Design and validation of a high-efficiency planar solar thermophotovoltaic system using a spectrally selective...

This paper presents a detailed-balance analysis required for the achievement of a high-efficiency spectral selective STPV system utilizing thermodynamic and optical modeling approaches. Key parameters affecting the design and optimization of spectrally selective surfaces that are essential for high-efficiency STPV applications are investigated. A complete GaSb-based planar STPV system utilizing a micro-textured absorber and a nanostructure multilayer metal-dielectric coated selective emitter was fabricated and evaluated. The micro-textured absorber features more than 90% absorbance at visible and near-infrared wavelengths. The selective emitter, consisting of two nanolayer coatings of silicon nitride (Si₃N₄) and a layer of W in between, exhibits high spectral emissivity at wavelengths matching the spectral response of the GaSb cells. The performance of the STPV system was evaluated using a high-power laser diode as a simulated source of concentrated incident radiation. When operated at 1670 K, an output power density of 1.75 W/cm² and a system efficiency of 8.6% were recorded. This system efficiency is higher than those of previously reported experimental STPV systems. Optical and thermal losses that occurred at multiple stages of the energy transport process were modeled and quantified. Essential guidelines to mitigate these losses and further enhance the system performance are also provided.