported wind power would go primarily to New England. Additional wind power development potential in the immediate vicinity of Eastern Kings is dependent on a new transmission line that Maritime Electric [the primary electricity provider in the province] built out to the eastern end of PEI.

Suzlon, Areva Sign Framework

India-based wind turbine manufacturer Suzlon Energy Ltd. and French nuclear power developer Areva Group SA have signed a binding agreement governing a framework for the companies' shareholding in REpower. The agreement brings to an end a bidding contest between Suzlon and Areva for REpower that began in late January.

"Given our arrangement with Areva, we now directly and through voting pool agreements already control over 60 percent of REpower's capital, says Tulsi Tanti, chair and managing director of Suzlon [and eighth-richest individual in India].

Tanti adds that Areva likely will "continue to support the wind industry and growth of REpower," and the companies will expand their relationship in the areas of transmission and distribution.


By Jennifer Delony

There are "more acquisitions to come," and they will be "bigger, bigger, bigger," said Jeff Chester, a partner in Kaye Scholer LLP, during a session on developer consolidations at the American Wind Energy Association's Windpower 2007 conference last month. Chester explained that key drivers in the wind power market are causing an increase in developer consolidation. ...

"We see Iberdrola and BP that want to make a big impact quickly, and they are looking to enter in the biggest way possible, so they need to aggregate developers," Chester said.

Iberdrola entered the U.S. market through the acquisition of wind power developer Community Energy in 2006, and it has collected three more U.S. developers since then, adding nearly 20,000 MW to the company's project pipeline.

Making Wind Power Sustainable And Profitable

By David Marcus, General Compression

As the need for cleaner and safer sources of power grows, wind power continues to increase iin popularity. That growth, however, is limited by conventional wind technology. Wind is an intermittent resource, and current technologies convert wind energy immediately into intermittent power.

This intermittent power receives a poor price in many markets. It is not rewarded with time-of-day energy pricing, and it makes wind energy ineligible for most capacity payments. The industry can forecast the output of a wind farm within 3% over 20 years [though they usually choose to pad it — Ed.], but does not know if the wind will blow next Tuesday. Low pricing, restricted capacity payments and limited forecasting abilities hinder wind power's acceptance as a major source of generation.

Experts Release Integration Plan

In order to deliver reliably the anticipated 6,000 MW of wind energy to the region's end users, the [Northwest Wind Integration Action Plan] suggests addressing integration costs, building transmission resources and supplementing wind resources with non-wind generation.

Identifying And Avoiding RF Interference

By Lester E. Polisky, Comsearch

As new wind turbine generators are installed around the country, it is important to consider whether they pose an interference threat to existing microwave systems and broadcast stations licensed to operate in the U.S. Wind turbines can interfere with microwave paths by blocking the line of sight between two microwave transmitters.

Additionally, wind turbines have the potential to cause blockage and reflections (i.e., ghosting) to television reception. Blockage is caused by the physical presence of the turbines between the television station and the reception points. Ghosting is caused by multi-path interference that occurs when a broadcast signal reflects off of a large reflective object — in this case a wind turbine — and arrives at a television receiver delayed in time from the signal that arrives via direct path.

Because of the nature of radio wave propagation and the desire to obtain optimal placement of wind turbines, the combination of these factors can be disruptive to both microwave operation and television reception.

Educating Children About Clean Energy

By Ward Eames (National Theatre for Children), Brian F. Keane (Smart Power) & Kevin Plagman (marketing consultant)

The development of the secondary energy certificate market makes it easy for a company to claim that all of its energy is produced by solar, hydro or wind power. In fact, many leading companies — especially highly visible, brand-conscious retailers — are using these claims to woo investors, employees and the public at large.

Sound Defense For A Wind Turbine Farm

By Robert D. O'Neal & Richard M. Lampeter, Epsilon Associates

There are no federal, state or local noise regulations that apply to this facility [Horse Hollow Wind Energy Center].

