An Integrated Model of the Kite and Tether Dynamics of a Marine Hydrokinetic Energy Harvesting System

This paper models the dynamics of a marine tethered energy harvesting system focusing on exploring the sensitivity of the kite dynamics to tether parameters. These systems repetitively reels a kite out at high tension, then reels it in at low tension, in order to harvest energy. The kite’s high lift-to-drag ratio makes it possible to maximize net energy output through periodic cross-current flight. Significant modeling efforts exist in the literature supporting such energy maximization. The goal of this paper is to address the need for a simple model capturing the interplay between the system’s kite and tether dynamics. The authors pursue this goal by coupling a partial differential equation (PDE) model of tether dynamics with a point mass model of translational kite motion. One can simplify this model significantly by neglecting tether mass and compliance, effectively transforming the tether into a kinematic constraint. Simulation results show that the coupling effects discarded through such a simplification are non-trivial. For example, even when the tether is neutrally buoyant, its transverse vibrations can still cause significant oscillations in net kite forcing.