Compressed air energy storage

CAES involves compressing and storing air under pressure, either in underground geological caverns (e.g. salt caverns or digging artificial reservoirs) or in special above-ground containers. Electricity is converted into thermal and mechanical energy as hot compressed air. The compressed air is then heated and expanded in a gas turbine, which drives a generator to produce electricity. The process of compressing air from atmospheric pressure to a storage pressure (e.g. 70 bar) generates heat. In diabatic CAES plants, such as those currently existing, the heat generated is removed by coolers. However, the loss of this heat must then be compensated for during the expansion phase by heating the high-pressure air. Adiabatic CAES, in which the heat generated during the gas compression phase is stored and used to heat the compressed air during the expansion phase, is being researched, drastically reducing or even eliminating the need for additional heating, e.g. by burning natural gas, and thus potentially achieving higher efficiencies.