The BIGGEST problem with clean energy

Air getting hotter in compressed air storage is actually a disadvantage causing losses due to thermodynamics. It costs extra power to increase the temperature and not all of it can be harnessed again. The idea of using blocks of carbon and heating them up is actually not surprising precisely because of this reason; the hotter you can get the material, the smaller the thermodynamic loss. If you heated them up by say a few degrees the efficiency would be too low to be economical. Using photovoltaics is a bit weird though because steam turbines can have 50% efficiency which is better than (affordable) solar panels. Both have great potential imo!