In this Michael fundamentally misunderstands the full cycle thermodynamics and energy flows of CAES systems. He is very cocksure but actually wrong. For example Hydrostors system would be capable of storing more energy than an mgh équivalant phes plant with effective management of heat either towards an isothermal or adiabatic system. For example with an isothermal approach the substantial additional energy above the mgh potential of the reservoir can be extracted as heat from the environment through multistage expansion and heat exchange. At sufficient pressure that means that 2/3’s+ of the energy can come from the environment.