Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody
By Linxiao Zhu, Aaswath Pattabhi Raman, Shanhui Fan. Proceedings of the National Academy of Sciences of the United States of America, 2015
603 citations recorded by the source corpus.
Significance The coldness of the universe is an enormous but strikingly underexploited thermodynamic resource. Its direct utilization on Earth therefore represents an important frontier for renewable energy research. In many applications, including solar cells and outdoor structures, the absorption of sunlight is intrinsic either from operational or aesthetic considerations, but the resulting heating by sunlight is undesirable. Here we experimentally demonstrate a thermal photonic scheme that can cool these structures by thermal radiation to outer space, while preserving the structures’ solar absorption. Our work shows, for the first time to our knowledge, that radiative cooling can be used in combination with the utilization of sunlight, and opens new possibilities for using the coldness of the universe to improve the performance of terrestrial energy systems. 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. Here 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. Our work shows that the concept of radiative cooling can be used in combination with the utilization of sunlight, enabling new technological capabilities.
Subfields: Civil and Structural Engineering, Electrical and Electronic Engineering, Renewable Energy, Sustainability and the Environment
View Paper: https://www.semanticscholar.org/paper/a84931bc03d6fc4804682008bcd8024cc057f72c
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Citations in the corpus
- Radiative sky cooling: fundamental physics, materials, structures, and applications (2017, positive): “Indeed, bare silicon cells can operate up to 20°C higher than glass-encapsulated modules [18, 19, 22], which has much higher emittance.”
- Exploiting offshore wind and solar resources in the Mediterranean using ERA5 reanalysis data (2021, neutral): “45% in terms of conversion efficiency [12].”
- Advances and challenges in commercializing radiative cooling (2019, background): “If emitters are directly combined with bare photovoltaic panels, the improvement of the actual the conversion efficiency is limited [44,45] and even the service life of solar cells may be reduced due to the poor packaging.”