Project Owner
Docket Number
520 MW
8684 Sweetser Road in Rosamond, Kern County, California
Project Status
Under Review
Project Type
Application for Certification
Project Description

The Willow Rock Energy Storage Center (WRESC) is proposed compressed air storage energy storage facility by Gem A-CAES LLC (Applicant), a wholly owned subsidiary of Hydrostor, Inc. 

On December 3, 2021, the Applicant filed its original Application for Certification (AFC) for the project located at 8684 Sweetser Road in Rosamond, Kern County. In March 2024, the Applicant filed a Supplemental AFC for the project, changing the location to 88.6 acres of private land immediately north of Dawn Road and between State Route (SR) 14 and Sierra Highway within unincorporated Kern County, California, approximately 4 miles north of Rosamond, California. The new project site is on undeveloped land in an area zoned Limited Agriculture (A-1) District. The area surrounding the project boundary is largely undeveloped with very sparse residential development; the nearest residence is approximately 0.8 mile northwest of the northwest corner of the WRESC site.

WRESC would be a nominal 520-megawatt (MW) gross (500 MW net) and 4,160 megawatt-hour (MWh) gross (4,000 MWh net) facility using Hydrostor, Inc.’s proprietary, advanced compressed air energy storage (A-CAES) technology. The overall facility would consist of four nominal 130 MW (gross) power turbine trains, outputting a total of 500 MW net at the point of interconnection. Each train would contain an electric motor-driven air compressor drivetrain, heat exchangers, an air turbine generator, air exhaust stacks, and ancillary equipment. Each train would share a common set of thermal storage tanks (hot and cold water), as well as the air storage cavern. The WRESC would interconnect to Southern California Edison’s Whirlwind Substation located southwest of the WRESC at the intersection of 170th Street W and Rosamond Boulevard, via a new approximately 19-mile 230-kilovolt (kV) generation-tie (gen-tie) line.  

Presiding Member: Andrew McAllister, Commissioner

Associate Member: Noemi Gallardo, Commissioner

Hearing Officer: Renee Webster-Hawkins/Ralph Lee

  • 12/2/2021 - Application for Certification (AFC) filed
  • 12/30/2021 - Staff's Data Adequacy Recommendation
  • 1/27/2022 - CEC Order concurring with the executive director’s recommendation and finding that the filing is deficient
  • 7/5/2022 - Staff's second Data Adequacy Recommendation
  • 7/14/2002 - CEC Order concurring with the executive director’s recommendation and finding the AFC complete
  • 8/11/2022 - Informational Hearing and Public Site Visit
  • 8/9/2023 - Committee Order suspending proceeding
  • 3/8/2024 - Supplemental Application for Certification filed
  • 3/26/2024 - Supplemental application fee received

Power Plant Certification and Exemption Processes

The CEC has the exclusive authority to certify all thermal power plants 50 megawatts (MW) and larger and related facilities proposed for construction in California. The Application for Certification (AFC) process is a certified regulatory program under the California Environmental Quality Act (CEQA). As a certified regulatory program, the CEC does not prepare environmental impact reports (EIRs) in an AFC proceeding, but instead prepares environmental assessment documents that are functionally equivalent to EIRs. A certificate issued by the CEC is in lieu of any permit, certificate, or similar document otherwise required by any state, local or regional agency, or federal agency to the extent permitted by federal law, and supersedes any applicable statute, ordinance, or regulation of any state, local, or regional agency, or federal agency to the extent permitted by federal law.


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Leonidas Payne
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