A reservoir west of Dallas Center in central Iowa, 30 miles from Des Moines, has been selected as the site for a compressed air energy storage (CAES) facility, according to the Iowa Association of Municipal Utilities, the project's primary supporter. Energy derived from wind power in Iowa will drive compressors that push the air underground. The Iowa Stored Energy Park (ISEP) will use air that has been stored underground to generate energy. When generation is needed by utilities, the compressed air would be released to drive natural-gas fired combustion turbines. The project is being developed by the Iowa Stored Energy Park Agency, which says it is expected to provide 268 MW of CAES generating power and use approximately 75 MW of wind power. The US Department of Energy and Sandia National Laboratories have provided $2.9 million in funding and technical support for the project. "Construction is to be completed by May 2011, with commercial operation to begin about July of 2011," says John Bilsten, vice president of the Iowa Stored Energy Park Agency and general manager of Algona Municipal Utilities. The system will only be economic if the difference between market prices for electricity at peak times is consistently higher than the price paid for electricity to store the energy in off-peak periods. The difference must cover the capital and operating costs of the device, which is often not the case.