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Aquest projecte consisteix en la demostració per via del càlcul per CFD amb el programa Hyperworks, del rendiment d’una turbina eòlica en comparació a una quan aquesta l’hi incorporem un flap Gurney en el seu perfil aerodinàmic. L’objectiu d’aquest treball es d’agafar un perfil NACA 0012, utilitzat normalment en turbines eòliques, i calcular les forces que hi intervenen quan se li aplica una velocitat d’entrada del vent, i veure com reacciona el perfil aerodinàmic sol, i desprès agafar el mateix perfil però incorporant-li aquest flap Gurney, popularment conegut i utilitzat pels cotxes de Formula 1, i comparar els dos resultats. D’aquests resultats que n’obtindrem en farem un anàlisi i els compararem per comprovar si el rendiment de la turbina amb el flap Gurney ha augmentat o no. També s’estudiarà el comportament aerodinàmic de la velocitat i les pressions en el perfil., This project consists of demonstrating by CFD calculation with the Hyperworks program, of the efficiency of a wind turbine in comparison with one when a Gurney flap is incorporated in its airfoil. The aim of this work is to take a NACA 0012 airfoil, normally used in wind turbines, and calculate the forces involved when a wind speed is applied, and see how the airfoil reacts alone, and then take the same airfoil but incorporating this Gurney flap, popularly known, and used by Formula 1 cars, and compare the two results. From these results we will make an analysis and compare them to check if the efficiency of the turbine with the Gurney flap has increased or not. We will also study the aerodynamic behaviour of the speed and pressures in the airfoil.

This work deals with structural health monitoring for jacket-type foundations of offshore wind turbines. In particular, a vibration-response-only methodology is proposed based on accelerometer data and deep convolutional neural networks. The main contribution of this article is twofold: (i) a signal-to-image conversion of the accelerometer data into gray scale multichannel images with as many channels as the number of sensors in the condition monitoring system, and (ii) a data augmentation strategy to diminish the test set error of the deep convolutional neural network used to classify the images. The performance of the proposed method is analyzed using real measurements from a steel jacket-type offshore wind turbine laboratory experiment undergoing different damage scenarios. The results, with a classification accuracy over 99%, demonstrate that the stated methodology is promising to be utilized for damage detection and identification in jacket-type support structures., Peer Reviewed, Postprint (author's final draft)

Decommissioning is a key process in the offshore wind industry because all substructures, bottom fixed or floating, have to be removed and completely dismantled at the end of their service life. There is still no experience of decommissioning a floating wind substructure and only two very small offshore wind farms with bottom fixed platforms have already been decommissioned. Devising save and effective processes to dismantle wind offshore substructures is a challenge that has to be faced in civil engineering in near future.

