Selective Solar Absorber Coating for Low-Loss Laser Welding
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Solution Overview
Problem
Current solar collector materials face challenges with high infrared reflection leading to heat loss and inefficient heat transfer due to the high reflectivity of metallic surfaces, especially when joined with heat carrier tubes using laser welding, which requires high-power lasers and results in low productivity and heat conduction.
Innovation Solution
A composite material with an optically active multilayer system on one side and an optically active layer on the reverse side, designed to reduce infrared reflection minimally while enhancing solar radiation absorption and heat transfer efficiency, using layers such as titanium aluminum carboxynitride and chromium oxynitride, and applying an aluminum oxide layer to reduce laser reflection and prevent corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a metallic carrier material with high infrared reflection is used to minimize heat loss, then heat radiation losses are reduced, but laser welding efficiency deteriorates due to high reflectivity requiring high-power lasers
Solution Approach 1:
The patent applies different optical properties to different surfaces of the same component. The front surface (solar radiation side) maintains high infrared reflection to minimize heat loss, while the rear surface (laser welding side) is treated with an optically active layer that reduces infrared reflection to improve laser welding efficiency. This local differentiation resolves the contradiction by allowing each surface to optimize for its specific function.
Solution Approach 2:
The patent segments the single metallic carrier material into functionally distinct surfaces: a front surface optimized for thermal radiation control and a rear surface optimized for laser processing. By treating these surfaces differently with appropriate optically active layers, the system achieves both low heat radiation loss and high laser welding efficiency simultaneously.
2Loss of energy
If the rear surface is left uncoated to maintain high infrared reflection, then heat radiation loss is minimized, but laser welding becomes inefficient and costly
Solution Approach 1:
The patent applies different optical properties to different surfaces of the same component. The front surface (solar radiation side) maintains high infrared reflection to minimize heat loss, while the rear surface (laser welding side) is treated with an optically active layer that reduces infrared reflection to improve laser welding efficiency. This local differentiation resolves the contradiction by allowing each surface to optimize for its specific function.
3Productivity
If an optically active layer is applied to the rear surface to improve laser welding, then laser welding efficiency increases, but infrared reflection decreases leading to higher heat radiation loss
Solution Approach 1:
The patent applies different optical properties to different surfaces of the same component. The front surface (solar radiation side) maintains high infrared reflection to minimize heat loss, while the rear surface (laser welding side) is treated with an optically active layer that reduces infrared reflection to improve laser welding efficiency. This local differentiation resolves the contradiction by allowing each surface to optimize for its specific function.
4Ease of manufacture
If a simple single-layer coating is used on the rear surface, then manufacturing is simplified, but the balance between laser welding efficiency and heat radiation control is insufficient
Solution Approach 1:
The patent employs a composite optically active layer on the rear surface consisting of multiple components (metal oxide layer and organic compound layer) with complementary functions. The metal oxide provides infrared reflection control while the organic compound enhances laser absorption. This composite structure achieves superior optical performance balance compared to simple single-layer coatings.
Solution Approach 2:
The patent optimizes specific parameters of the optically active layer including thickness (5-50 nm), composition ratios, and material selection to achieve the desired balance between laser welding efficiency and heat radiation control. By carefully adjusting these parameters, the system achieves optimal performance for both functions.
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 composite material achieves high solar radiation absorption and low infrared heat radiation loss, improving heat transfer efficiency and enabling more efficient and cost-effective laser welding of heat carrier tubes, while maintaining stability and resistance to oxidation and corrosion.
Implementation Method 1
The optically active multilayer system on a carrier material, in particular aluminum or an aluminum alloy... absorbs the incident solar radiation (300-2,500 nm) and convert it into heat
Implementation Method 2
the optically active layer, which specifically affects the reflection of the uncoated carder material in such a way that the joining of heat carrier tubes to the composite material with the laser becomes more efficient
Implementation Method 3
the optical parameters of this optically active layer are selected to be such that this layer reduces the high reflection of the metallic carrier material in the infrared range only insignificantly and thus keeps heat radiation losses low
Data Source
AI summary
The present invention pertains to a composite material for use as a selective solar absorber with a carrier layer (1), wherein at least the following layers are present on a side (B) of the carrier layer: A reflection layer (3), an absorber layer (5) and a dielectric and/or oxidic antireflection layer (7), wherein a layer (4) consisting of a nitride, a carbide or a carbonitride of a metal or of a mixture of two or more metals from subgroup IV, V or VI is located between absorber layer (5) and reflection layer (3), and an optically active layer (6) consisting of a metal compound with stoichiometric composition is located between absorber layer (5) and the dielectric antireflection layer (7).In addition, the present invention pertains to a composite material for use as a selective solar absorber with a carrier layer (1) consisting of aluminum or an aluminum alloy, wherein an optically active layer (8), which reduces the reflection of the uncoated carrier material by at least 5% at a specific wavelength in λ the wavelength range between 200 nm and 10 μm and preferably between 200 nm and 2,500 nm during irradiation at a specific incidence angle and reduces the reflection of the uncoated carrier material by no more than 20% and preferably by no more than 5% in the wavelength range between 2.5 μm, is located on a side (A) of the carrier layer.