What quarries, helicopters and dams have to do with photovoltaics

3 Questions for Claudius Bösiger, Managing Director of Planeco GmbH from Münchenstein, Switzerland.

February 9, 2021

In the spring of 2020, work had begun in frosty conditions. Just in time for summer, our partner Planeco was able to commission the largest solar PV system in the Swiss canton of Graubünden – an extraordinary project which is well worth seeing. In the meantime, the company has also published a video that documents the exceptional installation work in Felsberg. A few questions remained ...

Mr. Bösiger, the video shows how the pre-assembled module tables are flown to their position by helicopter. Why was this necessary? 

The PV system is located on the site of a former quarry. After it was closed, excavated material from construction sites in Chur was deposited there. From the beginning, it was planned that a PV system could be installed on the landfill later.

The installation of the PV modules on a 30 degree steep south-facing slope is attractive because the plant is unshaded and very good solar yields are guaranteed. On the other hand, the terrain was not suitable for normal installation and transport. The module array sits around 150 meters higher than the inverters. The best alternative meant "taking off". The 24 square meter module tables were pre-assembled on the ground and then flown in by helicopter. 

Which consequences did the distance have on the installation of the inverters? 

None that would have given us a headache! KACO new energy's 'Virtual Central' concept was a natural fit here. The inverters and transformer station are easily accessible at the bottom of the hill. The DC combiners, including string monitoring, are located further up in the module array. We therefore have long DC lines to the valley, but short AC lines from the inverters to the transformer station. The high efficiency of the blueplanet 92.0 TL3 inverters can thus be used to its fullest.

Planeco is known for unusual projects. In 2017, for example, you realized the solar façade of the Grosspeter Tower in Basel which was awarded the "Prix Solaire Suisse" for best new building. Can you already tell us what's next? 

We are, in fact, now starting the implementation of the PV system at the Muttsee dam. A few weeks ago, we were awarded the contract for our concept, which is very similar to the one in Felsberg and relies on the proven partners and suppliers. With an output of over two megawatts from the modules along the dam wall, which is roughly 1,000 meters long, this will be a real milestone. We are very excited to make this happen. Commissioning is scheduled for fall 2021.

The lake is located at an altitude of 2,500 meters and the dam wall faces south. These are excellent conditions for unrestricted sunlight. Bad weather, such as fog in the lowlands and midlands, is not to be expected here – only extremely cold weather. This is why the DC combiners, which will be mounted outdoors near the PV modules, are custom-made from stainless steel and are temperature-resistant down to -35 degrees Celsius. For the blueplanet 105 TL3 inverters, we have found a place near the transformer station in the operating room of the PV power plant.

And we will again use helicopters in these heights, of course...

Congratulations on that! We are also looking forward to this project and will be happy to report on it. Thank you very much for the interview, Mr. Bösiger.