Passive directional sub-ambient daytime radiative cooling
Author(s)Bhatia, Bikramjit S; Leroy, Arny; Shen, Yichen; Zhao, Lin; Gianello, Melissa F.; Li, Duanhui; Gu, Tian; Hu, Juejun; Soljacic, Marin; Wang, Evelyn; ... Show more Show less
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Demonstrations of passive daytime radiative cooling have primarily relied on complex and costly spectrally selective nanophotonic structures with high emissivity in the transparent atmospheric spectral window and high reflectivity in the solar spectrum. Here, we show a directional approach to passive radiative cooling that exploits the angular confinement of solar irradiation in the sky to achieve sub-ambient cooling during the day regardless of the emitter properties in the solar spectrum. We experimentally demonstrate this approach using a setup comprising a polished aluminum disk that reflects direct solar irradiation and a white infrared-transparent polyethylene convection cover that minimizes diffuse solar irradiation. Measurements performed around solar noon show a minimum temperature of 6 °C below ambient temperature and maximum cooling power of 45 W m–2. Our passive cooling approach, realized using commonly available low-cost materials, could improve the performance of existing cooling systems and enable next-generation thermal management and refrigeration solutions.
DepartmentMassachusetts Institute of Technology. Institute for Soldier Nanotechnologies; Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science; Massachusetts Institute of Technology. Department of Materials Science and Engineering; Massachusetts Institute of Technology. Department of Mechanical Engineering; Massachusetts Institute of Technology. Department of Physics; Massachusetts Institute of Technology. Materials Systems Laboratory; Massachusetts Institute of Technology. Research Laboratory of Electronics
Nature Publishing Group
Bhatia, Bikram, Arny Leroy, Yichen Shen, Lin Zhao, Melissa Gianello, Duanhui Li, Tian Gu, Juejun Hu, Marin Soljačić, and Evelyn N. Wang. “Passive Directional Sub-Ambient Daytime Radiative Cooling.” Nature Communications 9, no. 1 (November 27, 2018).
Final published version