Thermal Impacts on the Performance of Nanoscale-Gap Thermophotovoltaic Power Generators

The thermal impacts on the performance of nanoscale-gap thermophotovoltaic (nano-TPV) power generators are investigated using a coupled near-field thermal radiation, charge, and heat transport formulation. A nano-TPV device consisting of a tungsten radiator, maintained at 2000 K, and cells made of indium gallium antimonide (In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.18</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.82</sub> Sb) are considered; the thermal management system is modeled assuming a convective boundary with a fluid temperature fixed at 293 K. Results reveal that nano-TPV performance characteristics are closely related to the temperature of the cell. When the radiator and the junction are separated by a 20 nm vacuum gap, the power output and the conversion efficiency of the system are respectively 5.83 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> Wm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> and 24.8% at 300 K, whereas these values drop to 8.09 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> Wm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> and 3.2% at 500 K. In order to maintain the cell at room temperature, a heat transfer coefficient as high as 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> Wm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> is required for nanometer-size vacuum gaps. The reason for this is that thermal radiation since thermal radiation enhancement beyond the blackbody from a bulk radiator of tungsten is broadband in nature, while only a certain part of the spectrum is useful for maximizing nano-TPV performance. In future studies, near-field radiation spectral conditions leading to optimal performance characteristics of the device will be investigated.