DYK-Compressed Air Energy Storage (CAES)
CAES captures and stores compressed air in an underground cavern. To create electricity, the pressurized air is heated and expanded in an expansion turbine, driving a generator.
As of June 2018, there are 4 operating CAES systems in the U.S. with a combined rated power of 0.114 GW.
Existing CAES plants are based on the diabatic method, where the compression of the combustion air is separate from the gas turbine. The diabatic method can generate 3 times the output for every natural gas input, reduce CO2 emissions by 40-60%, and enable plant efficiencies of 42-55%.