Bioinspired daytime radiative cooling performance: a new experimental protocol for scaling up passive cooling through the atmospheric windows

Urban overheating is a widely recognized consequence of human activities that contribute to climate change at the urban scale. This phenomenon has devastating effects, including increased energy demand for cooling, heightened air pollution, and associated health risks, particularly during heat waves and in energy-poor conditions. Consequently, cities worldwide are implementing strategic measures to mitigate and adapt to these urban heat islands. One effective approach to mitigation involves the use of cool materials, which possess the ability to reflect or re-emit thermal radiation due to various factors. Daytime radiative cooling is a specific application of cool materials that has the potential to achieve sub-ambient surface temperatures, making it suitable for urban surfaces such as roofs, facades, and streets. Despite the acknowledged potential of radiative cooling, there is a lack of detailed, replicable experimental protocols and numerical assessments in the existing literature. This gap can be addressed by adapting the Solar Reflectance Index (SRI), a crucial metric for quantifying this potential, and further enhancing its capabilities. In order to advance our understanding and application of radiative cooling, it is imperative to develop a comprehensive experimental protocol and conduct thorough numerical assessments. By doing so, we can unlock the full potential of cool materials and their ability to combat urban overheating. This research will contribute to the ongoing efforts to create sustainable and resilient cities that are better equipped to tackle the challenges posed by climate change.