Impact of structural arrangement and electrical series-parallel connections on performance of semi-flexible crystalline silicon building-integrated photovoltaic systems

Semi-flexible crystalline silicon Building-Integrated Photovoltaic (BI-SFPV) systems provide a feasible clean energy solution for low-load-bearing rooftops. However, their unique structural configuration and cooling mechanism may cause non-uniform temperature distributions among modules, leading to electrical mismatch issues and increasing system design complexity. In this study, a coupled thermo-electrical model was developed to numerically investigate the temperature differences between modules under varying airflow velocities and their impacts on system electrical performance. The results indicate a nonlinear relationship between airflow velocity and inter-module temperature gradients. Under low airflow conditions, significant heat accumulation occurs at the downstream end of the flow channel, resulting in a maximum temperature difference of 14.70 °C. Increasing airflow velocity markedly reduces module temperatures (with a maximum reduction of 23.52 °C), although the cooling effect exhibits diminishing returns. In terms of electrical performance, the I–V and P–V curves of series-connected modules generally retain a unimodal shape but show slight local discontinuities. In contrast, parallel-connected modules display more pronounced irregularities and greater sensitivity to temperature mismatch. Under extreme temperature gradients, the maximum output power of the series configuration reached 840.50 W with negligible loss, whereas that of the parallel configuration decreased to 804.10 W, corresponding to a 4.33 % reduction.