Amrumbank West

Amrumbank West in a German offshore wind farm under construction in the North Sea. It is owned by E.ON. It is located about 35 km northwest of the island of Heligoland and around 18 km south-west of the Amrum Bank sandbank. As of 2015 it consisted of 80 turbines resting at 19–24 m depth.ConstructionThe cost is around 1 billion euros. The project was delayed 15 months by the lack of power lines. The 80 wind turbines are type Siemens SWT-3.6–120 which have a rated power of 3.6 MW and a rotor diameter of 120 meters. Offshore construction began in 2013, and the first turbine was installed in February 2015. Until the wind farm is operational, diesel is burnt in generators to maintain the rotors. Two 1250 kW diesel generators were announced as delivered in April 2014. The full commissioning of the wind farm is planned for autumn 2015.Seabed protectionThe seabed surface at the construction site mainly consists of sand. It was initially reinforced by a 2.4-m-thick layer of large stones. However, this hindered installation of the turbine piles, which should be driven through the protection layer deep into the seabed. Therefore, stones were replaced by two layers of geotextile containers, i.e., sandbags made of a special damage-resistant nonwoven geotextile. Empty bags had a size of 1.45 × 2.38 m and could accommodate 1 m3 of sand; they were filled on the Rømø island up to 80 vol% and weighed 1400 kg each. The seabed protection withstood the St. Jude storm in October 2013 and Cyclone Xaver in December 2013. Starting from December 2013, turbine piles 6 m in diameter were driven through the erosion protection layers.