In the renewable energy field, wind turbines have played an important step, but today the future of wind energy may come from the underground. The compressed-air energy storage plants could be the solution. Air is pumped into large underground formations where it can be used later to deliver the large amount of energy that it previously received.
During the night, the electricity is very cheap, and by running compressors, air can be pumped into a cavern or vessel at 750 psi. In the middle of the day, when electricity is expensive, the compressed air is preheated with the heat generated and stored during compression and then used to help power a turbine.
Unlike lead acid battery storage (about $3000 per kilowatt), the compressed air energy storage (CAES) is relatively low on efficiency and prices can go to about $1000 per kilowatt of storage, according to a study made by Electric Power Research Institute (EPRI).
Currently, the U.S. government has a few CAES projects underway:
- Pacific Gas and Electric is working at a 300MW CAES project
- New York State Electric and Gas is currently planning a CAES project that involves pumping compressed air into a salt cavern in upstate New York
According to the Electric Power Research Institute, up to 80 percent of the U.S. has geology suitable for CAES. The institute also established that a single 300MW CAES plant would require about 22 million cubic feet of storage space, yielding about eight hours of electricity.