High-efficiency solar-thermophotovoltaic system equipped with a monolithic planar selective absorber/emitter

Shimizu, Makoto; Kohiyama, Asaka; Yugami, Hiroo

doi:10.1117/1.jpe.5.053099

Cited by 73 publications

(54 citation statements)

References 16 publications

(13 reference statements)

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“…Spectrally selective absorbers and emitters are key components in various energy conversion applications such as solar thermophotovoltaics (STPV), radiative cooling, solar steam generation, etc. In order to maximize the utilization of solar energy, STPV requires the cooperative spectral manipulation of a broadband solar absorber and a narrowband infrared emitter.…”

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confidence: 99%

“…In addition, thanks to the narrowband emission, our HAE‐based STPV can earn 10% efficiency increment compared to the counterpart of broadband emitters (Part III, Supporting Information). Note that in a real system, the unavoidable conduction loss through the absorber/emitter's holder and the nonideal view factor of emitter would introduce extra heat loss, leading to the currently low system efficiency of no more than 10% . Our HAE‐based cage‐type STPV system can provide a feasible route to essentially increase this efficiency limit.…”

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confidence: 99%

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Hybrid Solar Absorber–Emitter by Coherence‐Enhanced Absorption for Improved Solar Thermophotovoltaic Conversion

Wang

Lin

Zhang

et al. 2018

Advanced Optical Materials

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etc. In order to maximize the utilization of solar energy, STPV requires the cooperative spectral manipulation of a broadband solar absorber and a narrowband infrared emitter. An ideal STPV absorber must simultaneously absorb input power and suppress radiation loss, while an STPV emitter should possess high emissivity only at the target infrared wavelength matching well with the base PV cell. [9] Extensive efforts have been devoted to design and fabricate such absorbers and emitters, including intrinsically spectrally selective materials, [10][11][12] multilayer structures, [13][14][15][16][17] cermets, [18] plasmonic metamaterials, [19][20][21][22][23][24][25][26] and photonic crystals. [27][28][29][30][31] Up to now, most of the reported absorbers and emitters are demonstrated by two isolated structures, [1,2] such as the compound metallic structures patterned on both sides of a substrate in a recently developed STPV system. [30] Such an optical design is intuitive and straightforward. However, the double-side lithography process severely increases the fabrication and systematic complexity. A hybrid absorber-emitter (HAE) with the two functions built on the same surface of the structure is beneficial for STPV. Great efforts have been made to integrate these two functionalities of broadband-absorption and narrowband-emission into one metasurface or plasmonic structure. [32][33][34] However, these structures are rather complicated and the well-defined morphologies are unstable at high temperature that the STPV system requires. An integrated HAE with ideal spectral selectivity, high temperature tolerance as well as scalable fabrication process is highly pursued but still elusive.Most specifically, in this work, we present a much simpler HAE design of a layered structure on a metallic surface based on multiple coherence-enhanced absorption, especially the coherent perfect absorption (CPA) effect. Such a structure is lithography-free, scalable, and possesses excellent thermal stability. In addition, the full spectrum responses demonstrate weak angular-dependence and polarization sensitivity, all of which make it beneficial for the STPV applications.The CPA phenomenon was first proposed for the case that two coherent counter-propagating light beams can be totally absorbed in a dielectric Fabry-Pérot cavity, [35][36][37] which was Spectrum selective absorbers and emitters, with advantages of high temperature tolerance, wide angle insensitivity, and scalable fabrication processes, are crucial components for solar thermophotovoltaics (STPV). A bifunctional hybrid absorber-emitter (HAE) for efficient STPV by sequentially depositing HfO 2 /Mo/HfO 2 films on a metallic surface is demonstrated here. Simultaneous broadband solar absorption and narrowband infrared emission are enabled by the same surface of the structure. By fine steering coherent perfect absorption of the ultrathin Mo film and destructive interference of interfacial reflections across the top HfO 2 layer, the HAE exhibits a measured emissivity of 0.97 at 1.8...

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confidence: 99%

Hybrid Solar Absorber–Emitter by Coherence‐Enhanced Absorption for Improved Solar Thermophotovoltaic Conversion

Wang

Lin

Zhang

et al. 2018

Advanced Optical Materials

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“…Until about 2013, the reported experimental system efficiencies, in which the input power has been directly measured, were around 1% (16)(17)(18)(22)(23)(24). Then, beginning with 2015, system_exp exceeding 5% started to appear in the literature (19)(20)(21) Si-MIM structure on a tungsten substrate for the emitter (26).…”

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confidence: 99%

High-Efficiency Thermophotovoltaic System That Employs an Emitter Based on a Silicon Rod-Type Photonic Crystal

et al. 2019

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Thermophotovoltaic systems in principle enable utilization of heat that is usually regarded as wasted energy. However, the wavelength selectivity of the thermal emitter required for high efficiencies is rather difficult to control with conventional designs.Here, we design a thermophotovoltaic system comprising silicon rods as thermal emitter with a relatively narrow emission spectrum and a photovoltaic cell with a band gap corresponding to 1.76 m, and verify efficient power generation. By accurately measuring the heat flux that enters the emitter, the emitter temperature, and the electrical output power of the photovoltaic cell, we find that the actual system efficiency (ratio of ingoing heat flux to output power) is 11.2% at an emitter temperature of 1338 K, and that the output power density footprint is 0.368 W/cm 2 . The obtained efficiency is relatively high, i.e., 1.65 times that of the previously reported record value (6.8%).Further efficiency improvements in the future may lead to development of distributed energy supplies using combustion heat.

