Power Output and Downstream Wake Modifications of Floating Turbines Subjected to Ocean Motions Using a Tension-Leg Platform

Abstract. A concern in the deployment of large wind turbines on ocean floating platforms is the effect of floating platform motions on their electrical power generation. Further, it is not clear how floating motions influence waking, which might affect the combined power generation of collections of turbines. We examine the average power output of a single and a collection of 5 MW wind turbines, mounted on a Tension-Leg Platform (TLP) under the action of fully developed ocean wave motions, coupling floating motions with Large Eddy Simulation (LES) of atmospheric and rotor dynamics. The ocean dynamics enter as fully developed waves derived from the Pierson-Moskowitz spectrum. To assess the influence of ocean motions we performed simulations under multiple turbulence intensities, reporting comparisons of average power output when the platforms are allowed to move to when they are held rigidly in place. In all simulations, we find that the effects of TLP floating platform's induced motions have a minor effect on single and multiple turbine power production and wake structure. Even when using coherent and large amplitude harmonic floating induced perturbations, any significant wake modifications from floating motions are confined to the near-wake region, where downstream turbines are unlikely to be located. The relatively small amplitude of TLP motions relative to pre-existing turbulent fluctuations are the primary reason for low wake and power modifications downstream.