The U.S. Department of Energy's Pacific Northwest National Laboratory is conducting a feasibility study into a unique energy storage method combining geothermal heat and underground compressed air energy storage.
When power is abundant, compressed air energy storage plants use it to power a large air compressor which pushes pressurized air into an underground geologic storage structure. 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.
There are two existing compressed air energy storage plants. One is in Alabama, the other is in Germany. Both use salt mine caverns to store excess energy.
The current study proposes to store the compressed air in natural porous basalt reservoirs deep underground in the Yakima Canyon north of Selah in Washington State. The region sometimes has more wind and hydroelectric power than it can use – particularly in Spring from the combination of heavy runoff from melting snow and a large amount of wind, which often blows at night when demand for electricity is low,
The proposed 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.
Project leader, Pete McGrail says that "Our hybrid facility concept significantly expands geothermal energy beyond its traditional use as a renewable baseload power generation technology."