Trapezoid Grating Thermal Emitter for TPV Spectral Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional thermal emitters for thermophotovoltaic (TPV) systems lack spectral control, resulting in significant waste of emission power, as they fail to optimally emit photons with energies higher than the photovoltaic cell's bandgap while minimizing emission of photons with lower energies.

Innovation Solution

A thermal emitter with a grating surface featuring equidistant trapezoid-shaped structures that support gap plasmon modes, coupled with a dielectric layer, to achieve a tailored emittance curve with high emission at wavelengths shorter than the photovoltaic cell's bandgap and low emission at longer wavelengths, enhancing power conversion efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a flat emitting surface is used, then the device complexity is low, but the spectral selectivity is insufficient resulting in significant energy waste

Engineering Contradiction:

Improveemission power wasteVSAvoidemitter structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The emitting surface is segmented into a grating structure with multiple equidistant grooves, dividing the continuous surface into discrete periodic elements that can independently support plasmon modes. This segmentation enables spectral control through geometric parameters while maintaining manufacturing feasibility

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The grating structures are designed with specific local geometric properties (trapezoid cross-section, equidistant grooves, optimized width and depth) that create localized surface plasmon resonances. These local structural qualities enable high emittance at specific wavelengths while maintaining overall device simplicity

Inventive Principle:

Principle #3Local quality

2Loss of energy

If conventional grating structures are used, then the manufacturing is simpler, but the emittance spectrum has significant drops between resonant modes

Engineering Contradiction:

Improveemittance drop between modesVSAvoidgrating structure

Core Design Contradiction:

Loss of energyVSEase of manufacture

Solution Approach 1:

The grating structures employ a trapezoid cross-section rather than symmetric rectangular profiles. This asymmetric geometry creates overlapping plasmon modes that fill in the emittance gaps between resonant peaks, achieving a smoother spectrum without complicating the manufacturing process

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The geometric parameters of the grating (groove width, depth, spacing, and trapezoid angles) are optimized to control the plasmon resonance frequencies and their overlap. By adjusting these parameters, the emittance spectrum is shaped to minimize drops between modes while maintaining manufacturing simplicity

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the high emittance zone is extended to increase bandwidth, then the power conversion efficiency improves, but the emission at longer wavelengths increases causing energy loss

Engineering Contradiction:

Improvepower conversion efficiencyVSAvoidemission at wavelengths longer than bandgap

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The grating structures convert what would normally be wasted thermal radiation at long wavelengths into useful high-emittance emission at short wavelengths by supporting localized surface plasmon resonances. The plasmon modes are engineered to enhance emission precisely in the photovoltaic cell's responsive range while suppressing long-wavelength emission through the periodic structure's bandgap effects

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 significantly increases the bandwidth of high emittance, leading to improved power conversion efficiency in TPV systems by minimizing energy loss and optimizing photon emission within the desired spectral range.

Implementation Method 1

surface plasmons (SPs) are coherent delocalized electron oscillations that exist at the interface between any two materials where the real part of the dielectric function changes sign across the interface (e.g. a metal-dielectric interface, such as a metal sheet in air)

Methodology Applied

Scientific EffectSurface plasmon:

Implementation Method 2

The total excitation, including both the charge motion and associated electromagnetic field, is called either a surface plasmon polariton at a planar interface, or a localized surface plasmon for the closed surface of a small particle

Methodology Applied

Scientific EffectLocalized surface plasmon:

Implementation Method 3

Thermal emitters, which are devices to convert heat into radiation

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Implementation Method 4

a thermal emitter device suitable for energy conversion such as thermophotovoltaic (TPV) energy conversion

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Data Source

PatentUS10797633B2Thermal emitter for energy conversion technical field

Publication Date: 2020.10.06 MITSUBISHI ELECTRIC RESEARCH LABORATORIES INC

AI summary

A thermal emitter including a substrate and a grating arranged atop the substrate, the grating includes a plurality of equidistant structures having a cross-section with a trapezoid shape. Material of the substrate and the grating converts incoming heat into radiation.