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

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.

Disordered and densely packed ITO nanorods as an excellent lithography-free optical solar reflector metasurface for the radiative cooling of spacecraft

“…In addition, the presented results are very promising in application areas of thermal-imaging with labeled-security, and daytime radiative coolers. 12,13,69 However, adaptation of the overall absorption response of the device over thermal infrared region to the atmospheric absorption lines should be fulfilled, which is an present ongoing study.…”

“…Metamaterials and their sub-wavelength thick counterparts, metasurfaces, represent a class of synthetic, man-made materials, whose sub-wavelength inclusions offer strong light-matter interactions. Their broad [5][6][7][8][9][10][11][12][13][14][15] or narrow [16][17][18][19][20][21][22][23][24] resonant responses enable the efficient harvesting of the confined radiation by an absorbing layer such as metals, or semiconductors.…”

Switchable Cavitation in Silicone Coatings for Energy‐Saving Cooling and Heating

“…All-day radiation constitutes a powerful energy-saving method for summer cooling. [19][20][21][22][23][24][25] Recent studies have suggested that introducing light scattering particles/cavities into a polymer matrix can increase passive daytime radiative cooling by reflecting solar radiation. [26][27][28][29] Such materials should be designed to reflect the light in the wavelength (λ) range of ≈0.3-2.5 µm but allow thermal emission into the cold outer space through the atmospheric longwave infrared (LWIR) transmission window (λ ≈ 8-13 µm).…”

Mirroring Solar Radiation Emitting Heat Toward the Universe: Design, Production, and Preliminary Testing of a Metamaterial Based Daytime Passive Radiative Cooler

“…Their proposed metamaterial is an alternating dielectric layers stack, obtained based on hafnium and silicon oxides deposited by evaporation. Other solutions based on metamaterials or porous alumina were developed more recently [24][25][26].…”