The proposed project, known as the Iowa Stored Energy Park (IESP), will use low-cost, off-peak electricity -- and wind energy that is not being sold on the grid at that time -- to store air in an underground geologic structure of porous rock located 3,000 feet underground, beneath layers of impermeable cap rock. The air will be injected under pressure, pushing back water stored in the rock.

The rock will hold air much like a sponge holds water. Then, as demand for electricity rises, the stored air will be released, heated, and used to drive generators -- in turn producing electricity for residents in Iowa, Minnesota and the Dakotas.

"Iowa is a leader in wind production but we have not developed a feasible way to store the abundant energy produced by wind. ISEP is the solution for storing energy. The project just makes sense. As an Iowan, I want to keep the clean and healthy quality of life here. The Iowa Stored Energy Park will provide needed electricity for our state, and also be environmentally friendly. We all want to lessen our dependence on fossil fuels. ISEP helps us accomplish that as well," said John Bilsten, general manager for the Algona Municipal Utilities.

Although CAES has been in use for over 20 years -- and similar methods are used to store natural gas underground in numerous parts of the world -- currently cavern air storage is only used in two other locations. The first CAES plant, a 290 MW facility, was started up in Huntorf, Germany in 1978, and a 110 MW plant commenced operation in McIntosh, Alabama in 1991.

In 2003, interested members of the Iowa Association of Municipal Utilities (IAMU), a group representing publicly owned utilities, formed a study committee to develop the concept of the ISEP. Several underground rock structures in Iowa were investigated, and within the past six weeks, studies confirmed that a site in Dallas Center, Iowa, has the adequate size, depth, and cap rock structure - all necessary geologic features - to allow development of the project to proceed.

"A study commissioned by IAMU several years ago suggested that municipal's needs in the future would include intermediate generation. At about the same time, we became acquainted with CAES technology, which is an intermediate resource. Finally, Bob Haug, Executive Director of IAMU, suggested that combining wind energy for compression with CAES would be a logical combination. We put it all together and have been working on it ever since," said Kent Holst, Development Director of the Iowa Stored Energy Park.

While the U.S. Department of Energy is fully backing the project, with both research and financial support, the board of trustees for ISEP is also working to secure additional funding from investors for further development. The cost of the storage infrastructure, generating facility, and associated components is estimated at $200,000-225,000. This does not include any wind facilities, said Holst.

Further studies of the site are now underway, and Holst hopes that construction on the park will commence in two years. The project is expected to be fully operational and providing electricity to Iowa and surrounding states by May 2011.

"It's a milestone for Iowa. It's a milestone for the Department of Energy. And, it's a milestone for the country. The Iowa Stored Energy Park could be a role model for other states and it could help the United States become a greener country," Imre Gyuk, Energy Storage Research Program Manager for the U.S. Department of Energy.