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Homogeneous Polymer Films for Passive Daytime Cooling : Optimized Thickness for Maximized Cooling Performance

Title data

Herrmann, Kai ; Lauster, Tobias ; Song, Qimeng ; Retsch, Markus:
Homogeneous Polymer Films for Passive Daytime Cooling : Optimized Thickness for Maximized Cooling Performance.
In: Advanced Energy & Sustainability Research. (16 November 2021) .
ISSN 2699-9412
DOI: https://doi.org/10.1002/aesr.202100166

Project information

Project financing: Andere
ERC VISIRday, 714968

Abstract in another language

Passive radiative cooling materials that spontaneously cool below ambient temperature can save tremendous amounts of energy used for cooling applications. A multitude of materials, structures, and fabrication strategies have been reported in recent years. Important material parameters like a tailored or broadband emissivity, angle selectivity, or the influence of nonradiative heat losses were discussed in detail. The material thickness has been far less researched and is typically chosen sufficiently thick to ensure high emission in the atmospheric transparency window between wavelengths of 8–13 μm. However, not only the material emittance but also atmospheric and solar energy uptake depend on the material thickness. This broadband interplay has been less addressed so far. Herein, it is shown how an optimum thickness of a passive cooling material can be predicted when the optical properties of the material are known. Using complex refractive index data, the thickness-dependent cooling performance of polydimethylsiloxane (PDMS) in back-reflector geometry as exemplary material is calculated. For both day- and nighttime operation, an optimum emitter thickness is reported. The findings are verified experimentally by measuring the equilibrium temperatures of PDMS films with different thicknesses in a rooftop experiment. The presented analytical approach is directly transferable to other materials.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Physical Chemistry I > Chair Physical Chemistry I - Univ.-Prof. Dr. Markus Retsch
Profile Fields > Advanced Fields > Polymer and Colloid Science
Profile Fields > Advanced Fields > Advanced Materials
Profile Fields > Emerging Fields > Energy Research and Energy Technology
Research Institutions > Research Centres > Bayreuth Institute of Macromolecular Research - BIMF
Research Institutions > Research Centres > Bayreuth Center for Colloids and Interfaces - BZKG
Research Institutions > Affiliated Institutes > Bavarian Polymer Institute (BPI)
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 540 Chemistry
Date Deposited: 18 Nov 2021 10:32
Last Modified: 18 Nov 2021 10:32
URI: https://eref.uni-bayreuth.de/id/eprint/67914