Plasmonic Thin-Film Absorber-Emitter for Selective IR Thermal Control
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Solution Overview
Problem
Existing thin-film structures fail to simultaneously function as efficient broad-band absorbers of solar radiation and spectrally selective infrared emitters, limiting the conversion efficiency in concentrated solar thermal and thermophotovoltaic systems.
Innovation Solution
A novel thin-film integrated spectrally-selective plasmonic absorber/emitter (ISSAE) that absorbs solar radiation in the 250 nm<λ3.5 μm range and emits infrared radiation in the 1.5 μm<λ<2.5 μm range, providing thermal insulation and matching the bandgap of thermophotovoltaic cells for enhanced energy conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional thin-film structures are used, then manufacturing is simpler, but they cannot simultaneously achieve efficient broad-band solar absorption and spectrally selective infrared emission
Solution Approach 1:
The thin-film structure is segmented into multiple functional layers, each with specific optical properties. The structure includes a metal layer for infrared reflection, a dielectric layer for thermal insulation, and a solar absorber layer for broad-band solar radiation absorption. This segmentation allows each layer to be optimized for its specific function while working together to achieve both broad-band absorption and spectrally selective emission.
Solution Approach 2:
The invention employs composite material structures combining metals (e.g., aluminum, silver, gold), dielectrics (e.g., silicon dioxide, silicon nitride), and solar absorber materials. These composite layers create a multi-functional coating that simultaneously provides solar absorption, infrared reflection, and thermal insulation, resolving the contradiction between spectral selectivity and structural complexity.
2Productivity
If the hot surface emits infrared radiation, then energy conversion occurs, but infrared radiation loss reduces thermal efficiency
Solution Approach 1:
The coating structure implements local quality by having different optical properties at different spectral regions. The metal and dielectric layers are designed to reflect infrared radiation specifically, while allowing solar radiation absorption in the visible and UV ranges. This spectral differentiation allows the surface to maintain high temperature by reducing infrared losses while still enabling energy conversion through controlled emission in specific bands.
Solution Approach 2:
The invention converts the harmful infrared radiation loss into a beneficial feature by using the metal layer to reflect infrared radiation back to the hot surface, maintaining higher temperatures. The dielectric layer further enhances this by providing thermal insulation. Meanwhile, the structure still allows controlled infrared emission in specific bands for energy conversion, effectively turning potential energy loss into thermal maintenance and controlled energy release.
3Temperature
If solar concentration is increased to achieve higher temperatures, then temperature increases, but system complexity and cost increase
Solution Approach 1:
The invention changes the optical parameters of the surface coating to achieve higher temperatures without proportionally increasing solar concentration. By modifying the coating's solar absorptivity and infrared emissivity through the multi-layer structure, the system achieves enhanced temperature performance through material property optimization rather than purely geometric concentration increases, thereby reducing overall system complexity.
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
Enables day-and-night electricity production with reduced infrared radiation loss, allowing for higher temperature achievement and efficient energy conversion, even without direct sunlight, by wrapping around heat-exchange pipes for continuous operation and reduced solar concentration requirements.
Implementation Method 1
thin-film integrated spectrally-selective plasmonic absorber/emitter
Implementation Method 2
efficient broad-band absorber of solar radiation in the spectral region 250 nm-3.5 μm
Implementation Method 3
spectrally selective infrared emitter that can be tuned to emit in the 1.5 μm-2.5 μm range
Implementation Method 4
performs all three functions at once: absorption, thermal insulation against radiative energy loss, and selective emission
Data Source
AI summary
Thin-film integrated spectrally-selective plasmonic absorber/emitter (ISSAE) that is simultaneously (i) an efficient sunlight absorber; (ii) an efficient heat insulator that enables modest sunlight concentration to produce a high temperature by reducing infrared emission by a hot surface; (iii) a spectrally-selective infrared emitter that supplies infrared photons of the right energy to a targeted photovoltaic cell, thereby matching its bandgap. Additionally, said ISSAE is sufficiently thin to enable its use as a wrapping/cloaking material for use with hot storage pipes containing heat exchange fluid. Said ISSAE is incorporated into a number of solar-conversion apparatus, taking advantage of the unique properties of said ISSAE.