Market Demand Boosts Blade Production

As turbines age, blade repair has become a niche. ... "It's a delicate process at installation, and it's susceptible to error," says Mike Jeffrey, president of Composotech. He says the company can tell, from the ground, whether a blade was installed even one degree out of alignment. "We see problems with 10 percent of blades," he adds.

Blade misalignment can lead to less power being generated and can create vibration that reduces the lifespan of the blade. Jeffrey adds that blades also suffer damage from lightning.

Wind developers clearing the woods for industry

"The site was nothing but forest when we originally started, and the number of bears onsite was a bit startling to some of the people we had working there." —Daniel Girard, S&C Electric Co., on the Prince I & II wind energy facility in Ontario: 126 1.5-MW turbines on 10,000 hectares (24,710 acres), two 34.5 kV collector systems (underground for Prince I, underground and overhead for Prince II) and 240 kV interconnect substations, 11 km transmission lines for Prince I, and more lines to tie in Prince II

"Construction took place on bedrock that required blasting and excavation for tower foundations and access to roads."

—Prince Rises As Brookfield's Model, by Jennifer Delony, North American Windpower, April 2007

Tax Credits Drive Innovative Finance Structures

In an equity flip structure, a project developer enters into an equity partnership with an investor. The investor owns a percentage of the project for the life of the tax credit and is the recipient of most cash distributions from the wind power project as well as the benefits of the tax credit and depreciation. When the equity investor reaches a predetermined rate of return, the majority ownership flips to the project developer. In order for the tax credit to be available to an investor, the investor must have an ownership interest in the project.

The flip structure used by [GE Energy Financial Services] is common in the wind power industry, says Tom Woolsey, a partner with Washington, D.C.-headquartered Hogan & Hartson LLP. "If the equity investment of the sponsor has not been paid back at a predetermined point, there will be a cut-off and all of the cash flows will flip over to the equity investors," explains Woolsey.

"The investor typically targets an internal rate of return, and at that point, there will be a second flip where the sponsor and the equity investors take percentage interests in the cash flows of the project," he says. Furthermore, the internal rate of return of the equity investor is driven by the investor's ability to use the tax benefits of the project. ...

"Many large corporations and financial institutions, whose primary operations have nothing to do with the energy business, have figured out a way to use the tax credit equity for an investment." says Valley. ...

Even organizations that cannot take advantage of tax credits directly because they have no, or too little, U.S. or Canadian income are not being deterred from seeking wind power finance deals in the North American market.

In fact, these organizations are arranging wind power finance deals with companies that can benefit from federal tax credits, and their deals will bring money from other markets into North America over the next two years, says Karen Wong, a partner with Milbank, Tweed, Hadley & McCloy LLP, a global law firm that represents energy organizations. ...

"Iberdrola has made several [wind power] acquisitions in the U.S.," says Woolsey, "and they have an interest in growing their U.S. portfolio." A February 1 statement from Iberdrola details the company's plan to invest 3.25 billion euros in renewable energy worldwide over the next three years, with the U.S. set as a "strategic priority" due to its wind power market potential and favorable tax regime for renewable energy.

"BP also has made significant acquisitions in the U.S.," he says. BP Alternative Energy has slated $8 billion for renewable energy development worldwide, with a five-year investment plan for 2,015 MW worth of wind power projects in New York, Texas and South Dakota.

Funds Slated For Canadian Renewables

Canadian Wind Energy Association (CanWEA) president Robert Hornung says CanWEA would be advocating 3,000 MW out of the 4,000 MW covered by the program be set aside to ensure wind energy development receives, in essence, what had been committed to it by the announced expansion of the [Wind Power Production Incentive] program in 2005. ...

Some technologies may require certification under Environment Canada's Environmental Choice Program for electricity produced from low-impact renewable energy sources.

The prescribed time period noted in the discussion paper is 12 months, which has some renewable energy developers concerned.

"A lot of hydro and large wind cannot be finished in 12 months. This would preclude massive projects that take longer to build," says John Keating, CEO of Canadian Hydro Developers, Inc., which has two large wind developments in Ontario, Wolfe Island and Melacthon II, currently in progress ...

