A pioneer of technology that stores renewable energy as compressed air has unveiled $250m of backing from finance behemoth Goldman Sachs in what’s claimed as a “transformational” deal for long-duration storage.

Canada-based Hydrostor said the Goldman Sachs investment will be used to help build more than 1GW/8.7GWh of its Advanced Compressed Air Energy Storage (A-CAES) systems in California and Australia that would include the largest non-hydro-based energy storage plants seen globally.

CAES is one of a clutch of long-duration storage options tipped to rival battery technology as a means to store huge amounts of renewable energy over long periods, allowing wind and solar to more effectively integrate into grids.

Charlie Gailliot, partner and head of energy transition private equity investing for Goldman Sachs Asset Management, said: “As the world continues transitioning to sustainable and renewable energy sources, the need for utility-scale long-duration energy storage is clear, and Hydrostor’s A-CAES solution is well positioned to become a leading player in this emerging global market.”

Global ambitions

Hydrostor claims a differentiator for A-CAES from others of its ilk by using purpose-built caverns to store compressed air, rather than the underground salt caverns needed for other CAES systems that consequently face restrictions on where they can be deployed.

It tested the technology at its 1.75MW/10MWh Goderich facility in Ontario, completed in 2019, and now has almost 900MW of capacity under development in California and a 200MW project at Broken Hill in New South Wales, Australia.

Hydrostor said the Goldman Sachs preferred equity financing investment – which will be tied to project milestones – will also support the group’s expansion ambitions.

Its website shows a total 6GW pipeline that includes further projects in North and South America.

Hydrostor CEO Curtis VanWalleghem said: “this investment by Goldman Sachs... is transformational for Hydrostor and validates the competitiveness of our proprietary A-CAES solution as well as the strength of our pipeline of potential projects.”

How A-CAES works

Hydrostor’s A-CAES technology uses electricity from the grid or a renewables project to run a compressor that produces heated compressed air. The heat is extracted from this air stream and stored for later use inside the company's proprietary thermal store. The compressed air is meanwhile pumped into a purpose-built cavern part-filled with water, pushing the water to the surface of a closed-loop reservoir.

When electricity is required, the system is basically unlocked — the pressure of the stored water on top of the compressed air pushes the gas up a pipeline back to the surface, where it is then reheated by the stored heat. This hot, compressed air is then expanded through a turbine to generate electricity.