Enlarge / A rendering of Silver City Energy Centre, a compressed air energy storage plant to be built by Hydrostor in Broken Hill, New South Wales, Australia. (credit: Hydrostor)

The need for long-duration energy storage, which helps to fill the longest gaps when wind and solar are not producing enough electricity to meet demand, is as clear as ever. Several technologies could help to meet this need.

But which approaches could be viable on a commercial scale?

Toronto-based Hydrostor Inc. is one of the businesses developing long-duration energy storage that has moved beyond lab scale and is now focusing on building big things. The company makes systems that store energy underground in the form of compressed air, which can be released to produce electricity for eight hours or longer.