Structure Design And Performance Study Of The Thermal Collector Of Photovoltaic Thermal Integrated System

Photovoltaic/Thermal (PV/T) system combines the function of photovoltaic cellsand solar thermal collector, which converts the solar energy into electricity, and at thesame time outputs thermal energy through the fluid heated by the thermal collector.The system yields both electricity and heat, thus the integrate utilization efficiency ofsolar energy is improved. The paper aims at enhancing the photo-thermal performanceof PV/T system at the conditions of the generating efficiency is not decreased. As thethermal efficiency of the system mainly depends on its collector structure, design thestructure becomes the main work of this paper. Then the heat transfer performance ofPV/T system with this structure has been researched.Firstly, the paper conducted the theoretical analyses of flow and heat transfer inthe thermal collector of the PV/T system. Through the study of the mechanism ofcoupled heat transfer both conduction and convection, the process of energytransitivity in the system and the trend of energy flow has been understand. After thecorrelation between heat transfer and flow been analyzed, we know what the maininfluence factors on the photo-thermal efficiency is, and how to improve it.The paper works on improving the photo-thermal efficiency mainly by the meansof designing a better structure of thermal collector. The major structure parametersaffecting the heat transfer performance are the type of collector plate wrapping aroundthe tube, the diameter and wall thickness of collector tube, the thickness of plate, andthe spacing between tubes. As the CFD simulation method has the advantage of lowcost and short period to solve this kind of question, this paper employs the commonlyused CFD software Fluent to simulate the different thermal collector models, whichare combinations of varied parameters mentioned above. And the heat transferperformance of different structure model has been studied. Then the optimal thermalcollector structure has been determined, which makes the photo-thermal efficiency ofPV/T system reach the best.The research shows that the heat transfer performance of thermal collector isbetter when the type of collector plate wrapping around tube chooses completelywrapping rather than partially wrapping. As to the collector parameters of thediameter and thickness of collector tube and the plate thickness, the performance ofthe collector reaches the best when they are5mm,0.8mm and0.8mm respectively.Then the heat transfer performance of3models with different tube spacing has been compared, we get that the tube spacing between collector tubes should choose50mm.After the optimal PV/T thermal collector structure has been determined, research onthe photo-thermal efficiency of the PV/T system with this collector structure. Mainlythe influence of inlet velocity to the heat transfer performance has been studied. Withthe increase of inlet velocity, the heat carried off by water of unite flow volume andthe outlet temperature both decrease.