Floating Offshore Wind Turbines: Tension Leg Platform and Taught Leg Buoy Concepts Suppoting 3-5 Mw Wind Turbines

The development is presented of two low weight, motion resistant stiff floating wind turbine concepts for deployment in water depths ranging from 30 to several hundred meters in seastates with wave heights up to 30 meters supporting 3-5 MW onshore wind turbines. The floating wind turbines may be fully assembled at a coastal facility in their upright position prior to being towed to the offshore site by a stabilizing floater. The Tension Leg Platform (TLP) is moored to gravity anchors with tensioned vertical tethers while the Taught Leg Buoy (TLB) is moored to the gravity anchors with taught mooring lines inclined relative to the seafloor. The linear and nonlinear wave loads on the floater are obtained using methods developed for the design of oil and gas offshore platforms. The wind loads are obtained from wind turbine models that do not require the full coupling of the wind turbine aero elastic dynamics with the tower, floater and mooring system dynamics. Simulations are presented of the floater responses in seastates with significant wave heights up to 14 meters and in water depths ranging from 30 to 150 meters demonstrating low nacelle accelerations and mooring line dynamic tensions.