TenneT completes installation of DolWin kappa offshore platform

TenneT has installed the 900 MW DolWin kappa offshore platform off the coast of Lower Saxony. It is part of the DolWin6 direct current link, which will bring electricity from offshore wind farms in the German North Sea to shore.

After only three years of construction in the Spanish port city of Cadiz, the rig was shipped to Rotterdam (Netherlands) in early August, where it was reloaded onto the service vessel “Pioneering Spirit”. From there, the offshore converter station was transported to its final destination and installed in a 12-day campaignAll components of the offshore platform were assembled in a single offshore installation campaign. DolWin6 is expected to go live in 2023.

“TenneT is the leading offshore transmission system operator in the EU. We proved this once again with the timely installation of the DolWin kappa offshore platform. DolWin6 is already the 13th offshore grid connection in our German portfolio and will increase security of supply in Germany and Europe,” said Tim Meyerjürgens, COO of TenneT, about the successful installation of the platform.

“In addition to our reliable partners, we also have our many years of experience and our unique expertise in expanding the offshore network to thank for this success”,Meyerjurgens added.

The “pioneer spirit” completed the installation in 12 days. The 382 meter long vessel brought the Rotterdam offshore platform to its final destination. Once there, the foundation structure (jacket), which is nearly 44 meters high and weighs more than 5,000 tons, was installed first. Around, 10 piles were driven up to 68 meters deep into the seabed. Finally, the “Pioneering Spirit” placed the approximately 11,000 ton superstructure (topside) above the foundation structure. The two have a combined height of around 82 meters, so the platform will rise around 53 meters above the surface of the North Sea.

From 2023, the platform will convert alternating current generated by offshore wind farms into direct current, which will then be transmitted to Hilgenriedersiel on the mainland via an approximately 45 kilometer long undersea cable. From there, the electricity will be transmitted to Emden via an overland cable, which will also be 45 kilometers long. Here, TenneT built the Emden/Ost converter station and transformer station to convert direct current back to alternating current and then feed it into the high-voltage grid at the required voltage level.