A phase-change-material-assisted absorption thermal battery for space heating under low ambient temperatures

Abstract

Solar-driven Absorption Thermal Battery (ATB) is a promising technology for space heating. However, providing heating under low ambient temperatures seriously degrades the storage performance of ATB, which is still a major challenge. Therefore, this study proposed a Phase-Change-Material (PCM)-assisted ATB to recover and store the condensation heat in the charging process. Then, the recovered heat is used to heat the evaporator to strengthen the evaporation-absorption process. This study investigates two different PCMs: organic paraffin and inorganic hydrated salt. The dynamic behaviors and cycle performance of the basic and two PCM-assisted ATBs are compared. Then, parametric studies are conducted for a better system design. Results indicate that the PCM-assisted ATB can significantly enhance the Energy Storage Density (ESD) and slightly improve the Energy Storage Efficiency (ESE). The hydrated-salt-assisted ATB yields the best storage performance with an ESD of 141.5 kWh/m3 and an ESE of 0.78. In contrast, the basic ATB only obtains an ESD of 70.7 kWh/m3 and an ESE of 0.73. The discharging process is strengthened with the increase of phase change temperature, but the charging process is weakened. The maximum ESD of 160.1 kWh/m3 is achieved at the phase change temperature of 28 °C.