Traction Power Generation with Tethered Wings

A tethered wing can be used in two different ways, to lift payload or to provide traction power. The latter is the basis of several innovative technical applications, such as kite-assisted ship propulsion and pumping-kite wind energy conversion. This chapter presents a theoretical analysis of traction power generation by a tethered wing, with the objective to establish the fundamental relationships between system and operational parameters on the one hand, and achievable mechanical power output on the other hand. In a first step, it is assumed that the instantaneous flight state of the wing can be approximated by the steady equilibrium of aerodynamic and tether forces. The analysis considers controlled flight along an arbitrary predefined trajectory, distinguishing the cases of varying tether length with fixed point anchoring and constant tether length with anchoring at a point moving in the ground plane. Theoretical results are compared with literature. In a second step, the analysis includes the effect of weight and centrifugal acceleration of the wing.