An Adiabatic Compressed-Air Store in a Salt Cavern: Air Mass, Cavern Volume, Compression Heat Recovery and Round-Trip Budget for Twenty Thousand Usable Kilowatt-Hours

This paper sizes a adiabatic compressed-air storage system for a wind farm requiring overnight shifting of surplus generation. The duty calls for 2e+04 usable electrical kilowatt-hours delivered at a rated power of 3e+03 kilowatts. Working from a stated specific energy of 8 watt-hours per kilogram, an energy density of 4 watt-hours per litre, a usable depth-of-discharge fraction of 0.95, and a round-trip efficiency of 65 percent, the calculation gives a gross stored energy of 2.11e+04 kilowatt-hours, an active-store mass of 2.63e+06 kilograms, a complete system mass of 2.89e+06 kilograms, and a complete system volume of 5.79e+06 litres (5.79e+03 cubic metres). Full discharge at rated power lasts 6.67 hours, and a full recharge takes 10.4 hours at the stated charge power. Losses amount to 9.14e+03 kilowatt-hours per complete cycle, appearing as heat at average rates of 438 kilowatts during charging and 685 kilowatts during discharge. Standing loss is 0.01 percent of the stored energy per day. Life is limited by the cycle limit, giving 1e+04 effective full cycles, about 40 years at the assumed cycling rate, and a lifetime delivered throughput of 2e+05 megawatt-hours. All values are computed from the stated assumptions; the system is a design study and has not been built or measured. Status: SIMULATED, NOT MEASURED.