As per energy storage news, approval is being sought for a 400MW advanced compressed air energy storage (A-CAES) project with eight hours of storage to be built in California by technology provider Hydrostor. 

The Canada-headquartered company is the first in the world to have built an operating commercial A-CAES facility, a much smaller 1.75MW project in Goderich, Ontario, with about 10MWh capacity based on its own technologies. 

Hydrostor has now filed an Application for Certification with the California Energy Commission for the 400MW / 3,200MWh Pecho Energy Storage Center it wants to build in the state’s San Luis Obispo County. Application for Certification (AFC) is the standard licensing process for power plants 50MW or greater that fall within the commission’s jurisdiction. 

The long-duration project would be bigger than even the gigawatt-hour scale lithium-ion battery storage systems that are being built in California, at double the size of the 1,600MWh Moss Landing Energy Storage Facility that was completed earlier this year. California lithium-ion battery plants also have an upper limit of four hours’ duration for which they can be economical to build while capturing market opportunities. 

The A-CAES technology developed by Hydrostor uses electricity to compress air which is then stored in a large underground cavern. Heat produced by the compression process is simultaneously run off as thermal storage. 

The compressed air is stored at constant pressure using water reservoirs which provide hydrostatic compression. When electricity is needed, the system is discharged by forcing air to the surface using hydrostatic pressure. The air is then combined with the stored heat and passes through turbines, generating electricity.