Ultraefficient thermophotovoltaic power conversion by band-edge spectral filtering

Omair, Zunaid; Scranton, Gregg; Pazos-Outón, Luis M.; Xiao, T. Patrick; Steiner, Myles A.; Ganapati, Vidya; Peterson, Per F.; Holzrichter, J. F.; Atwater, Harry A.; Yablonovitch, Eli

doi:10.1073/pnas.1903001116

Cited by 168 publications

(135 citation statements)

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“…Back Surface Reflector (BSR), the spectral control technique focused upon in this paper, is placed behind the TPV cell to reflect photons, that are below bandgap and not absorbed by the cell, to the emitter. BSRs have proved to be a very useful technique for photon recycling [29] and are simple to incorporate as a mirror [28] or an element with high reflectivity in the infrared region, such as gold (Au) or silver (Ag) [18,47], can be used as a BSR.…”

Section: Spectral Control: Back Surface Reflectormentioning

confidence: 99%

“…To establish the competitiveness of TPV systems, as a beneficial solid-state engine in a CSP plant, it is important to establish their ability to have an efficiency that is comparable to that of turbines running on Brayton or Rankine Cycles (efficiency = 30%). Recently, a TPV conversion efficiency of 29.1% [28], with the use of reflectors behind the TPV cells, has been recorded. Therefore, the primary focus of this study is to present the conditions needed to achieve an efficiency of the TPV conversion process beyond 30%.…”

Section: Introductionmentioning

confidence: 99%

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Efficiency Enhancement of a Thermophotovoltaic System Integrated With a Back Surface Reflector

et al. 2020

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This work aims to investigate the various factors which may affect a thermophotovoltaic (TPV) system's performance, with a special focus on the importance of incorporating a back surface reflector (BSR), which enables below-bandgap photons' recycling. The possible extent to which common PV materials can be used in TPV applications is investigated by comparing them on a Planck distribution curve. The effects of varying BSR reflectivity, TPV cell's external quantum efficiency, and emitter temperature are investigated on the TPV module's efficiency using open-circuit voltage, empirical relations for fill factor, maximum voltage, and photogenerated current. It is shown that TPV applications require materials with smaller (e.g. 0.6 eV < Eg ≤ 0.74 eV) bandgap energy, e.g. In0.53Ga0.47As (0.74 eV), due to their high percentage of energy (> 26%) abovebandgap without a spectral control and a small difference between peak and bandgap wavelength. It is shown that the inclusion of a BSR (reflectivity = 1) results in an increase of 15% in TPV efficiency. The results show that by the collective changes of an added BSR, high emitter temperature (> 2000 K), and improved external quantum efficiency (EQE ≈ 1), the present TPV systems can attain efficiency values more than 30% which makes them a favorable prospective choice for Concentrated Solar Power.

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Section: Spectral Control: Back Surface Reflectormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Efficiency Enhancement of a Thermophotovoltaic System Integrated With a Back Surface Reflector

et al. 2020

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“…The rapid growth of world population and industrial development poses a major threat to the global energy supply, causing escalatory environmental degradation and social unrest [1][2][3]. To address the challenge, solar energy harvesting techniques, such as photovoltaics, thermal photovoltaics, and solar thermal techniques [4][5][6][7], are sustainable alternatives. Even so, the electrical power demand for lighting peaks during nighttime.…”

Section: Introductionmentioning

confidence: 99%

Maximal nighttime electrical power generation via optimal radiative cooling

Lu¹,

Li²,

Jin³

et al. 2020

Opt. Express

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We present a systematic optimization of nighttime thermoelectric power generation system utilizing radiative cooling. We show that an electrical power density > 2 W/m 2 , two orders of magnitude higher than the previously reported experimental result, is achievable using existing technologies. This system combines radiative cooling and thermoelectric power generation and operates at night when solar energy harvesting is unavailable. The thermoelectric power generator (TEG) itself covers less than 1 percent of the system footprint area when achieving this optimal power generation, showing economic feasibility. We study the influence of emissivity spectra, thermal convection, thermoelectric figure of merit and the area ratio between the TEG and the radiative cooler on the power generation performance. We optimize the thermal radiation emitter attached to the cold side and propose practical material implementation. The importance of the optimal emitter is elucidated by the gain of 153% in power density compared to regular blackbody emitters.

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“…In TPV, a wide variety of thermal sources, such as solar heat and, waste heat from industries and, chemical and nuclear processes, can be turned into electricity using spectrally selective emitters [17][18][19][20][21] . Even though TPV technology has been developed many years ago, the commercial deployment of TPV is hindered due to lack of thermally stable emitter structures at temperatures higher than 1200 °C 5,[22][23][24][25][26][27][28][29][30][31] . According to the Stefan-Boltzmann law 16 , the radiative power of any object is proportional to T 4 .…”

mentioning

confidence: 99%

“…Front surface filters placed between the emitter and PV cell revert back the out-of-band photons to the emitter [32][33][34] . Alternatively, by introducing a highly reflective mirror surface at the rear of the PV cell, out-of-band photons can be directed back to reheat the emitter 29,35 . Still, the filters and mirrors have residual absorptivity which might result in a reduction of efficiency.…”

mentioning

confidence: 99%

Thermal stability of tungsten based metamaterial emitter under medium vacuum and inert gas conditions

Chirumamilla

Krishnamurthy

Rout

et al. 2020

Sci Rep

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commercial deployment of thermophotovoltaics (tpV) is lacking behind the implementation of solar pV technology due to limited thermal stability of the selective emitter structures. Most of the tpV emitters demonstrated so far are designed to operate under high vacuum conditions (~10 −6 mbar vacuum pressure), whereas under medium vacuum conditions (~10 −2 mbar vacuum pressure), which are feasible in technical implementations of TPV, these emitters suffer from oxidation due to significant o 2 partial pressure. In this work, the thermal stability of 1D refractory W-HfO 2 based multilayered metamaterial emitter structure is investigated under different vacuum conditions. The impact of the o 2 partial pressure on thermal stability of the emitters is experimentally quantified. We show that, under medium vacuum conditions, i.e. ~10 −2 mbar vacuum pressure, the emitter shows unprecedented thermal stability up to 1300 °C when the residual O 2 in the annealing chamber is minimized by encapsulating the annealing chamber with Ar atmosphere. This study presents a significant step in the experimental implementation of high temperature stable emitters under medium vacuum conditions, and their potential in construction of economically viable TPV systems. The high TPV efficiency, ~50% spectral efficiency for GaSb PV cell at 1300 °C, and high temperature stability make this platform well suited for technical application in next-generation TPV systems.

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Ultraefficient thermophotovoltaic power conversion by band-edge spectral filtering

Cited by 168 publications

References 50 publications

Efficiency Enhancement of a Thermophotovoltaic System Integrated With a Back Surface Reflector

Efficiency Enhancement of a Thermophotovoltaic System Integrated With a Back Surface Reflector

Maximal nighttime electrical power generation via optimal radiative cooling

Thermal stability of tungsten based metamaterial emitter under medium vacuum and inert gas conditions

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