Refractory solar selective coatings
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Solution Overview
Problem
Current solar selective coatings fail to achieve high solar absorptivity and low infrared emissivity at elevated temperatures, leading to inefficiencies in solar energy conversion and thermal storage, as they either degrade at high temperatures or lack tunability and conformal application capabilities.
Innovation Solution
A photonic device with a mesoporous photonic coating infiltrated by an optical coating, comprising nanoparticles of specific sizes in an amorphous matrix, engineered to maintain high solar absorptivity and low IR emissivity at temperatures above 720°C, utilizing advanced fabrication methods like Atomic Layer Deposition and sol-gel processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solar selective coatings (e.g., Pyromark 2500, cermets) are used, then manufacturing simplicity is maintained, but solar absorptivity and thermal stability at high temperatures cannot be simultaneously achieved
Solution Approach 1:
The patent employs a composite coating structure consisting of a photonic crystal layer with embedded metal nanoparticles (Au, Ag, Cu) within a dielectric matrix (SiO2, TiO2, ZrO2). This composite structure enables simultaneous achievement of high solar absorptivity (α ≥ 0.90) and low thermal emissivity (ε ≤ 0.05) at temperatures above 720°C, while maintaining manufacturing feasibility through established techniques like atomic layer deposition (ALD) and sol-gel processes.
Solution Approach 2:
The coating implements local quality optimization by incorporating metal nanoparticles with specific sizes (10-100 nm) and concentrations (5-50 wt%) within specific layers of the photonic crystal structure. The nanoparticle distribution and size are locally tuned to enhance optical absorption in the solar spectrum while maintaining thermal stability at high temperatures.
2Adaptability or versatility
If existing absorber coatings are used, then ease of manufacture is maintained, but tunability of optical properties is lost
Solution Approach 1:
The patent achieves optical property tunability by systematically varying key parameters: metal nanoparticle size (10-100 nm), nanoparticle concentration (5-50 wt%), photonic crystal layer thickness (50-500 nm), and dielectric matrix composition. These parameter adjustments enable optimization of solar absorptivity and thermal emissivity for different concentrated solar power applications while using standard fabrication techniques.
Solution Approach 2:
The coating structure incorporates dynamic tunability through adjustable photonic crystal lattice constants and nanoparticle distributions, allowing the optical properties to be adapted for different operating conditions and temperature ranges in concentrated solar power systems.
3Manufacturing precision
If conventional coatings are applied to complex structures, then manufacturing simplicity is maintained, but conformal coating coverage is insufficient
Solution Approach 1:
The patent replaces conventional mechanical coating methods with atomic layer deposition (ALD) and sol-gel processes, which provide superior conformal coverage on complex three-dimensional structures. These deposition techniques enable uniform coating thickness and complete surface coverage on receivers with complex geometries, ensuring consistent optical properties throughout the entire surface.
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 solution achieves solar absorptivity ≥90% and IR emissivity ≤0.05 at high temperatures, enhancing the efficiency of solar energy conversion and storage while providing thermal stability and tunability, surpassing the limitations of existing coatings.
Implementation Method 1
the ideal material is one that can absorb all the visible light, but that blocks all the thermal energy to minimize the radiation losses
Implementation Method 2
as more solar energy is concentrated in a small spot, the temperature increases and a fraction of the energy is lost as thermal radiation. The reason for this is that the power lost to radiation of a black object evolves as T to the fourth power
Implementation Method 3
utilizing advanced fabrication methods like Atomic Layer Deposition and sol-gel processes
Implementation Method 4
utilizing advanced fabrication methods like Atomic Layer Deposition and sol-gel processes
Data Source
AI summary
Selective receiver coatings provide high performance for concentrated solar power applications. The solar selective coating provides high solar absorptivity (90% or greater) with low IR emissivity (0.1 or less) while maintaining stability at temperatures greater than 700° C. The coating comprises a composite of a mesoporous photonic matrix with a conformal optical coating. One example composite coating includes a mesoporous photonic coating comprising a plurality of particles having sizes between 100 nm and 2000 nm, and a conformal optical coating formed by Atomic Layer Deposition (ALD) that infiltrates the mesoporous structure of the photonic coating and comprises metal nanoparticles and an amorphous dielectric matrix.