Perrakis George, Tasolamprou Anna C, Kenanakis George, Economou Eleftherios N, Tzortzakis Stelios, Kafesaki Maria
Opt Express. 2020 Jun 22;28(13):18548-18565. doi: 10.1364/OE.388208.
The radiative cooling of objects during daytime under direct sunlight has recently been shown to be significantly enhanced by utilizing nanophotonic coatings. Multilayer thin film stacks, 2D photonic crystals, etc. as coating structures improved the thermal emission rate of a device in the infrared atmospheric transparency window reducing considerably devices' temperature. Due to the increased heating in photovoltaic (PV) devices - that has significant adverse consequences on both their efficiency and life-time - and inspired by the recent advances in daytime radiative cooling, we developed a coupled thermal-electrical modeling to examine the physical mechanisms on how a radiative cooler affects the overall efficiency of commercial photovoltaic modules and how the radiative cooling impact is compared with the impact of other photonic strategies for reducing heat generation within PVs, such as ultraviolet and sub-bandgap reflection. Employing our modeling, which takes into account all the major intrinsic processes affected by the temperature variation in a PV device, we additionally identified the validity regimes of the currently existing PV-cooling models which treat the PV coolers as simple thermal emitters. Finally, we assessed some realistic photonic coolers from the literature, compatible with photovoltaics, to implement the radiative cooling requirements and the requirements related to the reduction of heat generation, and demonstrated their associated impact on the temperature reduction and PV efficiency. Consistent with previous works, we showed that combining radiative cooling with sub-bandgap reflection proves to be more promising for increasing PVs' efficiency. Providing the physical mechanisms and requirements for reducing PV operating temperature, our study provides guidelines for utilizing suitable photonic structures for enhancing the efficiency and the lifetime of PV devices.
最近研究表明，利用纳米光子涂层可显著增强物体在白天直射阳光下的辐射冷却效果。多层薄膜堆栈、二维光子晶体等涂层结构提高了器件在红外大气透明窗口的热发射率，从而大幅降低了器件温度。由于光伏（PV）器件发热增加——这对其效率和寿命均有显著不利影响——并且受白天辐射冷却领域最新进展的启发，我们开发了一种热电耦合模型，以研究辐射冷却器影响商用光伏组件整体效率的物理机制，以及如何将辐射冷却的影响与其他用于减少光伏器件内热产生的光子策略（如紫外线和子带隙反射）的影响进行比较。利用我们的模型，该模型考虑了光伏器件中受温度变化影响的所有主要内在过程，我们还确定了当前将光伏冷却器视为简单热发射体的现有光伏冷却模型的有效性范围。最后，我们评估了文献中一些与光伏兼容的实际光子冷却器，以满足辐射冷却要求以及与减少热产生相关的要求，并展示了它们对温度降低和光伏效率的相关影响。与先前的研究一致，我们表明将辐射冷却与子带隙反射相结合对于提高光伏效率更具前景。我们的研究提供了降低光伏工作温度的物理机制和要求，为利用合适的光子结构提高光伏器件的效率和寿命提供了指导。
