Investigation on the energy performance of using air-source heat pump to charge PCM storage tank

•The thermal and energy performance of using air-source heat pump to charge PCM storage is qualitatively and quantitatively investigated.•The effect of different water mass flow rate on the charging time is analyzed.•The effect of different water mass flow rate on the total energy use is analyzed.•The optimal water mass flow rate is identified for minimizing the total energy use in different stored thermal energy demand. Nowadays air-source heat pumps are widely used to collect heat from ambient air, which can reduce operating cost and protect environment when compared with fossil-based heating systems. To increase the flexibility of heat collection and supply, air-source heat pump should be used together with a thermal storage tank. In this heating system, air-source heat pump needs to charge the storage tank regularly based on a predefined time schedule. When a PCM storage tank is used, the charging completion time and the total energy use are nonlinearly relative to the charging water flow rate. This study, therefore, systematically investigates the relationships between the charge water flowrate and the charging completion time and the total energy use. These relationships are analyzed qualitatively and then evaluated quantitatively using case studies, according to which optimal water flow rate is identified.