Abstract

This research work presents the dynamics and performance of tethered airborne wind energy systems. To this end, aerodynamic theories for crosswind kite power systems (CKPSs) and an aerostatic power system (APS) have been developed along with the tether models for the respective systems. Two semi-analytical aerodynamic models based on the blade element momentum (BEM) theory considering the effects of induction factor, reel-out ratio, solidity factor, rotor incidence angle, side slip and tether drag are developed for CKPSs. Aerodynamic model 1 is for lift mode CKPSs while Aerodynamic model 2 is for lift mode or drag mode CKPSs or a combination of both. Verification and parametric studies proved the accuracy of the models and gave insights into the combined effects of the operational and geometric parameters. In addition, a semi-analytical aerodynamic model is developed to predict the quasi-steady aerodynamic performance of APS using BEM considerations. The theory which assumes a variable inflow is validated against an autogyro and yawed wind turbine. Variation of aerodynamic performance parameters and optimum rotational speed for the rotor of a $300$ kW APS is studied. Moreover, two tether models based on lumped mass modelling approach, one rigid and the other elastic, accounting for reel-in/reel-out had been developed to analyze the coupled dynamics of the tether and airborne modules. The results from the elastic and rigid tether models for a kite power system and an APS show the shortcomings and advantages of one model over the other.