Airborne wind energy (AWE) is an emerging and potentially disruptive technology that aims at converting wind energy by flying crosswind patterns with a tethered flying device (See Figure 1). It has the potential to increase the wind energy yield by capturing wind energy at locations and heights unreachable for conventional horizontal-axis wind turbines. This technology can thus have a strong impact on the transition to a sustainable energy system by generating more green electricity, with higher availability and at a lower cost, which is some of the main limitations today.
Figure 1: Two phases of a ground generation AWE system. [source: Airborne Wind Energy Systems: A review of the technologies. Cherubini A. et al.]
An AWE aircraft performs a highly dynamic flight maneuver (in case of a figure-8 pattern) when compared to conventional aircraft. The transition between pumping and reel-in mode is additionally highly dynamic. Simulation of these AWE systems requires accurate dynamic models for all systems involved; these include the ground station, tether (connecting cable), and the aircraft. In the current state-of-the-art modeling, the tether is modeled either using assuming it to be straight or by multiple particle systems given by point masses and spring-damper elements. However, these models do not consider important effects such as unsteady aerodynamics. Nevertheless, due to its long length, the tether is found to have a significant effect on the performance and behavior of an AWE system.
Figure 2: Clear picture of all components involved: ground station, tether, aircraft [Source: Ampyx Power B.V.]
This master thesis aims to fill this research gap by developing a high-fidelity tether model. This will be done by first developing a computational fluid dynamics model for the flow field and a finite element model for the tether. The two high-fidelity solvers will be coupled using the in-house code CoCoNuT to perform aeroelastic simulations. Boundary conditions at both ends of the tether will need to be applied. A steady circular motion at the tether end and fixed at the ground station will be used as a starting point. This can be extended to more dynamic motion (e.g. Figure 1) by including the other components of the AWE system, either given by data (e.g. aircraft forces) or models.
You will compare the obtained tether model with the current state-of-the-art (simple) models and indicate possible shortcomings of these models. Furthermore, you will analyze the simulation results and make conclusions on the possible effects on the AWE system performance and behavior.
In general, in this master thesis you will learn to: