Solar PV Shading

ShadingHow does shading affect solar PV performance?
The power that Solar PV cells produce depends on the amount of sunlight they receive. In lower light conditions, such as cloud cover or shade, less power is generated.

What happens if a PV System is only partially shaded?
Even if only one panel of a PV system is shaded, then the performance of the whole array will drop. This is because the panels are connected in series. The shaded cell cannot produce as much current as the unshaded panels, creating a bottleneck. To protect the panel, bypass diodes drop the current through the connected panels to the level of the shaded panel, reducing the power of the whole system.

How much will partial shading reduce the PV System output?
Modest shading will reduce the power of the whole array by about 20%. Significant shading will reduce the power of the array by about 40%. For example, a 14 x 180W system would produce 2100 kWh in unshaded conditions, and 1680 kWh in modestly shaded conditions.

What can be done about partial shading in a PV System?
If partial shading occurs, then a smaller system may generate more electricity than a larger one. For example, a 16 panel system that has shading will produce 1921kWh/ year, whereas a 14 panel system with no shading will produce 2100kWh/year. So, it may be better to opt for a system that completely avoids shade than to install a larger system that results in a few shaded panels.