A-CAES Project

About the project

The Rosamond A-CAES Project is a full scale Advanced Compressed Air Energy Storage (A-CAES) facility that is under advanced development in the United States. The proposed facility will provide 500 MW of capacity, turning California’s growing solar and wind resources into on-demand peaking capacity while allowing for the closure of emitting fossil fuel generating stations and maximizing transmission system utilization. 

  • Location:Rosamond,  California, USA
  • Capacity/Energy: 500 MW and up to 12 hours
  • Owner:Hydrostor along with project development partners
  • Application: Renewables integration, replacement of fossil fuel generation, 
  •                            transmission optimization
  • In-service:As early as 2024

As California moves towards the objective of achieving 100% carbon-free electricity by 2045, it will require bulk-scale, long-duration storage in order to integrate increasing renewables and provide the necessary alternatives to meeting peak demand without the use of fossil fuels. The Rosamond A-CAES Project represents a cost-effective, emissions-free option to provide incremental new, non-emitting capacity and integrate large amounts of renewable resources in the High Desert area.

Project Location

The Rosamond A-CAES Project will be located near Rosamond, a census-designated place (CDP) in Kern County, California, USA. 


General A-CAES Benefits

As a long duration energy storage resource, A-CAES offers unique capabilities to the grid, including:

  • Long-duration storage: Essential for integrating increasing supply of renewable energy.
  • Lower environmental footprint: Uses only air, rock and weight of water. No chemicals or contaminants, no disposal liabilities, no fire risks unlike batteries. Smaller land and water footprint and no need for additional, expensive transmission lines as compared to pumped hydro.
  • Low cost: Much more cost effective than commercial alternatives, 50-year lifespan, unlimited cycling, no performance degradation.
  • Flexible siting capability: Enabling locations close to grid needs in most cases, unlike pumped hydro.
  • Grid reliability & ancillary services: Similar generating characteristics to fossil-fired power plants, providing key services in support of grid reliability.

Rosamond A-CAES Project Benefits

The Rosamond A-CAES Project provides a number of benefits to the regional electricity system and local stakeholders, including:

    • Facilitating delivery of renewables: Deliver renewable energy into the LA Basin by eliminating curtailment and enabling further growth in the High Desert Solar Resource Area and Tehachapi Wind Resource Area, while facilitating near-term delivery of solar generation into the Rosamond Switching Station (already 970 MW of renewables in the interconnection queue).
    • Enabling firm capacity: Delivery of firm capacity in-region and into the LA Basin along the Owens Valley Corridor, while ensuring reliable capacity well into the future as long duration storage becomes increasingly important to reliably serve load.
    • Providing synchronous storage capacity: Address forward-looking voltage support issues along the Barren Ridge corridor due to increasing levels of asynchronous renewable penetration through the provision of synchronous inertia (A-CAES provides 2x level of synchronous inertia as compared to Static VAR Compensators per unit of capacity).
    • Delivering transmission system value: Maximize transmission system utilization by relieving transmission constraints on energy delivery, shaping wind output to reduce the need for reserving transmission capacity, as well as potential to improve local reliability for Owens Valley distribution system.
    • Offering staged expansion options: Options to cost-effectively expand either storage duration (i.e. MWh’s of storage) or capacity (i.e. MW’s of capacity) allowing for adjustment of the project’s configuration in the future as circumstances and needs change.
    • Achieving environmental objectives: Supports California’s objectives of reducing its GHG emissions 40% below 1990 levels by 2030 and achieving 100% carbon-free electricity by 2045, providing an emission-free alternative to meeting peak demand without the use of fossil fuels.
    • Supporting technological diversification: Offers both a technology hedge as well as different value streams relative to the other storage technologies, supporting a portfolio of clean energy technologies, each providing certain benefits.
    • Driving economic growth: Provides diversified job opportunities and generates significant regional economic development from both the construction and operation of the project. Delivers greater direct and indirect benefits versus lithium-ion batteries.

                  Project Activity              Direct Jobs                                   Indirect Jobs
                  Construction                   Up to 2,600 person-years           Up to 2,800 person-years
                  Operations (ongoing)    Up to 25 full-time equivalents    Up to 90 full-time equivalents


The Rosamond A-CAES Project is being led by the following consortium and preferred delivery partners: 

Meridiam Logo (PRNewsFoto/Meridiam) (PRNewsFoto/Meridiam)

International infrastructure fund and global developer with experience across multiple sectors, specializing in sustainable infrastructure and energy transition projects.


Leading compressed air energy storage company with differentiated long duration, synchronous storage technology that can be flexibly sited. 

AECOM logo

Preferred vendor and global provider of architecture, design, engineering, and construction services headquartered in southern California. 

Rosamond image by SkiDragon – Own work, CC BY-SA 3.0.