Radiative cooling structures and systems
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Solution Overview
Problem
Current radiative cooling technologies face challenges in efficiently cooling surfaces during the day due to high solar absorption and energy density mismatch between solar irradiance and infrared radiation flux, particularly in achieving scalable and cost-effective solutions for large area applications.
Innovation Solution
Development of polymer-based selective radiative cooling structures with wavelength-selective emissive layers that transmit solar radiation and emit infrared radiation through atmospheric transmission windows, utilizing polymer matrix composite materials with dielectric particles to enhance emissivity and reduce solar absorption, allowing for high radiative cooling powers while maintaining transparency to solar radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional radiative cooling structures are used, then infrared radiation emission is achieved, but solar absorption is high during the day reducing cooling effectiveness
Solution Approach 1:
The radiative cooling structure is segmented into multiple functional layers: a polymer matrix composite layer with wavelength-selective emissive properties, and a separate solar reflective layer. This segmentation allows each layer to independently optimize its function - the polymer layer emits infrared radiation while the reflective layer blocks solar absorption, resolving the contradiction between infrared emission and solar absorption.
Solution Approach 2:
The invention uses composite materials combining a polymer matrix with dielectric particles (such as glass beads or ceramic spheres) to create a material with tailored optical properties. The composite structure enables simultaneous infrared emissivity and solar reflectivity, as the dielectric particles resonate at infrared frequencies while the polymer matrix provides solar transparency or reflectivity, thus resolving the contradiction between infrared emission and solar absorption.
2Loss of energy
If inorganic multilayer optical coatings are used for wavelength-selective emission, then radiative cooling performance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The invention replaces expensive, complex inorganic multilayer optical coatings with a simpler, more cost-effective polymer-based composite material that can be manufactured using conventional techniques. The polymer composite achieves comparable or superior radiative cooling performance at lower cost and with simpler manufacturing processes, effectively substituting a cheap, easily manufactured solution for an expensive, complex one.
Solution Approach 2:
The invention changes the material parameters from inorganic coatings to organic polymer composites, utilizing the unique optical properties of polymers and dielectric particles. By adjusting the polymer composition, particle size, and concentration, the radiative cooling performance can be optimized without requiring complex multilayer structures, thus simplifying manufacturing while maintaining or improving cooling effectiveness.
3Power
If the cooling structure emits infrared radiation through atmospheric windows, then radiative cooling power increases, but the energy density mismatch between solar irradiance and infrared radiation flux limits daytime cooling
Solution Approach 1:
The invention converts the harmful effect of solar irradiance (which creates energy density mismatch and heating) into a beneficial effect by incorporating a solar reflective layer. This layer reflects the harmful solar radiation while allowing the polymer composite layer to emit infrared radiation through atmospheric windows, thus converting the harmful solar energy into a non-absorbed element and maximizing the beneficial infrared emission for daytime cooling.
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 polymer-based selective radiative cooling structures achieve high cooling powers exceeding 100 W/m² during both day and night, with enhanced infrared emissivity and reduced solar absorption, making them suitable for large-scale, cost-effective applications in cooling surfaces such as solar cells, windows, and buildings.
Implementation Method 1
Radiative cooling features the release of heat from an object or surface in the form of thermal radiation, thereby lowering the temperature of the object or surface
Implementation Method 2
a selective radiative cooling device may preferentially emit infrared radiation at wavelengths corresponding to a 'atmosphere window', also known as an 'atmospheric transmission window' or an 'atmospheric transparent window'. The Earth's atmosphere is practically non-absorbing in these 'window' wavelength ranges
Implementation Method 3
the selective radiative cooling structures limit absorption of solar energy... maximize the infrared radiation in one or more atmospheric transmission windows
Data Source
AI summary
Polymer-based selective radiative cooling structures are provided which include a selectively emissive layer of a polymer or a polymer matrix composite material. Exemplary selective radiative cooling structures are in the form of a sheet, film or coating. Also provided are methods for removing heat from a body by selective thermal radiation using polymer-based selective radiative cooling structures, and a cold collection system comprising a plurality of the polymer-based selective radiative cooling structures.