Numerical simulation and experimental validation of a micro-channel PV/T modules based direct-expansion solar heat pump system

This paper presents a novel solar driven direct-expansion heat pump system employing micro-channel PV/T modules as the evaporator. The system can provide both the electrical power and thermal energy used for space heating for buildings. Experimental work was carried out to investigate the performance of the system under real-life condition and numerical simulation work was carried out for the same condition as the experimentation using a two-dimensional model developed by the authors. This specialist simulation model contains energy balance calculation of individual models of components, i.e., models of the micro-channel PV/T module (evaporator), compressor, heat storage tank (condenser), electric expansion valve and testing room. The experimental and simulation results showed a good agreement each other, with the maximum error of 7.2% which is the temperature of refrigerant at the outlet of PV/T modules. The experimental average electrical, thermal and overall efficiencies of the PV/T module are 13.1%, 56.6% and 69.7%, respectively. While the simulated results are 13.7%, 55.0% and 68.7%, respectively. The average experimental and simulated COP of the system is 4.7 and 5.0, respectively. With the solar heat pump system providing energy for the room of 150 m2 in the real-life testing condition, the temperature of the room can remain at 18.5 °C which was high enough for the space heating. Comparison among the simulation and testing results indicated that the simulation model was reasonable for predicting the performance of the system and provided feasibility for analyzing the annual energy performance in the future.