Research On Photovoltaic/Thermal Collector/Evaporator Used In Sahp Water Heating System

PV/T solar assisted heat pump(SAHP)water heating system can realize comprehensive utilization of photovoltaics and thermal energy which is beneficial to gain higher energy efficiency and economic viability.In the PV/T collector/ evaporator,the heat absorbed by the PV plane is extracted by the refrigerant and provided for the heat pump cycle,which can rise the evaporating temperature and enhance the performance of the system.At the same time,as the PV plane has been cooled,the electrical efficiency can be higher.Both theoretical and experimental analyses were performed on the performance of PV/T-SAHP.Experiments had been carried out under different circumstance conditions,and conventional solar assisted heat pump and PV plane without cooling are set as control group.The system COP is rising with increasing solar radiation and air temperature,but declining with increasing water temperature in the tank.While the sun radiation is high,the system COP can reach 5.In the experiment in May,the system average COP is 4.29,and in July,it is 3.75.Compared with conventional solar assisted heat pump,the thermal performance of PV/T system makes no big difference.Considering the electricity produced by PV/T,the energy consumption sharply decline and the integrated photovoltaic/thermal COP could be far higher than that of conventional solar assisted heat pump;Compared with the PV plane without cooling,PV/T system can effectively reduce the temperature of PV plane,which is as high as 70 ? without the heat pump working,and can decline to about 40 ? while it is operating,and even lower than the atmosphere temperature with weak solar radiation.The average electrical efficiency is 15.4 %,increasing by 26% compared to the PV plane without cooling.The simulation model is established for PV/T collector/evaporator,compressor,water tank,expansion valve and calculated in MATLAB.The data obtained in experiments is used for verification.The result shows that the average error of the simulation is about 5% which is acceptable in engineering application.Based on the simulation,the effects of solar radiation,air temperature,water temperature,evaporator size and the installation angle on the performance of PV/T-SAHP have been analyze.The effects of environmental parameter agree with the experimental results.The ideal installation angle in Shanghai is 27°.The annual operation simulation in Shanghai is analyzed.With average COP of 3.71,average thermal efficiency of 0.71 and overall energy efficiency of 1.04,PV/T-SAHP can work well in the whole year.