During power generation, the rotor of wind turbine needs to be aligned with the incoming wind for optimal energy production. On state-of-the-art upwind wind turbines, this step is usually achieved through the yaw control system in the nacelle. This mechanism, however, adds complexity and provides an additional source for errors for offshore turbines since the offshore condition is humid and salty. The salt-laden air may corrode the steel structures, such as the yaw bearing, increasing the cost and difficulty of maintaining. A new design concept of a semi-submersible floating offshore downwind wind turbine (FOWT) moored by a single-point mooring (SPM) system is proposed to address this issue. Due to this improvement, the operation and maintenance cost will be reduced. Based on a 5MW offshore wind turbine, a 3-column semi-submersible floating foundation with a SPM system is designed to support the wind turbine. This system allows the floating foundation to rotate freely for wind alignment. Through weathervane, the yaw control system will be simplified and the power generation efficiency will be improved. In this study, a coupled system model is developed to simulate the dynamic response of the FOWT system and check its feasibility. The result shows that the combination of the single point mooring and the downwind type wind turbine is effective in terms of weathervane. Under the design condition, the dynamic response of the system is relatively small.
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