Selective Solar Coating With Multilayer Absorber for Low Emissivity
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Solution Overview
Problem
Existing selective solar absorbent coatings face challenges in achieving precise stoichiometry control and material composition due to the codeposition techniques used for cermet layers, leading to limitations in solar energy absorption and thermal radiation management.
Innovation Solution
The use of alternating multilayered dielectric and metal structures with subnanometer thickness, deposited using reactive sputtering and DC sputtering techniques, respectively, eliminates the need for precise stoichiometry control and allows for a wider range of material compositions, enhancing solar energy absorption and low emissivity properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If codeposition techniques through reactive sputtering are used to deposit cermet layers, then solar energy absorption capacity is improved, but manufacturing precision deteriorates due to difficulty in controlling stoichiometry
Solution Approach 1:
The cermet layer is segmented into multiple thin alternating layers of dielectric material and metal, each deposited separately through sputtering. This segmentation allows independent control of each layer's thickness and composition, eliminating the stoichiometry control problems associated with codeposition while maintaining the optical absorption properties of the original cermet layer.
Solution Approach 2:
The patent uses composite multilayer structures combining dielectric and metallic layers to replace the homogeneous cermet material. This composite approach allows optimization of each component's properties - the dielectric layers provide structural stability and the metal layers provide absorption - while avoiding the manufacturing complexity of codeposition.
2Stability of the object's composition
If reactive gas is used during sputtering to form dielectric compounds, then material composition is improved, but device complexity increases due to stringent control requirements
Solution Approach 1:
The deposition process is segmented into separate steps for dielectric layers and metal layers. Dielectric layers are deposited with reactive gas to form stable compounds, while metal layers are deposited without reactive gas interference. This segmentation simplifies process control by eliminating the need to manage complex gas reactions during simultaneous codeposition.
Solution Approach 2:
The dielectric layers are deposited first through reactive sputtering to form a stable base structure, followed by metal layer deposition. This preliminary action ensures proper material composition and adhesion before adding the metallic components, simplifying the overall process control.
3Use of energy by moving object
If multiple alternating subnanometer layers are used to achieve selective absorption, then solar energy absorption is improved, but manufacturing precision requirements increase
Solution Approach 1:
Instead of requiring extremely precise control of each subnanometer layer, the patent uses multiple slightly thicker layers (totaling several hundred nanometers) to achieve the same optical effect. This partial action approach - using more layers with greater thickness - reduces the precision requirements for each individual layer while maintaining the selective absorption performance.
Solution Approach 2:
The patent changes the scale parameters from subnanometer thickness to nanometer-scale thickness for individual layers. This parameter change makes the manufacturing process more feasible with standard sputtering equipment while achieving the same optical functionality through increased total layer thickness and number of layers.
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
This approach results in a robust and reliable selective solar coating with improved solar energy absorption and low emissivity characteristics, facilitating greater design flexibility and efficiency in solar energy capture systems.
Implementation Method 1
The use of alternating multilayered dielectric and metal structures with subnanometer thickness, deposited using reactive sputtering and DC sputtering techniques, respectively
Implementation Method 2
a structure of multiple alternating subnanometer thickness dielectric and metallic layers in which solar energy absorption is produced
Implementation Method 3
coatings with a great capacity for solar energy absorption and low emissivity characteristics to reduce energy losses through thermal radiation in far infrared
Data Source
AI summary
Selective solar absorbent coating and manufacturing method, with solar absorption and low emissivity properties. The coating comprises a substrate (1) of metal, dielectric or ceramic material, at least one highly reflective metal layer (2) in mid-far infrared applied to the substrate itself which provides low emissivity properties, a mufti-layer structure of alternating dielectric and metallic layers (3) of subnanometric thickness applied to the reflective metal layer and at least one dielectric layer (4) that acts as an anti-reflective layer for the solar spectrum. The coating is applicable as a selective absorbent coating in absorbent tubes for parabolic-trough solar collectors, in solar panels for hot water, heating or domestic cooling, both in the form of absorbent tubes and absorbent sheets, in capture systems in tower solar thermoelectric power plants, and in capture systems in Stirling disk systems.