[ comment: It may be that a project that takes more than a year to build is unlikely to be "low impact."]

Montana Set to Export Its Future Wind Power

"If there are new transmission lines, there is a chance new coal generation could squeeze out the wind generation," [says Dave Ryan, energy specialist for the National Center for Appropriate Technology]. ...

"One challenge is to get transmission users to commit to use new facilities and be willing to pay some of the freight going forward," [says Ray Brush, manager of regional transmission policy for NorthWestern Energy, and a member of the Northern Tier Transmission Group's steering committee]. They are not going to build without this commitment. "We're not in the field of dreams business."

[ comment: At a capacity factor around 25% and a highly variable and unpredictable production pattern, wind energy cannot support the new transmission lines it requires. Thus it spurs other plants to be built to use the lines ...]

The 2006 Minnesota Wind Integration Study

By Ken Wolf (Minnesota Public Utilities Commission), Matt Schuerger (Energy Systems Consulting), Mark Ahlstrom (Windlogics), and Bob Zavadil (Enternex)

The problem. Wind energy has many attractive attributes and is becoming an increasingly popular choice for new electricity generation around the world. However, because the "fuel supply" is the wind, the power from a wind plant is variable and the power delivery schedule is subject to uncertainty. Energy from wind generating facilities must be take "as delivered," which necessitates the use of other system resources to keep the demand and supply of electric energy in balance. To the extent that wind generation increases the required quantity of these system services, additional costs are incurred. ...

The operating characteristics of wind generation increase the need for flexible generation to compensate for changes in the net of load and wind generation. These changes occur across all time scales, from seconds to minutes to hours.

[See the critique of the "Minnesota Wind Integration Study" (by these same authors) at the Kirby Mountain blog , where it is noted that the study not only smoothed the fluctuating wind to hourly averages but also assumed an exaggerated output of 40% capacity (the U.S. average in 2005, according to the EIA, was 21%).]

Developers Accept The Island Challenge

By Jeff Siegel

The grids are tiny and con only handle so much wind. ...

"Wind in Hawaii is a function of how much the grid can accept," says [Ross] Newlin [director of assets management for Enxco]. "You can only do so much given the generation base and an intermittent supply like wind. Sometimes, you're talking in the low single figures." ...

In addition, Maui Electric, which will buy the power [from Ulupalakua Ranch], expects to do interconnection and transmission work to handle the increased wind load.

Wind requires major expansion of transmission grid

[Note that there's no word about the developers paying for any of this. If you build a house, you have to pay for the connection that allows you to buy electricity, but if you build a wind farm you apparently don't have to pay for the connection that allows you to sell electricity. And this new transmission infrastructure has to be able to handle the full load of the generating facilities on it, even though wind plants rarely, if ever, reach that and average an output of only 20-25% capacity.]

This goal [to deliver 25% retail electric energy with wind power], however, is conditional on investment in transmission to support the growth. —Windbearings, Jennifer Delony

In December 2006, the Public Utility Commission of Texas (PUCT) adopted a rule pertaining to the establishment of competitive renewable energy zones (CREZs) The rule outlines procedures for both the PUCT to designate CREZs and the process of siting and constructing transmission to facilitate the delivery of electricity from renewable energy generation to consumers in Texas. ... The impetus for this rule comes from Texas Senate Bill (S.B. 20, which gives the PUCT authority to support development of transmission infrastructure in the state in order to meet Texas' renewable energy goal (S.B.) 20, which gives the PUCT authority to support development of transmission infrastructure in the state in order to meet Texas' renewable energy goal (i.e., 10,000 MW by 2025) and to coordinate construction of transmission facilities with construction of renewable energy generation facilities. —Texas Adopts CREZ Rule, Jennifer Delony

In addition, Maui Electric, which will buy the power [from Ulupalakua Ranch], expects to do interconnection and transmission work to handle the increased wind load. —Developers Accept The Island Challenge, Jeff Siegel

