Generalized aerodynamic models for crosswind kite power systems

Abstract

This paper presents two novel semi-analytical models for predicting the aerodynamic performance of crosswind kite power systems (CKPSs), where the kite induction effects on the oncoming flow are taken into account. The blade element momentum theory forms the backbone of the models. The effects of reel-out ratio, solidity factor, rotor incidence angle, side-slip angle and tether drag are included in the formulation for the axial induction factor and power output. For simplicity, the wake rotation and the tangential induction factor are neglected. Aerodynamic model 1 is developed for predicting the reel-out power with uniform inflow assumption, and it is suitable for CKPSs with ground-based power generation. Aerodynamic model 2, on the other hand, can predict both the reel-out and torque powers with either uniform or non-uniform inflow assumption, and the model can be used for CKPSs with ground-based, or on-board power generation, or with the combination of the two. Some parametric studies have been conducted for a generic kite system with pre-defined aerodynamic efficiency parameters to highlight the effects of incidence and side-slip angles. In addition, a particular CKPS and its variants are examined to show the individual and combined effects of incidence angle, side-slip angle, tether drag and airfoil shape on the induction factor and power output.