Canadian company Hydrostor is developing a 500 MW plant based on Advanced Compressed Air Energy Storage (A-CAES) technology in California, i.e. a system Generates electricity from turbines powered by compressed air previously stored underground.

Hydrostor was founded in 2010, and built its first pilot plant in 2015, then built a small operational A-CAES installation in Canada in 2019, which distributes more than 10 MWh of energy to commercial facilities and is a reserve for peaks. Power is required from the electric grid.

Hydrostor’s goal is precise Replacing computers are powered by lithium batteries, which are more expensive and can save fewer hours of energy. Usually these accumulators charge electricity from renewable sources and can be used not only to meet peak demand but also to replace renewables when there is no sun for photovoltaic panels or wind for wind turbines.

Air instead of batteries

The A-CAES system consists of an underground plant that drives compressors. By compressing, the air heats up and this heat is stored in an adiabatic thermal system, which means that heat cannot be exchanged but work is done. Meanwhile Compressed air is pushed into the subsoil to a depth of about 600 meters in tanks that contain it.

When energy is needed, the system releases compressed air, which returns to the surface, adding stored heat, and It sends gas through wind turbines to generate electricity.

The system is hydrostatically balanced: until the wind blows, underground tanks are filled with water and connected by pipes to a tank on the surface, a kind of swimming pool. As compressed air fills the cave, it pushes the water through the tubes to the surface. The process is reversed when compressed air is used for energy. This balance ensures that the compressed air is always at the same pressure.

A 500 megawatt (4,000 MW) plant to be built by Hydrostar in California’s San Joaquin Valley will include reservoirs. Two American football fields (about 110 meters by 50 meters) are about 100 meters high.

Canada has an operational 1.75 MW plant 60% efficiency compared to 90% obtainable from a system with lithium batteriesBecause each step of compression, heat transfer, and water balance subtracts energy from the system.

However, the construction of the plant does not require new technologies and uses components that have been used by the oil and gas industry for decades. Also, stored energy is represented metaphorically by compressed air stored underground, which is maintained by hydrostatic equilibrium and allows for energy storage. It can store more time than the charge of lithium batteries.