Investigating the impact of solar cells partial shading on photovoltaic modules by thermography

In order to understand how partial shading at the cell level affects modules normal operation, a standard monocrystalline silicon PV module, divided in three equivalent cell strings by bypass diodes, was submitted to several shading fractions ranging between 10% and 100% of a solar cell area. The modules were characterized by thermal imaging using a thermal camera and I-V curves were also obtained. A loss in the current produced in the string containing the shaded cell was verified. Such current loss increases with the shaded area, plummeting the electrical power produced by the module by one third for larger shading fractions. For all the shadings tested, a significant and non-uniform increase of temperature of the shaded cell was detected. For shaded fractions of 50% and 70%, the temperature differences between the shaded cell and the rest of the module were as high as 36.6 °C and 56.9 °C respectively.