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Background: Wind energy is one of the leading renewable energies that take part in the current transition from the usage of traditional fossil-fuel energies to green ones. The potential and development of wind power is increasing constantly. Therefore, continuous studies are being carried out in order to improve the power extraction of wind farms. Study: This Master’s Thesis aims to obtain multiple-Input-multiple-Output Reduced-Order Models (IOROMs) that are able to capture the main dynamics present in wind turbine wake flows within wind farms during transients and during operation. This dynamics can be excited via different inputs, such as wind turbine’s yaw angle, generator torque, pitch angle, among others. In this work, the study will be conducted by analyzing the response of the system to yaw angle variations, although the same procedure explained is valid for other inputs. The models developed are also mainly intended for capturing the relation between output magnitudes, such as wind turbine power output, bending moments, lateral forces, etc., and the given inputs to the system. Beside, order reduction is key to this work, since the models are expected to reproduce with acceptable fidelity high computationally costly simulations. The study has been conducted based on CFD (Computational Fluid Dynamics) simulation data that are considered as the starting point of the work. Results & Conclusions: The models developed in this work present considerable agreement with respect to the results obtained via CFD simulations. Owing to the symmetry that the yawing motion presents for the system, the operational range has been divided into two sides, namely the positive yaw angles side and the negative yaw angles side. The results for both cases are successful in terms of flow and power output reconstruction. Therefore, the models can predict within seconds the behavior of wind farms whose performance takes days to be known through CFD simulations. This work also presents several improvements as future upgrade for reduced-order models obtained from CFD data. Some of these improvements deal with operational ranges, sample time, and data collection, inter alia.

The expected exhaustion of fossil sources of energy requires the improvement of other renewable sources, such as wind turbines. Vertical-axis wind turbines present very attractive performance characteristics but extremely complicated aerodynamics. Therefore, research is still needed on this field. A code is developed in order to apply the blade element momentum theory to these wind turbines. BEMT is shown to give considerably reliable results, compared to its fast convergence. BEMT is improved with dynamic stall and wake interaction modifications, in order to include more physical effects. Modified BEMT models will help obtain fast and qualitatively reliable data on VAWT performance. Comparisons with other authors prove that the generated code provides data that are close to the real results. Outgoing

This thesis aims to analyze the importance of airfoils geometry in the yield of wind turbines using computational fluid dynamics (CFD) approach. It pretends to interpret the most important aerodynamic design features of the rotor, and aerodynamic parameters associated with blades airfoils geometry, related with the improvement of wind turbines efficiency for vertical and horizontal axis generators. Moreover the project pretends to explain basic concepts of wind energy converters of both generators named before, and the physical principles of wind energy conversion. All this study will be proven using some specific cases of airfoil shapes for aircraft wings standardized by the National Advisory Committee for Aeronautics (NACA)1. These different shapes will be simulated through CFD changing the mainly influent variables. The numerical simulation of the flow field around the blades will be conducted with ANSYS® Fluent Software2. Finally, the conclusions obtained by the simulation will be compared with the physical explanation demonstrated before, thus obtaining information about how to optimize the airfoil shape. Outgoing