Cologne From a great height they look like fat eyes on a soup, and they are supposed to bring power, the floating solar collectors on the sea – six platforms, each 65 meters in diameter. RWE wants to harvest solar power off the Dutch coast this year and test offshore photovoltaics with the “Merganser project”. With the Norwegian-Dutch maritime technology company Solarduck, RWE wants to develop the sea as a future location for solar parks.
The photovoltaic systems are installed several meters above the sea surface – on combinable triangular floats. “Due to their shape, the modules lie on the waves like a carpet,” says Martin Dörnhöfer, Director Floating at RWE Offshore Wind. Although the PV constructions are anchored, they practically float on the sea.
Rapid progress inspires the expansion of photovoltaics in new places. Around a dozen PV systems have already been installed on German lakes. According to a decision by the coalition committee, a lot of photovoltaics should also be installed along railway lines and motorways.
“Autobahn GmbH, Deutsche Bahn AG and third parties will expedite the expansion,” says the paper from the end of March. The responsible Federal Ministry of Transport does not express concrete plans on request, but the commitment to solar energy as a cheap source of electricity is there.
The increased attractiveness is also due to the lower production costs of solar power. In 2021 alone, these fell by 13 percent, reports the International Renewable Energy Organization. Calculated over a whole decade, the price for photovoltaic modules has fallen by 90 percent, says Harry Wirth, Head of Photovoltaics with a focus on modules and power plants at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg. A square meter of solar cell now only costs about 20 euros, and at the same time the efficiency has increased significantly.
However, the expansion is not a sure-fire success. “In order to achieve the expansion goals, we have to increase the number of photovoltaics sixfold,” says Wirth, looking at the current stock. However, residential construction and nature conservation are also in competition with PV expansion. “If we don’t want any more land use and solar modules that are as inconspicuous as possible, we have to build integrated photovoltaics,” says Wirth. “We should use the areas that we are already sealing or otherwise using,” says Wirth.
New layers of paint help, for example, to resolve conflicts with monument protection: In a research project, Fraunhofer ISE was able to equip a historic building in Eppingen with brick-red solar panels. They still let 90 percent of the light through – and are not noticeable.
Transparent on both sides
Another milestone is the so-called bifacial technology. The solar panels are transparent on both sides. This means that the PV modules can also be placed upright, for example as a fence.
In addition to aesthetics and yield, there is a question that is at least as important: How robust is the construction? The London-based company Bankset Energy even wants to place photovoltaics directly in the track bed on railway lines. The idea: A small solar panel is attached to each threshold. A spokesman for Bankset Energy explains that trains are already thundering along the route at a speed of up to 150 kilometers per hour on a test field operated by Deutsche Bahn. “The test was very positive. Our system has proven itself and works.” There is no danger to trains or passengers.
Significantly higher speeds are also conceivable, although the company sees the best use for routes with little traffic. According to the company, the capacity of three nuclear power plants could be installed on 38,000 kilometers of German rail network.
Initial tests show that the modules can withstand the load, they only make sense on routes with little traffic.
(Photo: Bankset Energy)
TÜV Rheinland is also currently testing the potential of solar energy along the railway line on behalf of the Federal Railway Authority. Among other things, the use of PV modules in the track bed is also being examined. It is unclear whether Bankset Energy will do business in Germany. The company spokesman says he hopes for a quick decision from the federal government. Deutsche Bahn only confirms the test on its premises. “Further-reaching plans for cooperation do not currently exist,” says a Bahn spokeswoman.
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An innovator waiting for decisions from others – Reinhard Kohlhauer, who plans and builds noise protection systems along roads throughout Europe with his company founded in Gaggenau 30 years ago, is also familiar with this role. “For more than 20 years I have also been involved with photovoltaics on noise barriers,” says Kohlhauer. “So far we have only installed ten units, all pilot projects. For me, this is more of a hobby than a business model.”
More than 13,000 kilometers of noise protection systems are installed in Germany, which can also be retrofitted. Kohlhauer puts the potential in the gigawatt range. PV noise barriers have existed in Switzerland since the 1990s. “That’s not new, but it just wasn’t done,” comments Fraunhofer researcher Wirth.
Municipalities care
Kohlhauer finally wants to leave tests and pilot projects behind. He doesn’t see any risks. “The systems work,” he says. Kohlhauer calculates that the additional costs for the solar modules, which he estimates at ten to 15 percent, will be refinanced within ten years. But there are many problems: the Autobahn company often doesn’t want to know anything about it, and photovoltaics creates more work for planners, he says. In addition, the question often remains as to who takes the electricity or earns money from feeding it into the grid.
More is happening at the community level. A 250 meter long PV noise protection wall was inaugurated in Augsburg in May. The city hopes to generate 105,000 kilowatt hours a year from the 356 solar modules installed, enough for 33 households. Kohlhauer was also involved in the showcase project. He is now hoping for a “noise protection wall bonus” for photovoltaics and nationwide regulations. Many projects could then be refinanced more quickly and would be more economical for operators.
Fraunhofer researcher Wirth hopes that PV projects will be accelerated and that additional benefits will be recognized. There are also synergies in agriculture, for example by using solar systems to provide shade for the plants underneath. “Photovoltaics in agriculture can increase resilience to climate change,” says Wirth. The so-called Agri-PV is still underdeveloped in Germany compared to the rest of the world – “due to stricter laws”, as Wirth says.
Meanwhile, RWE man Dörnhöfer is counting on the fact that his sea tests not only demonstrate technical feasibility, but that costs can also be reduced through technology improvements. “Challenges in the project are corrosion from salt water and the loads from wind and waves in the North Sea,” he says.
If successful, RWE wants to operate Floating Solar commercially for the first time at the end of the decade in a planned offshore wind farm in the North Sea – then ten times the size. Dörnhöfer is already thinking ahead. He sees great potential in the Mediterranean. “Less wind, more sunshine” – that fits into his plan.
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