On a drive down through Germany, it is hard to escape the sight of the huge high-voltage connections that cut through the landscape. Here, there are sometimes up to four three-phase alternating current systems of up to 380 kV hanging on a single transmission tower line, which corresponds to a transmission capacity of 2,400 MW when rounded off, or a capacity that could serve half of Denmark on an autumn day.
But despite the many high-voltage lines, the power connection between northern and southern Germany is weak. This has been the case for decades, and as an increasing number of wind turbines is being built in the north, including offshore wind turbines in the Danish part of the North Sea, the problem has intensified. On top of that, Germany has decided to shut down its nuclear power plants, some of which are located in the southern part of the country, which is also the part with the highest power consumption.
The challenge, however, has been the fact that old-fashioned high-voltage connections via transmission towers are something that neither environmental organizations nor residents’ associations are crazy about. Therefore, new connections must be laid as direct current cables, and this results in both a huge additional cost and a complicated approval process.
But now, there is a prospect that a large part of the problem will be solved, and when the German power grid is strengthened, that will also benefit Denmark, according to Morten Pindstrup, international chief engineer at Energinet.
“We would have liked the expansion to have taken place somewhat faster. But now we will get the connections we have demanded for years in Denmark. There is no doubt that it will be helpful in our area to be able to move energy south more easily,” Morten Pindstrup says.
It is especially the cable connection called SuedLink, which consists of two 525 kV HVDC connections, which the Danish power grid will initially benefit from. One of them, which will be supplied by Danish cable manufacturer NKT, will be 702 km long and run from Brunsbüttel in Schleswig-Holstein in the north to Grossgartach in Baden-Württemberg in the south. The other will be 558 km long and run from Wilster to Grafenrheinfeld near Schweinfurt. The total transmission capacity will be 4 GW, and it will also be connected to the NordLink cable, which runs from Germany to Norway.
However, getting the connections approved has not been without its problems. The work started in 2012, and it was actually planned for the construction to start in 2016 and for the connection to be put into commission in 2022.
Two German companies—TenneT TSO and TransnetBW—are responsible for the connection. However, numerous delays, partly due to protests by residents along the route and environmental organizations, mean that the connection will not be operational until 2028. This is despite the fact that the new German government, which took office in 2021, has declared it a project to be “accelerated” and “implemented as a high political priority”.
Although SuedLink will initially be the most important connection for Denmark, another connection will also be built slightly further to the east, under the name SuedOstLink. The transmission system operators responsible for that connection are TenneT and 50hertz.
With SuedOstLink, northern state of Mecklenburg-Western Pomerania will be connected to a transformer station at the Isar nuclear power plant in Bavaria with two 550-km-long 525 kV cables that together can transmit 4 GW. NKT is in on this project as well, supplying cables for the last 275 km. The connection was approved in 2015, but is not expected to go into operation until 2027:
“In the short run, SuedOstLink will not mean that much to Denmark. But for Bornholm Energy Island and its expected connection in Germany, it may be interesting to move more wind energy further south in Germany,” Morten Pindstrup says.
Despite the delays, Axel Happe, who is responsible for planning and regulatory approval at 50hertz, does not think it could have gone much faster:
“We have been in dialogue with public authorities, interest groups, and the general public since the start of the planning process in 2016. Over the years, a lot of questions have been raised and answered. In some cases where the route passed villages, we had to explain our planning in more detail. And in many cases, we found solutions to sometimes very specific problems together with residents, farmers, or landowners along the route. Strong local opposition or general opposition to the cable project has been rare,” he writes in a reply to Ingeniøren.
Also further west in Germany, the network will be reinforced with a cable connection called A-Nord from Emden in northwestern Germany to Osterath near Düsseldorf and on to Phillipsburg just south of Frankfurt with another cable called Ultranet.
The question then is whether the new north-south connections in Germany will already be insufficient when the expansion in the North Sea picks up speed.
“Every other year, we make a forecast for the power system of the future in the grid development plan. According to our latest outlook for 2035, the planned transmission capacity between Börde and Isar will be sufficient,” Alex Happe writes.
At the same time, he emphasizes that increased power consumption in northern Germany has also been taken into account. This is both due to the production of hydrogen and new highly electrified industries such as Tesla and Intel. On top of that comes increased consumption due to electric cars and heat pumps:
“With all these factors included, our projections still show that the planned connections have a sufficient capacity,” Alex Happe writes and adds that the Russian invasion of Ukraine also emphasizes the need for a rapid and reliable energy transition in Germany and Europe.
At Energinet, there is support for the German initiatives.
“Electricity is not the only way to move energy. Hydrogen pipelines and the production of methanol and ammonia for use in trucks and ships are also likely to be needed. But now we will get the connections we’ve been asking for years. It needs to move faster than it has so far, and the question is whether it will be enough when the expansion of wind power in the North Sea begins,” Morten Pindstrup says.
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