Thermophotovoltaic Converter Performance for Radioisotope Power Systems

Crowley, Christopher J.; Elkouh, Nabil A.; Murray, Susan L.; Chubb, Donald L.

doi:10.1063/1.1867178

Cited by 53 publications

(28 citation statements)

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“…In TPV systems, thermal radiation from a heat source at high temperature drives a suitable small bandgap photovoltaic cell. The heat can be produced by hydrocarbon combustion ideal for lightweight, high power density portable power sources, [1][2][3][4] by radioisotopes such as a radioisotope general purpose heat source (GPHS) ideal for space missions and remote missions requiring power sources with long lifetimes and low maintenance, 5 or by solar radiation absorbed by a suitable absorber and converted to heat.…”

Section: Introductionmentioning

confidence: 99%

Performance of tantalum-tungsten alloy selective emitters in thermophotovoltaic systems

et al. 2014

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A tantalum tungsten solid solution alloy, Ta 3% W, based 2D photonic crystal (PhC) was designed and fabricated for high-temperature energy conversion applications. Ta 3% W presents advantages compared to the non-alloys as it combines the better high-temperature thermomechanical properties of W with the more compliant material properties of Ta, allowing for a direct system integration path of the PhC as selective emitter/absorber into a spectrum of energy conversion systems. Indeed metallic PhCs are promising as high performance selective thermal emitters for thermophotovoltaics (TPV), solar thermal, and solar TPV applications due to the ability to tune their spectral properties and achieve highly selective emission. A 2D PhC was designed to have high spectral selectivity matched to the bandgap of a TPV cell using numerical simulations and fabricated using standard semiconductor processes. The emittance of the Ta 3% W PhC was obtained from near-normal reflectance measurements at room temperature before and after annealing at 1200• C for 24h in vacuum with a protective coating of 40 nm HfO 2 , showing high selectivity in agreement with simulations. SEM images of the cross section of the PhC prepared by FIB confirm the structural stability of the PhC after anneal, i.e. the coating effectively prevented structural degradation due to surface diffusion. The mechanical and thermal stability of the substrate was characterized as well as the optical properties of the fabricated PhC. To evaluate the performance of the selective emitters, the spectral selectivity and useful emitted power density are calculated as a function of operating temperature. At 1200• C, the useful emitted irradiance is selectively increased by a factor of 3 using the selective emitter as compared to the non-structured surface. All in all, this paper demonstrates the suitability of 2D PhCs fabricated on polycrystalline Ta-W substrates with an HfO 2 coating for TPV applications.

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Section: Introductionmentioning

confidence: 99%

Performance of tantalum-tungsten alloy selective emitters in thermophotovoltaic systems

et al. 2014

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“…In particular, metallic PhCs have been shown to possess a large bandgap (9-12) and consequently superior modification of the intrinsic thermal emission spectra is readily achievable. This is extremely promising for many unique applications, especially high-efficiency energy conversion systems encompassing hydrocarbon and radioisotope fueled thermophotovoltaic (TPV) energy conversion (13,14) as well as solar selective absorbers and emitters for the emerging field of solar thermal, including solar TPV (15-18) and solar thermochemical production of fuels (19). The selective emitters can also be used as highly efficient infrared radiation sources for infrared spectroscopy and sensing applications including highly selective gas and chemical sensing (20,21).…”

mentioning

confidence: 99%

Enabling high-temperature nanophotonics for energy applications

Yeng

Ghebrebrhan²,

Bermel³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

216

181

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The nascent field of high-temperature nanophotonics could potentially enable many important solid-state energy conversion applications, such as thermophotovoltaic energy generation, selective solar absorption, and selective emission of light. However, special challenges arise when trying to design nanophotonic materials with precisely tailored optical properties that can operate at hightemperatures (>1,100 K). These include proper material selection and purity to prevent melting, evaporation, or chemical reactions; severe minimization of any material interfaces to prevent thermomechanical problems such as delamination; robust performance in the presence of surface diffusion; and long-range geometric precision over large areas with severe minimization of very small feature sizes to maintain structural stability. Here we report an approach for high-temperature nanophotonics that surmounts all of these difficulties. It consists of an analytical and computationally guided design involving high-purity tungsten in a precisely fabricated photonic crystal slab geometry (specifically chosen to eliminate interfaces arising from layer-by-layer fabrication) optimized for high performance and robustness in the presence of roughness, fabrication errors, and surface diffusion. It offers nearultimate short-wavelength emittance and low, ultra-broadband long-wavelength emittance, along with a sharp cutoff offering 4∶1 emittance contrast over 10% wavelength separation. This is achieved via Q-matching, whereby the absorptive and radiative rates of the photonic crystal's cavity resonances are matched. Strong angular emission selectivity is also observed, with shortwavelength emission suppressed by 50% at 75°compared to normal incidence. Finally, a precise high-temperature measurement technique is developed to confirm that emission at 1,225 K can be primarily confined to wavelengths shorter than the cutoff wavelength. E ver since photonic bandgaps were predicted to exist in appropriately designed periodic subwavelength structures (1-3)-i.e., photonic crystals (PhCs), significant interest has garnered in recent years to exploit this property. Coupled with the recent advancements in nanofabrication techniques, many applications have been made possible, ranging from room-and cryogenic-temperature optoelectronic devices for development of all-optical integrated circuits (4), to highly sensitive sensors (5), low-threshold lasers (6), and highly efficient light emitting diodes (7). PhCs also enable us to accurately control spontaneous emission by virtue of controlling the photonic bandgap (1, 8). In particular, metallic PhCs have been shown to possess a large bandgap (9-12) and consequently superior modification of the intrinsic thermal emission spectra is readily achievable. This is extremely promising for many unique applications, especially high-efficiency energy conversion systems encompassing hydrocarbon and radioisotope fueled thermophotovoltaic (TPV) energy conversion (13,14) as well as solar selective absorbers and emitters for the...

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“…The selections included five larger "Development" contracts using more mature technology (Technology Readiness Level (TRL) 3 to 5) and five smaller "Research" contracts using less mature technology (TRL 1 to 3). The selections included a broad range of conversion technologies including free-piston Stirling (Wood, et al, 2006), turbo-Brayton (Zagarola, et al, 2005), thermoelectrics (TE) (Flanders, et al, 2005), and thermophotovoltaics (TPV) (Crowley, et al, 2005 andHorne, et al, 2005). Each RPCT NRA contract had a period of performance of up to three years, divided into three one-year phases, with options to continue the following phase after the conclusion of the prior phase.…”

Section: Radioisotope Power Conversion Technology (Rpct) Projectmentioning

confidence: 99%