A Thermochemical Lime Store for Seasonal Building Heat: Quicklime Mass, Hydration Heat, Reactor Volume and Summer-to-Winter Retention for Fifteen Hundred Usable Thermal Kilowatt-Hours

This paper sizes a thermochemical lime storage system for a housing block requiring summer heat to be carried into winter without standing losses. The duty calls for 1.5e+03 usable thermal kilowatt-hours delivered at a rated power of 80 kilowatts. Working from a stated specific energy of 220 watt-hours per kilogram, an energy density of 350 watt-hours per litre, a usable depth-of-discharge fraction of 0.9, and a round-trip efficiency of 85 percent, the calculation gives a gross stored energy of 1.67e+03 kilowatt-hours, an active-store mass of 7.58e+03 kilograms, a complete system mass of 1.17e+04 kilograms, and a complete system volume of 7.38e+03 litres (7.38 cubic metres). Full discharge at rated power lasts 18.8 hours, and a full recharge takes 25.8 hours at the stated charge power. Losses amount to 271 kilowatt-hours per complete cycle, appearing as heat at average rates of 5.25 kilowatts during charging and 7.23 kilowatts during discharge. Standing loss is 0 percent of the stored energy per day. Life is limited by the cycle limit, giving 1e+03 effective full cycles, about 4 years at the assumed cycling rate, and a lifetime delivered throughput of 1.5e+03 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.