With the help of Europe’s largest mobile crane and the Super Puma transport helicopter, the preassembled units consisting of 20 kW inverters and photovoltaic modules were raised from the ground onto the roof and mounted on the unique steel structure.
What was being lifted here is currently Switzerland’s most powerful rooftop photovoltaic system, which has been installed on the flat roof of a production hall in the municipality of Zuchwil. The owner of the building is Swiss Prime Anlagenstiftung. The local company Helion Solar was contracted with the planning, execution and maintenance of the rooftop system.
»The photovoltaic system is unique in terms of its construction.« – Dominik Stierli, Project manager at Helion Solar
“The photovoltaic system is unique in terms of its construction since it was erected on the roof of an existing production hall. A special steel structure on which the photovoltaic modules were mounted four metres high above the existing gable and shed roofs, provides easy access for subsequent maintenance work,” reports Dominik Stierli, project manager at Helion Solar. “Due to the cut-off date for the feed-in remuneration, we had a strict deadline of 30 September. We managed to stick to the tight project schedule through measures such as prefabricating the installation units. But also partners such as Weidmüller, who supported us with high standards and dedication, are a big reason behind the success of this project.”
Initial ready-to-connect solutions in no time at all
On the 36,000 m² roof area, 22,000 solar panels now generate 5.6 MW of power. That covers the demand of several thousand single-family homes – around a third of the population of Zuchwil. The CO2 savings amount to approximately 595 tonnes annually, which is equivalent to the fuel emissions of a new car driving around the globe 104 times. 284 combiner boxes assembled individually for Helion Solar helped produce this result, by reliably bundling the output from the individual strings and connecting that output to the inverter.
With the aid of a giant mobile crane and helicopter, the prefabricated units were lifted onto the roof
The installation was carried out on the prepared supporting structure, which means the flat roof is accessible at all times for maintenance purposes
Beneath the “sunroof”, Weidmüller combiner boxes reliably transmit and protect the generated power
“When the Helion Solar project manager came to us with the request for customised combiner boxes, there were still around three months before the planned commissioning date. We told him this wouldn’t be a problem and delivered the first ready-to-connect solutions, including initial samples, within just two weeks,” reports David Schütz from Weidmüller, who supervised the project as a specialist for application-specific solutions. “Thanks to our knowledge of technical regulations in Switzerland, we were able to develop solutions for Helion Solar which are fully standard-compliant and carefully configured for the planned system architecture. Our prototypes therefore directly passed the test during the application stage. We then delivered the combiner boxes fully assembled and tested, so that the installation time on site was reduced to simply the commissioning itself.”
Effectively reducing interference coupling from surge voltages
Due to the installation height and large extension of the rooftop photovoltaic system in Zuchwil, there is always a risk of lightning strikes. Resulting damage can affect individual components or take down the entire system. In order to prevent repair costs and impaired cost-effectiveness, Weidmüller integrated surge protection into the combiner boxes. This protection was developed specifically for the DC side of the photovoltaic systems.
The most suitable location for surge protection components in a rooftop photovoltaic system depends
on the type of system, the system design and the distance. In the case of large industrial buildings, such as that in Zuchwil, the wiring distances are over 10 metres. Accordingly, not only should the DC input of the inverter be protected, but protecting the installation of the surge protection devices near the photovoltaic module is also recommended.
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Published in May 2016
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