Study On The Performance Of A New Type Of PV/T-air Double Heat Source Heat Pump Hot Water System

The technology of solar energy and heat pump is an effective way to solveenergy crisis and improve existing energy efficiency. In recent years, solarphotovoltaic power generation has been widely promoted and applied, but theefficiency of photovoltaic power generation is still low, the majority solar radiationabsorbed is converted into heat energy and not been effectively utilized; Air sourceheat pump has a good energy savings, but the surface of the evaporator frost willoccur the phenomena of frosting with decreasing outdoor temperature when thesystem runs in cold winter of northern,which seriously affect the performance ofheating performance.Firstly, after summarizing the results of previous researchers perfected theexisting laboratory bench of new type of solar-air double heat source composite heatpump system. Preliminary, replaced and updated the components of heat pump system,then built the system of solar photovoltaic/thermal collector and heat dissipation endsin the later. Pre-experiments mainly used power heating instead of solar lowtemperature hot water, adjusting the size of the electrical heating power guaranteesolar water temperature entering the evaporator. Latter, the joint run of the solarphotovoltaic/thermal collector and air source heat pump were experimental studied,analyzing solar photovoltaic power and solar thermal power of the solarphotovoltaic/thermal and instantaneous heat gain of heat pump system changed withsolar irradiance and running time, while the efficiency of photovoltaic and thermalefficiency of solar photovoltaic/thermal collector, overall efficiency, COP of heatpump and EER were evaluated.Secondly, the experimental results of double heat source composite heat pumpsystem in the operation mode of double heat source heat pump and single air heatsource heat pump showed that COP of the operation mode of double heat source heatpump and single air heat source heat pump operation mode decreased with runningtime, while improved with ambient temperature. The evaporation temperature ofdouble heat source heat pump operation mode was higher than single air heat sourceoperation mode, thus the performance of the former was superior to the later.Then, a mathematical model of double heat source composite heat pump systemis established, the results showed that the establishment of the system model is feasible, but still needs further improvement for the aim of optimization and laidingthe foundation of future systems.Finally， the experimental results of the later showed: During the solarphotovoltaic/thermal collector and air source heat pump run, solar irradiance changed638W/m2-773W/m2, ambient temperature was1.7℃-3.1℃, the maximuminstantaneous photovoltaic efficiency was18.03%, thermal efficiency was35.3%,overall efficiency was53.33%, comprehensive efficiency was81.96%. The dischargepressure of compressor increased from7.73bar to19.72bar, the compression ratiofrom1.98to5.43, the maximum heating power was2.79kW, and the minimum was1.34kW, while COP with an average of3.03reduced from5.61to1.69.Comprehensive energy efficiency of the system with an average of2.99ranged from1.33to6.07. Compared with the pre-experiments, solar-air double heat sourcecomposite heat pump system has certain advantages. EER is a majorevaluationindicator of the heat pump system performance, we can see from the results analysis,the system has some practical value.