Toward high-energy-density, high-efficiency, and moderate-temperature chip-scale thermophotovoltaics

Abstract

The challenging problem of ultra-high-energy-density, high-efficiency, and small-scale portable power generation is addressed here using a distinctive thermophotovoltaic energy conversion mechanism and chip-based system design, which we name the microthermophotovoltaic (μTPV) generator. The approach is predicted to be capable of up to 32% efficient heat-to-electricity conversion within a millimeter-scale form factor. Although considerable technological barriers need to be overcome to reach full performance, we have performed a robust experimental demonstration that validates the theoretical framework and the key system components. Even with a much-simplified μTPV system design with theoretical efficiency prediction of 2.7%, we experimentally demonstrate 2.5% efficiency. The μTPV experimental system that was built and tested comprises a silicon propane microcombustor, an integrated high-temperature photonic crystal selective thermal emitter, four 0.55-eV GaInAsSb thermophotovoltaic diodes, and an ultrahigh-efficiency maximum power-point tracking power electronics converter. The system was demonstrated to operate up to 800°C (silicon microcombustor temperature) with an input thermal power of 13.7 W, generating 344 mW of electric power over a 1-cm 2 area.catalytic combustion | micro generator | thermal radiation W ith the recent proliferation of power-hungry mobile devices, significant research efforts have been focused on developing clean, quiet, and portable high-energy-density, compact power sources. Although batteries offer a well-known solution, limits on the chemistry developed to date constrain the energy density to ∼0.2 kWh/kg, whereas many hydrocarbon fuels have energy densities closer to 12 kWh/kg. The fundamental question is, How efficiently and robustly can these widely available chemical fuels be converted into electricity in a millimeter-scale system? Indeed, it is difficult to tap the full potential of hydrocarbon fuels on a small scale. However, their high energy density allows even relatively inefficient generators to be competitive with batteries. To this end, researchers have explored different energy conversion routes, such as mechanical heat engines (1), fuel cells (2, 3), thermoelectrics (4, 5), and thermophotovoltaics (TPVs) (6, 7).TPVs present an extremely appealing approach for small-scale power sources due to the combination of high power density limited ultimately by Planck blackbody emission, multifuel operation due to the ease of generating heat, and a fully static conversion process. Small-scale TPVs have yet to be demonstrated and are particularly challenging because of the need to develop strong synergistic interactions between chemical, thermal, optical, and electrical domains, which in turn give rise to requirements for extreme materials performance and subsystems synchronization.In this work, we present a proof of concept microthermovoltaic (μTPV) system, shown in Fig. 1, that validates the theoretical foundation and paves the way toward a new breed of ultra-highenergy-density, hi...

Performance of tantalum-tungsten alloy selective emitters in thermophotovoltaic systems

“…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.…”

Tuning Transpiration by Interfacial Solar Absorber‐Leaf Engineering

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Integrated photonic crystal selective emitter for thermophotovoltaics

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