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“…An ideal STPV system has a solar-to-electric energy conversion efficiency much higher than that of a stand-alone PV cell, as a carefully designed STPV intermediate structure can fully capture the incident sunlight and convert it into narrowband thermal emission right above the bandgap of the PV cell 10 . It has been theoretically shown that the STPV efficiency could significantly surpass the aforementioned Shockley-Queisser limit, reaching 85% and 54% under fully concentrated and unconcentrated solar radiation, respectively 11 .Recently, several proof-of-concept STPV experiments have been reported employing various absorber/emitter intermediate structures [12][13][14][15][16] , including multi-walled carbon nanotubes, photonic crystals (PhCs), and two-dimensional multilayers. Although these initial demonstrations are quite…”

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confidence: 99%

“…Recently, several proof-of-concept STPV experiments have been reported employing various absorber/emitter intermediate structures [12][13][14][15][16] , including multi-walled carbon nanotubes, photonic crystals (PhCs), and two-dimensional multilayers. Although these initial demonstrations are quite…”

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confidence: 99%

High-Temperature Refractory Metasurfaces for Solar Thermophotovoltaic Energy Harvesting

et al. 2018

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Solar energy promises a viable solution to meet the ever-increasing power demand by providing a clean, renewable energy alternative to fossil fuels. For solar thermophotovoltaics (STPV), hightemperature absorbers and emitters with strong spectral selectivity are imperative to efficiently couple solar radiation into photovoltaic cells. Here, we demonstrate refractory metasurfaces for STPV with tailored absorptance and emittance characterized by in-situ high-temperature measurements, featuring thermal stability up to at least 1200 ºC. Our tungsten-based metasurface absorbers have close-to-unity absorption from visible to near infrared and strongly suppressed emission at longer wavelengths, while our metasurface emitters provide wavelength-selective emission spectrally matched to the band-edge of InGaAsSb photovoltaic cells. The projected overall STPV efficiency is as high as 18% when employing a fully integrated absorber/emitter metasurface structure, much higher than those achievable by stand-alone PV cells. Our work opens a path forward for high-performance STPV systems based on refractory metasurface structures.3 TEXT Photovoltaics (PV) 1 directly convert sunlight to electricity using semiconductor PV cells, and have been the most prevalent solar energy-harvesting technology. Despite the development over the past few decades, the efficiency of state-of-the-art, single-junction PV cells is still far below the fundamental limit predicted by Shockley and Queisser 2 , which is dictated mainly by energy losses due to below-bandgap photons and hot-carrier thermalization, owing to the broad distribution of the solar spectrum. To minimize these losses, numerous novel PV device concepts have been proposed and realized 3-7 . While they indeed improve the PV efficiency to some extent, they all suffer from their own respective problems, including high manufacturing cost, complex device fabrication processes, as well as material instability and degradation. Solar thermophotovoltaics (STPV) 8, 9 represent a promising alternative to traditional photovoltaics for solar energy harvesting, where an absorber/emitter intermediate structure first absorbs the incoming sunlight, heats up, and then emits thermal photons towards the PV cell to excite charge carriers for power generation. An ideal STPV system has a solar-to-electric energy conversion efficiency much higher than that of a stand-alone PV cell, as a carefully designed STPV intermediate structure can fully capture the incident sunlight and convert it into narrowband thermal emission right above the bandgap of the PV cell 10 . It has been theoretically shown that the STPV efficiency could significantly surpass the aforementioned Shockley-Queisser limit, reaching 85% and 54% under fully concentrated and unconcentrated solar radiation, respectively 11 .Recently, several proof-of-concept STPV experiments have been reported employing various absorber/emitter intermediate structures [12][13][14][15][16] , including multi-walled carbon nanotubes, photonic crystals (PhCs), and two-d...

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High-efficiency solar-thermophotovoltaic system equipped with a monolithic planar selective absorber/emitter

Cited by 73 publications

References 16 publications

Hybrid Solar Absorber–Emitter by Coherence‐Enhanced Absorption for Improved Solar Thermophotovoltaic Conversion

Hybrid Solar Absorber–Emitter by Coherence‐Enhanced Absorption for Improved Solar Thermophotovoltaic Conversion

High-Efficiency Thermophotovoltaic System That Employs an Emitter Based on a Silicon Rod-Type Photonic Crystal

High-Temperature Refractory Metasurfaces for Solar Thermophotovoltaic Energy Harvesting

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