Absorbent material and solar panel using such a material
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Solution Overview
Problem
Conventional thermal solar panels face high stagnation temperatures due to inefficient infrared radiation management, leading to rapid degradation of heat transfer fluids and the need for high-performance materials and complex hydraulic systems, which increases costs and complexity.
Innovation Solution
A multilayer material comprising a support with high infrared reflectance and a selective layer of Vanadium oxides (VO2 and VnO2n+/-1) that maintains high solar absorbance while adjusting transmittance and reflectance with temperature, reducing infrared emissivity and reflectance, thereby controlling stagnation temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional absorbent material is used in thermal solar panels, then high solar energy absorption is achieved, but stagnation temperature becomes excessively high (220-250°C)
Solution Approach 1:
The absorbent material is divided into multiple functional layers: a top selective absorbent layer for solar energy absorption, an intermediate phase change material layer for thermal regulation, and a bottom reflective layer for heat retention. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between absorbing solar energy and controlling stagnation temperature.
Solution Approach 2:
The patent utilizes the phase change material's ability to change physical state (parameter) at specific temperatures. When the absorbent layer reaches the phase change temperature, the PCM absorbs excess heat through phase transition (e.g., solid to liquid), effectively capping the stagnation temperature while maintaining high solar absorption capability.
2Reliability
If high-performance materials are used to withstand high stagnation temperatures, then panel reliability improves, but manufacturing cost increases
Solution Approach 1:
The phase change material layer acts as a thermal buffer that prevents the stagnation temperature from reaching levels that would require expensive high-temperature resistant materials. By cushioning the thermal load in advance through phase change, the patent enables the use of standard, lower-cost materials while maintaining panel reliability.
3Reliability
If complex hydraulic systems are used to manage high stagnation temperatures, then heat transfer fluid degradation is reduced, but device complexity increases
Solution Approach 1:
The phase change material provides passive thermal regulation without requiring active control systems. The PCM automatically absorbs excess heat when temperature reaches the phase change point and releases it when temperature drops, creating a self-regulating system that protects the heat transfer fluid without complex hydraulic controls.
4Temperature
If the infrared transmittance is increased to reduce stagnation temperature, then solar energy absorption efficiency decreases
Solution Approach 1:
Different layers of the absorbent material have different optical properties optimized for their specific functions. The top selective absorbent layer has high solar absorption and low infrared transmittance for heat retention, while the phase change material layer provides thermal regulation. This local optimization of properties resolves the contradiction between infrared transmittance and solar energy absorption.
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 multilayer material achieves a lower stagnation temperature, reducing heat transfer fluid degradation and allowing for the use of less expensive materials, while maintaining high solar energy absorption efficiency and thermal performance.
Implementation Method 1
having a solar absorbance greater than 75% for radiation of wavelength between 0.4 and 2.5μm
Implementation Method 2
a support having a reflectance R greater than 80% for radiation of wavelength greater than 5μm
Implementation Method 3
having, for radiation of wavelength between 6 and 10 μm, a transmittance Tr such that: Tr > 85% for T < Tc
Data Source
Figure 1~5
Figure 6~7
AI summary
The invention relates to a multilayer material including at least: one substrate having a reflectance R greater than 80% for radiation having a wavelength greater than 5 μm, one selective layer including a combination of vanadium oxides VO2 and VnO2n+/-i, where n > 1, said selective layer having a solar absorbance greater than 75% for radiation having a wavelength of 0.4 to 2.5 μm regardless of what the temperature T is, and having, for radiation having a wavelength of 6 to 10 μm, a transmittance Tr such as: > Tr > 85% for T < Tc, a critical temperature, > 20% ≤ Tr ≤ 50% for T > Tc. The invention is used to produce thermal solar panels having a low stagnation temperature and a high yield.