高倍聚光下耦合液冷接收器中密排III-V电池组件特性的影响规律研究

High concentration photovoltaics (HCPV) have been considered as an effective way to reduce the photovoltaic (PV) electricity cost. However, the solar cells under high illuminations will have increases in temperature. And the cells will experience both short-term (efficiency loss) and long-term (irreversible damage) degradation due to excess temperature. Therefore, cooling of photovoltaic cells is one of the main concerns when desiigning HCPV systems. Otherwise, HCPV will not have measurable contribution to the PV market. Based on the latest developments of the cooling methods of HCPV systems, a direct liquid-immersion cooling method is proposed for the densely packed III-V cells module under high concentrations. And the influence law of the characteristics of densely packed III-V cells module in the PV receiver coupled with direct liquid-immersion cooling for HCPV systems application is investigated in this project. Firstly, the effect of an change in the electrical performance of III-V cells by their immersion in candidate liquids is measured by I-V measurement technology. The mechanisms of the change in the electrical performance of III-V cells are explored based on the photometry theory. Then, the physical and mathematical models are constructed for energy transfer process description of the PV receiver coupled with direct liquid-immersion cooling. Also,a CFD model of the receiver is developed. In addition, the temperature-dependent electrical models of the III-V cell used in the receiver are defined. Based on these models, the mechanisms on the heat transfer process in the novel PV receiver are explored. And the characteristics of the III-V CPV cells module in the receiver can be achieved. Combined with the simulated light indoor experiment, the prediction model of the characteristics of the III-V cells module in the novel receiver related to operating conditions, flow channel structure and immersion liquid physical properties is developed. Thus, it can reveal the influence law of the characteristics of densely packed III-V cells module in the receiver coupled with liquid-immersion cooling. This project results provide the theoretical and technical foundation in the new solution for the thermal management issue in the development of HCPV systems, as well as in the development of the PV receiver coupled with liquid-immersion cooling for the HCPV systems with densely packed III-V cells module.

高倍聚光光伏技术在降低光伏发电成本上被寄予厚望。然而，高倍聚光下电池温度急剧上升使其转换效率下降，长时间会影响系统可靠运行，成为制约该项技术推广应用的主要瓶颈。本项目在总结高倍聚光光伏冷却技术等的研究基础上，提出液浸冷却高倍聚光下的密排电池组件。以高倍聚光下耦合液冷光伏接收器中密排III-V族电池组件为研究对象，基于I-V测试技术和光度学理论，研究分析电池在液体中电特性变化的规律和机理；构建描述耦合液冷接收器能量传递过程的物理数学模型和接收器三维计算流体力学模型，耦合电池电特性与温度关系模型，探索换热机理及多种情况下电池组件的特性，结合室内模拟光试验，建立基于工作条件、流道结构、液体物理属性多因素复杂耦合的电池组件特性预测模型，揭示液冷接收器中III-V族电池组件特性的影响规律。本研究为有效解决采用密排电池组件的高倍聚光光伏系统散热难题和研制出系统用液冷光伏接收器奠定理论和技术基础。

高倍聚光光伏技术在降低光伏发电成本上被寄予厚望。然而，如何有效地散热是采用密排电池组件的高倍聚光光伏系统面临的技术挑战，本项目提出直接液体浸没冷却高倍聚光下的密排电池组件。首先利用双光程测试方法表征了候选液的光学性能，通过引入归一化光电流密度参数评价分析了液体的存在对III-V族聚光三结电池电性能的影响，结果表明，除丙三醇外其余9种候选液均可用于浸没冷却聚光三结电池，Therminol VP-1引起的功率损失最小，其次为二甲基硅油。接着通过设计的加速老化试验考察分析了候选浸没冷却液体的可靠性，其中，二甲基硅油老化试验后引起的功率衰减最小，除合成油外的其余5种矿物油均具有优良的可靠性。在此基础上，利用室内太阳模拟器装置考察了InGaP/InGaAs/Ge聚光三结电池在不同种类浸没冷却液体、不同液膜厚度下的电性能及长期可靠性。从光线的收集变化（光学效应）和液体分子的吸附引起电池表面复合的变化（电学效应）两方面定量分析了液体浸没引起III-V族聚光电池电性能变化的规律和机理，结果表明，III-V族聚光三结电池的转换效率先随着液膜厚度的增加而提高，在4 mm厚度下，电池效率最高，然后随着液膜厚度的进一步增加其转换效率开始下降；4 mm液膜引起聚光电池表面菲涅尔反射降低的光学效应和液体分子的吸附引起电池表面复合速率降低的电学效应是薄液膜浸没时电池转换效率提高的主要原因。另外，液浸InGaP/InGaAs/Ge电池经过紫外加速老化试验后的性能变化很小。然后，结合碟式高倍聚光器的焦斑特点和液浸冷却方式的优势等，设计了一种用于碟式高倍聚光系统的液冷光伏接收器，建立了描述光伏接收器能量传递过程的物理数学模型，探索了III-V族聚光三结电池组件所在耦合液冷光伏接收器能量传递过程的机理、预测了多种情况下接收器内电池组件的性能。结果表明该接收器中的电池组件在高倍聚光下可以维持在低且均匀的温度下，效率显著提高。此外，本项目还初步研制了耦合液冷光伏接收器，采用数值模拟和室内试验获得了各因素对III–V族电池组件性能的影响规律，为接收器内III–V族电池组件性能的预测提供科学判据。本项目的成功实施为有效解决采用密排电池组件的高倍聚光光伏系统的散热问题及研制出适合该系统用的液冷光伏接收器奠定了理论和技术基础，具有重要的理论意义和工程应用价值。

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