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Thermally Responsive Hydrogels for Passive Temperature Regulation under Direct Sunlight

Authors :
Dajie Xie
Wei Li
Corey A. Richards
Haibo Gao
Chen Chen
Nenad Miljkovic
Shanhui Fan
Jae Lee
Shailesh N. Joshi
Paul V. Braun
Source :
Advanced Photonics Research, Vol 4, Iss 4, Pp n/a-n/a (2023)
Publication Year :
2023
Publisher :
Wiley-VCH, 2023.

Abstract

By spontaneously emitting midinfrared radiation to outer space through the atmospheric window and reflecting sunlight, daytime radiative coolers achieve notable passive cooling performance. However, existing daytime radiative cooling systems generally lack the ability to adaptively switch between heating and cooling states based on ambient conditions. Herein a passive thermal regulation system that features a temperature‐dependent switchable solar reflectance from 0.05 (low temperature) to 0.8 (high temperature) is presented. This, along with a ≈0.95 midinfrared emittance, it enables automatic switching between radiative cooling and solar heating. Switchablity is enabled using a poly(N‐isopropylacrylamide) (PNIPAM) hydrogel which exhibits high solar scattering above its tunable lower critical solution temperature (LCST) and transparency below its LCST. The lower part of the hydrogel is loaded with graphite to absorb solar energy in the heating state. In testing under sunny and partly cloudy outside conditions, this system maintains a temperature close to the set LCST.

Details

Language :
English
ISSN :
26999293
Volume :
4
Issue :
4
Database :
Directory of Open Access Journals
Journal :
Advanced Photonics Research
Publication Type :
Academic Journal
Accession number :
edsdoj.0ac1e46a7e646fda86396ac0d45197a
Document Type :
article
Full Text :
https://doi.org/10.1002/adpr.202200253