Integrated design of wind turbines

The design of wind turbine is a complex problem and multi-disciplinary optimization procedures are here proposed marrying the overall sizing of the machine in terms of rotor diameter and tower height with the detailed sizing of its aerodynamic and structural components. Differently from monolithic design approaches presented in literature, here a more complex algorithmic architecture is proposed adopting a nested structure and multi-level analyses. The approach aims at sizing the overall machine while taking into full account the subtle and complicated couplings that arise due to the mutual effects of aerodynamic and structural choices. The procedure, driven by detailed cost models, results in a complete aerostructural design of the machine, including its associated control laws. Additionally, an optimization methodology for the selection of the composite materials used in wind turbine blades is proposed. The novel design methodologies are used to investigate traditional and advanced configurations with the ultimate goal of minimizing the cost of energy generated by wind turbines at three different sizes: 2 MW, 3.35 MW and 10 MW. The work also includes a preliminary investigation on the quantification and propagation of uncertainties permeating wind turbine simulation. Different formulations from the family of Non-Intrusive Polynomial Chaos Expansion as well as Ordinary and Universal Kriging are tested and compared in terms of accuracy and computational efficiency with respect to a standard Monte Carlo approach. The thesis is concluded with a discussion on the main outcomes of this work as well as on the limitations that should be addressed by future research studies.