compressed air battery using underground caverns

Alternate battery technology to chemical energy includes gravity and compressed air battery technology. What is the probability that these may see commercial reality? Storage of energy as heat, and then used as heat are widely used in heat pumps and direct storage of energy, but these technologies take renewable energy and instead of converting through chemistry, rely on gravity or pressure.

For a look at heavy blocks using gravity check out the article on gravity batteries

Compressed Air Batteries

Compressed air storage works on a similar theme to pumped hydro, using times of low prices to “charge up” and store significant amounts of energy. Instead of using water, rare in remote areas, it compresses air in suitable caverns, the type that can be found in old mines. One company, Hydrostor’s has A-CAES technology and claims to be able to deliver vast amounts of storage – in the case of the Broken Hill project in Australia up to 1,500MWh – enough to supply the town for days or even weeks.

Hydrostor announced in Jan 2022 it had secured a preferred equity financing commitment of $US250 million from Goldman Sachs for over 1.1GW, 8.7GWh of Advanced Compressed Air Energy Storage (A-CAES) projects in Australia and California.

Hydrostor's advanced compressed air energy storage (A-CAES) pilot plant in Ontario, Canada
Image from Hydrostore

Warning: Much hype. (See AFR) The potential for Energy Vault’s gravity-based, building block storage technology has attracted some of the world’s biggest participants in the decarbonisation journey – Saudi Aramco, BHP and now Korea Zinc. A potential $US32 billion ($44.6 billion) of projects using the technology could be deployed over the next five-10 years, the Switzerland-based company says.

Pumped Hydro is an alternate battery technology

For a full discussion check out this article on pumped hydro. The key metrics for pumped hydro is the head height (300 m or more) and the volume of water available.