Simulation study on operational performance of photovoltaic/thermal combined CO2 heat pump water heater systems

In this paper, a simulation model for the photovoltaic/thermal (PV/T) combined CO2heat pump water heater system is developed using TRNSYS software and validated using measured data. The year-round operational characteristics and energy consumption characteristics of the system are simulated for supplying domestic hot water in a target building application in Beijing, and compared with those of the independent PV and independent CO2heat pump water heater system. The results show that the annual photovoltaic performance, system annual energy consumption and system COP of the PV/T combined CO2heat pump water heater system are better than those of the independent PV and independent CO2heat pump water heater system for supplying domestic hot water throughout the year. The annual average photovoltaic efficiency of the system is 12.61%, which is 2.56% higher than that of the independent PV and independent CO2heat pump water heater system. The annual energy consumption is 2 705.50 kWh, which is 3.41% lower than that of the independent PV and independent CO2heat pump water heater system. The annual average system COP is 3.20, which is 7.74% higher than that of the independent PV and independent CO2heat pump water heater system.