Simultaneous materials and layout optimization of non-imaging optically concentrated solar thermoelectric generators

A 4 × non-imaging optically concentrated solar thermoelectric generator (STEG) was simulated and its layout was optimized depending on materials characteristics. The performances of seven state-of-the-art thermoelectric materials were realistically compared considering direct normal irradiances (DNI) between 400 and 900 W/m2 and temperature dependence of the thermoelectric parameters. The model was tested with experimental data from literature and leg aspect ratios, fill factor (or thermal concentration), and leg number per STEG unit area were also used as variables. Due to the high values of thermal concentrations at maximum efficiency, different materials filling the gap among STEG legs were also considered. Maximum efficiency weakly decreases for filler thermal conductivities typical of common insulating materials, opening novel opportunities for STEGs not requiring vacuum. Results of the analysis show that skutterudites, lead telluride and bismuth telluride exhibit the highest efficiencies (≈7%) in the studied range of thermal concentrations and for a DNI equal to 900 W/m2. However, skutterudites and lead telluride were found to be very sensitive on the DNI level, differently from bismuth telluride, which therefore qualifies as the best solution for energy conversion. Moreover, optimal layouts for STEGs based on bismuth telluride more easily meet manufacturing constraints.