A novel thermochemical composite sorption heat storage cycle was described using reversible solid-gas chemical reaction.The thermal energy storage and energy upgrade characteristics for the low-grade thermal energy was analyzed theoretically.Meanwhile

the experimental research was carried out by employing the MnCl2/SrCl2/NH3 as the working pair.The theoretical analysis suggested the thermochemical composite sorption heat storage cycle not only reduces the driving temperature of external heat source

but also can enhance significantly energy upgrade capacity compared to the thermochemical adsorption heat storage cycle.Compared to the thermochemical resorption energy storage cycle

it can provide the stable heat output temperature and further improve the thermal energy grade.Under the operation condition of charging temperature of 135℃ for the desorption of MnCl2 and temperature of 12℃ for the adsorption of SrCl2

desorption temperature of 90℃ for the regeneration of SrCl2

condensation/evaporation temperature of 12℃

discharging temperature of 40℃ for MnCl2 and SrCl2

the obtained thermal energy storage efficiency is 93.31%.The heat storage density of MnCl2-based composite sorbents is 4393.36 kJ·kg-1 MnCl2 or 3734.36 kJ·kg-1 composite sorbents.Meanwhile

the heat storage density of SrCl2-based composite sorbents is 1947.28 kJ·kg-1 SrCl2 or 1655.19 kJ·kg-1 composite sorbents.The heat storage density of materials is as 10 to 20 times as that of the sensible heat storage and phase change heat storage materials.Therefore

thermochemical composite sorption heat storage is feasible and a very potential way in storing heat.It can be used for recovering the low-grade thermal energy to promote the highly efficient utilization of thermal energy.