Metamaterial-Based Radiative Cooling: Towards Energy-Free All-Day Cooling

Byoungsu Ko,Junsuk Rho,Trevon Badloe,Dasol Lee

doi:10.3390/en12010089

Byoungsu Ko, Junsuk Rho + Show 2 more

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https://doi.org/10.3390/en12010089

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Abstract

In the light of the ever increasing dangers of global warming, the efforts to reduce energy consumption by radiative cooling techniques have been designed, but are inefficient under strong sunlight during the daytime. With the advent of metamaterials and their selective control over optical properties, radiative cooling under direct sunlight is now possible. The key principles of metamaterial-based radiative cooling are: almost perfect reflection in the visible and near-infrared spectrum (0.3–3 µm) and high thermal emission in the infrared atmospheric window region (8–13 µm). Based on these two basic principles, studies have been conducted using various materials and structures to find the most efficient radiative cooling system. In this review, we analyze the materials and structures being used for radiative cooling, and suggest the future perspectives as a substitute in the current cooling industry.

Highlights

As the awareness of the dangers of global warming grows, many novel ideas are being put forward to prevent the problem from developing further
Various nighttime radiative cooling research has been reported by constructing selective emitters in the atmospheric transparency window [4,5,6] but the same techniques are inefficient during the daytime under strong sunlight
The focus was on the thermal control of gratings on multi-layer structures that consist of boron nitride (BN), silicon carbide (SiC), and SiO2 [57] (Figure 3i)

Summary

Introduction

As the awareness of the dangers of global warming grows, many novel ideas are being put forward to prevent the problem from developing further. 2019, 12,cooling radiative entered a new phase after influential research by Raman et al [14,24,25] optimized the structure design to have optical properties that reflect the solar spectrum and emit thermal energy in the infrared (IR) atmospheric window [26,27]. An ideal radiative cooling system would have 100% reflectance over the whole solar spectrum while heat from high-temperature terrestrial bodies (~300 K) can always flow towards a low-temperature simultaneously having 100% thermal emission in atmospheric window (Figure 1b). There is a transparent a metamaterials design these two conditions can be satisfied, so passive, energy-free cooling can window in the atmosphere (8–13 μ m) that can be used to exchange heat between the Earth and be achieved. In order to optimize the radiative cooling power, it is necessary to minimize Psun , Patm , and Pc·d+c·v , while selectively emitting thermal radiation in the transparent atmospheric window to maximize Prad

Metamaterial-Based Radiative Cooling Using a Film Structure

Metamaterial-Based

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Discussion and and Perspective

Conclusions