Numerical study of high-temperature, disk-based tungsten and molybdenum thermophotovoltaic selective thermal emitters

This work investigates the design of two-dimensional metal-disk-based selective thermal emitters (STEs) for thermophotovoltaic (TPV) applications. A parametric analysis is conducted to study the effect of geometrical parameters on the emittance of the STEs. We focus on STEs made from two refractory metals, tungsten (W) and molybdenum (Mo), including a hafnia spacer. For both metals, we employ a temperature-dependent complex permittivity model to examine the influence of high temperatures on the spectral emission of the STEs. The designed STEs show high emittance, in the electron-hole pair generation range, even at larger angles. Furthermore, we implement a model to quantify the conversion efficiency of a GaSb photovoltaic cell and evaluate the performance of the proposed STE systems at room and high temperatures. The model predicts efficiencies of 20.99% for W and 20.38% for Mo at 1685 K. We found that magnetic polaritons, surface plasmon polaritons, and cavity resonances are responsible for the high broadband emittance obtained and that the emittance at shorter wavelengths is more stable as a function of temperature than longer wavelengths. Additionally, when considering properties at room temperature, the efficiency of the TPV system is overestimated by 15% and 22% for STEs based on W and Mo, respectively, showing the importance of considering the effect of temperature in the design of STEs.