Emerging Materials and Strategies for Passive Daytime Radiative Cooling

Abstract

In recent decades, the growing demands for energy saving and accompanying heat mitigation concerns, together with the vital goal for carbon neutrality, have drawn human attention to the zero‐energy‐consumption cooling technique. Recent breakthroughs in passive daytime radiative cooling (PDRC) might be a potent approach to combat the energy crisis and environmental challenges by directly dissipating ambient heat from the Earth to the cold outer space instead of only moving the heat across the Earth's surface. Despite significant progress in cooling mechanisms, materials design, and application exploration, PDRC faces potential functionalization, durability, and commercialization challenges. Herein, emerging materials and rational strategies for PDRC devices are reviewed. First, the fundamental physics and thermodynamic concepts of PDRC are examined, followed by a discussion on several categories of PDRC devices developed to date according to their implementation mechanism and material properties. Emerging strategies for performance enhancement and specific functions of PDRC are discussed in detail. Potential applications and possible directions for designing next‐generation high‐efficiency PDRC are also discussed. It is hoped that this review will contribute to exciting advances in PDRC and aid its potential applications in various fields.

Ordered Porous Polymer Films for Highly Efficient Passive Daytime Radiative Cooling

“…Among them, a higher scattering efficiency is achieved when IO-PMMA has a 3 μm pore size. In addition, IO-PMMA 3 manifests superior infrared absorption efficiency, ascribed to the impedance match of the air–polymer interface (Figure b). In order to verify the actual effect of pore size on the spectral performance of IO-PMMA films, experiments were carried out.…”

Scalable Bacterial Cellulose‐Based Radiative Cooling Materials with Switchable Transparency for Thermal Management and Enhanced Solar Energy Harvesting

“…Future research should focus on the judicious design and scalable fabrication of advanced adaptive radiative cooling materials in response to ever‐changing environmental conditions. [ 23 ] The ideal advanced adaptive radiative cooling materials should possess a dynamic switchable ability between cooling and heating modes upon temperature changes, where the cooling mode requires low solar absorption and high MIR emissivity and the heating mode should have low solar reflection and MIR emissivity. The research disclosed herein is expected to open up a new arena for the design and fabrication of bioinspired radiative cooling materials with sophisticated and dynamic functionalities, which is of paramount significance for the development of all low‐ and zero‐carbon technologies and their promising applications in diverse fields ranging from advanced smart thermal management to sustainable energy‐saving buildings with high energy efficiency and low carbon emissions.…”

Colloidal inorganic nano- and microparticles for passive daytime radiative cooling

“…Insulating CaCO 3 and BaSO 4 NPs or MPs have been used to eliminate the limitation that ZnO and TiO 2 -based paints absorb UV [ 51 , 54 ]. Although CaCO 3 has a low refractive index, its broad size distribution and assemblies consisting of large numbers of particles enhance its solar reflection properties [ 72 , 73 ]. The solar reflectance of RCMs was increased by increasing the CaCO 3 concentration to induce the optical crowding effect.…”