Cells in a module are connected in series, like the cells and modules in this way means that they all produce the same current under the same irradiance. Most cases of shading however, are not uniform across the module string, so if the current drops at one point, the whole chain is restricted and output is reduced. This creates
a mismatch - a difference in the characteristics of an electrical system
which reduces the electricity flow to the level determined by the
lowest performer in the series – for example, if all modules in one string
are working to produce a current of 8A and then a shaded module can
no longer conduct these 8A, then the string will only be able to produce
the current that the shaded module can conduct. In order to manage such situations, solar modules use bypass diodes to divert current around cells unable to conduct in line with others. In standard modules, a bypass diode covers 20 cells out of 60, meaning that when activated, one third of the module is lost to production.