I don't think you have a problem with thermo. The lower pressure gas will come out at a lower temperature. However heat is pretty common and cheap in the environment, so I suspect they simply plan to use free environmental heat to reheat the gas to nearly ambient temperature. The energy in the first place came from the compression process (work = pressure times change in volume). The compressed gas was initially hot, but this heat was likely lost during storage by conduction through its container. The PV work done on the gas is stored as both kinetic energy (moving gas molecules), and internal energy within the molecules themselves. In any case, some of this workenan be recovered during re-expansion, but whenever energy is transferred via non-adiabatic processes (heat flow) potential work is lost (i.e. system entropy increased).

I don't think you have a problem with thermo. The lower pressure gas will come out at a lower temperature. However heat is pretty common and cheap in the environment, so I suspect they simply plan to use free environmental heat to reheat the gas to nearly ambient temperature. The energy in the first place came from the compression process (work = pressure times change in volume). The compressed gas was initially hot, but this heat was likely lost during storage by conduction through its container. The PV work done on the gas is stored as both kinetic energy (moving gas molecules), and internal energy within the molecules themselves. In any case, some of this work can be recovered during re-expansion, but whenever energy is transferred via non-adiabatic processes (heat flow) potential work is lost (i.e. system entropy increased).