【作者】 孙勇；

【导师】 王一平；

【作者基本信息】 天津大学 ， 环境化工， 2014， 博士

【摘要】 聚光光伏（CPV）发电技术能够有效的提高光伏系统发电效率，降低光伏系统发电成本，近年来越来越受到人们的重视。但是，如何有效地实现聚光太阳电池的冷却是聚光光伏发电系统设计中的一个难点。针对传统聚光光伏冷却方式的不足，提出把直接接触式液浸冷却技术用于聚光光伏系统，并以线性聚光光伏为应用实例，建立了线性液浸聚光光伏冷却系统，从如下方面对其性能进行了实验研究和模拟分析。1、研究了二甲基硅油液膜厚度对太阳电池电性能的影响。结果表明：与无液浸液体时电池电性能相比，一定厚度的薄液膜液浸能够提高聚光硅电池和聚光三结砷化镓电池的电性能；但电池正面有液浸液体存在时，电性能随液膜厚度的增加而下降，因此较薄的电池正面的液膜厚度有利于电池电性能的提高。2、设计了线性条形平面镜聚光系统，通过几何关系推导得出：聚光器相邻镜片互不遮挡时的最小安装间距随镜片位置角和阳光入射角的增大而增大，当阳光入射角和接收器安装角度均为45°时，最小安装间距为镜片宽度的1.414倍；通过实验测量得出由24片镜片组成的聚光器原型的聚光比为12.90X。3、设计了矩形窄缝流道接收器，对其性能实验研究表明：聚光比为9.61X、太阳直射辐照度（DNI）920W/m2、硅油进口15℃条件下，当接收器电池段雷诺准数Re范围在1671~8359时，组件平均温度31~20℃，对流传热系数280~1000W/(m2K)；经270天二甲基硅油长期液浸后聚光硅电池电性能没有发生衰减。4、建立了矩形窄缝流道接收器的数值模型，模拟分析表明：电池组件最优安装位置为流道高度方向上的中间位置，接收器进、出口段长度对电池温度影响不大，流道高度越小越有利于获得好的传热性能，但流动阻力也越大，流道的优化高度为10mm；通过拟合分析得到了接收器对流传热系数和摩擦系数关联式。5、设计了用于液浸液体冷却的二甲基硅油-甲醇物系液液直接接触相变换热实验，实验结果表明：升液管轴向温度随高度增加呈先降低然后趋于稳定的趋势，升液管体积传热系数能够达到22~34kW/(m3K)，平均气含率能够达到0.05~0.5，此气含率范围内，以甲醇蒸气气提为推动力的条件下，在具有优化结构的矩形窄缝液浸接收器中能够实现硅油在接收器电池段Re范围在1500~7500。更多还原

【Abstract】 Concentration photovoltaic (CPV) systems have high sunlight to electricityefficient, and has been considered as an effective way to reduce the cost ofphotovoltaic systems, so more and more attention has been paid to CPV technology inrecent years. However, effectively cooling of CPV solar cells is one important issuewhen designing CPV systems. Aiming at eliminating the shortages of conventionalCPV cooling method, a direct liquid-immersion cooling method was proposed forlinear CPV systems. In the present thesis, experimental and numerical simlationworks on performance study of liquid-immersion cooling for linear CPV systemswere carried out as follows.1. Effect of silicon oil thickness on solar cell electricity performance wasinvestigated experimentally. The results show that the electrical characteristics of bothconcentrator silicon solar cells and concentrating triple-junction (CTJ) GaAs solarcells are improved compared with solar cells without liquid immersion. However, theelectrical characteristics of both concentrator silicon solar cells and CTJ GaAs solarcells are decreased with increasing silicon oil thickness when immersed by liquid.This indicates that the thickness of immersion liquid on front surface of solar cellshould be as thin as possible.2. A linear flat mirror concentrator system was designed, and according to resultsdeduced from the geometric relation, it can be seen that the minimum distancebetween two adjacent mirrors without shadow increases with mirror location angleand sunlight incident angle. When the mirror location angle and sunlight incidentangle is equal to45o, the minimum distance between two adjacent mirrors is equal to1.414times of mirror width. According experimental test result, the concentrationratio of the concentrator prototype is12.90X.3. A narrow rectangular channel receiver was designed and its performance wasinvestigated experimentally. The results show that the cell temperature can becontrolled in the range of20-31°C at a DNI of920W/m2, silicon oil inlet temperatureof15°C and Reynolds numbers of receiver solar cell region variation from8359to1671, and the correspondging convective heat transfer coefficient was280-1000W/(m2K). Electrical performance of the cells immersed in the silicon oil is stable andno obvious efficiency degradation was observed after immersed for270days. 4. Computational fluid dynamics models of narrow rectangular channel receiverswere established and the simulation results show that the optimum installationposition of solar cells is in the middle along the channel height direction. The lengthof the channel inlet and outlet region has minor effect on cell temperature. Smallerchannel makes for better heat transfer performance, however, receivers with lowerchannel heigth means larger flow resistance. The channel height is optimized as10mm. By regression analysis, general correlations of convective heat transfercoefficient and friciton coefficient were obtained.5.Liquid-liquid direct contact and phase change heat transfer experiment ofdimethyl silicon oil-methanol system was designed for cooing of immersion liquid.Experimental results show that lift tube temperature on axial direction is increasedfirstly and then tends to be stable. The volumemetric heat transfer coefficient canreach22-34kW/(m3K); The range of average gas holdup of lift tube is0.05-0.5, andunder this average gas holdup range, the dimethyl silicon oil Reynolds numbers ofreceiver solar cell region in the optimized rectangular channel receiver can reach1500-7500when only using methanol steam lift as driving force.更多还原