KU Leuven

Promotor / Supervisor

Prof. dr. Johan Meyers

Samenvatting van het onderzoek / Summary of Research

The current dissertation investigates the use of optimal control techniques in large-eddy simulations of wind farm boundary-layer interaction with the aim of increasing the total energy extraction in wind farms. The individual wind turbines are considered as flow actuators and their energy extraction is dynamically regulated in time so as to optimally influence the flow field and the vertical turbulent energy transport. The dissertation focuses on the development of a framework for a gradient-and adjoint-based scheme for wind-farm power optimization. In the first optimization studies, the optimal control of an infinite wind farm is investigated. The first control case focuses on the direct maximization of the energy extraction. It is found that the energy extraction increases by 16% compared to the uncontrolled reference. Two additional optimal control cases study the penalization of turbulent dissipation. For the current wind-farm geometry, it is found that the ratio between the wind-farm energy extraction and turbulent boundary-layer dissipation remains roughly around 70%, but can be slightly increased by a few percent by penalizing the dissipation in the optimization objective. For a pressure-driven boundary layer in equilibrium, it is estimated that such a shift can lead to an increase in wind-farm energy extraction of 6%. Subsequently, the application of the optimal control is investigated for a finite-sized wind farm. A fringe region is employed to impose non-periodicity to the domain. It is found that the energy extraction increases by 7.3% compared to the uncontrolled case. The value is significantly lower when compared to the optimization of the infinite wind farm. However, even the 7.3% gain achieved in this dissertation can be beneficial, especially for large wind farms.

Volledige tekst van het doctoraat / full text

Examencommissie / Board of examiners

  •   Prof. dr. Johan Meyers (promotor)
  •   Prof. dr. Adhemar Bultheel (voorzitter/chairman)
  •   Prof. dr. Nicole Van Lipzig (secretaris/secretary)
  •   Prof. dr. Moritz Diehl
  •   Prof. dr. Fernando Porté-Agel , School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne
  •   Prof. dr. Jeroen van Beeck , von Karman Institute for Fluid Dynamics
  • Jan-Willem van Wingerden , Technische Universiteit Delft