Hydrostor’s Toronto Island system

A Canadian company called Hydrostor has a new compressed-air energy storage system that it says is half the cost of grid-scale batteries and on par with adding a new natural gas plant to a grid.

The system, called Hydrostor Terra, uses electricity when it’s plentiful to compress air and send it underneath the ground into a specially constructed tank. While the system is compressing the air, it also takes the heat generated by the compressors and stores it in a thermal management system. Then, when electricity is in short supply, the Terra system sends that compressed air back up from underground and heats the surfacing air stream using the heat that was captured in the compressing process. The heated air moves a turbo-expander connected to a generator, which creates electricity.

Hydrostor’s method of capturing heat from the compression process is what sets the Terra project apart from other compressed-air energy systems (or CAES systems). Traditionally, CAES systems burn natural gas to heat […]