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On the effective spectral emissivity of clear skies and the radiative cooling potential of selectively designed materials

机译：关于晴朗天空的有效光谱发射率和选择性设计材料的辐射冷却潜能

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Thermophotonic devices are optically designed to be spectrally selective in order to reject heat to outer space through atmospheric windows of low thermal absorption. The determination of thermal equilibrium temperatures for thermophotonic devices requires the knowledge of the effective spectral emissivity of the sky. In this work, individual contributions of participating gases and aerosols to the spectral values of the sky emissivity are analyzed in the entire infrared spectrum as well as in seven distinct bands for which water vapor either dominates or is virtually transparent to infrared radiation. We also propose high-fidelity correlations for the effective sky emissivity as functions of the normalized ambient partial pressure of water vapor (p(w)) for both broadband and for the seven spectral bands. The correlations are derived using a combination of ground experimental data, high resolution spectral data for the main atmospheric constituents and spectral models to reconstruct the spectral distribution of infrared thermal radiation from the atmosphere to the ground. These results enable direct calculation of the equilibrium temperature and cooling efficiency of radiative cooling devices in terms of meteorological conditions observed at the surface level. For hot and dry conditions, the passive radiative coolers have a cooling potential of 150.8 W m(-2) while for humid conditions, the coolers are mostly ineffective. (C) 2019 Elsevier Ltd. All rights reserved.
机译：热光子器件在光学上设计成具有光谱选择性，以便通过低热吸收的大气窗口将热量排到外部空间。确定热光子设备的热平衡温度需要了解天空的有效光谱发射率。在这项工作中，分析了整个红外光谱以及七个不同的波段（其中水蒸气占主导地位或实际上对红外辐射透明），分析了参与气体和气溶胶对天空发射率光谱值的贡献。我们还为宽带和七个频谱波段的有效天空发射率提出了高保真度相关性，作为水蒸气归一化环境分压（p（w））的函数。使用地面实验数据，主要大气成分的高分辨率光谱数据和光谱模型的组合得出相关性，以重建从大气到地面的红外热辐射的光谱分布。这些结果使得能够根据在地面水平观察到的气象条件直接计算辐射冷却装置的平衡温度和冷却效率。对于炎热和干燥条件，无源辐射式冷却器的冷却潜力为150.8 W m（-2），而在潮湿条件下，冷却器大多无效。 （C）2019 Elsevier Ltd.保留所有权利。

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