Generalized bioinspired approach to a daytime radiative cooling "skin"

TL;DR

This paper presents a flexible, reusable daytime radiative cooling skin inspired by polar bear fur, combining a polydimethylsiloxane film with a highly-scattering polyethylene aerogel to achieve significant cooling effects in urban environments.

Contribution

It introduces a novel bilayer cooling skin with high solar reflectance and thermal transparency, inspired by bioinspired thermo-optical effects, advancing daytime radiative cooling technology.

Findings

Achieves 5-6°C midday cooling in urban environments

High solar reflectance of 0.96 and thermal transparency of 0.8

Potential to reach 14°C cooling under ideal conditions

Abstract

Energy-saving cooling materials with strong operability are desirable towards sustainable thermal management. Inspired by the cooperative thermo-optical effect in fur of polar bear, we develop a flexible and reusable cooling skin via laminating a polydimethylsiloxane film with a highly-scattering polyethylene aerogel. Owing to its high porosity of 97.9% and tailored pore size of 3.8 +- 1.4 micrometers, superior solar reflectance of 0.96 and high transparency to irradiated thermal energy of 0.8 can be achieved at a thickness of 2.7 mm. Combined with low thermal conductivity of 0.032 W/m/K of the aerogel, the cooling skin exerts midday sub-ambient temperature drops of 5-6 degrees in a metropolitan environment, with an estimated limit of 14 degrees under ideal service conditions. We envision that this generalized bilayer approach will construct a bridge from night-time to daytime radiative cooling and pave the way for economical, scalable, flexible and reusable cooling materials.