The performance of PV panels is affected by the shading effect due to trees, passing of clouds, neighboring buildings and any other means. A direct correlation was found between short circuit current and solar irradiation under uniform shading conditions. On the other hand, non uniform shading conditions yielded a variety of performance behavior. Such shading conditions should be avoided for better performance of solar panels.
Sathyanarayana, P., Ballal, R., Lakshmi Sagar, P.S, and Kumar, G. (2015). Effect of shading on the performance of solar PV panel. Energy and Power, 5(1A), p.1-4.View Resource