Heat pump assisted open three-phase sorption thermal battery for efficient heat storage.

• Heat pump assisted open three-phase sorption thermal battery is proposed. • System performs three patterns in liquid desorption, crystallization and dehydration stages. • The maximum average system COP is 7.54, corresponding charging temperature is 40 °C. • The optimal end state of sorbent for LiCl is either liquid desorption or dehydration stage. Open three-phase sorption thermal battery has recently received particular attention for its high energy storage density. Meanwhile, air source heat pump can be considered a potential heat source for open three-phase sorption thermal battery due to its broad applicability and high energy efficiency. However, research on the intergration of these two systems are rarely reported. A heat pump assisted sorption thermal batttery is proposed and evaluated based on a general thermodynamic analysis for charging process. Three indicators are targeted in terms of coefficient of performance (COP), energy storage rate and energy storage density. Results show that system characteristics present three different patterns, i.e., liquid desorption, crystallization and dehydration stages. When ambient condition is 20 °C and 60% RH, the maximum system average COP is 7.53, the corresponding charge temperature is 40 °C and end-state sorption capacity is 2.33 g/g. The optimal charging condition for comprehensive performance index is greatly affected by the weights of basic indicators. When the weight of energy storage density is dominating, three-phase sorption performs better. Within the range of this study, the optimal sorbent end state locates on either liquid desorption stage or dehydration line. [ABSTRACT FROM AUTHOR]