4 ms·

CAES? Pumped hydro? I suspect even well insulated thermal stores end up more efficient.

• pfdietz 6y ago
  CAES? Obviously you have not bothered to do the arithmetic. The energy storage for CAES per unit of underground storage volume is two orders of magnitude lower than hydrogen. It's good for diurnal storage, not seasonal. As for pumped hydro. Let's suppose we want to store 10% of the annual US power demand in a pumped hydro reservoir with a 200m head. The volume required is about 2000 cubic kilometers, about four years of the total flow of the Mississippi River. I don't think this is terribly practical. Thermal storage may be competitive for efficiency, but the capital cost is likely to be higher, as you need more heat exchangers and cooling systems. Combustion turbines are cheap, especially simple cycle.
  • jacknews 6y ago
    Who said anything about underground storage?
    • pfdietz 6y ago
      Large scale use of hydrogen for grid-connected storage would involve storing the hydrogen underground. This is an order of magnitude cheaper (per unit of energy storage capacity) than storing it above ground. CAES also uses underground storage, and for the same reason. Trying to use CAES with above-ground storage for seasonal load leveling would be even more ludicrous. But in any case, the energy density argument I made is independent of just where the compressed gases are being stored.