A comparative study of load estimation methods for offshore wind turbines using a simplified and a high fidelity methods

This paper compares the critical loads calculated for offshore wind turbines (OWTs) at mudline level using a simplified approach and a high-fidelity approach. Three OWTs, NREL 5MW, DTU 10MW and IEA 15MW are used as reference models. Extreme Turbulence Model wind load at rated wind speed combined with the 50-year Extreme Wave Height (EWH) and Extreme Operating Gust (EOG) wind load combined with the 1-year maximum wave height are used as the load combinations in this study. OpenFAST simulations are used as the high-fidelity approach, where the results are then compared with a simplified load estimation approach previously proposed. It is shown that the simplified method provides conservative results for the estimated loads compared to the OpenFAST results. This means that the simplified approach can be effectively used during initial phases of the monopile foundation design by using factor as 1.5 and 2 for shear force and bending moment, respectively.