Comparison study on performance of a hybrid solar-assisted CO2 heat pump

This paper studies the cooling performance and the energy-saving potential of a novel hybrid solar-assisted CO2 heat pump. This novel hybrid heat pump integrates a solar thermal driven absorption chiller (ABS) and a conventional CO2 heat pump together. The solar thermal driven absorption chiller is used to super-cool CO2 in vapor-compression loop when working fluid leaves the gas cooler. Comparison study of the ideal cycles shows the feasibility and the advantage of the studied hybrid heat pump over the unit without solar cooling. With solar-assisted absorption cooling, the COP of the device can reach 3.8 when temperature difference of super-cooling is 7.7 °C (Gas cooler outlet temperature and evaporator temperature are assumed as 38 °C and 7 °C). Moreover, simulation in TRNSYS for heating, ventilation and air-conditioning (HVAC) system is performed. The simulation results are validated by experiment. The influences of some external factors, such as: weather, domestic hot water (DHW) load and indoor load, are analyzed. Energy consumption in one case study shows that the hybrid CO2 heat pump can save 19.3% electricity consumption per year compared with conventional CO2 heat pump for whole year operation in Shanghai.