An important problem in wind turbine design is the prediction of the 50-year load, as set by the IEC 61400-1 Design Load Case (DLC) 1.1. In most cases, designers work with limited simulation budgets and are forced to use extrapolation schemes to obtain the required return level. That this is no easy task is proven by the many studies dedicated to finding the best distribution and fitting method to capture the extreme load behavior as well as possible. However, the issue that is often overlooked is the effect that the sheer uncertainty around the 50-year load has on a design process. In this paper, we use a collection of 96 years’ worth of extreme loads to perform a large number of hypothetical design problems. The results show that, even with sample sizes
exceeding N D 103 10 min extremes, designs are often falsely rejected or falsely accepted based on an overor underpredicted 50-year load. Therefore, designers are advised to be critical of the outcome of DLC 1.1 and should be prepared to invest in large sample sizes.@en

Wind turbine design is subject to load calculation standards. These determine material use which in turn affects wind turbine costs. Wind turbine cost reductions are important as they contribute to the economic feasibility of wind turbines. Therefore careful evaluation of the load standards is paramount for wind turbine design. This thesis offers an evaluation of 50-year ultimate load estimates described in the IEC 61400-1 standard and a tool for wind turbine designers to manage the estimates...