Nebraska utility tests underground storage of air

COLUMBUS, Neb. (AP) _ A Nebraska utility will pump compressed air 3,000 feet underground to see whether it can be stored there for later use in generating electricity.

The Nebraska Public Power District will use 14 compressors to inject 3 billion cubic feet of air into an underground geological formation that had been mined for natural gas, the Columbus Telegram said (http://bit.ly/O3P10V).

The one-year test was expected to cost about $8.14 million. NPPD's board of directors was told last week that the project was needed to determine whether the formation would hold air stored at 830 to 1,000 pounds per square inch over a long period of time.

NPPD has an agreement with KEBRH Operating LLC, a Colorado-based natural gas provider, to use the more than the 40,000-acre underground storage facility. The formation is situated near the Nebraska Panhandle town of Big Springs in Deuel County. It's part of the Dakota sandstone formation that covers parts of Kansas, Nebraska, Iowa, Minnesota and Wisconsin.

The site was mined for natural gas during the 1950s and `60s until supplies were exhausted.

NPPD will use natural gas-powered compressors for the test, but units operated by electricity would be installed if the project were to move forward.

The test will begin in 2014, after the injection well has been installed.

A decision on whether to build a power plant on the site won't be made until mid-2015, with construction beginning the following year. The plant would become operational in 2019.

Michael Matheson, an NPPD generation strategies engineer, said the facility would be designed to generate between 100 and 300 megawatts, depending on the test results. NPPD spokesman Mark Becker said 300 megawatts is enough energy to serve between 20,000 and 45,000 average Nebraska homes.

A smaller unit could be installed at first, Matheson said, with upgrades made as the need arises.

The price per kilowatt hour would be comparable to electricity generated by a natural gas plant, Matheson told The Associated Press.

``When the demand for electricity is down at night, for example, you have excess capacity,'' Matheson said, that could then be used to store compressed air for use in generating power when the demand is higher.

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