Details

The Ten Noorden van de Waddeneilanden Wind Farm Zone (TNW) study area is located approximately 60 km north of the Dutch Wadden Islands and has a foreseen capacity of 700 MW. Aim of this assessment is to estimate scour depths for various monopile diameters, to provide insight into different scour mitigation strategies and into the effect of morphodynamics on cable burial. The presented results will aid wind farm developers in their choice and design of wind turbine foundations and cable paths. Based on hydrodynamic timeseries scour calculations were made for the entire TNW for multiple monopile diameters (8, 10 and 12 m). The study presents a wide selection of scour mitigation strategies for wind turbine foundations. First strategies are presented for seabeds without significant morphodynamics, thereafter strategies are presented for seabeds where significant changes of the seabed levels are expected. The most common and widely accepted scour protection consider one or multiple rock layers. Next to this several other concepts such as block-matrasses, rock-filled mesh bags and artificial vegetation are presented. It can be concluded that for monopiles an easy-applicable, well-proven solution is to place the monopiles in areas with limited seabed dynamics such as TNW and to apply a scour protection to maintain a more or less fixed seabed level around the foundation. Next to foundations, this report also discusses general considerations for cable routing in a morphodynamic area such as TNW. It is expected that cables can be buried sufficiently deep to avoid cable exposure, when smart cable routing techniques are adopted, which avoid the areas with largest morphodynamic seabed lowering or other “expensive” areas with higher risks.