Ceramic-Based Radiative Cooling Structure for Enhanced IR Selectivity
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Solution Overview
Problem
Existing radiative cooling structures face challenges with poor scalability, high cost, short lifespan, and limited cooling performance under high humidity due to inadequate infrared selectivity and UV resistance, particularly in designs that rely on polymer materials.
Innovation Solution
A radiative cooling structure comprising a reflective layer, a ceramic infrared-selectively emissive layer, and a ceramic emission boosting layer, where the ceramic IR-selectively emissive layer is sandwiched between the reflective and emission boosting layers, utilizing silicon-based ceramic materials with precise thickness and packing to enhance emissivity within the 8-13 μm wavelength range while maintaining high reflectivity outside this range, and employing inorganic materials for durability and scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polymer materials are used in the cooling layer to achieve high IR emissivity and solar transmittance, then the cooling performance is improved, but UV degradation occurs leading to short lifespan
Solution Approach 1:
The patent changes the material parameter from organic polymer to inorganic ceramic particles, fundamentally altering the chemical composition to achieve UV resistance while maintaining radiative cooling performance. The ceramic particles with specific size distribution (0.5-5 μm) provide both high IR emissivity and UV stability, resolving the contradiction between cooling performance and lifespan.
Solution Approach 2:
The patent creates a composite structure by combining ceramic particles (such as SiO2, TiO2, ZnO) with a polymer binder. This composite approach allows the ceramic particles to provide UV resistance and high IR emissivity, while the polymer matrix provides structural integrity and ease of application, achieving both long lifespan and effective cooling performance.
2Ease of manufacture
If existing scalable radiative cooler structures are used, then large-scale fabrication is achieved, but IR selectivity is poor limiting temperature reduction
Solution Approach 1:
The patent applies local quality by using ceramic particles with specific size ranges (0.5-5 μm) that selectively interact with different wavelengths. The particle size distribution is optimized to enhance emissivity in the atmospheric window region (8-13 μm) while maintaining simplicity in large-scale fabrication processes such as spray coating or dip coating.
Solution Approach 2:
The patent changes the material composition parameter from conventional polymers to ceramic-based composites, which inherently provide better IR selectivity. The ceramic materials have natural phonon resonance frequencies that align with the atmospheric window, providing enhanced emissivity in the 8-13 μm range without requiring complex multilayer structures.
3Power
If high emissivity is achieved in other infrared areas, then thermal radiation is increased, but temperature reduction is limited due to atmospheric absorption
Solution Approach 1:
The patent applies local quality by designing the ceramic particle coating to have wavelength-selective emissivity. The ceramic materials naturally exhibit high emissivity in the atmospheric window region (8-13 μm) where the atmosphere is transparent, while having lower emissivity in other infrared regions where atmospheric absorption is strong. This selective emission maximizes cooling efficiency by directing thermal radiation only through atmospheric transmission windows.
Solution Approach 2:
The patent utilizes the concept of spectral selectivity analogous to color changes, where the ceramic coating is engineered to have different emissivity 'colors' at different wavelengths. The coating appears to emit thermal radiation preferentially in the 8-13 μm atmospheric window, similar to how selective surfaces are designed to reflect or absorb specific wavelengths of solar radiation.
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 solution achieves improved cooling performance with enhanced IR selectivity, extended lifespan, and UV resistance, enabling efficient heat dissipation and scalability for large-scale applications, particularly in high-humidity environments.
Implementation Method 1
Radiative cooling is a process that the thermal radiation emitted from a surface or object is stronger than the thermal energy absorbed from the ambient environment
Implementation Method 2
a ceramic emission boosting layer comprising a monolayer of ceramic particles for boosting an overall emissivity of the radiative cooling structure within the wavelength region
Implementation Method 3
coolers with high reflectivity for solar irradiation (0.3-2.5 μm) and high emissivity (absorption) for infrared (2.5-25 μm) have been developed
Implementation Method 4
some infrared radiation can be dissipated to outer space through the so-called 'atmosphere windows ', within which radiation can pass through the atmosphere with little absorption
Data Source
AI summary
The present invention provides a radiative cooling structure that can be fabricated using solution-based processes and offer great IR-selectivity referring to low absorptivity within solar spectrum and high emissivity within the atmosphere transmission window (8-13 microns) for daytime radiative cooling. This structure includes a reflective layer, a ceramic IR-selectively emissive layer and a ceramic emission boosting layer, and the ceramic emission boosting layer is able to boost the overall emissivity of the radiative cooling structure within the atmosphere transmission windows and avoid infrared emission outside the atmosphere transmission window. The IR-selectivity contributes to larger temperature reduction, especially in high humidity area.