Uncertainty models for the structural design of floating offshore wind turbines: A review

Floating offshore wind turbines have arisen as a promising option to access massive wind energy resources in deep water, where the existing fixed-type offshore wind turbine is no longer practical. However, due to the nature of the oceanic environmental conditions, large uncertainties are involved in the aerodynamic/hydrodynamic calculations, which are coupled with those within the structures and materials. This not only threatens its reliability but also drastically increases the manufacturing cost of floating offshore wind turbines. To understand the uncertainty within the system and properly predict its reliability, first, the uncertainties involved in the environments and subsystems need to be defined. Therefore, this paper aims to provide an extensive review of the uncertainty models involved in the structural design of floating offshore wind turbines. The presented uncertainties within the structures include those inherent in the material and geometrical/mechanical properties of the wind turbine, floating structures, and mooring lines. The uncertainties within hydrodynamics include empirical parameters and nonlinearities involved with the hydrodynamics modeling of the floaters. Within the environmental loads, the parameter uncertainties as well as the randomness of wind and wave loads are presented. The uncertainties growing over time caused by fatigue, corrosion, and climate hazards are also discussed. In addition, the correlation between the random variables, such as the correlation of the wind and wave, is presented. Finally, the method of treating those uncertainties is discussed, including the probabilistic model which incorporates the uncertainties and the correlations between the random variables, as well as modeling errors.