Engineering360: "Long duration energy storage at the seabed"

Call me skeptical, but everything in the past regarding compressed air energy storage schemes are notoriously inefficient. Some have attempted to store the heat when compressing the air and then use that heat when extracting the energy from the compressed air, but those systems add significant complexity and cost. Not to mention you need very deep water nearby to access this pool of potential energy, akin to those who are able to harness pumped storage which has far fewer challenges than compressed air but most, if not all suitable sites have all been taken. Think of the energy you could store in Yosemite Valley.