Tuesday, May 21, 2013

DOE Studies Compressed Air Wind Energy Storage

RICHLAND, Wash. – Enough Northwest wind energy to power about 85,000 homes each month could be stored in porous rocks deep underground for later use, according to a new, comprehensive study. Researchers at the Department of Energy's Pacific Northwest National Laboratory and Bonneville Power Administration identified two unique methods for this energy storage approach and two eastern Washington locations to put them into practice.

Compressed air energy storage plants could help save the region's abundant wind power — which is often produced at night when winds are strong and energy demand is low — for later, when demand is high and power supplies are more strained. These plants can also switch between energy storage and power generation within minutes, providing flexibility to balance the region's highly variable wind energy generation throughout the day.

All compressed air energy storage plants work under the same basic premise. When power is abundant, it's drawn from the electric grid and used to power a large air compressor, which pushes pressurized air into an underground geologic storage structure. Later, when power demand is high, the stored air is released back up to the surface, where it is heated and rushes through turbines to generate electricity.  Compressed air energy storage plants can re-generate as much as 80 percent of the electricity they take in.

The world's two existing compressed air energy storage plants — one in Alabama, the other in Germany — use man-made salt caverns to store excess electricity. The PNNL-BPA study examined a different approach: using natural, porous rock reservoirs that are deep underground to store renewable energy.

Interest in the technology has increased greatly in the past decade as utilities and others seek better ways to integrate renewable energy onto the power grid. About 13 percent, or nearly 8,600 megawatts, of the Northwest's power supply comes from of wind. This prompted BPA and PNNL to investigate whether the technology could be used in the Northwest.
To find potential sites, the research team reviewed the Columbia Plateau Province, a thick layer of volcanic basalt rock that covers much of the region. The team looked for underground basalt reservoirs that were at least 1,500 feet deep, 30 feet thick and close to high-voltage transmission lines, among other criteria.
They then examined public data from wells drilled for gas exploration or research at the Hanford Site in southeastern Washington. Well data was plugged into PNNL's STOMP computer model, which simulates the movement of fluids below ground, to determine how much air the various sites under consideration could reliably hold and return to the surface.

Analysis identified two particularly promising locations in eastern Washington. One location, dubbed the Columbia Hills Site, is just north of Boardman, Ore., on the Washington side of the Columbia River. The second, called the Yakima Minerals Site, is about 10 miles north of Selah, Wash., in an area called the Yakima Canyon.

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