Germany Offshore construction work has started on the Sandbank offshore wind farm in the North Sea. Vattenfall and its partner Stadtwerke München will invest EUR 1.2 billion in its second major wind farm in the North Sea, expected to supply 400,000 German homes with renewable power by 2017.

The new wind farm will be built 20 kilometres northwest of DanTysk, Vattenfall and Stadtwerke München’s first joint wind farm which was inaugurated on 30 April 2015. Sandbank is scheduled to be commissioned in 2017 and will have an installed capacity of 288 MW. 

72 foundations
The installation of the first four of the 72 Sandbank foundations – each consisting of a monopile and a transition piece - has now started. 

Markus Lapke, Package manager for civil works for the Sandbank project, explains that four monopiles at a time are loaded onto a barge in Rostock. “The barge then sails to Aalborg and loads another four transitions pieces. From there it sails to Esbjerg where the monopiles and transition pieces are loaded onto the installation vessel, the Pacific Orca before it reaches the Sandbank site.” 

Heavy work
Each monopile weighs up to 890 tonnes and the transitions piece another 290 tonnes. “The monopiles will be hammered into the seabed. We will use a hydro sound damper together with a bubble curtain for noise mitigation in order to protect sea mammals.” 

The installation process for each monopile and transition piece is expected to last a day. “All 72 foundations will be in place by November this year,” Lapke states. 

New way of working
One of the lessons learned from the DanTysk project is to use a new efficient technique to assemble the monopiles and transition pieces. “The transition piece was previously grouted into place but now we use flanges to fasten the different parts. It increases efficiency and reduces the use of expensive installation vessels. This way of working is also safer and less weather-sensitive,” Lapke says.

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