Investigation Of Regenerative Direct-expansion Photovoltaic-solar Assisted Heat Pump With Composite Phase Change Materials

Solar energy is a high-quality renewable energy.With the development of society,the application of improving its utilization efficiency has been constantly innovative and concerned.As one of the main ways of solar energy utilization,the comprehensive utilization of solar photovoltaic/photothermal energy can not only generate electricity effectively in the application process,but also reduce the working temperature of photovoltaic modules when the thermal energy is utilized,so as to improve the photoelectric efficiency and the comprehensive utilization efficiency of solar energy.Solar assisted heat pump is a kind of solar photothermal utilization method which uses the solar energy as the evaporative heat source of the heat pump cycle.Based on the comprehensive utilization of solar photovoltaic/photothermal and solar assisted heat pump,a direct-expansion photovoltaic/solar assisted heat pump system with composite phase change materials(PCM-PV-SAHP)is proposed in this paper.The heat pump system is applied to the comprehensive utilization of solar photovoltaic/photothermal energy,and the heat on the photovoltaic cells is actively utilized to solve the problem that the photovoltaic panel's photoelectric efficiency decreases due to the rising temperature,so as to improve the performance of the heat pump system,improve the comprehensive utilization efficiency of solar energy and the stability of the system.In this paper,the paraffin/expanded graphite composite phase change material was prepared according to the actual temperature requirements of photovoltaic cells and heat pump systems,and a photovoltaic heat storage evaporator(PCM-PV-E)integrated with the composite phase change material was designed,the performance test platform of pcm-pv-sahp system was established,and the performance of pv-sahp system was tested.The experimental results showed that the average evaporation temperature of working medium increased to 22.26?.The COP of the system is 3.42,and the average power consumption of the compressor is lower than the rated power.The average photoelectric conversion efficiency of the system is 17.76%,which is 2.76% higher than the rated conversion efficiency of the components.The average comprehensive utilization efficiency of solar energy is 346.56%.In this paper,based on the physical model of PCM-PV-E,the numerical simulation of its temperature change process under sunshine is established,and the reliability of the simulation is verified by experiments.It is found that the temperature curve in the experiment and simulation results has the same trend of change,and the average error is 7.05%.In this paper,the temperature change process of PCM-PV-E using composite phase change materials with different density and ratio and under different environmental conditions are analyzed by numerical simulation,which has certain guiding significance for the application of the composite phase change materials in PCM-PV-E and the selection of its working environment.