| The photoelectric efficiency of ordinary solar cell is10%-20%, besides a asmall part of the incident solar radiation（80%—90%）which are not converted intoelectricity is reflected back out, the rest will be transformed into heat andradiation,then lost, so full utilization of the remaining heat energy and transmissionthermal in the process of photovoltaic power generation will help improve thecomprehensive utilization rate of solar energy in unit area of the whole system.Therefore, the photovoltaic is integrated with the heat, which constitute photovoltaicand thermal (PV/T) system, has the vital significance.This dissertation designed a set of PV/T system, the transparent photovoltaiccomponent with the conventional flat-plate collector were directly coupled as a whole,and described the principle and features of solar photovoltaic, solar thermal utilization,analyzed the current development level and utilization status of the solar system athome and abroad, and has made the summary.The prepared PV/T composite system, independent photovoltaic system andconventional flat-plate collector were experimental study under the solar radiation inKunming area. The test results show that the average electrical efficiency, thermalefficiency, comprehensive efficiency of the composite system of PV/T is13.2%,44%,54.2%, respectively, The test also showed that the lower the initial temperature, themore the water production of system, and the smaller the heat loss, the higher thecomprehensive performance of the solar PV/T system.Contrasting the electrical characteristics of PV/T system and the stand-alonephotovoltaic system, results show that the electrical characteristics of PV/T systemreduced by0.2%compare with independent photovoltaic system. the reasons for thisphenomenon lies that the heat on the back of the transparent photovoltaic componenthas not been timely absorbed by the heat collecting plate, lead to the rise oftemperature of the transparent photovoltaic component, the decline of electricalefficiency.Contrasting the thermal performance of PV/T and conventional flat-plate collector,the results show that the thermal efficiency of the PV/T system is lower about30% compare with the collector. On one hand, there exist air layer between the transparentcomponent and a heat absorbing plate, and the thermal resistance is high, theeffectiveness of heat transfer is limited, so the overall efficiency is not high. On theother hand, due to low transmittance of occlusion of solar cell (only0.37), it producedless heat through direct radiation to the heat collecting plate. In addition, there maybehave some connection with arrangement of transparent assembly cell sheet.Heat transfer in a PV/T system is analyzed, photovoltaic cell coverage and airinterlayer spacing have effect on the thermal performance of the system, which isanalyzed. Contrasting coverage rate of photovoltaic cells for PV/T system0.33andthat0.63, the following several aspects is different. First, the average watertemperature rose from45.3℃to51.4℃, second, daily useful energy increases from5.56MJ to7.80MJ, third, efficiency increased from34.18%to45.82%, increased by11.64%, fourth, electrical efficiency increased from13.03%to13.16%, increased by0.13%. The water tank temperature and daily yield can reach the requirements ofthermal performance test of the domestic water heating system after the battery coverwas reduced. This shows that the design scheme which directly coupled thetransparent component and the conventional flat-plate collector for integrated PV/Tsystem is feasible. Besides, the spacing between the transparent component and thecollector air layer were analyzed. Finally, this paper presents the optimizationscheme.This system can be used in City Industrial and business park, residential,community hospitals, in particular to the power shortage, no water supply area.
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