excerpt:
American Electric Power�^TMs batteries will be used to smooth the power delivery from wind turbines. They can charge at night, when the wind is strong but prices are low, and give the electricity back the next afternoon, when there is hardly any wind but power prices are many times higher, company officials said. That strategy would reduce the amount of power generated from inefficient peak-demand units.

The batteries can also insert energy into the grid during brief voltage drops, reducing the chance of a blackout and stabilizing the grid for all users. They may also delay or eliminate the need for transmission upgrades in some areas, the company said.

At least at this stage, saving money by storing a windmill�^TMs production for peak-price hours will be difficult. The cost is very high, $27 million for six megawatts of capacity, or about $4,500 a kilowatt, including the price of substation improvements. Building a gas turbine of that size to meet peak needs would cost substantially less. But the battery system would be able to store power made from wind, a form of generation that does not produce any carbon dioxide.

The batteries can each deliver one megawatt of power �" enough to run a medium-size shopping center �" for a little more than seven hours. Replenished nightly, they give back about 80 percent of the electricity put into them. Each is the size of a double-decker bus, and installation is not permanent; they can be moved to another site as the need arises.

• http://www.nytimes.com/2007/09/11/business/11battery.html?ei=5089&en=ee88fae88ab8ea85&ex=1347163200&partner=rssyahoo&emc=rss&pagewanted=print

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