Gallery: DolWin kappa Offshore Substation Sails Away

Dutch/German grid operator TenneT said Monday that the 900 MW offshore substation platform DolWin kappa had sailed away from the Dragados Offshore shipyard in Cádiz, Spain. 

"TenneT will soon be reliably bringing even more green wind power from the German North Sea to land via the direct current connection DolWin6," TenneT said in the announcement of the sailaway which took place on August 5, 2022.

"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 over 1 million households," TenneT said.

“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. 

“We also have our partners to thank for the fact that we are reaching this milestone on schedule. 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. This is an outstanding achievement – and proof that we have strong, reliable partners,” Meyerjürgens added.©TenneT

The platform consists of a foundation structure (jacket) and a superstructure (topside). The two have a combined height of about 82 meters, so the platform will rise about 53 meters 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 wascommissioned in 2016, to efficiently use the already existing infrastructure of the parent platform. 

Also, the overall optimized design of the platform has significantly reduced the size of DolWin kappa. 

“The well-thought-out construction of the offshore platform conserves important resources while minimizing impacts on the environment. This clearly illustrates that protecting the environment and nature is our top priority when planning and implementing our grid connections,” Tim Meyerjürgens said.

Once it arrives in Rotterdam, the platform will be reloaded onto the world’s largest service vessel. Owned by Allseas, the 382-metre-long “Pioneering Spirit” will carry all platform components (jacket, topside, piles, and bridge) to their final destination in the German North Sea. 

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-kilometer-long subsea cable.

From the landfall in Hilgenriedersiel, the electricity will be transmitted to Emden by a land cable, which will also be 45 kilometers long. Here 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.