Connecting the cells in series means that only the weakest cell can be generated in the module.
Partial shading of a PV module has a significant impact on the performance and energy yield of a solar system. This is due to the way photovoltaic panels work.
A PV module consists of many interconnected solar cells that convert light into electricity. If a portion of the module is shaded, the flow of sunlight through that portion is blocked and the affected solar cells produce less power.
Since solar cells are connected in series, the current flow in the entire cell chain is determined by the weakest exposed cell. So if even a small part of the module is shaded, it can affect the performance of all cells. The shadow can come from various sources, such as trees, buildings, chimneys or dirt on the surface of the module.
In addition, modern PV modules often have so-called bypass diodes, which divert the current flow around the affected cells in the event of shading. These bypass diodes minimize the negative effect of shading, but they cannot prevent a significant portion of the performance degradation from occurring.
Overall, partial shading leads to a significant loss of energy yield because the affected cells generate less electricity. Therefore, it is important to avoid shading when planning and installing a solar system to ensure maximum performance and efficiency.