The poor generation of electricity from wind

Every wind turbine has a "rated" wind speed at which its generator will be able to produce its full rated, or nameplate, capacity, which is typically 1.5 MW in today's models designed for on-shore use. The rated wind speed is usually around 30 mph.

The turbine also has a "cut-in" wind speed at which it will begin producing power, usually a little less than 10 mph. At that speed, however, the power output is almost nil. The power output rises in a cubic relation to the wind speed. That is, if the wind speed doubles, the power output is able to increase eightfold (2³). If the average wind speed of a site is 15 mph -- one half of the rated wind speed -- the average power output will be one eighth of the nameplate capacity, or less than 200 KW.

At a wind speed around 60 mph, the turbine locks down.

Even so, whatever power they add to the grid is a good thing, right? Not exactly: Because of the nature of electricity and the impossibility of large-scale storage (not to mention that storage would entail a certain loss of energy), the grid is designed to generate exactly the amount of electricity exactly when users need it. Wind turbines don't fit this requirement of a useful source, because they respond only to the wind speed. They can't be told to increase or decrease their generation according to user demand. Their production may drop off or surge at any moment, depending only on the wind.

The grid can, of course, consider wind facilities as they might large erratic users and deal with their fluctuating production as part of the overall demand in the system. In other words, it views a surge in wind power as a drop in demand, a drop in the wind power as a surge in demand.

At best, then, it might reduce the demand for other sources of electricity. But it can never replace the main sources of power that provide what is called "base load." And though it may reduce the use of other sources somewhat, it can never eliminate them, because the wind may drop at any moment -- even over a very wide area -- and they have to be ready to cover for it. In fact, running such plants with the frequent rampings up and down that large installations of wind power would require is not only more expensive but also less efficient, i.e., more polluting. [Click here for further discussion of these issues.]

As serious as those problems are, however, the main objection to wind power is probably that the turbines, about 350 feet tall each, can not be placed just anywhere. They require unobstructed wind, which is usually found on mountaintops and open prairies (and at sea). And they can not be too close to each other for the same reason. The U.S. Environmental Protection Agency has stated that a 25-MW project might cover 1,500 acres. That's 60 acres per megawatt.

Even a small facility would have a huge impact on the landscape. Any substantial amount of wind power would be devastating.


Energy Use in the U.S.

According to the Department of Energy, the U.S. used 3.66 billion MW-h of electricity in 2002, 35%, or 1.27 billion MW-h, of which was for residential use. Total electricity use was therefore about 12.6 MW-h per person, with residential use representing 4.4 MW-h of that. One MW of installed generating capacity would produce 8,760 MW-h/yr at full capacity, which value is reduced by the capacity factor to represent the actual output over a year. For wind the factor is typically assumed to be 0.3 (although it is usually closer to 0.2); therefore, 1 MW of rated power would produce only 2,628 MW-h/yr, so a 1-MW wind turbine would theoretically produce the amount of electricity used annually by fewer than 400-600 people residentially or about 135-200 totally.

It is said that the average household in the U.S. uses 10 MW-h/yr, an average load of 1,140 watts. Therefore, 1 MW of wind power would theoretically produce the amount of electricity used by 175-263 homes; yet the wind industry generally claims 333 (or more) homes per MW. Such figures are almost meaningless, however, because a) two-thirds of the time wind towers are effectively not producing electricity at all, and even at the odd moment of peak generation they would be producing much less than the average load of the number of "average" homes claimed; b) household use varies considerably through the day, with peak demand being considerably higher than the average load, as well as season to season; c) household use varies also region to region, urban to rural, vacation homes to at-home businesses; d) what's a "household"? -- a certain number of individuals? a single-family dwelling, whether occupied or not or however used?; and e) only a third of total electricity use is residential (see above), and only a third of total energy use is in the form of electricity (see below).

Electricity represented 39% of the total energy consumed in the U.S. in 2002. Wind power provided less than 5 million MW-h, about 0.17% of the electricity. At the end of 2001, the U.S. had 4,275 MW of wind power capacity installed (according to the American Wind Energy Association) and 4,685 MW at the end of 2002, an average during 2002 of 4,480 MW. (the useful output of <5 million MW-h therefore represents a capacity factor of 12.7%). Extrapolating this data to reach the Department of Energy's goal of 5% of electricity from wind in 2010 would require a 30-fold increase for a total installation of 88,000 1.5-MW towers, costing about $200 billion and covering over 10,000 square miles. As utilities start to rely on wind as a source, more towers over much wider areas and a larger high-capacity grid are required to try evening out the variability and providing enough surplus to meet demand peaks. As electricity use increases, even more will be required.