Hydrostor’s 4000 MWh compressed air storage project in line for U.S. DoE funding

North American LDES developer and operator Hydrostor received a conditional commitment from the DOE for a loan guarantee of up to $1.76 billion to develop a major LDES in project in California.

If the loan guarantee is finalized, Hydrostor’s Willow Rock Energy Storage Center could provide 500 MW/4000 MWh of LDES for the southern California grid. Located in Rosamond, California, Willow Rock will deploy advanced compressed air energy storage (CAES) that will provide more than eight hours of backup power to the region’s grid.

The final green light for Willow Rock depends on the DOE’s environmental review and Hydrostor must prove it can satisfy legal, technical, commercial, and financial conditions before the DOE makes a definitive decision to fund the loan guarantee. The proposed facility is also under review with the California Energy Commission.

If it gets the go-ahead on all fronts, construction is expected to begin in 2025, and commissioning in 2030.

Hydrostor’s CEO and co-founder, Curtis VanWalleghem, said the conditional commitment from the DOE was “a huge vote of confidence in Hydrostor’s technology, and shows how important energy storage will be as we prioritize the reliability and resiliency of the grid for years to come.”

Willow Rock would deploy Hydrostor’s advanced CAES technology, which the company claims improves on conventional CAES by solving problems that have thus far impeded its efficiency and wide-scale adoption. With conventional CAES less than 50% of energy is typically recoverable, but Willow Rock will pair a proprietary thermal storage system with the CAES to ensure that heat from the compression cycle is captured and stored and reused, instead of being released as waste.

Another problem with traditional CAES that Willow Rock claims to solve is the generation of power at a non-constant rate depending on the remaining underground air pressure. To overcome this limitation, Hydrostor uses water from an above-ground reservoir to maintain constant pressure in the cavern. Water condensed during the compression process will be captured and reused. This innovation also allows Hydrostor’s systems to be installed in a greater variety of underground conditions, whereas CAES has historically required the durability of salt caverns to overcome stress cycles from varying pressure.