Global engineering and project delivery firm Hatch has formed a strategic project execution partnership and equity investment with long‑duration energy storage (LDES) developer Hydrostor around the Willow Rock Energy Storage Center in California. The agreement will see Hatch lead the design and delivery of the 500 MW Advanced Compressed Air Energy Storage (A‑CAES) facility, one of the first large‑scale LDES assets of its kind in the US.
Willow Rock, in late‑stage development, has already secured final permitting approval from the California Energy Commission and is designed to deliver 4,000 MWh of energy, equivalent to about eight hours of full power output. The project is intended to provide dispatchable, long‑duration storage for California’s grid as electricity demand and renewable penetration grow.
Hydrostor’s A‑CAES technology, which uses underground air storage caverns and low temperature systems, grew out of earlier “liquid air” storage concepts yet relies strictly on compressed air with water‑based cooling and heating. The company and Hatch say the project reflects a shared focus on scalable, bankable LDES solutions that can support grid reliability over decades.
The partnership includes a direct equity stake in Hydrostor by Hatch, underscoring confidence in both the technology and the firm’s global project pipeline. Executives from both companies said the collaboration will help accelerate the transition from demonstration‑scale storage to commercial‑scale deployment at a time when many LDES technologies still struggle to secure long‑term revenue mechanisms.
Willow Rock is slated to become the largest A‑CAES project in the world, with groundbreaking expected later this year.
