Ceramic Nanoparticle Radiative Cooling for Sky Window Emissivity
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Solution Overview
Problem
Current passive radiative cooling materials face challenges in achieving high emissivity, durability, and cost-effectiveness while maintaining high transmittance or reflectance for sunlight and high absorptivity in the 8 μm to 13 μm wavelength range corresponding to the sky window section of the atmosphere.
Innovation Solution
A radiative cooling device is developed using a ceramic nanoparticle mixture, comprising a solar reflective layer and an infrared radiation layer. The infrared radiation layer is formed by mixing ceramic nanoparticles with specific intrinsic emissivity profiles in different wavelength ranges to maximize absorptivity and emissivity in the sky window section of the atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If polymer materials are used for radiative cooling, then high emissivity for long-wavelength infrared rays is achieved, but durability and lifespan are reduced due to deterioration by ultraviolet rays and moisture
Solution Approach 1:
The patent uses composite materials combining inorganic ceramic particles (such as silicon oxide, aluminum oxide, silicon nitride) suspended in a polymer matrix. This composite structure allows the material to maintain high infrared emissivity from the polymer while the inorganic ceramic particles provide UV resistance and improved durability, resolving the contradiction between emissivity and durability.
2Reliability
If multi-layer thin film made of inorganic material is used, then lifetime and stability are guaranteed, but production cost increases and large-area production is limited due to vacuum deposition process requirement
Solution Approach 1:
The patent extracts the essential function of inorganic materials (high stability and UV resistance) and incorporates it into a polymer-based coating system through suspended ceramic particles. This eliminates the need for complex vacuum deposition processes while maintaining the stability benefits of inorganic materials, enabling cost-effective large-area production.
Solution Approach 2:
The patent changes the manufacturing approach from vacuum deposition of thin films to a solution-based coating process where ceramic nanoparticles are suspended in a polymer binder. This parameter change in the manufacturing process enables simple spray coating or dip coating methods that are suitable for large-area applications at low cost.
3Temperature
If a material with high absorptivity in the entire area of the sky window section is used, then ideal passive radiative cooling is achieved, but such material is absent in reality
Solution Approach 1:
The patent applies local quality by selecting specific ceramic particle types and size distributions that optimize emissivity in different sub-regions of the sky window spectrum (8-13 μm). By combining particles with different emissivity characteristics, the composite material achieves high overall absorptivity across the entire sky window range, making the ideal material practically available.
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 device achieves efficient radiative cooling below ambient temperature without energy consumption, both during the day and at night, while maintaining stability and cost-effectiveness, thus improving energy efficiency and extending the lifespan of the cooling system.
Implementation Method 1
radiating radiative heat (8 to 13 μm) energy that can escape out of space
Implementation Method 2
Heat dissipation, a high absorptivity or emissivity in the long-wavelength infrared region is required so that heat can be radiated well into space
Implementation Method 3
reflecting the wavelength (0.3 to 2.5 μm) corresponding to sunlight during the day
Data Source
AI summary
The present invention relates to a technical idea of cooling the surface of a material or the internal temperature under the material by emitting heat under an element to the outside while minimizing absorption of light in the solar spectrum, and more particularly to a technology for developing a material having a high transmittance or high reflectance with respect to incident sunlight and a high absorptivity selectively in a wavelength range of 8 μm to 13 μm corresponding to the sky window section of the atmosphere.