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Title: Collimated thermal radiation transfer via half Maxwell's fish-eye lens for thermophotovoltaics

Thermophotovoltaics (TPV) convert heat into electricity by capturing thermal radiation with a photovoltaic (PV) cell, ideally at efficiencies of 50% or more. However, excess heating of the PV cell from close proximity to the emitter substantially reduces the system efficiency. In this paper, we theoretically develop and numerically demonstrate an approach to fundamentally improving TPV systems that allow for a much greater separation of an emitter and a receiver. Thus, we solve the excess heating dilemma, required for achieving theoretically high efficiencies. It consists of a spherically graded index lens known as Maxwell's Fish-Eye (MFE) structure, capable of collimating hemispherical emission into a much narrower range of angles, close to the normal direction. To fully characterize the power radiation profile of the MFE, we perform finite-difference time-domain simulations for a quarter MFE and then map it onto a Gaussian beam approximation. The modeled beam properties are subsequently used to study a half MFE. In an optimized half MFE design, 90% of all thermal photons reach a receiver at a distance of 100 λ; by comparison, only 15.6% of a blackbody emitter reach a receiver in the same geometry. It is also shown that the emission achieved by a half MFEmore » can lead to a photon recycling rate above 95% for below bandgap photons at an emitter-receiver separation of 100 λ. Finally, by applying a half MFE, the absolute TPV efficiency can be improved from 5.74% to 37.15%, which represents a significant step forward in realizing high-efficiency TPV systems.« less
Authors:
ORCiD logo [1] ;  [1] ; ORCiD logo [1]
  1. Purdue Univ., West Lafayette, IN (United States). Birck Nanotechnology Center
Publication Date:
Grant/Contract Number:
EE0004946; EEC1454315-CAREER
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 110; Journal Issue: 20; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Research Org:
Purdue Univ., West Lafayette, IN (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; finite difference time domain calculations; Maxwell equations; photons; solar cells; band gap; Einstein Maxwell radiation; thermal radiation; magnetic fields; refractive index
OSTI Identifier:
1466218
Alternate Identifier(s):
OSTI ID: 1361901

Chung, Haejun, Zhou, Zhiguang, and Bermel, Peter. Collimated thermal radiation transfer via half Maxwell's fish-eye lens for thermophotovoltaics. United States: N. p., Web. doi:10.1063/1.4983679.
Chung, Haejun, Zhou, Zhiguang, & Bermel, Peter. Collimated thermal radiation transfer via half Maxwell's fish-eye lens for thermophotovoltaics. United States. doi:10.1063/1.4983679.
Chung, Haejun, Zhou, Zhiguang, and Bermel, Peter. 2017. "Collimated thermal radiation transfer via half Maxwell's fish-eye lens for thermophotovoltaics". United States. doi:10.1063/1.4983679. https://www.osti.gov/servlets/purl/1466218.
@article{osti_1466218,
title = {Collimated thermal radiation transfer via half Maxwell's fish-eye lens for thermophotovoltaics},
author = {Chung, Haejun and Zhou, Zhiguang and Bermel, Peter},
abstractNote = {Thermophotovoltaics (TPV) convert heat into electricity by capturing thermal radiation with a photovoltaic (PV) cell, ideally at efficiencies of 50% or more. However, excess heating of the PV cell from close proximity to the emitter substantially reduces the system efficiency. In this paper, we theoretically develop and numerically demonstrate an approach to fundamentally improving TPV systems that allow for a much greater separation of an emitter and a receiver. Thus, we solve the excess heating dilemma, required for achieving theoretically high efficiencies. It consists of a spherically graded index lens known as Maxwell's Fish-Eye (MFE) structure, capable of collimating hemispherical emission into a much narrower range of angles, close to the normal direction. To fully characterize the power radiation profile of the MFE, we perform finite-difference time-domain simulations for a quarter MFE and then map it onto a Gaussian beam approximation. The modeled beam properties are subsequently used to study a half MFE. In an optimized half MFE design, 90% of all thermal photons reach a receiver at a distance of 100 λ; by comparison, only 15.6% of a blackbody emitter reach a receiver in the same geometry. It is also shown that the emission achieved by a half MFE can lead to a photon recycling rate above 95% for below bandgap photons at an emitter-receiver separation of 100 λ. Finally, by applying a half MFE, the absolute TPV efficiency can be improved from 5.74% to 37.15%, which represents a significant step forward in realizing high-efficiency TPV systems.},
doi = {10.1063/1.4983679},
journal = {Applied Physics Letters},
number = 20,
volume = 110,
place = {United States},
year = {2017},
month = {5}
}