With a dozen operating offshore connection systems for wind farms in the German North Sea totalling a transmission capacity of 7.132GW, the Dutch-German transmission system operator (TSO) TenneT has already in 2019 exceeded the German government’s expansion target for offshore wind energy capacity for 2020 by more than half a million GW. A further 900MW will be provided by DolWin6, like the predecessor projects DolWin3 and BorWin3 a high-voltage direct current (HVDC) connection. The DolWin kappa offshore platform in the Wadden Sea near the island of Norderney will convert the three-phase wind current into DC for transmission via a 45 kilometre submarine cable to the East Frisian mainland and from the landing point via an underground cable, also around 45 kilometres long, to the TenneT site in Emden/East.
Here, the TSCNET shareholder is constructing the DolWin6 onshore converter station and a substation on 23,500m² to reconvert the DC into three-phase current for feeding into the onshore extra-high voltage grid. A significant milestone for DolWin6 was reached on 27 May: The laying of the foundation at the converter construction site was celebrated in Emden/East by embedding a time capsule with coins, a regional daily newspaper, and construction plans into the foundation stone. Due to the Covid-19 pandemic, the event was only celebrated with the most important project managers from TenneT and the plant constructor Siemens.
Concrete preparations for DolWin6 began in the summer of 2017 and 2018 with horizontal drilling on Norderney. In September 2019, the foundation work commenced in Emden/East. Work on the DolWin kappa offshore platform at a dockyard in Cádiz/Andalusia also started in mid-2019 and the DolWin6 cable laying will follow from summer this year. The completion of the HVDC offshore connection is scheduled for 2023.