Electrical Characteristic And Thermal Performance Of BIPV Under Partial Shading Conditions

With the increase of building energy consumption,solar energy as a clean and renewable energy used in buildings has been greatly improved.The Building Integrated Photovoltaic(BIPV)projects in China are gradually increasing,but the shadows caused by dense urban buildings have adverse effects on the electrical and thermal characteristics of photovoltaic(PV)modules.Shadows can significantly reduce the power output of PV system,which has become an obstacle to the promotion of BIPV.In this paper,the electrical and thermal performance of BIPV under shadow condition is studied by experiment and simulation,and methods to maximize the output power of BIPV under shadow is proposed,which can provide data reference and guidance for future planning and design of BIPV.Effects of partial shadow on the photocurrent and series resistor is analyzed,relationship of shaded cell area proportion with photocurrent and series resistor is obtained respectively,and has been verified by experiments.Based on this,a simplified mathematical model to describe the relationship between shaded cell area proportion and current-voltage,power-voltage characteristics of a photovoltaic module under covering and shading conditions is proposed respectively.The electrical performance of photovoltaic modules under different shadow conditions was simulated by using MATLAB/Simulink software.The BIPV experimental platform under shadow condition was built,and the experimental and simulation results were compared and analyzed.The results show that:under same shaded area proportion,the shadow distributing in parallel with the short edge,which makes photovoltaic modules power output 3W/m~2 under 10%shaded area,has much more negative effects than distributing in parallel with the long edge.The power output of a photovoltaic string depends on the largest shaded cell area proportion,but not shaded cell number.The power output of PV module under covering conditions is always lower than it under shading conditions.Based on the results,a simple drawing method of predicting the PV module I-V curves has been proposed.BIPV design methods were proposed in order to minimize the influence of shadow on the power output of a photovoltaic module,The three-dimensional model and heat transfer process of photovoltaic module are simplified.And based on this,the numerical heat transfer model and the thermal-structural coupling model of photovoltaic module in BIPV system is established,and validated by experiments.The highest temperature of the PV cells appears at the junction box,and the maximum thermal stress appears at the edge of the photovoltaic cell.The maximum temperature difference of the photovoltaic module between under shadow conditions and under unshadow conditions is about 10 C.