The realization of any wind power generation goal in the U.S. — whether it is 20% by 2020 or a state-specific renewable portfolio standard — depends on the development of a modern national transmission grid. ... The [Energy Policy Act of 2005] allows [the Federal Energy Regulation Commission] to issue permits when: a state does not have the authority to approve siting of facilities or to consider the interstate benefits that would result from new or updated facilities; the entity seeking to build or upgrade facilities is a utility that does not qualify to apply for siting approval in a state because the entity does not supply power for customers in that state; the state siting authority withholds approval for the facilities for more than one year after an application is filed or one year after the designation of a national corridor; or the state establishes conditions for building or upgrading that will reduce benefits of the construction. —DOE Set To Designate National Corridors, Jennifer Delony

That means [Southern California Edison] has a lot of planning to do. Between now and 2013, the company will spend $2.85 billion on building a transmission collector delivery system to bring the electricity generated in the 50-square-mile [Tehachapi] area near the Mojave desert to customers in central, coastal and southern California. —SCE Secures 1,500 MW, Nora Caley

This study shows that the electric power system in the Minnesota region can reliably accommodate the addition of wind generation to supply 20% of Minnesota retail electric energy sales if sufficient transmission investments are made to support it. —The 2006 Minnesota Wind Integration Study, Ken Wolf, Matt Schuerger, Mark Ahlstrom, and Bob Zavadil

Study Helps Direct Ontario's Renewables Action Plan

The Ontario Wind Integration Study was commissioned by the Ontario Power Authority, the Independent Electric System Operator and the Canadian Wind Energy Association. The study was performed by a GE Energy Consulting team. [The Canadian Wind Energy Association, of course, is a trade group to promote the wind industry, and GE is North America's primary manufacturer of wind turbines (as well as gas-fired generators, of which more will be needed to balance larger amounts of wind).]

Based on the results of this study and similar studies of other control areas, large penetration levels of wind power are expected to increase the requirement for load following in the Ontario control area significantly. At the 10,000 MW level, load following requirements are expected to be about 50% higher than the level required to serve customer load alone. ...

Low load periods present a supply mix challenge that can be addressed in a number of ways, including:

— Shed wind or use wind farm controls to provide flexibility. Shedding the wind has significant disadvantages as a solution to the low load issue, as it results in lost renewable energy production. However, under some light load conditions, the most economic option may include selective and controlled curtailment.

— Export wind output to other control areas. Neighboring utilities may be in a position to take excess wind production during low load periods.

— Load modifications. Instead of, or in combination with, wind curtailment, adding load during the low-load hours can help to lessen the impact on the online dispatchable generation resources. Yes: Use more electricity so the wind isn't wasted!

— Develop a more accommodating supply mix. No mitigation measure is a replacement for a good supply mix strategy that addresses the low load issue. As the load moves down in the dispatch stack, the remaining generation will be subjected to increase ramping (both up and down) requirements due to the wind.

Report: Renewable Energy Storage

"Watts In Store — Storing Renewable Energy," a research report by Dublin-based Research and Markets, says that while wind energy is available outside of the solar belt and during darkness hours, it remains intermittent. Therefore, when considering the wide-scale use of renewable energy, providers must find a way to store that energy for transportation from one region to another and for deployment in a way that overcomes the intermittent supply.

Concerns Over Sound Emissions Become Syndrome

A group of symptoms allegedly caused by wind turbine sound emissions has been labeled as "wind turbine syndrome."

Sound emissions from wind turbines were documented officially by Dr. Anthony Rogers of the University of Massachusetts' Renewable Energy Research Laboratory in a January 2006 amendment of a June 2002 white paper, titled "Wind Turbine Acoustic Noise." The paper identifies the sounds that are emitted by wind turbines as tonal, broadband, impulsive and low frequency/infrasound. ...

Even when a community has established a noise standard, it cannot be assumed there will be no complaints from community members about wind turbine noise.

"This is due to the changing of the relative level of broadband background turbine noise with change in background noise levels," says Anthony Rogers of the University of Massachusetts' Renewable Energy Research Laboratory. ...

