Multi-surface passive cooling articles
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Solution Overview
Problem
Existing cooling technologies, such as air conditioning and refrigeration, require significant energy consumption and have limitations in effectively managing temperature regulation, especially in outdoor environments like buildings and vehicles, where passive cooling methods are underdeveloped.
Innovation Solution
The use of multi-surface passive cooling articles with high emissivity elements facing upwards towards the sky and low emissivity elements facing downwards or shaded by the high emissivity elements, which reflect solar energy and radiate heat in the atmospheric window region, facilitating cooling both during the day and night without external energy sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If passive cooling surfaces are oriented vertically, then they can be applied to buildings and vehicles, but the cooling performance is reduced compared to horizontal surfaces
Solution Approach 1:
The cooling surface is divided into multiple tilted segments or facets that collectively form a vertical structure. Each segment is angled to optimize radiative cooling toward the sky, while the overall assembly maintains vertical orientation for building/vehicle application. This segmentation allows the surface to achieve both vertical adaptability and optimal cooling performance.
Solution Approach 2:
The invention transitions from a simple flat vertical surface to a three-dimensional faceted structure with multiple tilted planes. By adding this dimensional complexity, the surface can simultaneously present optimized cooling angles to the sky while maintaining vertical attachment to buildings or vehicles, resolving the contradiction between orientation adaptability and cooling effectiveness.
2Reliability
If high emissivity materials are used for passive cooling, then radiative cooling efficiency is improved, but solar heat absorption increases during the day
Solution Approach 1:
The cooling surface incorporates spatially varying emissivity properties, with different regions having optimized emissivity values for different wavelengths. High emissivity in the atmospheric window region (8-13 μm) enables efficient thermal radiation to space, while low emissivity in the solar region (0.3-2.5 μm) minimizes solar heat absorption. This local quality differentiation resolves the contradiction between radiative cooling efficiency and solar heat rejection.
Solution Approach 2:
The invention employs composite material structures combining multiple layers with different optical properties. These composite materials achieve spectrally selective behavior, allowing high emissivity in the infrared atmospheric window for effective cooling radiation while maintaining low absorptivity in the solar spectrum, thus simultaneously improving radiative cooling efficiency and reducing solar heat gain.
3Reliability
If cooling surfaces are designed for nighttime operation, then passive cooling is more effective, but daytime cooling capability is limited
Solution Approach 1:
The cooling surface is designed with universal functionality to operate effectively both during the day and at night. By incorporating spectrally selective properties and optimized geometric configurations, the surface maintains high radiative cooling efficiency regardless of ambient conditions, enabling continuous cooling operation across different times of day rather than being limited to nighttime only.
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 articles provide efficient temperature reduction by reflecting solar energy and radiating heat, reducing the need for energy consumption and greenhouse gas emissions, while maintaining suitable temperatures in structures and vehicles, thus lowering operational costs and environmental impact.
Implementation Method 1
high emissivity elements at least partially defining first element surfaces... in an atmospheric window wavelength range from 8 to 13 micrometers
Implementation Method 2
low emissivity elements at least partially defining second element surfaces... defining a second average reflectance of greater than or equal to 60% in a solar wavelength range from 0.4 to 2.5 micrometers
Implementation Method 3
The plurality of first elements define a first absorbance of greater than or equal to 0.6 in an atmospheric window wavelength range from 8 to 13 micrometers
Data Source
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AI summary
Passive cooling article (120) includes a plurality of first elements (122) defining a high absorbance in the atmospheric window wavelength range and defining high average reflectance in the solar wavelength range and a plurality of second elements (124) defining a low absorbance in the atmospheric window wavelength range and defining high average reflectance in the solar wavelength range, wherein the plurality of first (122) and second (124) elements are interspersed to form a major structure having a first major surface (130) comprising the first element outer surfaces (126) and the second element outer surfaces (128), wherein the first element outer surfaces (126) face a first direction toward a first end region (136) of the major structure (130) and the second element outer surfaces (128) face a second direction toward a second end region (136) of the major structure. The article (120) may be applied to a substrate (104), for example, on a generally vertical surface of a vehicle or stationary structure.