In 2005, Highview Power Storage began researching the possibility of utility scale energy storage using liquid air. Excess energy (during low-demand times) is used to compress air into a liquid, which can then be stored in insulated low-pressure tanks. When demand exceeds production, the liquid air is warmed and the resulting steam is used to drive the turbine of a generator.

According to Highview, cryogenic energy storage offers the following benefits:

It uses proven technology that’s been been around for years.

Regulations for cryogenic storage already exist.

Storage is at low pressure, making tanks less costly. (Tanks are insulated to keep the liquid air cold, but they’re still less expensive than room-temperature compressed air storage tanks.)

Air doesn’t explode and it’s non-toxic.

Liquid air has four times the energy density of compressed air.

During the storage process, ambient air is filtered to remove impurities. Water and CO2 are also removed because they’ll freeze solid. The resulting air is refrigerated. Some of the air condenses into a liquid at -196oC. That liquid air is stored in tanks. The remaining unliquified air is very cold, so it’s recycled and used to assist in the cooling process.

During the recovery process, exhaust gas is added to heat the liquid air. When the liquid is gasified, it drives a steam engine that generates electricity. In the process of heating the liquid air, the exhaust gas is chilled to -160oC. The “cold” is stored in a gravel bed and later recovered to help the chilling process used during energy storage. This reduces the amount of work the compressor has to do, making the process more efficient. Read Tom Lombardo's Full Article.