"Because of the wide variation in the levels of individual tolerance for noise, there is no satisfactory way to measure the subjective effects of noise of of the corresponding reactions of annoyance and dissatisfaction."

[Not noted is that when a family is forced to flee their home in Pubnico Point, Nova Scotia, because of physical and mental health problems after the nearby turbines begin operating, the measurements that found an acceptable level of noise are obviously meaningless. The telling measure is the health of the individuals affected.]

Change Takes Hold In New York's Wind Industry

Bob Bellafiore, a former press secretary for Gov. Pataki and a partner in the public relations firm Eric Mower and Associates, says wind developers often hire firms such as his to gauge community support before they start a project. "The days of siting power projects over public opposition are over in New York." In addition, there are historical preservation issues. "New York has been around so long that a lot of times developers are on historic property, and when you start digging, you run into issues." ...

Bellafiore does not buy the idea that Tom Golisano [founder of Save Upstate New York but then Empire State Wind Energy] now supports wind. Bellafiore thinks Golisano is trying to set up wind development for failure. Municipalities are not in the renewable energy business; they are in the police and fire business. "He knows it's economically impossible for municipal wind to succeed." Bellafiore says. "It's a trap."


I had the good fortune to hear the keynote address from Nora Brownell, former commissioner of the Federal Energy Regulatory Committee, at the American Wind Energy Association's fall symposium last month. ... She told attendees that as the industry continues its promising expansion ... members must remember to declare victory as early and as often as possible. For every project, Brownell believes the industry should exclaim, "We built this." {Works for al Qaeda!]

She noted that while the wind industry is capable of helping states meet their renewable portfolio standards [since those RPS's don't require actual reduction of nonrenewable sources], it cannot deliver on that promise without building transmission.

Wind Power Income Trusts Hang In Balance

A political waiting game over Canadian income trusts is leaving no financial roadmap for future development.

[That is to say, an attractive tax shelter is under threat.]

Iberdrola Receives Approval For Wind Farm In Mexico

Iberdrola, an electric utility and wind power developer headquartered in Spain, has received approval from the Spanish Designated National Authority regarding climate change, which reports to the Ministry of the Environment, for the La Ventosa wind farm in Mexico.

According to the company, the project was approved as a clean development mechanism (CDM), one of the flexibility elements included in the Kyoto Protocol. The wind farm, located in the state of Oaxaca, will have a capacity of 102 MW of installed power.

The La Ventosa project, which also received a letter of approval from the Mexican Designated National Authority, is in the validation phase, which is expected to conclude at the end of December. It will be registered with the executive board of the CDM, an entity that reports to the United Nations Framework Convention on Climate Change, at the end of February 2007.

[Build a wind power facility in Mexico (not bound by Kyoto) to "reduce emissions" in Spain — an obvious shell game.]

Initiative 937 Sets 15% by 2020

Without the support of hydropower, Washington's wind industry would be disadvantaged. ...

Even with increasing costs for fish mitigation, hydropower remains one of the most inexpensive and efficient sources of electricity in the region. In the Northwest, for example, electricity from hydropower typically costs about $10 per MWh to produce. Comparatively, a recent staff report from the Northwest Power and Conservation Council says that the "cost of new wind projects has risen substantially."

Today the projected cost of near-term wind energy projects is between $72 and $98 per MWh. Just two years ago, the Northwest Power and Conservation Council estimated new utility-scale wind power projects to cost between $42 and $53 per MWh.

California Seeks Link With East Coast Program

Inclusion of wind and other renewable power generators in the model, for example, could create a market-based incentive for zero-emission generators through sales of their emissions credits. In addition, it is possible to tap renewable resources through a set-aside or an allocation of a program's emission allowances for specific energy technologies.

[In other words, the goal is no longer reduction of emissions: just another subsidy for wind energy (which does not reduce the use of other fuels) and a means of avoiding controls on existing energy sources.]

Design Considerations For Large Collector Systems

The composition of the land and ice throw from wind turbines will, in large part, determine whether the collector system is installed overhead or underground. [emphasis added]