Compressed air energy storage (CAES) is a way to store massive amounts of renewable power by compressing air at very high pressures and storing it in large underground caverns, depleted wells or aquifers. The compressed air can be released and run through turbines to generate power when wind turbines and solar plants reduce output and power is needed. Hundreds of hours of output can be stored, providing the ability to cover long doldrum wind periods or a series of cloudy days.
Compressed air is a gas, or a combination of ga...(WhatIs.com)
Currently, underground caverns and depleted wells are used to store natural gas. A nationwide network of CAES plants could use the same types of geographical formations to offer very economical energy storage. In the extreme event a cavern becomes fully depleted of air, most CAES turbines can also run in natural gas-only mode. Unlike a nuclear or coal plant, a plant that uses CAES is able to supply fully dispatchable power, which means that the plant is able to increase and decrease its output to match fluctuating customer demand. This flexibility is a major advantage for usefulness to the electric grid.
Dr. Joseph Romm explains more about CAES in "The Holy Grail of clean energy economy is in sight: Affordable storage for wind and solar."
Contributor: Dr. Joseph Romm