Pigmented Radiative Cooling Coating Color Paradox
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Solution Overview
Problem
Current passive radiative cooling paints are limited by their white color, as the addition of pigments or dyes interferes with cooling performance by absorbing radiation and converting it into heat, lacking scalable and affordable solutions to introduce color without significantly impacting cooling efficiency.
Innovation Solution
A pigmented radiative cooling composition comprising a reflective component with >55% reflectance in the 0.2-2.5 μm range, a thermally emissive component with >0.85 peak emissivity in 4-35 μm, and a pigmented component such as phosphors or quantum dots that emit absorbed energy, allowing for color addition while maintaining cooling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pigments or dyes are added to passive radiative cooling paint, then color is introduced, but cooling performance deteriorates due to radiation absorption and heat conversion
Solution Approach 1:
The patent changes the optical parameters of pigment particles by controlling their size (reducing to sub-visual dimensions) and material composition (using specific inorganic pigments like titanium dioxide, zinc oxide, or barium sulfate). This parameter transformation allows pigments to scatter visible light for color while maintaining high infrared reflectance and emissivity for radiative cooling, thus resolving the contradiction between color introduction and cooling performance preservation.
Solution Approach 2:
The patent creates a composite coating formulation combining multiple components: infrared-reflective pigments (titanium dioxide, zinc oxide, barium sulfate), infrared-emissive materials (metal oxides, ceramic particles), and binders. This composite structure enables simultaneous achievement of visible color through pigment scattering and thermal radiation management through the other components, resolving the contradiction between color and cooling efficiency.
2Adaptability or versatility
If conventional pigments are used to add color, then aesthetic versatility is improved, but solar radiation absorption increases and cooling efficiency decreases
Solution Approach 1:
The patent transforms the physical parameters of pigment particles by reducing them to sub-visual sizes (0.1-10 micrometers, preferably 0.5-5 micrometers). This size parameter change enables the pigments to scatter visible light effectively for color while having minimal impact on infrared radiation transmission, thus maintaining cooling efficiency while achieving color variety through different pigment combinations.
Solution Approach 2:
The patent applies different functional properties to different components within the coating: specific inorganic pigments provide visible color through scattering, while other components (metal oxides, ceramic particles) provide infrared reflectance and emissivity. This local functional differentiation allows the coating to simultaneously achieve color versatility and cooling reliability without mutual interference.
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 composition achieves comparable cooling rates to white coatings while allowing for color variation, expanding application possibilities without substantial heat absorption, and maintaining temperature below ambient levels.
Implementation Method 1
a first component disposed on the substrate having >55% reflectance in a wavelength range of 0.2 to 2.5 μm
Implementation Method 2
A second component has >0.85 peak thermal emissivity for at least one wavelength in a range of 4-35 μm
Implementation Method 3
A third pigmented component is configured to emit at least a fraction of absorbed energy
Data Source
AI summary
A radiative cooling composition comprises a first component having >55% reflectance in a wavelength range of 0.2 to 2.5 μm and a second component having >0.85 peak thermal emissivity for at least one wavelength in a range of 4-35 μm. A third pigmented component of the composition is configured to emit at least a fraction of absorbed energy, and in certain embodiments the pigmented component comprises at least one phosphor.