I too was wondering that as the ideal gas law states that PV = nRT. When you compress a gas it gets hotter, conversely, allowing it to decompress cools it. I as

I too was wondering that as the ideal gas law states that PV = nRT. When you compress a gas it gets hotter, conversely, allowing it to decompress cools it. I assume they store the heat energy... https://en.wikipedia.org/wiki/Compressed-air_energy_storage https://en.wikipedia.org/wiki/Compressed-air_energy_storage