Wake affected offshore tower and foundation loads

Based on the recorded data material basic mechanisms driving the increased loading experienced by WT’s operating in offshore wind farm conditions has been identified, characterized and modeled, and in general a very good agreement between predictions and measurements is obtained. However, for single wake situations the predictions seem to under-predict loading in the above rated wind speed regime.

The, a priory, conjectured load peak in full wake loading cases, for a certain downstream spacing, has been identified in the simulations. As for the measurements, the considerable scatter in these prevents a firm conclusion on this issue. However, it can be concluded: 1) that tower bottom bending fatigue equivalent moments seem to level out in the range between 6D and 9D and decrease at longer downstream distances; and 2) that tower top yaw fatigue equivalent moments seem to level out in the range between 5D and 7D and decrease at longer downstream distances.

Finally, generic WF studies combined with analyses of the Nysted II layout has revealed that, from a load perspective, it is recommended to avoid straight line topology layouts, at least if these lines is oriented along predominant wind directions.