Performance evaluation of a natural convective-cooled concentration solar thermoelectric generator coupled with a spectrally selective high temperature absorber coating

• Thermal performance of high temperature spectrally selective absorber coating (α=0.956, ε=0.07).
• High temperature experimental emittance measurements for the coating in the range of 100–500 °C.
• Theoretical efficiency modeling of STEG coupled with the selective absorber:predicted efficiency of 9.3% at 300 °C hot side temperature in vacuum.
• Experimental performance of natural air cooled STEG coupled to selective coating and 3 commerical Bi2Te3 TE modules.
• Output power of 660 mW and efficiency of 1.2% obtained at 280 °C under optical concentration ratio of 62.

Solar energy can be directly harnessed for power generation by using solar thermoelectric generator (STEG) technology, which comprises of solar absorbers integrated with thermoelectric materials. STEGs behave as solid state heat engines, which can utilize the heat energy of the sun to produce a temperature gradient across a thermoelectric device, which is in turn converted to electrical energy. In this paper, we focus on investigating the performance of the solar absorber subsystem that employs a high temperature spectrally selective coating on a stainless steel substrate. We have performed temperature measurements on the absorber coating exposed to solar irradiation flux at different optical concentration ratios (10–100) and validated the experimental data using a numerical heat transfer model in COMSOL Multiphysics. This has been combined with the high temperature emittance measurements of the coating to develop a predictive efficiency model for the STEG system as a function of the thermoelectric figure of merit at a hot side temperature range of 100–500 °C. Further, we have experimentally examined the performance of a natural convective cooled STEG consisting of a series combination of three commercial Bi2Te3 thermoelectric modules coupled to the selective absorber coating. The maximum power generated from the STEG has been measured at different concentration ratios and the peak efficiency of the system has been calculated in the feasible temperature range of the thermoelectric module.