Compressed-air energy storage (CAES) uses off peak electricity to compress air into either an underground structure (e.g., a cavern, aquifer, or abandoned mine) or an above ground system of tanks or pipes. The compressed air is then mixed with natural gas, burned, and expanded in a modified gas turbine. In a conventional gas turbine, roughly two thirds of the power produced is consumed in pressurizing the air before combustion. CAES systems produce the same amount of electric power as a conventional gas turbine power plant using less than 40% of the fuel. Recent advancements in the technology include above-ground storage in empty natural gas tanks and ‘mini-CAES’, a transportable technology that can be installed at or near individual loads (e.g., on urban rooftops).
The first commercial CAES was a 290-MW unit built in Hundorf, Germany in 1978. The second commercial CAES was a 110-MW unit built in McIntosh, Alabama in 1991. Several more CAES plants are in various stages of the planning and permitting process.
Research is also ongoing to develop adiabatic CAES systems in which the heat of compression is stored and reused to heat the compressed air before expansion thus eliminating the use of natural gas in the system.
Updated April 2010
Ridge Energy Services
Electricity and Air Storage Enterprises (EASE)
Energy Storage and Power
Iowa Stored Energy Plant
New York State Electric & Gas Corporation
Pacific Gas & Electric (PG&E)
Southwest Solar Technologies