Full Daytime Sub-ambient Radiative Cooling with High Figure of Merit in Commercial-like Paints

TL;DR

This study demonstrates a commercial-like paint capable of full daytime sub-ambient radiative cooling by achieving high solar reflectance and sky-window emissivity, with field tests confirming significant cooling performance.

Contribution

The paper introduces a novel CaCO3-acrylic paint with high radiative cooling efficiency, combining high reflectance and emissivity in a commercially feasible formulation.

Findings

Solar reflectance of 95.5%

Cooling power exceeding 37 W/m2

Surface temperature more than 1.7°C below ambient at noon

Abstract

Radiative cooling is a passive cooling technology by reflecting sunlight and emitting radiation in the atmospheric sky window. Although highly desired, full daytime sub-ambient radiative cooling in commercial-like single-layer particle-matrix paints is yet to be achieved. In this work, we have demonstrated full daytime sub-ambient radiative cooling in CaCO3-acrylic paint by adopting large bandgap fillers, a high particle concentration and a broad size distribution. Our paint shows the highest solar reflectance of 95.5% among paints and a high sky-window emissivity of 0.94. Field tests show cooling power exceeding 37 W/m2 and lower surface temperature more than 1.7C below ambient at noon. A figure of merit RC is proposed to compare the cooling performance under different weather conditions. The RC of our cooling paint is 0.62, among the best radiative cooling performance while offering unprecedented benefits of the convenient paint form, low cost, and the compatibility with commercial paint fabrication process.