Design loads for an offshore wind turbine using statistical extrapolation from limited field data

When interest is in establishing design loads for wind turbines, it is common to either carry out extensive simulation studies or undertake a field measurement campaign. At the Blyth offshore wind farm in the United Kingdom, a 2MW wind turbine was instrumented, and environment and load data were obtained in a pervious study. Here, we discuss how such data, even though very limited, may be used along with parametric models to establish design loads associated with return periods on the order of 20-50 years. The environmental characteristics at the Blyth site are such that wind and waves are of primary importance. Distributions for the extreme mudline bending moment at the tower base are established using parametric models. Long-term design loads are derived for different wind regimes possible at the site and the results are compared. Using bootstrap techniques, the effect of variability in the parameters for load distribution is investigated.