A group of utilities in Iowa, Minnesota and the Dakotas plan to spend $200 million on a project in Iowa that would store energy generated by wind turbines.
The Iowa Stored Energy Park would essentially act as a “battery” for wind energy, said Bob Haub, executive director of the Iowa Association of Municipal Utilities. Wind farms in Iowa, Minnesota and the Dakotas would ship energy over the power grid to the storage park near Des Moines.
Excel Energy and the federal government are experimenting with ways to “store” wind power in the form of hydrogen, but the Iowa project would employ a far simpler strategy that would include the following steps:
–Pressurized air would be injected into a sandstone aquifer, temporarily displacing some of the water in the aquifer.
–Electricity from wind turbines would power compressors, and a pipe would deliver underground air compressed to 900 to 1,000 pounds per square inch.
–The compression of millions of cubic feet of air would be used to turn the blades of a generator during nights and weekends, when wind power often sells for next to nothing.
The cavern complex would produce 268 megawatts of electricity to be sold to Midwest utilities on the grid – enough to turn on the lights in 268,000 homes.
Wind parks pay for themselves when demand and electricity rates are higher – during weekdays and on hot summer days. But when electricity is most needed, sometimes the wind isn’t blowing.
The storage park would get around that problem by slowly releasing pressurized air from the aquifer to turn the blades of a generator otherwise powered by natural gas. Metered valves would control the release of the pressurized air. Similar operations already are used to store natural gas underground across the nation.
Kent Holst, development director of the stored energy park, said the plan could transform the economics of wind power.
With the storage park option, the utility owners will be able to store and produce energy at a price equivalent to 6.5 cents per kilowatt hour, then sell the energy at peak times for 8 to 10 cents a kilowatt hour.
Similar plants already are operating in Alabama and Germany.
23 March 2007
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