December 24, 2004


Every announcement of a wind-farm proposal includes the claim of how many homes it "will" power, misleading people to think that it is a steady source. (Not to mention that the unit, "homes," is whatever the salespeople want it to be and ignores the fact that most electricity use is not residential.) In fact, two-thirds of the time the output from wind turbines is not significant.

Only occasionally does the output approach the nominal power rating, so that rare event is cited with the conditional tense, typically a claim of how much of a district's electricity "could" be produced by the wind turbines. Here again, not mentioned is the fact that such an event is more like an unwelcome surge on the grid, since demand is already being met by other sources when the wind suddenly picks up. And if the grid can adjust quickly, then it must also be prepared for the moment the wind generation suddenly drops.

So, as the west Danish grid manager, Eltra, has admitted, most wind-generated electricity must be dumped.

Another rare event is when the industry moves beyond the easily manipulative "will" and "could" to cite actual figures for existing facilities. Even there, they confuse the facts.

As in Denmark's famous "20% electricity from wind," the number reflects the output from the turbines as a percentage of the electrical energy consumed. It does not, however, tell us how much of the wind-generated power was actually used. In western Denmark, for example, only 16% of the wind production did not have to be dumped. That is, the 20% figure should be corrected to barely 3% of Denmark's electricity provided by wind.

That is obviously why Denmark has not closed down a fifth of their fossil-fueled generating plants. In fact, they haven't been able to close down even one.

The clear test of wind power is whether it is able to change existing patterns of energy use. It is not enough to say how much power the turbines generate. How much do they actually contribute? And does that contribution actually affect the use of other sources?