Determination of kite forces using three-dimensional flight trajectories for ship propulsion

For application of kites to ships for power and propulsion, a scheme for predicting time averaged kite forces is required. This paper presents a method for parameterizing figure of eight shape kite trajectories and for predicting kite velocity, force and other performance characteristics. Results are presented for a variety of maneuver shapes, assuming realistic performance characteristics from an experimental test kite. Using a 300m2 kite, with 300m long flying lines in 6.18ms−1 wind, a time averaged propulsive force of 16.7tonne is achievable. A typical kite force polar is presented and a sensitivity study is carried out to identify the importance of various parameters in the ship kite propulsion system. Small horizontally orientated figure of eights shape kite trajectories centred on an elevation of 15° is preferred for maximizing propulsive benefit. Propulsive force is found to be highly sensitive to aspect ratio. Increasing aspect ratio from 4 to 5 is estimated to yield up to 15% more drive force.