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Sustaining Efficiency at Elevated Power Densities with InGaAs Air Bridge Cells
Authors:
Bosun Roy-Layinde,
Tobias Burger,
Dejiu Fan,
Byungjun Lee,
Sean McSherry,
Stephen R. Forrest,
Andrej Lenert
Abstract:
Here we investigate the use of single-junction InGaAs airbridge cells (ABCs) at elevated power densities. Such conditions are relevant to many thermophotovoltaic (TPV) applications, ranging from space to on-demand renewable electricity, and require effective management of heat and charge carriers. Experimental characterization of an InGaAs ABC with varying emitter and cell temperature is used to d…
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Here we investigate the use of single-junction InGaAs airbridge cells (ABCs) at elevated power densities. Such conditions are relevant to many thermophotovoltaic (TPV) applications, ranging from space to on-demand renewable electricity, and require effective management of heat and charge carriers. Experimental characterization of an InGaAs ABC with varying emitter and cell temperature is used to develop a predictive device model where carrier lifetimes and series resistances are the sole fitting parameters. The utility of this model is demonstrated through its use in identifying near-term opportunities for improving performance at elevated power densities, and for designing a thermal management strategy that maximizes overall power output. This model shows that an InGaAs ABC with material quality that leads to the longest reported carrier lifetimes can attain efficiencies exceeding 40% at 0.5 W/cm2, even when considering the power necessary to cool the cells.
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Submitted 18 August, 2021; v1 submitted 16 August, 2021;
originally announced August 2021.
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Extending the thermal near field through compensation in hyperbolic waveguides
Authors:
Sean McSherry,
Andrej Lenert
Abstract:
A promising method to leverage near-field power densities without the use of nanoscale vacuum gaps is through hyperbolic metamaterial (HMM) waveguides. When placed between a hot and cold reservoir, an ideal HMM can transmit surface waves across several microns, enabling an extension of near-field enhancements. However, when accounting for transmission loss due to realistic levels of absorption wit…
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A promising method to leverage near-field power densities without the use of nanoscale vacuum gaps is through hyperbolic metamaterial (HMM) waveguides. When placed between a hot and cold reservoir, an ideal HMM can transmit surface waves across several microns, enabling an extension of near-field enhancements. However, when accounting for transmission loss due to realistic levels of absorption within the waveguide, previous studies have shown that the enhancements are significantly curtailed at wide separations. In our study, we investigate the role of internal sources within realistic non-isothermal HMMs. We demonstrate that, in some cases, the emission from the HMM accounts for over 90% of the total heat transfer to the receiver, and that these additional sources can largely compensate for optical losses associated with decreased transmission from the emitter to the receiver. Lastly, we investigate the spectral transport in a realistic 3-body system which has mismatching optical properties between the boundaries (emitter and receiver) and the waveguide (HMM). Our model shows that the near-field thermal transport remains spectrally selective to the boundaries, even as major radiative contributions come from the waveguide. This work may enable the design of non-isothermal emitter-waveguide-receiver systems that transmit near-field power levels over wider separations.
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Submitted 7 July, 2020; v1 submitted 30 March, 2020;
originally announced March 2020.
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Radiative thermal runaway due to negative differential thermal emission across a solid-solid phase transition
Authors:
David M. Bierman,
Andrej Lenert,
Mikhail A. Kats,
You Zhou,
Shuyan Zhang,
Matthew De La Ossa,
Shriram Ramanathan,
Federico Capasso,
Evelyn N. Wang
Abstract:
Thermal runaway occurs when a rise in system temperature results in heat generation rates exceeding dissipation rates. Here we demonstrate that thermal runaway occurs in thermal radiative systems, given a sufficient level of negative differential thermal emission. By exploiting the insulator-to-metal phase transition of vanadium dioxide, we show that a small increase in heat generation (e.g., 10 n…
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Thermal runaway occurs when a rise in system temperature results in heat generation rates exceeding dissipation rates. Here we demonstrate that thermal runaway occurs in thermal radiative systems, given a sufficient level of negative differential thermal emission. By exploiting the insulator-to-metal phase transition of vanadium dioxide, we show that a small increase in heat generation (e.g., 10 nW/mm2) can result in a large change in surface temperature (e.g., ~35 K), as the thermal emitter switches from high emissivity to low emissivity. While thermal runaway is typically associated with catastrophic failure mechanisms, detailed understanding and control of this phenomenon may give rise to new opportunities in infrared sensing, camouflage, and rectification.
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Submitted 31 December, 2017;
originally announced January 2018.