TenneT installs DolWin kappa offshore platform in North Sea

The DolWin kappa offshore platform was successfully installed by transmission system operator TenneT off the coast of Lower Saxony.

It will serve as the focal point of the direct current link known as DolWin6, which will reliably transmit renewable energy generated by wind farms in the German North Sea to the German mainland. After only three years of construction in Cádiz, Spain, the platform was transported to Rotterdam, the Netherlands, at the start of August, when it was reloaded onto the service vessel Pioneering Spirit.

The offshore converter station was then shipped to its ultimate location and installed in a single 12-day operation. Over a million homes will have access to renewable energy once the DolWin6 grid connection system is commissioned in 2023.

In just 12 days, the Pioneering Spirit had the system up and running. The offshore platform was transported from Rotterdam to its final location by the world’s longest service vessel. The over 44-meter-tall, over 5,000-ton foundation structure (jacket) was the first thing to go in. The foundation was then linked to ten piles that were driven up to a depth of 68 meters into the seafloor. Once the base was complete, the Pioneering Spirit lifted the roughly 11,000-ton superstructure (topside) and set it in place. The aggregate height of the two is roughly 82 meters, which means the platform will be about 53 meters above the North Sea’s surface.

In 2023 onwards, the platform will begin converting the alternating power produced by offshore wind farms into direct current, which will subsequently be delivered to Hilgenriedersiel on the mainland through a subsea cable spanning around 45 kilometers. It will then travel another 45 kilometers via land cable to Emden. TenneT has constructed the Emden/Ost converter station and transformer station to reverse the alternating current into direct current and then feed it into the high voltage grid at the necessary voltage.

Image source: TenneT

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