Chitosan-Coated Metallic Substrate for Radiative Cooling
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Solution Overview
Problem
Existing radiative cooling substrates are unsuitable for daytime use due to solar radiation absorption and have complex manufacturing processes, limiting their applicability and efficiency.
Innovation Solution
A radiative cooling substrate is developed by depositing a chitosan layer on a metallic substrate using an electrophoretic process, which reflects solar radiation and emits thermal energy through the atmospheric window, enhancing thermal dissipation without energy input, and is environmentally friendly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional radiative cooling substrates use coating layers (polyethene, silicon oxide) to achieve high emissivity in the atmospheric window, then thermal radiation emission is improved, but solar radiation absorption increases making them unsuitable for daytime use
Solution Approach 1:
The patent uses a composite structure consisting of a metallic substrate (aluminum, stainless steel, or copper) combined with a chitosan coating layer. The metallic substrate provides high solar radiation reflectivity, while the chitosan layer contributes to thermal radiation emission in the atmospheric window, achieving both low solar absorption and high thermal emission simultaneously
Solution Approach 2:
The patent changes the material parameter from conventional polymer or oxide coatings to chitosan, a natural biopolymer with specific optical properties. The chitosan layer thickness is optimized to 0.5-10 μm to achieve the desired balance between solar reflectivity and thermal emissivity, enabling effective radiative cooling during daytime
2Loss of energy
If radiative cooling substrates use one-dimensional photonic crystals or metamaterials to achieve wavelength-selective radiation, then thermal emission control is improved, but manufacturing complexity increases due to additional nanometer-thickness metal layers
Solution Approach 1:
The patent extracts and eliminates the complex photonic crystal or metamaterial structures from the design, replacing them with a simple chitosan coating on a metallic substrate. This removes the need for additional nanometer-thickness silver or aluminum reflecting layers, significantly simplifying the manufacturing process while maintaining radiative cooling functionality
Solution Approach 2:
The patent changes the structural approach from complex photonic crystals to a simple thin-film coating with optimized thickness parameters. The chitosan layer thickness of 0.5-10 μm provides the necessary optical properties without requiring the intricate nanoscale structures of photonic crystals, making the manufacturing process more accessible and cost-effective
3Loss of energy
If conventional radiative cooling coatings are applied to achieve high thermal emissivity, then cooling efficiency is improved, but the manufacturing process becomes more complex and costly
Solution Approach 1:
The patent employs chitosan, a inexpensive natural biopolymer derived from crustacean shells, as the cooling coating material. This replaces expensive conventional coatings and eliminates the need for costly additional metal layers, making the radiative cooling technology more economically viable and easier to manufacture at scale
Solution Approach 2:
The patent creates a composite material system using readily available metallic substrates (aluminum, stainless steel, copper) combined with chitosan coating. This composite approach leverages the inherent properties of common materials to achieve high cooling efficiency without requiring complex or expensive manufacturing processes
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 substrate effectively dissipates thermal energy both day and night, is biocompatible, and simplifies the manufacturing process, reducing costs and environmental impact while maintaining high emissivity in the atmospheric window.
Implementation Method 1
depositing a chitosan layer including the chitosan with a first thickness on the metallic substrate in an electrophoretic process
Implementation Method 2
Radiative cooling method utilizes thermal radiation as the only way for transporting thermal energy... High radiative heat flux is emitted to reduce temperature of the object surface and dissipate the thermal energy
Data Source
AI summary
A radiative cooling substrate and a manufacturing method of the radiative cooling substrate are provided. The radiative cooling substrate includes a metallic substrate and a chitosan layer disposed on the metallic substrate with a thickness of 0.5 μm to 10 μm. The chitosan layer emits radiation within a waveband between 8 μm and 13 μm.