Wind Power Facts

The most frequently unknown or misunderstood facts about industrial wind power


How big are the towers?

Industrial wind turbines are not the benign little structures you might see in a schoolyard or behind someone's house.

The widespread GE 1.5-megawatt model, for example, consists of 116-ft blades atop a 212-ft tower for a total height of 328 feet. The blades sweep an area just under an acre. The 1.8-megawatt Vestas V90 from Denmark is also common. Its 148-ft blades (sweeping more than 1.5 acres) are on a 262-ft tower, totaling 410 feet. Also gaining use in the U.S. is the 2-megawatt Gamesa G87 from Spain, which sports 143-ft blades (just under 1.5 acres) on a 256-ft tower, totaling 399 feet.

Many existing models and new ones now coming out reach well over 400 feet high, with higher towers and extra-long blades designed to turn the generator in less-than-ideal sites.

The base of the steel tower is anchored in a platform of more than a thousand tons of concrete and steel rebar, 30 to 50 feet across and anywhere from 6 to 30 feet deep. Pylons may be driven down farther to help anchor the platform.

The gearbox -- which transforms the slow turning of the blades to a faster rotor speed -- and the generator are massive pieces of machinery housed in a bus-sized container, called the nacelle, at the top of the tower. The blades are attached to the rotor hub at one end of the nacelle. Some nacelles include a helicopter landing pad.

On the GE 1.5-megawatt model, the nacelle alone weighs more than 56 tons, the blade assembly weighs more than 36 tons, and the tower itself weighs about 71 tons, for a total weight of 164 tons. The corresponding weights for the Vestas V90 are 75, 40, and 152, total 267 tons, and for the Gamesa G87 72, 42, and 220, total 334 tons.

Besides the noise and vibrations such huge moving machines unavoidably generate, they must be topped with flashing lights day and night to increase their visibility.


So the footprint is less than 50 feet?

Hardly. First of all, new roads have to be built, or existing ones need to be extensively "upgraded." It requires more than an old dirt logging track to get a 150-ft blade, a 70-ton nacelle, or the huge crane needed to put it all together up a mountain. The road needs to be wide, straight, and very strong.

Several acres around each turbine have to be cleared as well. For best performance, the GE 1.5-megawatt turbine needs 82 unobstructed acres around it and the Vestas V90 needs 111. On a ridgeline, the sloping away of the land and the hope that the wind is always perpendicular to the line of the ridge mean that about 5 acres are actually cleared around each turbine.

Access to the area around the turbines must be strictly limited because of physical danger.

A facility may also require a new substation or two, as well as new transmission lines.

The combination of all this -- road building, extensive clearing, and the installed facility itself -- not only significantly degrades and fragments wildlife habitat but also has a serious effect on erosion and water flow, not to mention the aesthetics of a mountainside or open land.

And of course the visual intrusion affects the landscape for miles around.


Still, we need to reduce our dependence on foreign oil.

Wind turbines produce electricity, not gasoline or heating oil. In the U.S., oil (mostly in the form of the otherwise unusable sludge left by gasoline refinement) is used to produce only 1% of our electricity. Our electricity has nothing to do with our dependence on oil, either domestic or foreign.


We need to reduce our use of coal, then, or nuclear.

Burning coal provides around half, atomic fission more than a fifth, and burning natural gas about a sixth of our electricity. All of these have serious environmental and geopolitical shortcomings that we do indeed need to reduce.

Unfortunately, wind turbines can't replace them -- or even reduce their use or slow their growth.

Because of the way the electric grid works, constantly matching supply with demand to avoid dips and surges of power, the variable production of wind turbines is treated as part of the demand side of the equation. A base level of power is provided from large plants, and other plants are kept burning to be able to provide the maximum likely power (peak load) needed as it varies through the day. As demand drops, those plants are diverted from power generation, and as demand rises they are brought back on to resume generating the needed power. These plants burn fuel whether or not they are producing electricity.

In other words, these peak load plants must continue burning fuel when demand falls or wind production rises, because either trend may reverse at any time. The effect of wind turbines, because they are out of the control of the grid's dispatchers, just like user demand, is only to bring the spinning standby plants in and out of production. But, again, the plants continue to burn their fuel. And the additional fluctuations of wind power add to the cost and inefficiency of that burning.

A further irony is that because an increase in wind power capacity is seen on the grid as an increase in demand fluctuation, it requires dedication of other grid capacity to cover it. Rather than reducing other sources, wind power requires building more conventional capacity, particularly natural gas–fired plants, which it then forces to operate less efficiently.


Also see National Wind Watch FAQs and factsheets.

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