Green roof meets PV

One thing is for sure, it doesn’t get any greener than installing a photovoltaic system on a green roof. Recent reports have shown that this combination is very effective and has a positive effect on the performance of PV modules, for example, green roofs improve the PV yield. On top of that, the ecological aspect is of course also interesting, as green areas enable new species-rich habitats for flora and fauna due to the partial shading of the roof. There is no doubt that the combination of PV and green roof has its advantages, but there are also some things to consider.

There is absolutely nothing wrong with installing a PV system on a green roof. On the contrary, there are even many advantages. From improved PV performance to more habitat for biodiversity. However, if one decides to install a PV system on a green roof, some points should be considered.

Plant growth

Plants always try to grow towards the light. Of course, no PV system can prevent this. Even the smallest gaps are enough for the plant to make its way. And that this happens is guaranteed. There are always cases where plants grow unhindered. At the latest when the modules are reached, shading then comes into play, which in turn reduces the performance of the PV system.

In this context, we are often asked whether the subsequent attachment of additional sheets prevents possible shading due to plant growth. Although this is the case, this method cannot be recommended under any circumstances. This is because this measure changes the aerodynamics of the PV system to the disadvantage of the operator and a warranty can no longer be given.

So what should be done?

Before installing a PV system on a green roof, it is important to think about the issue of plant growth so that such examples cannot occur in the first place.

One possibility would be to lay a growth-inhibiting protective fleece in the area of the PV system. This should prevent the plants from spreading in this area. To prevent the plants from growing through at the joints over time, the fleece should either be glued together at this point or overlapped very generously. Another alternative is to plan the correct design of a green roof as early as the design stage.

In this respect, a gravel layer could be used in the area of the PV system alone, while the planned green roof can take place unhindered in the remaining roof area. With this solution, not only the roof cladding would be optimally protected. One still benefits from the calculated yields of the PV system and the green area continues to exert a positive influence on the performance of the PV system.

If you have any questions about photovoltaics on green roofs, please write in the comments below. Our experts will be happy to help you.