Sol-Gel Solar Absorber Coating With Low Infrared Emissivity
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Solution Overview
Problem
Current solar absorber coatings for thermal solar collectors are costly to produce and have high emission values in the infrared spectrum, despite achieving high absorption of visible light, due to the use of metallic components and high-vacuum processes.
Innovation Solution
A solar absorber coating comprising metal-oxide or semi-metal-oxide components with added metal or carbon particles, produced using a sol-gel method, which reduces production costs and enhances absorption while minimizing infrared emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-vacuum processes like physical vapor deposition (PVD) or cathode sputtering are used to produce solar absorber coatings, then high absorption properties and low emissivity can be achieved, but production costs and equipment outlay increase significantly
Solution Approach 1:
The patent changes the fundamental parameters of the coating process by transitioning from high-vacuum physical vapor deposition to atmospheric pressure chemical vapor deposition. This parameter change allows the same functional outcome (high absorption, low emissivity) to be achieved without requiring expensive vacuum equipment, thereby resolving the contradiction between reliability and ease of manufacture
Solution Approach 2:
The patent employs inexpensive precursor materials and consumable chemicals in the CVD process that can be readily replenished, replacing the need for expensive, durable vacuum equipment. This approach trades durable expensive equipment for cheap consumable materials, resolving the cost contradiction
2Ease of manufacture
If more cost-effective coating methods are used to reduce production costs, then manufacturing expenses decrease, but absorption properties and emissivity values deteriorate
Solution Approach 1:
The patent creates a composite coating structure with multiple functional layers deposited via CVD. The composite nature of the coating, with different materials in each layer, enables cost-effective production while maintaining high absorption properties and low emissivity, thus resolving the contradiction between ease of manufacture and reliability
3Reliability
If metallic layer components are added to sol-gel coatings to improve absorption properties, then light absorption increases, but material costs and manufacturing complexity increase
Solution Approach 1:
The patent merges the functions of multiple separate coating steps into a single integrated CVD process. By combining precursor delivery, coating deposition, and material incorporation into one atmospheric pressure process, it achieves improved absorption properties without increasing manufacturing complexity, resolving the contradiction between reliability and device complexity
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 coating achieves high absorption of sunlight with low infrared emission, reducing production costs and maintaining thermal and chemical stability, thus improving the efficiency and cost-effectiveness of solar absorber coatings.
Implementation Method 1
at least one sol-gel precursor with at least two metal alkoxides and preferably at least one metal salt is provided
Implementation Method 2
The mixture of carbon particles and at least one metal oxide/semimetal oxide precursor can be applied as a sol to the surface to be coated
Implementation Method 3
where ideally almost the entire radiation spectrum of sunlight is converted into thermal energy by the surface of the solar absorber coating
Implementation Method 4
The coating is therefore required to have a low emissivity in the infrared range above about 2000 nm
Data Source
AI summary
Solar absorption coating comprises a (semi)metal oxide component to which particles are added to form a layer that absorbs light to generate heat. Independent claims are also included for: (1) process (P1) for producing a solar absorption coating from a mixed oxide gel, where at least two metal alkoxides and preferably a metal salt are incorporated as sol-gel precursors; (2) process (P2) for producing a solar absorption coating by mixing a silica dispersion with an alumina or titanium dioxide matrix precursor in the form of a metal alkoxide and optionally adding a metal salt; (3) process (P3) for producing a titanium dioxide layer by a sol-gel process comprising applying a titanium dioxide sol containing 40-95% silver, heating to 180-350[deg] C for 3-15 minutes, applying a titanium dioxide layer, heating to 300-500[deg] C for 5-30 minutes, heating to 400-600[deg] C for 3-15 minutes, preferably applying a zinc oxide layer and preferably heating to 300-450[deg] C for 5-30 minutes.