Electrical and thermomechanical evaluation of the bifacial PV-STEG and tandem PV-STEG units under uniform and nonuniform radiation conditions

Abstract

The structural failure threats the long-term stable operation of the photovoltaic-solar thermoelectric generator (PV-STEG) system. In this study, a comprehensive numerical model is developed to analyze the electrical and thermomechanical performance of the conventional tandem photovoltaic-solar thermoelectric generator (TA-PV-STEG) layout and bifacial structure of photovoltaic-solar thermoelectric generator (BI-PV-STEG) layout under uniform and nonuniform radiation conditions. The effects of sun concentration ratio (CR), inlet temperature, and leg height on the performance of the systems are examined in detail. In addition, the consequences of utilizing solar cells with varying temperature coefficients (cell1: 0.004 1/K and cell2: 0.001 1/K) and standard efficiencies (cell1: 15% and cell2: 10%) are also accounted for. The results demonstrate that the bifacial structure could provide better overall performance than the tandem structure. The maximum cell temperature difference under uniform radiation is greater than 19 K, and the corresponding percentage increase in cell power output is 9.28%. The increase in CR and leg height leads to higher STEG output, while the lower inlet temperature is preferable. Moreover, although cell2 possesses a lower temperature coefficient, the electrical performance of cell1 is higher than cell2 in most conditions. The maximum thermal stress observed in the bifacial structure is greater than that of the tandem structure due to the wider temperature gradient. Therefore, this study provides direction for designing the actual PV-STEG system in consideration of thermal stress distribution side effects.