Project Owner
Docket Number
500 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 by Gem A-CAES LLC, a wholly owned subsidiary of Hydrostor, Inc. The project would be located at 8684 Sweetser Road in Rosamond, Kern County, California.

WRESC would be a nominal 500-megawatt (MW), 4,000 MW-hour (MWh), advanced compressed air energy storage (A-CAES) facility capable of charging and discharging daily. WRESC would compress air into a purpose-built underground cavern, using electricity from the grid, most likely off-peak, excess, or surplus electricity. The heat from the air compression process would be captured and stored in an aboveground thermal storage system. The compressed air would then be stored in the cavern under the pressure of a hydrostatic head created by an onsite, aboveground water reservoir. When electricity is needed by the grid, the compressed air would be released using the hydrostatic head pressure, re-heated using the stored thermal energy, and directed through aboveground turbine-generators to produce electricity.

WRESC’s major equipment would consist of five all-electric air compressor trains, five 100-MW air-driven power turbine generators, heat exchangers, thermal heat storage, an underground compressed air storage cavern, an aboveground water reservoir, miscellaneous aboveground support facilities, and a 10.9-mile interconnection to the existing Southern California Edison (SCE) Whirlwind Substation.

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 Gem 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 Gem AFC complete
  • 8/11/2022 - Informational Hearing and Public Site Visit

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.


Project Manager

Leonidas Payne
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