Siemens and Dragados plan to complete BorWin4 as early as 2028, one year earlier than planned.
Amprion Offshore had tendered the construction of the converters in spring 2021. The award process is being completed on time.
The converter stations at sea are designed as unmanned platforms. All stations are serviced every year.
"Both aspects are innovative with regard to converter stations in the German North Sea and will ensure a significant cost reduction in the long term," said Peter Barth, managing director of Amprion Offshore.
Siemens Energy will be responsible for the maintenance of the converter systems for the first 10 years. The converters represent Amprion's largest single investment to date.
The DolWin4 and BorWin4 largely parallel offshore grid connection systems are among the most important energy transition projects in Germany, Amprion said. The company uses direct current technology for the cables, which can be used to transport large amounts of energy with low losses. The converter stations are required for the conversion of alternating current into direct current and vice versa.
DolWin4 and BorWin4 are scheduled to go into operation in 2028 and 2029. From the North Sea wind farms, the cables initially run 60 km or 125 km at sea, cross under the island of Norderney and reach the coast in the Hilgenriedersiel area. From there, they will run for another 155 km as underground cables in the direction of the Hanekenfähr substation in Lingen (Ems), where Amprion will connect them to its transmission grid. There, the Emsland nuclear power plant will be taken off the grid at the end of 2022.
Via DolWin4 and BorWin4, the resulting generation capacity will be replaced by 1.8 GW of offshore wind energy.