Multilayer Solar Absorber Coating for High-Temperature Stability
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Solution Overview
Problem
Existing solar absorber coatings for solar thermal or thermodynamic systems face challenges with high-temperature stability and performance degradation, particularly when using high or medium-high reflectance metals, which limits their effectiveness and service life.
Innovation Solution
A spectrally selective solar absorber coating is developed with a multilayer structure comprising an infrared reflecting base layer, a multifunction structure with additional infrared reflecting layers and stabilizing layers, and an anti-reflection multilayer structure, using materials like Ti, Zr, Mo, W, and their nitrides to enhance stability and performance, particularly with the use of Ag and Au for high-temperature applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high or medium-high reflectance metals are used in solar absorber coatings, then infrared reflectance is improved, but high-temperature stability deteriorates
Solution Approach 1:
The patent uses composite materials by combining highly reflective metal layers (Au, Ag, Cu, Al) with stabilizing ceramic or cermet layers. This composite structure allows the metal to provide high infrared reflectance while the ceramic/cermet component provides high-temperature stability, resolving the contradiction between reflectance performance and thermal stability.
Solution Approach 2:
The stabilizing layers act as intermediaries between the highly reflective metal layers and the substrate. These intermediate layers protect the metal from direct exposure to high temperatures and prevent degradation, enabling the metal to maintain its reflectance properties without suffering from high-temperature instability.
2Productivity
If complex multilayer structures are used to achieve ideal spectral selectivity, then photothermal efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The stabilizing layers serve multiple functions simultaneously: they provide high-temperature stability, act as diffusion barriers between layers, and maintain the structural integrity of the coating. This multi-functionality reduces the need for additional specialized layers, simplifying the overall manufacturing process while maintaining high photothermal efficiency.
3Quantity of substance
If thin film layers are used to achieve spectral selectivity, then material usage is reduced, but structural stability at high temperature deteriorates
Solution Approach 1:
The patent applies different material properties to different layers: the metal layers are kept thin to minimize material usage and maintain spectral selectivity, while the stabilizing ceramic/cermet layers are positioned strategically where thermal stress and diffusion occur. This local optimization allows thin films to provide spectral functionality while concentrated stabilizing material provides structural integrity at high temperatures.
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 improved photothermal performance and extended service life, maintaining high solar absorbance and low thermal emissivity even at elevated temperatures up to 550°C in vacuum and 300°C in air, with enhanced structural and chemical-physical stability.
Implementation Method 1
a first layer, consisting of a material with a high reflectance in the infrared spectral region
Implementation Method 2
one or more layers consisting of a cermet material that absorbs the solar radiation hitting the receiver and, at the same time, that is transparent to infrared radiation
Implementation Method 3
an anti-reflection multilayer structure
Data Source
Figure 1~2
AI summary
A spectrally selective solar absorber coating (2) for a receiver of a solar thermal or thermodynamic system and comprising in sequence: • - an infrared reflecting multilayer structure (21, 22); • - an absorbing multilayer cermet structure (23); and • - an anti-reflection multilayer structure (24). The infrared reflecting multilayer structure (21, 22) comprises: • (i) an infrared reflecting base layer (21) with barrier and adhesion layer functions, arranged in contact with a substrate (1) which is part of the receiver and consists of one or more transition metals selected from among Ti, V, Cr, Zr, Nb, Hf, Ta, Mo, W or of a nitride of one or more of said transition metals; and • (ii) a multifunction structure (22), which is placed on the infrared reflecting base layer (21) and comprising at least: • - multiple additional infrared reflecting layers (22a) with the function of increasing the infrared reflectance of the absorber coating (2), each of which consists of a metal selected from among Au, Ag, Cu, Al, Mo and W, and • - multiple stabilizing layers (22b) of the additional infrared reflecting layer (22a), each of which consists of ■ a ceramic material; or ■ a cermet material; or ■ a material consisting of one or more transition metals or of a nitride of one or more transition metals. The multiple additional infrared reflecting layers (22a) and the multiple stabilizing layers (22b) are arranged so that one reflecting layer alternates with one or more stabilizing layers. One of the stabilizing layers (22b) is placed in contact with the absorbing multilayer cermet structure (23).