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Published March 15, 2017 | Accepted Version
Journal Article Open

Daytime radiative cooling using near-black infrared emitters

Abstract

Recent works have demonstrated that daytime radiative cooling under direct sunlight can be achieved using multilayer thin films designed to emit in the infrared atmospheric transparency window while reflecting visible light. Here, we demonstrate that a polymer-coated fused silica mirror, as a near-ideal blackbody in the mid-infrared and near-ideal reflector in the solar spectrum, achieves radiative cooling below ambient air temperature under direct sunlight (8.2 °C) and at night (8.4 °C). Its performance exceeds that of a multilayer thin film stack fabricated using vacuum deposition methods by nearly 3 °C. Furthermore, we estimate the cooler has an average net cooling power of about 127 Wm^(-2) during daytime at ambient temperature even considering the significant influence of external conduction and convection, more than twice that reported previously. Our work demonstrates that abundant materials and straight-forward fabrication can be used to achieve daytime radiative cooling, advancing applications such as dry cooling of thermal power plants.

Additional Information

© 2017 American Chemical Society. Received: December 12, 2016. Published: February 3, 2017. This work is part of the 'Light-Material Interactions in Energy Conversion' Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001293. The authors thank Prof. George Rossman for FTIR assistance, the Kavli Nanoscience Institute at Caltech for cleanroom facilities, and the Molecular Materials Research Center of the Beckman Institute at Caltech for UV/vis/NIR measurement.

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