Radiative cooling device having multilayer structure
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Solution Overview
Problem
Current radiative cooling devices face challenges in achieving high radiative cooling performance due to limitations in materials with high extinction coefficients in the 8-13 μm wavelength range, which affects their ability to efficiently emit heat into space, and polymer materials degrade quickly when exposed to outdoor conditions.
Innovation Solution
A radiative cooling device with a multilayer structure comprising inorganic and polymer layers, which absorbs and emits infrared light in the atmospheric window range while reflecting sunlight, utilizing materials like Al2O3, SiO2, and polymers such as PDMS, and incorporating a solar reflective layer for enhanced reflectance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If polymer materials are used for radiative cooling, then high emissivity for long-wavelength infrared light is achieved, but durability and lifespan are reduced due to deterioration from ultraviolet light and moisture
Solution Approach 1:
The patent uses composite materials consisting of inorganic particles (such as TiO2, SiO2, Al2O3) dispersed in a polymer matrix. The inorganic particles provide UV resistance and structural stability, while the polymer provides flexibility and high infrared emissivity. This composite structure resolves the contradiction by combining materials with complementary properties to achieve both high emissivity and durability.
2Ease of manufacture
If thick polymer materials are used, then high transmittance and reflectance for incident sunlight are achieved, but radiative cooling performance is reduced due to broadband emission across all infrared wavelengths rather than selective emission
Solution Approach 1:
The patent applies local quality by creating a multilayer structure where each layer has specific optical properties tailored to different wavelength ranges. The top layer contains inorganic particles for sunlight reflection, while lower layers have progressively different compositions to achieve selective infrared emission. This allows the device to reflect sunlight effectively while maintaining selective high emissivity only in the atmospheric window region (8-13 μm), resolving the contradiction between manufacturability and radiative cooling performance.
3Device complexity
If a single-layer structure is used, then device complexity is reduced, but the ability to simultaneously achieve high sunlight reflection and selective infrared emission is compromised
Solution Approach 1:
The patent segments the radiative cooling device into multiple functional layers, each with specific thickness and composition. The top layer (5-20 μm) contains high refractive index particles for sunlight reflection, intermediate layers (10-50 μm each) provide transition zones with varying emissivity, and the bottom layer (20-100 μm) ensures structural integrity and baseline emission. This segmentation allows independent optimization of each layer for its specific function, achieving both high sunlight reflection and selective infrared emission while maintaining reasonable manufacturing complexity.
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
The multilayer structure enhances radiative cooling performance by maximizing emissivity in the atmospheric window range, maintaining stability under outdoor conditions, and achieving effective cooling without energy consumption, both during the day and at night.
Implementation Method 1
a radiative cooling layer for absorbing and emitting infrared light in a wavelength range corresponding to an atmospheric window
Implementation Method 2
emitting the energy of radiant heat (8 to 13 μm) that can escape into space
Implementation Method 3
reflecting wavelengths (0.3 to 2.5 μm) corresponding to daytime sunlight
Implementation Method 4
increasing sunlight reflection through differences in the refractive indexes of the device-forming materials
Data Source
AI summary
The present disclosure relates to a technical idea of reducing the surface temperature of a material or temperature under a material by emitting heat under a device to the outside by absorbing and emitting long-wavelength infrared light corresponding to the wavelength range of the atmospheric window while minimizing absorption of light of the solar spectrum. More particularly, the present disclosure relates to a technology for providing a radiative cooling device having a multilayer structure that is capable of increasing sunlight reflection through differences in the refractive indexes of the device-forming materials while performing selective emission over the wavelength range of the atmospheric window using a radiative cooling device having a multilayer structure composed of polymers and inorganic materials.