The Northwest’s geology holds the potential to offer a cavernous storage bank for excess energy on the regional power grid, according to a broad study released this week.Researchers with the Pacific Northwest National Laboratory and the Bonneville Power Administration believe the vast, porous underground basalt formations of eastern Washington and Oregon could provide relief for a transmission system sometimes strained by too much supply.The plan: Use storage plants to pump energy into the ground in the form of compressed air. The conversion would work two ways, allowing managers to deposit energy when it’s not needed, and withdraw it when it is. The study even developed conceptual designs for two large-scale facilities in Washington to make that happen at a practical cost.The findings give credence to a concept that’s been used elsewhere, but remains relatively unproven here.“We definitely have the geology in the Northwest that could work,” said Steve Knudsen, a BPA project manager involved in the study. “In a number of ways, it works even better.”The only existing compressed air energy storage plants are in Alabama and Germany. Both use man-made salt caverns. The energy bank concept is also used in the natural gas storage facilities that are common across the country.