Simulation-Based Assessment of Flap Scheduling and Operating Height for Ground‑Gen Airborne Wind Energy Systems

Abstract. Airborne wind energy systems (AWES) are able to access stronger and more persistent winds at higher operating altitudes, although system performance strongly depends on the choice of aerodynamic actuation, flight-path geometry, and height of operation under realistic wind conditions. In case of rigid-wing ground-generation (ground‑gen) AWES, the influence of such a combination of operating parameters on traction-phase performance is still inadequately understood at constant settings of the control algorithms and limitations of the hardware. This paper tries to fill this knowledge gap by studying the impact of several key operating parameters of the ground-gen system with the aid of a validated nonlinear kite–tether–winch simulator of the Kitemill KM1 rigid-wing Ground-Gen AWES. Using a one-factor-at-a-time simulation campaign, the influence of fixed flap deflection, lateral path geometry, wind-field formulation, minimum production height, and elevation angle of the helix axis on the reel-out mechanical power and operation margins was examined. Under the formulation of an altitude-dependent wind field with the time-varying ground-reference wind input, the baseline design produces an average reel-out power of 7.56 kW. Application of speed-scheduled flap deflection in the range of conservative values of 0°–10° increases the average reel-out power up to 11.10 kW, which corresponds to an increase of around 47 % while repeated crosswind operation was maintained in the evaluated simulations. Increasing the minimum production height further improves the average reel-out power to 12.96 kW, which is about 71 % above the baseline one. On the other hand, within the tested circle–ellipse comparison, lateral path shape has only a minor influence on average traction power, whereas circular loop radius has a clear effect. Tuning of the elevation angle does not allow increasing the reel-out power further than the minimum height optimization does in the considered operating envelope.