Air force propels clean energy plan

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Two other air-storage caverns already exist in Alabama and Germany, demonstrating that the technology is not far-fetched. But the Iowa wind hole would be roughly twice as large and the only one to use wind power to pump air under the earth.

The $200 million scheme, a brain-child of the Iowa Association of Municipal Utilities, is attracting curious interest as states and power providers across the country try to meet the nation's growing demand for energy while reducing the output of carbon dioxide and other gases blamed for global warming. 

Construction of the stored energy project is slated to begin in 2009, and the system is to be operating by 2011. It would work like this: giant wind-powered turbines would pump air into a porous rock formation roughly 3,000 feet below the earth, and that compressed air would later be released, spinning turbines that would generate up to 260 megawatts of electricity.

Air also could be pumped underground using conventionally generated power at times of non-peak demand for electricity, such as at night, and released to generate power when electric rates are high. That’s how the air storage sites in Alabama and Germany operate. 

While those sites store air in much smaller salt caverns, the Iowa aquifer can store potentially billions of cubic feet of air and should be able to generate electricity for eight to 10 hours a day, five days a week, said Bob Haug, director of the consortium behind the project.

The storage capacity boosts economic benefits of wind farms because it allows utilities to generate power even when the wind isn’t blowing, said Haug. Iowa ranks third in the nation in wind-energy production, trailing only Texas and California. 

Although the stored air is combined with natural gas to push the combustion turbines, the amount of gas is less than half that required by a conventional turbine, adding to the project's environmental benefits.

More than 100 municipal utilities from Iowa, Minnesota and the Dakotas are expected to join in financing the construction of the air storage site and will be able to tap into the power it produces. The U.S. Department of Energy provided $3.5 million to research the plan, along with $800,000 from the utilities association and $50,000 from the state of Iowa's Economic Development Fund. 

The project is just one example of how states are trying to develop cleaner alternative sources of power. Iowa Gov. Chet Culver (D) is pushing for a $100 million fund to develop the state's renewable energy industry, now based largely on producing ethanol from corn.

Iowa also is one of 23 states to set goals to produce as much as 30 percent of their electricity from renewable energies such as wind, solar, hydro- or geothermal sources.

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