CLASSICAL CAES

There are currently only two CAES facilities in operation worldwide. The first is a 270 MW unit that was constructed in Huntdorf, Germany in 1978 and the other, a 110 MW unit, was constructed in McIntosh, Alabama in 1991. Classical CAES facilities purchase inexpensive off-peak power and use it to adiabatically compress air into underground salt or limestone caverns. During peak-time, compressed air is drawn from the cavern to replace the compression phase in natural-gas-fired combustion turbines. The result is reduced operating costs for the gas turbine, as the compression phase typically consumes approximately one-half of the electricity generated.

Existing CAES systems suffer from poor thermal efficiency (due to adiabatic cycling), mandatory pairing with natural-gas-fired generation, are inherently large scale (with corresponding capital intensity) and are geographically constrained (i.e., limestone caverns are required).