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Title: A dual-layer structure with record-high solar reflectance for daytime radiative cooling

Abstract

We demonstrate a diffusive solar reflector with record high reflectance when integrated over the wavelength region from 0.28-4.0 μm. The reflector has a dual-layer structure consisting of a polytetrafluoroethylene (PTFE) sheet on top of a silver film. The thickness of the PTFE varies from 0.25 mm to 1 mm. Spectral reflectance and transmittance of the PTFE sheets (with and without a silver film) were measured using a monochromator and a Fourier-transform infrared spectrometer, with integrating spheres, at wavelengths from 0.28 μm to 15 μm. The scattering and absorption coefficients of the PTFE samples were obtained by fitting the reflectance and transmittance spectra. Integration over the solar irradiation spectrum (AM1.5) reveals that the total solar reflectance is approximately 0.99 for the reflector. This is the highest solar reflectance reported to date. A Monte Carlo ray-tracing method and a modified two-flux model were used to calculate the reflectance and compare with the experiments to shed light on mechanisms for the high reflectance. Our measurements also suggest that PTFE has a high emittance around 0.9 in the mid-infrared region. Therefore, we conclude the proposed structure holds promise for passive daytime radiative cooling.

Authors:
 [1];  [1];  [1]
  1. Georgia Inst. of Technology, Atlanta, GA (United States)
Publication Date:
Research Org.:
Georgia Inst. of Technology, Atlanta, GA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
OSTI Identifier:
1594763
Grant/Contract Number:  
SC0018369; CBET-1603761
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Solar Energy
Additional Journal Information:
Journal Volume: 169; Journal Issue: C; Journal ID: ISSN 0038-092X
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; Diffuse reflector; Polytetrafluoroethylene (PTFE); Radiative cooling; Solar radiation

Citation Formats

Yang, Peiyan, Chen, Chuyang, and Zhang, Zhuomin M. A dual-layer structure with record-high solar reflectance for daytime radiative cooling. United States: N. p., 2018. Web. doi:10.1016/j.solener.2018.04.031.
Yang, Peiyan, Chen, Chuyang, & Zhang, Zhuomin M. A dual-layer structure with record-high solar reflectance for daytime radiative cooling. United States. doi:10.1016/j.solener.2018.04.031.
Yang, Peiyan, Chen, Chuyang, and Zhang, Zhuomin M. Tue . "A dual-layer structure with record-high solar reflectance for daytime radiative cooling". United States. doi:10.1016/j.solener.2018.04.031. https://www.osti.gov/servlets/purl/1594763.
@article{osti_1594763,
title = {A dual-layer structure with record-high solar reflectance for daytime radiative cooling},
author = {Yang, Peiyan and Chen, Chuyang and Zhang, Zhuomin M.},
abstractNote = {We demonstrate a diffusive solar reflector with record high reflectance when integrated over the wavelength region from 0.28-4.0 μm. The reflector has a dual-layer structure consisting of a polytetrafluoroethylene (PTFE) sheet on top of a silver film. The thickness of the PTFE varies from 0.25 mm to 1 mm. Spectral reflectance and transmittance of the PTFE sheets (with and without a silver film) were measured using a monochromator and a Fourier-transform infrared spectrometer, with integrating spheres, at wavelengths from 0.28 μm to 15 μm. The scattering and absorption coefficients of the PTFE samples were obtained by fitting the reflectance and transmittance spectra. Integration over the solar irradiation spectrum (AM1.5) reveals that the total solar reflectance is approximately 0.99 for the reflector. This is the highest solar reflectance reported to date. A Monte Carlo ray-tracing method and a modified two-flux model were used to calculate the reflectance and compare with the experiments to shed light on mechanisms for the high reflectance. Our measurements also suggest that PTFE has a high emittance around 0.9 in the mid-infrared region. Therefore, we conclude the proposed structure holds promise for passive daytime radiative cooling.},
doi = {10.1016/j.solener.2018.04.031},
journal = {Solar Energy},
issn = {0038-092X},
number = C,
volume = 169,
place = {United States},
year = {2018},
month = {5}
}

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Cited by: 9 works
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