Haltern am See On the 75-hectare Silbersee in Haltern, the solar park floating on the water seems almost small. With its 5,800 solar modules, it is the largest of its kind in Germany. 25 kilometers of cable connect the power plant to the grid. The floating solar system on the site of the former quartz sand pit has been supplying electricity since the end of May – up to three million kilowatt hours per year.
This corresponds to the average consumption of 650 households. And all without government funding.
“In Europe, the development is still in its infancy, but given the current electricity prices, floating solar is already worthwhile for self-consumption,” Andrea Grotzke is convinced. The economist heads the global energy solutions business at the Bavarian developer Baywa Re. The potential of floating solar systems in Germany is “huge”. Even if the trend is just picking up.
The largest floating solar parks sail in China. But in the Netherlands and Germany interest is growing. Especially in densely populated countries with limited space, the floating systems can also provide urgently needed green electricity.
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In Germany, the Fraunhofer Institute for Solar Energy Systems (ISE) sees “enormous technical potential in flooded former opencast lignite mines and other artificial lakes, especially quarry ponds,” explains solar expert Harry Wirth. There are a total of 4,474 artificial bodies of water in this country, most of which were created from opencast mining for building materials.
Baywa Re estimates that around 20 gigawatts (GW) of additional solar power could be generated in Germany. That is almost a third of the capacity installed so far in the entire country. By 2030 it must be 250 GW to achieve the climate targets.
The advantage of floating solar systems is obvious: They open up additional space and are even more efficient. Photovoltaics love sun, but not heat. Cooler temperatures prevail on the water – this increases the yield.
And there could also be a positive side effect for the environment. Because they limit solar radiation on the water surface, the systems reduce evaporation losses and at the same time ensure lower water temperatures. Since the technology is still young, however, there are still no long-term studies on the ecological effects of the floating power plants.
Experts estimate that the number of floating solar systems installed worldwide will increase to six GW by the end of the year. By 2029, they could even account for ten percent of the photovoltaic capacity installed worldwide.
5800 modules float on the Silbersee in Haltern.
Companies like Baywa Re, but also energy groups like EnBW or RWE are planning more and more projects on the water. RWE only put its largest floating PV park to date into operation at the beginning of July. 13,400 solar modules are now supplying electricity for the Amer biomass power plant in Geertruidenberg in the Netherlands.
“Floating solar has untapped power generation potential worldwide,” says Katja Wunschel, CEO for the onshore wind and solar business in Europe and Australia. This not only applies to artificial lakes, but also to solar parks at sea. Where RWE is just beginning, competitor Baywa Re is pursuing specific goals for expansion in Europe.
“By 2025 we want to increase our floating solar business to 500 megawatts,” announces Grotzke. Baywa Re has also built the world’s largest facility outside of China – in the Netherlands. Overall, the developer currently has an installed floating solar capacity of 200 MW. Industrial customers are particularly interested.
In Haltern, too, a large part of the solar power goes directly into the production of the medium-sized family company Quartzwerke. The rest is fed into the grid – with the current record-breaking electricity prices, the raw material producer is doing good business with it. The company has invested a mid-single-digit million amount, and further projects of this type are already planned.
“In view of the increases and the volatility of the electricity price, it is primarily self-consumption that makes many projects interesting today,” agrees ISE expert Wirth. Because the system is firmly anchored and power cables have to be laid all the way to shore, the costs for a floating power plant are between 10 and 15 percent higher than for a comparable solar park on land. This is mainly due to the necessary water-compatible attachment.
The nearly 6,000 modules are mounted on metal frames and float on air-filled containers. So that they don’t sink or drift ashore, they are also held in place with 25 anchors at a depth of up to 20 meters and, of course, have waterproof cables. In two years, Grotzke believes, however, the costs could drop so much that they produce electricity at the same price as ground-mounted systems.
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Only the framework conditions in Germany slow down the enthusiasm for the floating power plants. In its new energy transition law, which was only passed by the Federal Council at the beginning of July, the Federal Ministry of Economics and Technology has massively limited the expansion options. Experts consider two things to be particularly problematic: the power plant must be at least 40 meters from the shore and may only cover 15 percent of the entire water surface.
“In the past, the restrictive framework conditions have already ensured that Germany overslept the rise of global floating solar technology for a few years,” criticizes Wirth. While around six gigawatts of solar power will be installed on bodies of water worldwide by the end of the year, in Germany it is just a few megawatts.
“With the new legal requirements, the potential in Germany drops from 20 gigawatts to just one GW,” says Baywa Re-Manager Grotzke. Whether the investments planned in this country are still worthwhile for the largest floating PV developer in Europe has to be recalculated first.
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