Compressed air converts natural gas to energy more efficiently
Utilities can use off-peak electricity to compress air and store it in airtight underground caverns. When released from storage, the air expands through a combustion turbine to create electricity.
The off-peak electricity powers a motor/generator that drives compressors to force air into an underground storage reservoir. This process typically occurs when utility system demands and electricity costs are the lowest. When electric power demand peaks during the day, the process is reversed. The compressed air is returned to the surface, heated by natural gas in combustors and run through high-pressure and low-pressure expanders to power the motor/generator to produce electricity.
In a conventional powerplant, a typical natural gas turbine consumes nearly two-thirds of the natural gas because the gas drives the machine's compressor. In contrast, a compressed-air storage plant uses low-cost, heated, compressed air to power the turbines and create on-peak electricity, conserving some natural gas.
The concept of using stored compressed-air energy to help generate electricity is more than 30 years old. Two plants currently exist—an 11-year-old plant in McIntosh, Ala., and a 23-year-old plant in Germany, both with the compressed air stored in caverns created by salt deposits.