Big Squeeze: Compressed Air For Wind Energy Storage

Compressed air is getting new attention as a large-scale energy storage technology from researchers in the Pacific Northwest, who have pegged two locations on the dry side of Washington as possible sites for putting different approaches to work.

The general idea: use often abundant excess wind power to squeeze air into an underground holding space. When energy demand is high, the air can be surfaced and heated, thus expanding to drive turbines and produce electricity.

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The Columbia Hills site could house a 207-megawatt conventional compressed air energy storage facility. (image via PNNL and BPA)

This first part of this equation – the excess wind power – isn’t just a theoretical proposition in the Northwest. The winds that drive the region’s thousands of turbines often blow hardest at night, when power demand is low. Plus, late-spring snowmelt flowing through dams on the Columbia and Snake rivers often leaves grid operators with more juice than they need, forcing big wind to actually shut down at times, to the dismay of turbine owners.

All of which explains why the Bonneville Power Administration was in on the hunt for potential compressed air storage sites with the Pacific Northwest National Laboratory.

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The Yakima Minerals site could house an 83-megawatt geothermal compressed air energy storage facility. (image via PNNL and BPA)

So what were the researchers looking for? “(U)nderground basalt reservoirs that were at least 1,500 feet deep, 30 feet thick and close to high-voltage transmission lines, among other criteria,” they said. They found two: “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.”

But because of the nature of the sites, different technologies – included a novel one – are envisioned by the scientists.

The Columbia Hills Site could access a nearby natural gas pipeline, making it a good fit for a conventional compressed air energy facility. Such a conventional facility would burn a small amount of natural gas to heat compressed air that’s released from underground storage. The heated air would then generate more than twice the power than a typical natural gas power plant.

The Yakima Minerals Site, however, doesn’t have easy access to natural gas. So the research team devised a different kind of compressed air energy storage facility: one that uses geothermal energy. This hybrid facility would extract geothermal heat from deep underground to power a chiller that would cool the facility’s air compressors, making them more efficient. Geothermal energy would also re-heat the air as it returns to the surface.

As promising as this sounds, note that there are only two commercial compressed air storage projects operating in the world today, one in Alabama and one in Germany. So there’s a reach element to this work. But the BPA plans to “perform an in-depth analysis of the net benefits compressed air energy storage could bring to the Pacific Northwest,” so we likely haven’t heard the last of this.

Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.