Daily sorption thermal battery cycle for building applications

Abstract

The study propose firstly an absorption thermal energy storage (ATES) system designed for repeated operations on a daily base without any additional manipulation. The performance of the sorption thermal battery was analyzed by varying four parameters (mass flow ratio, number of exchanger heat transfer units (NTU), heat source, and cooling water temperature). The lower the cooling water temperature, the better was the performance, particularly for improving the energy storage density (ESD). Additionally, if low-temperature cooling water is used, the coefficient of performance (COP) with a 65 °C heat source is comparable to that with 95 °C. ESD increased with the increasing the heat source temperature, and the maximum COP was obtained when using a 75–85 °C heat source. To solve the crystallization problem, [DMIM][DMP], a type of ionic liquid, was applied as an absorbent. However, the COP of H2O-[DMIM][DMP] with a heat source temperature of 120 °C was lower that of H2O–LiBr with 95–100 °C. Therefore, it is advantageous to use H2O–LiBr to improve the sorption thermal battery performance. ESD and COP of the sorption thermal battery are 451.13 kJ/kg and 0.728, respectively, when using a 95 °C heat source and 32 °C cooling water.