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Title: Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody

A solar absorber, under the sun, is heated up by sunlight. In many applications, including solar cells and outdoor structures, the absorption of sunlight is intrinsic for either operational or aesthetic considerations, but the resulting heating is undesirable. Because a solar absorber by necessity faces the sky, it also naturally has radiative access to the coldness of the universe. Therefore, in these applications it would be very attractive to directly use the sky as a heat sink while preserving solar absorption properties. In this paper, we experimentally demonstrate a visibly transparent thermal blackbody, based on a silica photonic crystal. When placed on a silicon absorber under sunlight, such a blackbody preserves or even slightly enhances sunlight absorption, but reduces the temperature of the underlying silicon absorber by as much as 13 °C due to radiative cooling. Lastly, our work shows that the concept of radiative cooling can be used in combination with the utilization of sunlight, enabling new technological capabilities.
 [1] ;  [2] ;  [2]
  1. Stanford Univ., CA (United States). Dept. of Applied Physics
  2. Stanford Univ., CA (United States). Dept. of Electrical Engineering. Ginzton Lab.
Publication Date:
Grant/Contract Number:
AR0000316; ECS-9731293
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 112; Journal Issue: 40; Journal ID: ISSN 0027-8424
National Academy of Sciences, Washington, DC (United States)
Research Org:
Stanford Univ., CA (United States)
Sponsoring Org:
USDOE Advanced Research Projects Agency - Energy (ARPA-E); National Science Foundation (NSF)
Country of Publication:
United States
42 ENGINEERING; radiative cooling; thermal radiation; photonic crystal; solar absorber
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1348350