Hydrostor Advanced Compressed Air Energy Storage (A-CAES)  is a long duration bulk energy storage solution that is synchronous, emission-free and flexible to locate, including the ability to repurpose retired coal plants and leverage existing mining infrastructure.

AECOM and Hydrostor are partnered to jointly market and deliver Hydrostor A-CAES globally, accelerating the deployment of low-cost, bulk-energy storage. Like traditional CAES, Hydrostor A-CAES stores electricity in the form of compressed air. However, Hydrostor A-CAES differs from traditional CAES in that:

  • Compressed air is stored in a purpose-built underground cavern which is hydraulically connected to a closed-loop reservoir or a nearby body of water in an open loop configuration. The hydrostatic pressure of water results in a constant pressure condition during system operation.
  • The lower-pressure design allows for the use of proven standard frame size equipment (e.g., compressor, expander).
  • The A-CAES process is adiabatic in that heat of compression is recovered during the charging cycle, stored, and used to heat the pressurized air during the discharge cycle, eliminating the need for a natural gas reheat and increasing round-trip efficiency.

Hydrostor A-CAES is ideal for long-duration energy storage needs in the range of 50 to 500+ MW / 4 to 12 hours duration. The underground cavern can be purpose-built at a greenfield site or by modifying an existing mine to leverage existing subsurface infrastructure. With the former approach, the A-CAES facility can be flexibly located and increase locational value on the grid.

Hydrostor integrates reliable off-the-shelf components in a modular storage system design that is robust and cost-effective. Hydrostor A-CAES is uniquely suited to help address electricity system needs for dispatchable capacity, renewable integration and optimization, transmission deferral, ancillary services and behind-the-meter or remote applications for mines and other large industrial operations.