Monday, January 03, 2005

The promise of green energy

An article by Alison Hawkes in todays' Intelligencer from northeast Pennsylvania states,
"Wayne-based Community Energy Inc. is set to build a $30 million wind farm early next year in Bear Creek Township [Pa.], 10 miles southeast of Wilkes-Barre. Thirteen wind turbines will pump 20 megawatts onto the grid, enough to power 10,000 homes."
According to Community Energy, 20 MW is the capacity, not the output. It will only very rarely "pump" 20 MW into the grid. Two-thirds of the time, it will be feeding less than its annual average of 3-6 MW (representing average output of 15%-30% of capacity). Divided by "10,000 homes," that's only 300-600 watts each on average (and much less two-thirds of the time).

The average load of a household in the U.S. is over 1,100 watts (more accurately, per-capita residential use averages 500 watts). Ignoring the fact the electricity use is highly variable by hour, day, and season, and ignoring the fact that only 35% of electricity use is residential, and ignoring the fact that wind production rarely corresponds with demand, the 20-MW facility would therefore produce the amount of electricity used by 2,600-5,300 "homes."

Because "homes" is a deliberately undefined unit, and because the aerogenerators would be providing electricity to offices and factories as well, it would be more informative to state that the 20-MW facility would produce the amount of electricity used by 2,100-4,100 people.

But very little of the power produced will correspond with moments of demand on the grid. In western Denmark, for example, only 16% of the aerogenerator infeed could be used. The rest had to be dumped. Considering that experience, this $30,000,000 subsidy-financed project to industrialize a mountain range with 400-ft windmills will actually supply the equivalent electricity needs of only 330-670 people.

And ignoring the fact that electricity accounts for only 39% of energy use in the U.S. . . .