Underwater compressed-air energy storage: Could it work?
My Clean Break column in today’s Toronto Star begins with a look at Toronto-based Hydrostor, an energy-storage startup with a unique idea. Hydrostor’s concept is simple, in many ways. It starts with big tubular balloons the size of a bus submerged 80 meters or more under water — anchored, for example, to a lake bed. On the surface a compressor system uses off-peak, low-cost electricity to pump air into the balloons at high pressure. As the balloons or bags expand the weight of the water above them compress the air. When electricity needs to be dispatched, the air is let out of the balloons and piped back to a turboexpander turbine on the surface that generates power. The company figures about 200 of these balloons, called accumulators, would create a system big enough to supply 2 megawatts for four hours. As far as cost goes, it would fall between conventional pumped storage and conventional compressed-air storage (in salt caverns), according to Hydrostor CEO Curtis VanWalleghem.
Neat idea — though obviously studies would have to be done to assess environmental impacts on the body of water. Still, the fact that 50 per cent of ther world’s population is located near bodies of water, and the fact that Hydrostor’s system uses off-the-shelf components and is highly scalable, this could be a nice niche in the emerging market for grid-scale energy storage. VanWalleghem estimates at this point that the round-trip efficiency of the system is in the ballpark of 70 per cent, which is competitive with other storage technologies, such as zinc-bromide flow battery systems offered by companies such as Premium Power.
The rest of my column urges Ontario to begin taking a more serious look at the regulatory and policy changes required to enable the integration of new technologies into the provincial grid.