Experimental investigation on a strontium chloride/ammonia sorption heat storage system

Abstract

• A thermochemical sorption heat storage system has been established. • The total highest heat storage density is 1871.03 kJ/kg SrCl 2 composite sorbent. • The total highest heat storage efficiency of the sorption system is 92.74%. Thermochemical sorption heat storage based on solid-gas interaction is considered as a cutting-edge technology for harvesting solar energy and industrial waste heat due to the significant advantages of high heat storage density, flexible working modes and long-term storage capacity with negligible heat loss. As a vital technology to enhance energy infrastructures, the thermochemical sorption heat storage has aroused extensive interest in the past decade. In this work, a solid-gas thermochemical sorption system was established and investigated for recovering the thermal energy. Working pair of strontium chloride/ammonia was selected, and strontium chloride composite sorbents were synthesized using the expanded graphite as matrix. The heat storage performances of strontium chloride/ammonia sorption system at the different temperatures were experimentally investigated. Under the condition of 92 °C charging temperature, 40 °C discharging temperature and -5 ℃ condensation/evaporation temperature, the highest sorption heat storage density of the sorption system obtained is up to 1630.78 kJ/kg SrCl 2 (or 1386.16 kJ/kg composite sorbent), and the total heat storage density can reach 2201.21 kJ/kg SrCl 2 (or 1871.03 kJ/kg composite sorbent). The total energy efficiency of the sorption system increases from 74.71% to 92.74% with the heat storage temperature rising from 68 ℃ to 92 ℃. Results indicated that strontium chloride and its composites are promising heat storage materials, and revealed great potentials of thermochemical sorption heat storage technology for rational and efficient utilization of thermal energy.