Thermophotovoltaic Emitter Design With Selective IR Energy Recycling
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Solution Overview
Problem
Existing thermophotovoltaic generators face inefficiencies in converting heat energy to electricity due to broad-band radiation absorption and heat loss, limiting the overall energy conversion efficiency.
Innovation Solution
A novel TPV design utilizing a material that emits characteristic radiation, combined with selective infrared mirrors and a counterflow heat exchanger to reflect unabsorbed light back into the combustion chamber and preheat reactants, enhancing the conversion of heat energy to electricity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If broad-band radiation is used to heat the emitter, then the emitter can be heated to high temperature, but the conversion efficiency to electricity is limited due to mismatch with PV cell bandgap
Solution Approach 1:
The emitter is designed with selective emission properties that emit radiation preferentially at wavelengths matching the PV cell bandgap, rather than emitting broad-band radiation. This localized spectral quality improvement ensures that the radiation delivered to the PV cell is optimally matched to its absorption characteristics, thereby improving conversion efficiency without sacrificing power output.
Solution Approach 2:
The system changes the spectral parameter of the radiation by using an emitter with selective emission characteristics. The emitter is engineered to radiate at specific wavelengths that correspond to the PV cell's bandgap energy, transforming the radiation spectrum from broad-band to a narrow, optimized band, thus resolving the efficiency-limiting mismatch.
2Loss of energy
If all radiation is directed to PV cells, then electricity generation is maximized, but heat energy that could be reused is lost
Solution Approach 1:
The system implements a feedback loop where radiation and heat that are not converted to electricity are redirected back to the combustion chamber or emitter. The mirrors and heat exchanger create a recirculation pathway that feeds unused energy back into the system, allowing multiple opportunities for energy conversion and reducing overall energy loss.
Solution Approach 2:
The radiation and heat exchanger system serves multiple functions: it redirects unabsorbed radiation back to the emitter for additional conversion opportunities, preheats incoming reactants to improve combustion efficiency, and maintains system temperature. This multi-functionality addresses both energy recovery and system efficiency without proportionally increasing complexity.
3Loss of energy
If infrared radiation is allowed to escape, then the system operates simply, but energy conversion efficiency is reduced
Solution Approach 1:
The system extracts and separates different wavelength components of the radiation using selective mirrors. Infrared mirrors are specifically designed to reflect infrared wavelengths back into the combustion chamber while allowing visible light to pass through to the PV cells. This extraction of specific wavelength bands enables targeted energy recovery without complicating the entire optical system.
Solution Approach 2:
Selective infrared mirrors act as intermediaries between the combustion chamber and the PV cells. These mirrors mediate the radiation path by selectively reflecting infrared wavelengths while transmitting visible light, enabling the system to recover infrared energy without interfering with the primary electricity generation function.
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 design significantly improves energy conversion efficiency by capturing a higher percentage of heat energy as electricity, with the use of characteristic radiation and multiple opportunities for heat energy excitation, achieving improved power output.
Implementation Method 1
combustion heats an emitter (typically a block of metal or graphite) to generate visible and infrared light via blackbody radiation
Implementation Method 2
combustion heats an emitter (typically a block of metal or graphite) to generate visible and infrared light via blackbody radiation
Implementation Method 3
That light is then incident on one or more photovoltaic cells which, in turn, generate electricity
Implementation Method 4
mirrors that selectively reflect light wavelengths that are poorly absorbed by the PV cells
Implementation Method 5
a counterflow heat exchanger that extracts heat from the outflowing combustion products and uses it to preheat the reactants
Data Source
AI summary
An apparatus for generating electricity via thermophotovoltaic (TPV) energy conversion is described. High efficiency is obtained by introducing a material into a combustion chamber that emits bright near-monochromatic visible light upon heating. This light is then directed to fall on an array of photovoltaic (PV) cells which convert the light to electricity. Heat and infrared radiation that is not absorbed by the PV cells is returned to the combustion chamber to further improve conversion efficiency.