International Dredging Review

International Dredging Review

Last summer the installation of the DolwinBeta the offshore High Voltage Direct Cur-rent (HVDC platform) that will connect three offshore wind farms in the German part of the North Sea was completed. The offshore converter station is part of the DolWin2 project which will be operated by transmission system operator TenneT. The Dolwin(2)Beta converter is presently being tested this spring and is expected to be fully connected to the grid in December 2016.

The platform is longer than a football field and once active will become the world’s most powerful offshore converter. The 320-kilovolt converter station has a 916 megawatts (MW) power transmission capacity and will convert the electricity generated by the North Sea’s DolWin cluster offshore wind farms from alternating current (AC) into high-voltage direct current (HVDC). This will supply clean energy to more than a million German households. 


Van Oord’s new offshore installation ship Aeolus stands on four legs above the water level and can work in water to a depth of 55 meters (180 feet).

Starting in 2014 Boskalis has played a major role in the installation of the DolWin Beta.  Boskalis was first asked to mark the site for other seafaring traffic by cardinal buoy installation. The company was then contracted for the pre- and post-installation of the scour protection and ballasting after the platform’s installation. Pre-laid scour protection was done by the flexible fallpipe vessel FFPV Rockpiper in late summer 2014. Through its subsidiaries Smit Lamnalco and Dockwise Boskalis transported the DolWin Beta platform from Dubai where it was built to Haugesund Norway. The platform was then towed by three of Boskalis’ 200-ton bollard pull Fairmount vessels from Haugesund to its final location 45 kilometers (28 miles) off the coast of Northern Germany. Additionally the Boskalis Union Sovereign anchor handling tug installed the anchor pattern where the platform was moored during the installation. 

Another Fairmount tug assisted with the positioning of the platform during installation. The platform was slowly ballasted down to the seabed onto the gravel bed that Boskalis’ fallpipe vessel had laid down by filling the six columns with water. This was later completely replaced by gravel to permanently ballast and secure the platform to the seabed. In April TennT issued a tender for the building and installation of the next offshore converter platform Dolwin(6). 

Boskalis is also partnering with VolkerWessels (Volker Stevin Inter-national) for another wind farm in the German North Sea. Veja Mate Offshore Project GmbH has awarded the contract to the joint venture of Boskalis-VolkerWessels for the design procurement fabrication supply transportation installation and testing of 67 foundations for the Veja Mate Offshore Wind Farm. The monopiles will be installed at water depths rang-ing from 39 to 41 meters (128 to 134 feet). The contract carries a value of approximately €500 million in which Boskalis has a 50 percent share. The Veja Mate Offshore Wind Farm is located 130 kilometers (80 miles) north of Eemshaven the Netherlands and will generate a total capacity of 400 MW. The project commenced at the end of 2015 and should be completed in the fourth quarter of 2016.

Situated 85 kilometers (about 52 miles) north of the coast of the Dutch province of Groningen four project partners have joined forces in the construction of the Gemini Project. These are: Canadian independent renewable energy company Northland Power (60 percent project interest) wind turbine manufacturer Siemens Wind Power (20 percent) the Dutch mari-time contractor Van Oord (10 percent) and renewable energy and waste pro-cessing company HVC (10 percent). Officially Gemini is being built on two locations close to each other Buitengaats and Zee-energie hence the name Gemini the Latin word for twins. In order to install each windmill Van Oord’s flexible fallpipe vessel FFPV Stornes – which can carry 26000 tons of protective material – is placing 2000 tons of material on the seabed at the site where each monopile will be driven into the seabed. To prevent erosion around the monopile the bed of stones is 1.5 meters (almost five feet) thick and has a diameter of about 30 meters (98 feet).

To install the monopiles and transition pieces as well as the towers and blades later on in the project Van Oord’s new offshore installation ship Aeo-lus has been deployed. The Aeolus stands on four legs above the water level and can work in water to a depth of 55 meters (180 feet). It is able to install three monopolies and transition pieces at one go before it must return to port to pick up new material. In addition Van Oord has deployed its new cable-laying vessel Nexus. 

Van Oord is the EPC (Engineering-Procurement-Construction) contractor for the Gemini offshore wind farm which will be one of the largest off-shore wind projects in the world. Van Oord’s activities include the supply and installation of the foundations the entire electrical infrastructure including the supply and installation of offshore and onshore high voltage stations inter-array and export cables and the installation of 150 4 megawatt (MW) Siemens wind turbines. These will supply a total of 600 MW of renewable energy to 785000 households by 2017. Van Oord’s part of the contract is valued at more than €1.3 billion the largest contract in the company’s history. 

Another energy supplier E.ON has awarded Van Oord the contract for the transport and installation of foundations at the Arkona offshore wind project located in the German Baltic Sea. Van Oord will install 60 monopiles and transition piece foundations. For installing foundations at the Arkona offshore wind project Van Oord intends to deploy its heavy lift installation vessel Svanen. The feeder concept is being used i.e. floating foundation components to the Svanen at the installation site. The Svanen has previously installed more than 500 monopiles using this method. The installation works are planned for 2017. With an installed capacity of 385 MW the Arkona offshore wind project will be located more than 35 kilometers (21 miles) North of Rügen Island Germany and will be able to supply renewable energy to 400000 households. E.ON will have responsibility for building and operating the wind farm. The energy company Statoil will have a 50-percent stake and be involved in the project from the start.