Abstract
Daytime radiative cooling has drawn much attention recently because a target surface can be passively maintained at sub-ambient temperature. In order to implement a daytime radiative cooling device (simply ‘radiative cooler’), strong thermal emission should be focused in the mid-infrared regime (8–13 µm), called ‘atmospheric transparent window’. At the same time, absorption of the solar irradiation should be minimized. In the present study, for optimal performance of daytime radiative cooling, a mixed-integer genetic algorithm was employed to achieve maximal infrared emission as well as minimal solar absorption. The combination of total number of layer, materials, and thickness of each layer in the multilayered radiative cooler were determined through optimization. The optimized multilayer structure exhibited the spectrally-averaged (in the 8–13 µm wavelength range) normal emissivity value of 0.96 and the solar-weighted absorptivity of 0.03. The corresponding net cooling power was found to be 101.0 W/m2, and a sub-ambient cooling temperature of 11.2∘C (i.e., below ambient temperature) was predicted in daytime at air-mas 1.5 condition. Besides, the mechanism of enhanced emission in the infrared region and suppressed absorption in the solar spectrum were thoroughly investigated. We also derived the expected performance of the optimized radiative cooler for various conditions of the environmental parameters, such as convection heat transfer coefficient, ambient temperature, and precipitable water level.
Original language | English |
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Article number | 107475 |
Journal | Journal of Quantitative Spectroscopy and Radiative Transfer |
Volume | 260 |
DOIs | |
Publication status | Published - 2021 Feb |
Bibliographical note
Funding Information:This research was supported by the Creative Materials Discovery Program (NRF-2018M3D1A1058998) as well as the Basic Science Research Program (NRF-2020R1A4A4078930) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT. This work was also supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20172010000850).
Funding Information:
This research was supported by the Creative Materials Discovery Program (NRF-2018M3D1A1058998) as well as the Basic Science Research Program (NRF-2020R1A4A4078930) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT. This work was also supported by the Korea Institute of Energy Technology Evaluation and Planning ( KETEP ) and the Ministry of Trade, Industry & Energy ( MOTIE ) of the Republic of Korea (No. 20172010000850 ).
Publisher Copyright:
© 2020 Elsevier Ltd
Keywords
- Daytime radiative cooling
- Multilayer structure
- Optimization
- Precipitable water level
ASJC Scopus subject areas
- Radiation
- Atomic and Molecular Physics, and Optics
- Spectroscopy