Germany's first large-scale photovoltaic plant is being refurbished

The aerial photograph shows the hybrid power plant with energy storage system on the North Sea island of Pellworm. The system at top right is being fitted with a new aluminium substructure; the one in the upper left of the photo was built on an almost maintenance-free substructure made of tropical wood. (Photo: HanseWerk AG)
The aerial photograph shows the hybrid power plant with energy storage system on the North Sea island of Pellworm. The system at top right is being fitted with a new aluminium substructure; the one in the upper left of the photo was built on an almost maintenance-free substructure made of tropical wood. (Photo: HanseWerk AG)

Thirty-two years ago in 1983, the first large-scale photovoltaic plant in Germany with an overall capacity of 300 kW was built on the North Frisian island of Pellworm. During the interim period, it evolved into a complete hybrid power plant, including wind energy and electricity storage. However, its photovoltaic systems now need to be refurbished.

To ensure that the PV systems on Pellworm continue to function properly and can withstand the salty, humid environment, MaxSolar GmbH is going to inspect the plant, perform maintenance work and partially refurbish it. The work order was issued by the operator and leaseholder of the facility, HanseWerk Natur GmbH, which had tendered three of the four PV system parts with a total output of approximately 550 kW for refurbishment. Pellworm, which is seven kilometres long and six kilometres wide, is the third-largest of the North Frisian islands. A total of 1,200 residents are supplied with power from the plant, which is one of the first hybrid power plants in Germany.

Since the weather on the North Sea island is usually very wet and windy between October and April, MaxSolar intends to complete the functional and performance tests as well as the refurbishment work by the end of September. The plant will go back online in October.

In addition to components such as modules that may need to be replaced, the company will above all be focusing on the substructures during refurbishment work. Two of the four PV systems were mounted on steel substructures, and one of these has been heavily corroded by the humid air and salty spray from the sea. It will be replaced with an aluminium frame, and the second steel structure will be freed from rust and receive a new protective coating.

Tropical substructure turns out to be a good choice

The third PV system that was tendered for inspection and maintenance was installed in the 90s for testing purposes on a substructure made of tropical wood. It only needs to be inspected: even though the tropical timber structure is the oldest of the three, it has withstood the harsh environment better than any of the others. The reason that the unusual building material was chosen is because the expectation in the 90s was that PV systems would increasingly be built in tropical regions and southern countries in the future, where tropical wood is cheap and easy to obtain. The structure on Pellworm was intended to test whether tropical wood is suitable as a building material for substructures. Interestingly, the tropical wood now has even proven to be maintenance-free and more robust than steel structures.

The weather will also make it more difficult to repaint the steel structure because paint cannot be applied when surfaces are wet. In addition, cloudy skies and rain would affect performance tests. Due to the fact that the islet can only be reached by ferry on an irregular basis, transporting materials, equipment and technicians must be carefully planned.

32 years of solar history

"We are very pleased to have received the order to refurbish this special photovoltaic site and are also a bit proud," Franz Hauk, managing director of MaxSolar GmbH admitted. "It is a special challenge to refurbish the photovoltaic system of Germany's oldest large-scale site. Pellworm, which can boast 32 years of solar power and continuous innovations, is a flagship project of the energy turnaround and an important part of international photovoltaic history."

The first photovoltaic system was installed on the North Sea island in 1983. It had a total output of 300 kilowatts. In 1992, newer modules were installed with another 300 kW of power, increasing the overall performance of the photovoltaic system on Pellworm to 600 kW. In 1995, the older part of the PV system installed in 1983 was shut down because lightning had destroyed the inverters. The old solar cells were finally recycled in 2004 and replaced with new PV modules.

Battery has been in use for two years

The hybrid power plant on Pellworm now has an overall capacity of 1,071 kW and consists of photovoltaic systems with 771 kW total power as well as a 300-kW wind turbine. Construction work was completed in 2006, and the hybrid power plant has been fully operational and connected to the grid since then. The hybrid power plant has also been part of a research project since 2013, for which a lithium-ion battery with 560 kWh storage capacity and a redox flow battery with 1.6 MWh storage capacity were installed to harmonise electricity generation and consumption.

Tanja Peschel

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