KiteGen project: control as key technology for a quantum leap in wind energy generators

The paper investigates the control of tethered airfoils in order to devise a new class of wind generators, indicated as KiteGen, able to overcome the main limitations of the present aeolian technology based on wind mills. A model taken from the literature is used to simulate the dynamic of a kite whose lines are suitably pulled by a control unit. Energy is generated by a cycle composed of two phases, indicated as the traction and the drag one. The kite control unit is placed on the arm of a vertical axis rotor, which is connected to an electric drive able to act as generator when the kite lines pull the rotor and as motor in dragging the kite against the wind flow. In each phase, control is obtained by "fast" implementations of suitable NMPC designs. In the traction phase the control is designed such that the kite pulls the rotor arm, maximizing the amount of generated energy. When the kite is not able to generate energy any more, the control enters the drag phase and the kite is driven to a region where the energy spent to drag the rotor is a small fraction of the energy generated in the traction phase, until a new traction phase is undertaken. Simulation results are presented, showing that KiteGen may represent a quantum leap in wind energy generation.