Shading is a problem in PV modules caused by shadows falling on a solar panel producing power. Current drops proportionally to the reduced irradiance; shading on just one cell can reduce power output to zero.The output declines proportionally to the amount of shading. Solar system owners should also be vigilant in making sure that there are no nearby trees/obstructions which may cause shading issues. Many modern panels, however, come equipped with devices called bypass diodes which minimise the effects of partial shading by essentially enabling electricity to ‘flow around’ the shaded cell or cells.
Shading of solar panels – Definition, Glossary, Details – Solar Mangoadmin