TenneT has now reached the next important milestone on its path to this objective: the sail-out of the 900-MW offshore platform DolWin kappa, which took place on Aug. 5 from the Dragados Offshore shipyard in Cádiz, Spain.
After only three years of construction, the platform is now on board the transport barge Iron Lady and on its way to the Dutch port of Rotterdam. There, it will be reloaded onto the world’s largest service vessel, the Pioneering Spirit, and then shipped to the installation site. The grid connection system is scheduled to be commissioned in 2023 and provide renewable energy to more than 1 million households.
“TenneT is taking its mission seriously and advancing the grid expansion in the North Sea step by step. With the successful sail-out of the offshore platform DolWin kappa, we have taken the next important leap. DolWin6 is already the 13th offshore grid connection in our German portfolio and will bolster Europe’s urgently needed energy independence beginning in 2023,” said TenneT COO Tim Meyerjürgens when the platform set sail. “Working closely with our contractors Siemens Energy and Dragados Offshore, my colleagues took only three years to build the platform despite the enormous challenges posed by the pandemic."
The platform consists of a foundation structure (jacket) and a superstructure (topside). The two have a combined height of about 82 m, so the platform will rise about 53 m above the surface of the North Sea. In addition, there will be a bridge that will connect DolWin kappa with DolWin beta (grid connection system DolWin2), which was already commissioned in 2016, to efficiently use the already existing infrastructure of the parent platform. What’s more, the overall optimized design of the platform has significantly reduced the size of DolWin kappa.
Once it arrives in Rotterdam, the platform will be reloaded onto the world’s largest service vessel. The 382-m-long Pioneering Spirit will carry all platform components (jacket, topside, piles and bridge) to their final destination in the German North Sea. Once there, DolWin kappa will be installed directly from the work boat. After the platform is commissioned in 2023, it will convert the alternating current generated by offshore wind farms into direct current, which will then be transmitted to Hilgenriedersiel on the mainland via an approximately 45-km-long subsea cable. From the landfall in Hilgenriedersiel, the electricity will be transmitted to Emden by a land cable, which will also be 45 km long.
On land TenneT has built the Emden/Ost converter station and transformer station to convert the direct current back into alternating current and then feed it into the high-voltage grid at the correct voltage level.