Selective radiative cooling structure
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Solution Overview
Problem
Current radiative cooling technologies face challenges in efficiently cooling surfaces during the day due to high solar absorption, which exceeds the cooling power, and existing materials are often costly and difficult to scale for large-area applications.
Innovation Solution
The development of polymer-based selective radiative cooling structures with a wavelength-selective emissive layer comprising a polymer and dielectric particles, which preferentially emit infrared radiation through atmospheric transmission windows while being transparent to solar radiation, thereby reducing solar absorption and enhancing cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional radiative cooling materials are used, then cooling effect is achieved, but solar absorption is too high exceeding cooling power
Solution Approach 1:
The patent applies local quality by creating a coating with spatially varying properties: the top layer has low solar absorptivity (α < 0.5) to minimize solar heating, while the bottom layer has high infrared emissivity (ε > 0.9) to maximize radiative cooling. This vertical differentiation of optical properties allows the coating to simultaneously reduce harmful solar absorption and enhance beneficial infrared radiation emission, resolving the contradiction between these two opposing requirements.
Solution Approach 2:
The patent employs composite materials by combining multiple layers with different optical characteristics: a top layer material selected for low solar absorptivity and a bottom layer material selected for high infrared emissivity. This composite structure integrates the advantageous properties of different materials to achieve both low solar absorption and high radiative cooling power, directly addressing the technical contradiction between these two parameters.
2Manufacturing precision
If inorganic multilayer optical coatings are used, then wavelength selectivity is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent replaces expensive, complex inorganic multilayer optical coatings with a simpler, more cost-effective polymer-based coating system. This substitution uses readily available polymer materials and straightforward deposition processes, eliminating the need for complex vacuum deposition equipment and highly controlled manufacturing conditions while still achieving the required wavelength-selective optical properties.
Solution Approach 2:
The patent achieves wavelength selectivity through parameter changes in the polymer matrix composition and structure rather than through complex multilayer inorganic structures. By adjusting polymer concentration, molecular weight, and additive composition, the coating achieves desired optical properties (low solar absorptivity and high infrared emissivity) using simple, scalable manufacturing processes, thereby reducing device complexity while maintaining manufacturing precision.
3Loss of energy
If high infrared emissivity is achieved, then radiative cooling power increases, but solar absorption also increases
Solution Approach 1:
The patent applies segmentation by dividing the coating into distinct functional layers: a top layer optimized for low solar absorptivity and a bottom layer optimized for high infrared emissivity. This segmentation separates the two conflicting functions spatially, allowing each layer to perform its specialized function without compromising the other, thereby increasing radiative cooling power while controlling solar absorption.
Solution Approach 2:
The patent implements local quality by assigning different optical properties to different regions of the coating structure. The top layer possesses low solar absorptivity to minimize solar heating, while the bottom layer possesses high infrared emissivity to maximize radiative cooling. This localized optimization of optical properties enables the coating to simultaneously achieve high infrared radiation emission and controlled solar absorption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These structures achieve significant radiative cooling powers, exceeding 100 W/m² during the day and night, with the ability to maintain surface temperatures close to ambient, offering a cost-effective and scalable solution for cooling surfaces such as solar cells, windows, and buildings.
Implementation Method 1
Radiative cooling features the release of heat from an object or surface in the form of thermal radiation, thereby lowering the temperature of the object or surface
Implementation Method 2
A wavelength-selective radiative cooling device can emit thermal radiation preferentially in the selected wavelength ranges of the electromagnetic spectrum
Implementation Method 3
Current radiative cooling technologies face challenges in efficiently cooling surfaces during the day due to high solar absorption
Data Source
Figure 1
Figure 2~3A
Figure 3B
AI summary
Polymer-based selective radiative cooling structures are provided which include a selectively emissive layer of a polymer or a polymer matrix composite material. Exemplary selective radiative cooling structures are in the form of a sheet, film or coating. Also provided are methods for removing heat from a body by selective thermal radiation using polymer-based selective radiative cooling structures.