Compressed air energy storage is the use of off-peak electricity to compress air, which is then stored underground, for example in a disused mine, a specially created cavern, or a natural geological feature. When electricity demand is high, the compressed air is burned with natural gas to run a turbine and generate electricity. Plants are designed to operate on a daily cycle, charging at night and discharging during the day.

 

The concept of compressed-air energy storage to help generate electricity is more than 30 years old. Two plants currently exist, in McIntosh, Alabama (completed in 1995), and in Huntorf, Germany (completed in 1983), both in caverns created by salt deposits. Another facility is under development in Norton, Ohio.