Abstract By strongly reflecting solar radiation and being highly emissive within the atmospheric window, daytime radiative coolers can achieve sub-ambient temperature under direct sunlight. Radiative cooling performance is strongly coupled to specific climatic conditions since cooling efficiency is strongly affected by ambient air temperature, wind speed, and solar and ambient radiation intensity. In this paper, using a well-validated thermal model, the cooling performance of three radiative cooling materials with varying optical properties was evaluated under three distinct and representative climates. This analysis permits us to better understand the sensitivity of daytime radiative cooling materials to different climatic conditions, present strategies for selecting the ideal spectral properties of materials and investigate how to enhance cooling performance under adverse climatic conditions. It is shown that radiative cooling materials have better performance in hot and arid climates. Most radiative cooling materials exhibit the greatest response to changes in ambient radiation. Higher ambient air temperatures correspond to larger sub-ambient temperature of the surfaces, but this change is lower than that of the corresponding air temperature. Furthermore, by coupling a special optical grating window onto the surface of a radiative cooler, cooling performance can be significantly enhanced by asymmetrically reflecting incoming radiation but permitting outgoing emission. While an ideal material that only emits in the atmospheric window wavelengths presents the best performance under a large range of solar radiation, ambient radiation, and air temperature, the broadband ideal emitter exhibits higher cooling potential when coupled with the optical grating window.

中文翻译：

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气候对日间辐射冷却材料性能的动态影响

摘要 通过在大气窗口内强烈反射太阳辐射和高辐射，白天辐射冷却器可以在阳光直射下达到低于环境温度。辐射冷却性能与特定气候条件密切相关，因为冷却效率受环境空气温度、风速以及太阳和环境辐射强度的强烈影响。在本文中，使用经过充分验证的热模型，在三种不同且具有代表性的气候下评估了具有不同光学特性的三种辐射冷却材料的冷却性能。这种分析使我们能够更好地了解白天辐射冷却材料对不同气候条件的敏感性，提出选择材料理想光谱特性的策略，并研究如何在不利的气候条件下提高冷却性能。结果表明，辐射冷却材料在炎热和干旱气候下具有更好的性能。大多数辐射冷却材料对环境辐射的变化表现出最大的响应。较高的环境空气温度对应于较大的表面亚环境温度，但这种变化低于相应的空气温度。此外，通过将特殊的光栅窗口耦合到辐射冷却器的表面，可以通过不对称地反射传入辐射但允许传出发射来显着提高冷却性能。