Porous polymer bilayer with near-ideal solar reflectance and longwave infrared emittance

This study explores the optical design of a daytime radiative cooler with near-ideal solar reflectance and longwave infrared (LWIR) emittance through materials selection and nanostructuring. Focusing on polymers as a materials platform, we introduce a bilayer architecture, comprising a porous poly(v...

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Bibliographic Details
Published in:Nanophotonics (Berlin, Germany) Germany), 2024-03, Vol.13 (5), p.669-677
Main Authors: Tsang, Yung Chak Anson, Varghese, Nithin Jo, Degeorges, Mathis, Mandal, Jyotirmoy
Format: Article
Language:English
Subjects:
Bilayers
Blackbody
Cooling
Emittance
Environmental engineering
Fluorides
Heat loss
Materials selection
metamaterials
nanophotonic design
Optical design
Polymers
porous polymers
radiative cooling
Reflectance
superwhite
sustainability
Thermoregulation
Vinylidene
Vinylidene fluoride
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Summary:This study explores the optical design of a daytime radiative cooler with near-ideal solar reflectance and longwave infrared (LWIR) emittance through materials selection and nanostructuring. Focusing on polymers as a materials platform, we introduce a bilayer architecture, comprising a porous poly(vinylidene fluoride-co-hexafluoropropene) (P(VdF-HFP)) topcoat that serves as a low-index LWIR emissive effective medium, over a nanofibrous, solar scattering polytetrafluoroethene underlayer. This novel configuration yields a superwhite coating with a near-ideal solar reflectance of >0.99, and a blackbody-like near-normal and hemispherical LWIR emittances of ∼0.98 and ∼0.96 respectively. Under humid and partially cloudy sky conditions unfavorable for radiative heat loss, these values enable the bilayer radiative cooler to achieve a sub-ambient of 2.3 °C. Given that the porous polymer bilayer uses scalable fabrication processes and commercially available materials, it holds significant promise for device-scale, as well as building thermoregulation applications.
ISSN:2192-8614
2192-8606
2192-8614
DOI:10.1515/nanoph-2023-0707