Dynamic Responses for WindFloat Floating Offshore Wind Turbine at Intermediate Water Depth Based on Local Conditions in China

Offshore wind energy, a clean energy resource, is considered to be a possible alternative to fossil energy. Floating offshore wind technology is considered to be a proper concept to develop abundant wind energy in deep water. Considering the reality of offshore wind energy development in China, the floating offshore wind turbine concept is expected to be developed at moderate water depths. In this paper, a mooring system of the WindFloat semisubmersible floating offshore wind turbine (SFOWT) at a water depth of 60 m is designed. The dynamic responses of the WindFloat SFOWT under different wind–wave combination conditions are investigated using the coupled method and the simplified method, which do not include the effect of the tower top motion in the aerodynamic calculation. The results show that the dynamic responses of the WindFloat SFOWT, including the platform motions, tower loads, and mooring line tensions, perform fairly well at a moderate water depth. A comparison between the coupled method and simplified method shows that the calculated results are slightly different between the different conditions for the time domain results, response spectra results, and fatigue results. In addition, mooring line 1 (ML 1) suffers higher fatigue damage than ML2, which should be paid more attention