Shading and yield losses: How to minimize losses due to shadows

The efficiency and performance of a photovoltaic system depends largely on the lighting conditions. One of the biggest challenges for owners of such systems is shading, which can be caused by buildings, trees, antennas or other objects. Shadows can significantly affect the energy yield of the entire system and lead to financial losses. In this guide, we explain how shading affects photovoltaic systems, how you can minimize yield losses and what technical solutions are available.

1. How does shading affect the photovoltaic system?

Photovoltaic modules convert sunlight into electricity, whereby optimal irradiation of all cells is necessary to achieve maximum performance. However, if parts of a module or several modules in the string are affected by shadows, the efficiency of the entire system drops. This is because photovoltaic cells in modules are connected in series. If one or more cells receive less light, the current flow through all cells in the row is reduced.

Even small shadows can lead to significant power losses, and these can be not only permanent shadows (such as those caused by neighboring buildings or trees), but also temporary influences, such as clouds, satellite dishes or leaves.

2. Typical causes of shading

The main causes of shading in photovoltaic systems can be divided into three categories:

• Buildings and structural structures: Neighboring houses, fireplaces, antennas or chimneys often cast shadows on parts of the solar system.

• Trees and vegetation: Particularly in residential areas with lots of greenery, trees can cast shadows on the roof. Another problem is the seasonal growth of trees, which can lead to more shade over the years.

• Other obstacles: Temporary sources of shade such as dirt, leaves, snow or clouds usually only mean short-term yield losses, but should not be underestimated.

3. Techniques for minimizing shading losses

There are various measures and technologies to reduce the negative effects of shading on photovoltaic systems:

The best prevention against shading begins with the planning of your photovoltaic system. The position and orientation of the modules should be chosen so that shadows are avoided or minimized. Professional installers often use simulation software to identify potential shaded areas and adjust module placement accordingly.

Orienting modules to the south (in the northern hemisphere) at an optimal tilt angle not only minimizes shade, but also increases solar radiation.

Many modern photovoltaic modules are equipped with bypass diodes that divert the flow of current around the shaded cells. This prevents a shaded area from affecting the performance of the entire module or string. Bypass diodes significantly reduce power loss, but are not installed as standard in all modules.

Power optimizers (or module optimizers) are small devices that are installed directly on the solar modules and maximize the output of each module individually. They monitor the performance of each individual module and prevent shaded modules from reducing the efficiency of the entire system. Power optimizers can enable significant increases in yield, particularly in systems with partial or changing shading.

An alternative solution to optimizers are microinverters, which also work on a module basis. In contrast to central inverters, which convert the power of all modules together, microinverters convert the direct current of each individual module into alternating current. This makes them less sensitive to shading, as the performance of the shaded modules has no effect on the rest of the system.

Shading caused by temporary obstacles such as dirt, leaves or snow can be minimized by regularly cleaning and maintaining the solar modules. Solar system owners should ensure that no leaves or snow cover the modules, especially in autumn and winter, as even small amounts of dirt can reduce the energy yield.

4. Long-term considerations: trees and structural changes

If your photovoltaic system is shaded by trees, you should consider long-term measures. Regular tree trimming can often help improve lighting conditions. In some cases, it may be useful to move or remove trees to maximize the efficiency of the solar system. If there are major structural changes in the neighborhood (e.g. new buildings), you may need to adjust the position or orientation of the modules.

Conclusion

Shading is one of the biggest challenges to the efficiency of photovoltaic systems. However, through careful planning, the use of modern technologies such as power optimizers or micro inverters, and regular maintenance, yield losses can be significantly minimized. Especially when installing the system, it is important to identify potential sources of shade and take appropriate measures to get the maximum benefit from your photovoltaic system.