California moves closer to attaining decarbonization and renewable energy penetration goals with plans for two 500 MW/5 GWh advanced compressed-air long-duration energy storage (A-CAES) projects. Each of these facilities engineered by Canada-based Hydrostor would be the world’s largest non-hydro energy storage system ever built.

A-CAES technology uses surplus electricity from the grid or renewable sources to operate an air compressor. The compressed air is then stored in an underground tank until energy is needed, at which point it is released through a turbine to generate electricity and fed back into the grid.3D modeling of a 500 MW project. Source: Hydrostor

Rather than vent the heat generated as the air is compressed, the Hydrostor system captures the heat generated during the compression process and stores it in a separate thermal storage tank. Use of this thermal resource to reheat air fed to the turbine stage increases system efficiency.

The A-CAES technology provides 12 or more hours of energy storage versus the one to four hours that current battery technologies can feasibly provide. The A-CAES systems also have longer lifespans of more than 50 years and a lower environmental impact than conventional alternatives currently available.

The first of the two California systems is expected to be operational by 2026.