Allseas’ Pioneering Spirit has installed TenneT’s 900-MW DolWin kappa offshore converter station in the German North Sea. Comprising an approximately 5000-tonne foundation jacket and 11,000-tonne topsides housing high-voltage direct current (HVDC) technology, DolWin kappa is Allseas’ first complete platform installation for the offshore wind industry.
DolWin kappa was constructed for the DolWin6 offshore grid connection system at the Dragados Offshore shipyard in Cadiz, Spain. Siemens Energy was commissioned by TenneT as general contractor to build the system.
Installation of DolWin kappa – including piling of jacket foundations – was completed on 4 September after a twelve-day campaign.
Complete transport and installation solution
DolWin kappa arrived in the Port of Rotterdam in mid-August on Allseas’ cargo barge Iron Lady. In a quick turnaround operation, all components – jacket, topsides, piles and connecting bridge – were transferred to the world’s largest construction vessel for transport to the installation site.
All components were installed directly from Pioneering Spirit, using both the topside and jacket lift systems. In another first for Allseas, the 5000-tonne special purpose crane was deployed to drive the ten foundation piles up to 68 metres deep into the seabed to secure the foundation jacket.
Suitable for offshore wind projects
According to Allseas, the project confirms that the company can adapt Pioneering Spirit’s single-lift capability to provide fast and efficient transport and installation solutions for the fast-growing offshore wind market. DolWin kappa follows substation installations at the end of 2021 and start of 2022 for the Hollandse Kust Zuid (HKZ) offshore project off the Dutch coast for German-Dutch green grid operator TenneT, and the Saint-Nazaire wind farm in France.
Allseas says it is also developing new concepts for the installation of next generation turbines and foundations required to meet growing demand for renewable offshore energy, but does not specify what these may be.
The installation of DolWin kappa is key to unlocking additional North Sea wind energy capacity, advancing offshore grid expansion in support of Europe’s energy security. TenneT’s DolWin6 connection will provide more than one million homes with renewable energy when it comes on line in 2023.
Pictures by Allseas.