A sorption thermal storage system with large concentration glide

In this paper, a sorption thermal storage system with large concentration glide is proposed to achieve long term thermal storage with high energy storage density. The system consists of a storage subsystem and a cooling subsystem. In the charging process, the condensation of the storage subsystem is cooled by the cooling subsystem. The pressure of storage subsystem is decreased and its concentration glide is enlarged. The ammonia-water solution is chosen as working pair considering the subzero working condition. Performances of the proposed system and the conventional system are calculated and compared under heat input temperature of 90 °C. For the heating supply with temperature of 40 °C under ambient temperature of −10 °C, the proposed system obtains COP of 0.18 and energy density of 293.9 kJ/kg. The conventional system cannot deliver heat output under the same condition. For the cooling supply with temperature of -5 °C under ambient temperature of 30 °C, the proposed system obtains COP of 0.27 and energy density of 466.9 kJ/kg. Compared with the conventional system, 138% energy density enhancement and 21% COP degradation are achieved. The proposed system has higher energy density than the conventional system, especially when the heat source temperature or evaporation temperature is low.