Solar-air hybrid source heat pump water heater: Performance characterization and comparison analysis

Abstract

Heat pump water heater(HPWH) can yield great energy saving for commercial and residential appliance. To enable the HPWH maintain efficient operation under diverse circumstances, the solar-air hybrid source heat pump water heater has been proposed. The configurations of solar-air series type, air-solar series type and solar-air parallel type have been discussed and compared in this paper. The dynamic model has been developed to identify the impacts of solar irradiation and environmental temperature. The results show that the solar-air hybrid source heat pump water heater can guarantee efficient operation under the ambient temperature of 10°C and solar irradiation of 100W/m2, with the average COPs of 2.68 for solar-air series type HPWH, 2.71 for air-solar series type HPWH and 2.69 for solar-air parallel type HPWH. The rise of ambient temperature can improve the evaporating capacity and condensing capacity leading to the increase of power consumption and COP for each type of solar-air hybrid source heat pump water heater. With the rise of solar irradiation, the heat gain at evaporation side increases leading to the rise of condensing capacity and COP. The air-solar series type HPWH can achieve the highest COP under a range of working conditions and solarair parallel type HPWH can provide the highest condensing capacity under lower solar irradiation.