Study Of Heat Transfer Performance And Mechanism Of Phase-change Cooling In High Concentration Photovoltaic(HCPV) System

With the increasing of solar cells power generation efficiency,more and more attention has been paid to the high concentrating photovoltaic(HCPV)systems in recent years.However,lots of heat was generated by solar cells under high concentration ratios.Thus,an effective cooling method for solar cells worked in HCPV system is a key issue.1.A cooling method of ethanol phase-change immersion cooling was proposed for thermal management of solar cells under high concentration ratios.An electric heating plate was adopted to simulate the heat generated by solar cells worked under high concentration ratios.A rectangular cooling receiver was designed and an indoor simulated concentrating photovoltaic self-running cooling system was developed.2.The feasibility of liquid phase-change immersion cooling method for heat dissipation of solar cells worked under high concentration ratios was investigated.The cooling system can worked self-running under concentrating ratios ranged between219.8X–398.4X and the circulating velocity can self-regulated according to the concentration ratios varying.The heat transfer performance results show that:the temperature of simulated solar cells is in the range of 87.3-88.5 ~oC,the surface heat transfer coefficient reaches up to 46.98 kW/(m~2·K)under 398.4X,which indicates the liquid phase-change immersion cooling method is effective for heat dissipation of solar cells.3.Electrochemical etching and mechanic drawing were adopted for surface modification of solar cells substrate and the effect of surface modification on heat transfer performance was analyzed.The results show the sample treated after electrochemical etching for 2h and mechanical drawing of 800 mesh show better heat transfer performance due to the porous and ravine structure of above treated surfaces,which will result in higher affinity of ethanol on the treated surface.The higher wettability leads to slower growth of bubbles formed on the surface and further declines the surface heat transfer resistance.During the process of boiling heat transfer,the higher local pumping action of the bubbles inside the porous and ravine structure towards the formed bubbles on the surface,which results in the increasing of the heat transfer coefficient.4.A triple-junction GaAs solar cell was adopted to study the effect of bubbles on incident light on the surface of solar cells by evaluating the electricity performance of solar cells.The results show the electricity performance without bubbles is better than that with bubbles,indicating the bubbles has negative effect on incident light.A mechanism model is developed to explain the bubbles effect on light and the results show that light loss in the interface of ethanol and bubble is the main reason to decline the electricity performance of solar cells.5.In order to avoid the bubbles effects on the solar cell performance,high power LED was adopted to simulate the dense-array solar cells.The liquid phase-change immersion cooling was applied for thermal management of high power LED and a self-running cooling system was developed.The cooling system can well control the temperature of LED and is more sensitive for higher heat.The junction temperature of LED is much lower than the limited value(120 ~oC)when the liquid filling ratio ranges between 33.14%-43.75%.The baffle set in the cooling receiver can improve the heat transfer performance of liquid phase-change immersion cooling by enhancing the update rate of bubbles on the surface of LED substrate.