Graded nanocomposite metamaterials for a double-sided radiative cooling architecture with a record breaking cooling power density

TL;DR

This paper introduces a double-sided radiative cooling system using graded nanocomposite metamaterials that achieves record-breaking cooling power density and significant temperature reduction without electricity.

Contribution

It presents a novel double-sided radiative cooling architecture with graded nanocomposite metamaterials, surpassing previous cooling power density limits.

Findings

Record cooling power density over 280 W/m2

Achieved 14°C temperature reduction indoors

Over 12°C cooling outdoors

Abstract

As an emerging electricity-free cooling technology, radiative cooling employs outer space as the heat sink. With this, a sky-facing thermal emitter is usually required. Due to the black-body radiation limit at ambient temperature, the maximum cooling power density for a single-faced radiative cooling device is ~156.9 W/m2. Here we report a double-sided radiative cooling architecture using graded nanocomposite metamaterials (GNM) designed for a vertically aligned thermal emitter. This GNM structure possesses an optical absorption of over 90% throughout the solar spectrum, and exceeds 90% reflection in the mid-infrared spectral region. With this configuration, both sides of a planar thermal emitter can be used to perform radiative cooling and a record cooling power density beyond 280 W/m2 was realized in a single thin-film thermal emitter. Under the standard pressure, we realized a temperature reduction of 14 degree Celsius below the ambient temperature in the laboratory environment, and over 12 degree Celsius in the outdoor test.