“What we do is quite different because we use water to compensate for our air pressure. This is what we’re building in Australia — we actually can purpose-build a cavity underground where we have an upper reservoir of water, and the cavity is like a lower reservoir, down about 300 m into bedrock.
“When we’re compressing air into that cavity, it’s displacing the water up to the upper reservoir. Then when we’re ready to generate electricity, just the weight of the water pushes the air out and up into the turbine that’s on the surface.
“We can generate a really large amount of electricity that way, and we can locate it very flexibly. We don’t need a pre-existing salt cavern — we can just site it and we build this cavity in areas of the grid where it’s actually required.”
Norman said CAES is similar to pumped hydro storage but doesn’t require as much water to provide the same generating capacity. It also has a long life, lasting over 30 years, as long as the rotating equipment on the surface is managed.
“We have a really big cost advantage over batteries as well,” he said, claiming that Hydrostar’s system would cost about half the price of a 50 or 100 MW battery system for the given scale."
