Evaluation of Heat losses in a non-concentrated solar thermoelectric generator with spectrally selective absorbers

Solar thermoelectric generator (STEG) has been widely studied in optical and thermal concentrating fields, and the spectral properties are mainly focused on the solar spectrum. However, limited attention has been paid to STEG without any concentrators and in the full spectral range. Therefore, in this work, a thermal-electrical coupled mathematical model for STEG systems is developed according to thermal resistance networks to investigate heat losses above the absorber and power generation performance. For the ideal selective absorber and emitter system, the main heat losses from the absorber occur due to radiative cooling to the sky as well as for the ideal broadband absorber system, as opposed to convection and ambient radiative losses. These sky radiative cooling losses account for approximately 83.8% and 73.7% of the total heat losses, respectively. The total water vapor has the greatest impact on radiative cooling power compared to other forms of heat loss, while wind speed has the largest effect on convective heat loss. Elevated ambient temperatures result in decreased heat loss across all forms. An increase in bottom surface temperature or solar irradiance results in an increase in various forms of heat loss. In light of its cost-effectiveness and environmentally-friendly characteristics, this paper offers recommendations on enhancing the system design of STEG aiming to minimize heat loss, enhance system performance, and pave the way for a promising future in various applications.