Compressed Air Energy Storage In The Northwest — Enough Wind Energy To Power 85,000 Homes For 1 Month Can Be Stored In Porous Rocks

Around 85,000 households in the Northwest could be powered every month by the energy that could be stored deep underground in the region’s porous rock, according to new research. By utilizing such an energy storage solution, the region’s substantial wind energy resources could be put to full use.

The work, done by researchers at the Department of Energy’s Pacific Northwest National Laboratory and Bonneville Power Administration, has identified two practical methods for putting this energy storage approach into practice, and also two very well-suited locations in Eastern Washington.

The compressed air energy storage solution is an extremely appealing one for the region because of the abundant wind energy potential there. This energy is often generated at night when the winds in the region are strongest. Unfortunately, energy demands are lowest at that time. So, a means of being able to produce maximum amounts of energy when the potential is highest and simply save this energy for later use is very appealing. One significant advantage of the compressed air solution is that such plants can be designed to switch between energy storage and power generation very quickly — within minutes.

“With Renewable Portfolio Standards requiring states to have as much as 20 or 30 percent of their electricity come from variable sources such as wind and the sun, compressed air energy storage plants can play a valuable role in helping manage and integrate renewable power onto the Northwest’s electric grid,” said Steve Knudsen, who managed the study for the BPA.

The press release gets into the details:

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 human-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.

After taking all of this data into account and analyzing it — two sites in Eastern Washington stood out for their potential. The Columbia Hills Site on the one hand, located just north of Boardman, Oregon, on the Washington side of the Columbia River. And the Yakima Minerals Site on the other, located around 10 miles north of Selah, Washington.

The two sites are quite different, though, and most-suited for two completely different types of compressed air energy storage. The Columbia Hills Site is more suited for what would be considered a conventional compressed air energy facility. This means that it would use small amounts 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 is quite a bit different, though. Since it doesn’t have access to gas, the researchers had to come up with a different type of design — one relying on geothermal energy. This design works by extracting geothermal heat from deep down, which is used to run a chiller that cools the facility’s air compressors, thus improving efficiency. The geothermal energy could then be used to re-heat the air as it is returning to the surface.

“Combining geothermal energy with compressed air energy storage is a creative concept that was developed to tackle engineering issues at the Yakima Minerals Site,” said PNNL Laboratory Fellow and project leader Pete McGrail. “Our hybrid facility concept significantly expands geothermal energy beyond its traditional use as a renewable baseload power generation technology.”

The researchers note that such energy storage systems could also be used to store the excess energy that is often produced during the spring by the region’s hydroelectric plants, as a result of melting snow.

The next step for those involved will be to do an in-depth analysis, quantifying the benefits that such systems could provide to the region. After that, a commercial compressed air energy storage demonstration project will hopefully be started by one of the region’s utility companies.

In closing, here’s a brief overview of the two potential projects:

Columbia Hills Site
• Location: north of Boardman, Oregon, on Washington side of Columbia River
• Plant type: Conventional, which pairs compressed air storage with a natural gas power plant.
• Power generation capacity: 207 megawatts
• Energy storage capacity: 231 megawatts
• Estimated levelized power cost: as low as 6.4 cents per kilowatt-hour
• Would work well for frequent energy storage
• Continuous storage for up to 40 days

Yakima Minerals Site
• Location: 10 miles north of Selah, Washington
• Plant type: Hybrid, which pairs geothermal heat with compressed air storage
• Power generation capacity: 83 megawatts
• Energy storage capacity: 150 megawatts
• Estimated levelized power cost: as low as 11.8 cents per kilowatt-hour
• No greenhouse gas emissions
• Potential for future expansion

Featured image credit: Kyle Field | CleanTechnica