Solar Receiver Absorbing Coating With Oxidation-Barrier Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing spectrally selective absorbing coatings for solar receivers operating in air face challenges in maintaining durability and photo-thermal efficiency at high temperatures due to oxidative degradation, limiting their effectiveness and lifespan.
Innovation Solution
A spectrally selective absorbing coating is developed that includes a protective structure comprising a metal layer alloyed with medium-high reflecting metals and a ceramic layer of sub-stoichiometric oxide, which forms a barrier oxide layer to protect against atmospheric oxidizing agents, allowing the coating to operate effectively up to 1200°C in air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the receiver tube operates at high temperatures in air, then the photo-thermal efficiency increases, but oxidative degradation occurs leading to reduced durability
Solution Approach 1:
The coating uses a composite structure with multiple layers including ceramic layers (e.g., alumina, silica) and metal layers (e.g., nickel, chromium) to achieve both high-temperature stability and oxidation resistance. The ceramic layers provide thermal stability and oxidation barrier, while the metal layers enhance adhesion and provide additional oxidation protection, allowing the coating to maintain durability at temperatures up to 550°C in air.
Solution Approach 2:
The patent creates a protective environment by depositing dense, low-porosity ceramic and metal layers that effectively isolate the underlying metal substrate from atmospheric oxygen. This barrier layer prevents oxygen diffusion to the metal substrate, creating an inert environment at the metal-coating interface even when operating in air at high temperatures, thus preventing oxidative degradation.
2Use of energy by moving object
If a multi-layered spectrally selective coating is applied, then photo-thermal efficiency improves, but manufacturing complexity increases
Solution Approach 1:
The coating applies different material compositions and properties to different layers, with each layer optimized for its specific function: the bottom metal layer provides adhesion and oxidation resistance, intermediate ceramic layers provide thermal stability and oxidation barrier, and top layers are optimized for solar absorption. This local optimization of material properties in each layer achieves high photo-thermal efficiency while managing the complexity through functional specialization.
Solution Approach 2:
The coating is divided into multiple discrete layers with distinct functions, allowing independent optimization of each layer's thickness, composition, and deposition parameters. This segmentation enables the complex multi-functional requirements to be met by combining simpler, well-understood material systems in a layered architecture, making the overall complex performance achievable through manageable individual components.
3Ease of manufacture
If the coating is exposed to air, then industrial production feasibility is maintained, but oxidative degradation accelerates
Solution Approach 1:
The coating structure is designed with built-in protective layers (ceramic and metal) that are deposited during manufacturing to pre-establish oxidation resistance before the product enters service. This preliminary protective action is incorporated into the coating architecture itself, allowing the coating to withstand air exposure during both manufacturing and operation without requiring post-manufacturing protective measures, thus maintaining industrial feasibility while preventing oxidation.
4Power
If the coating operates at high temperatures, then energy conversion efficiency improves, but thermal emissivity losses increase
Solution Approach 1:
The coating is designed with specific optical parameters including controlled emissivity in the thermal infrared range and high absorptivity in the solar spectrum. By carefully selecting material compositions and layer thicknesses, the coating achieves a favorable ratio of solar absorption to thermal emission, maintaining high energy conversion efficiency while minimizing thermal radiative losses at operating temperatures up to 550°C.
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 enhanced durability and photo-thermal efficiency by preventing oxidative degradation, enabling operation at high temperatures comparable to evacuated systems, while maintaining industrial production feasibility.
Implementation Method 1
a ceramic layer of sub-stoichiometric oxide, which forms a barrier oxide layer to protect against atmospheric oxidizing agents
Implementation Method 2
high photo-thermal efficiency, the coating has to show a behaviour as close as possible to the ideal one, that is zero reflectance (unitary absorbance) in the spectral region of the solar radiation
Implementation Method 3
a reflector in the infrared region... unitary reflectance (zero absorbance and emissivity) in the spectral region of the thermal infrared
Data Source
AI summary
A spectrally selective absorbing coating for receivers acting in air of thermal and thermodynamic solar systems having a substrate and at least a protective structure capable of protecting the metal component of the protective structure and the metal components of the absorbing coating against the atmospheric oxidizing agents, the protective structure which in turn includes a metal layer upon which a ceramic layer is arranged.