In the following work an aerodynamic study is explained, which consists in seeing the influence of the earth’s surface on the wind propagation. Specifically in plains, uphill and downhill slopes, basic geometries that represent terrestrial and mountainous areas. Once the wind passes through the mentioned domains, the resulting velocity profile is analysed. All in order to provide scientific evidence to the investigations of wind energy, showing the heights where a wind turbine takes advantage of the maximum kinetic energy of the wind. To make it possible, a free and commercial program in Computational Fluid Dynamics (CFD) called OpenFOAM is used. In it, the physical conditions of the boundaries of each geometry are specified. Like the inlet of the flow, the land through which it spreads, its outlet and the top limitation. The boundary conditions are examined and the most suitable ones for this work are concluded. The roughness is simulated by the ”wall functions”, which represent the obstacle of the terrain. The turbulence that appears in consequence, is analysed by the RANS model, specifically that of k-epsilon. And in order to reduce factors that may increase this turbulence, the inlet velocity that is imposed is reduced. Physical knowledge about the Atmospheric Boundary Layer is taken into account in the work. In addition to having as reference the studies carried out by Richard and Hoxey in 1993, which modelled a theoretical velocity profile adapted to the conditions of the Atmospheric Boundary Layer. Model that is used as the theoretical velocity of each simulation, so the results will be compared with it. Finally, the results obtained are discussed, as well as other factors that are taken into account throughout the work. The study ends with some conclusions about the results and the objective of the proposed research., En el siguiente trabajo se explica un estudio aerodinamico, que consiste en ver la ínfluencia que tiene la superficie terrestre sobre la propagacion del viento. Concre- ´ tamente en llanuras, pendientes de subida y de bajada, geometrías basicas que ´ representan desniveles terrenales de zonas montanosas. Una vez el viento atraviesa ˜ los dominios mencionados, se analiza el perfil de velocidad resultante. Todo con tal de proporcionar evidencia científica a las investigaciones de la energía eolica, ´ mostrando las alturas en donde un aerogenerador aprovecha la maxima energ ´ ía cinetica del viento. Para hacerlo posible, se utiliza un programa libre y comercial én Dinamica de Fluidos Computacional (CFD) denominado OpenFOAM. En ´ el, se éspecifican las condiciones físicas de los contornos de cada geometría. Como la entrada del flujo, el terreno por donde se propaga, su salida y la limitacion superior. ´ Se examinan las condiciones de contorno y se concluyen cuales son las m ´ asádecuadas para la tesis. La rugosidad se simula mediante las “funciones de pared”, las cuales representan la obstaculizacion del terreno. La turbulencia que aparece en ´ consecuencia, se analiza mediante el modelo RANS, concretamente el de k-epsilon. ´ Y con tal de reducir factores que puedan aumentar dicha turbulencia, la velocidad de entrada que se impone es reducida. Conocimientos físicos sobre la Capa Límite Atmosferica se tienen en cuenta en él trabajo. Ademas de tener como referencia los estudios realizados por Richard ´ y Hoxey en el 1993, los cuales modelaron un perfil de velocidad teorico adaptado á las condiciones de la Capa Límite Atmosferica. Modelo que se usa como ve- ´ locidad teorica de cada simulaci ´ on, por lo que los resultados se comparar ´ an con ´ este. ´ Finalmente se discuten los resultados obtenidos, así como otros factores que se tienen en cuenta a lo largo del trabajo. El estudio termina con unas conclusiones sobre los resultados y el objetivo de la investigacion plante

This paper presents a simplified model for the dynamic analysis of a floating off-shore wind turbine (FOWT), which can be suitable for early feasibility and pre-engineering studies, where the complete system has to modeled in order to predict its behavior and to assess the performance. The model solves the equation of motion in time domain and considers Morison equation for computing the hydrodynamic loads. The aerodynamic loads are included by considering the wind thrust at hub height and the loads from the mooring system have been computed as a non-linear model. A methodology is also presented for calculating the structural properties of the system. The model is tested for two load cases and compared to results obtained with the more complex model FAST. The comparison between the response of the models is satisfactory. The simplified model allows to capture the main motions of the FOWT with an acceptable accuracy. A further feature of the model is to calculate the power generation of the floating wind turbine. The results show that the losses in comparison with a bottom-fixed off-shore wind turbine are below 1% or 1.1% according to the load case, which confirms the good performance of the studied FOWT., Postprint (published version)

It is unassailable that Earth is undergoing some changes due to climate change, and fossil fuels are still the main power source all over the world. Rain regularity over the last years has become uncertain, what has significantly affected dams' water reservoirs. Hence their capacity for producing hydroelectric power has decreased and may continue to decrease. Indeed, this fact has forced governments to mainly use conventional power sources to supply energy. Consequently, electricity price has notoriously risen. In order to propose a solution to this issue, REDEEM Project (Recycling Dams for Eolic Energy Making), led by several professors and researchers of Universitat Politècnica de Catalunya (Barcelona, Spain), is studying the feasibility of installing small scale wind tur- bines in dam areas to reuse the existing infrastructure and take advantage of thermal winds. This Bachelor's Thesis has assessed the wind resource in several dam and valley areas located in Catalonia (Spain) by evaluating wind speed measurements taken in situ by weather stations belonging to MeteoCat (Catalan meteorology agency). Once the wind speed distribution at each location was known, it was possible to calculate the annual en- ergy output by a selected set of small scale wind turbines. Additionally, other interesting parameters have been calculated, such as the power coefficient (Cp), which determines how efficient the turbine is. All calculations are based on technical specifications provided by manufacturers. Moreover, the project has evaluated the possibility of employing floating structures and foundations, typically deployed in offshore environments. Eventually, an economic study has been carried out to determine the economic viability of the project at the best location. For this purpose, initial and variable costs, cost of energy, payback time and profit have been calculated for each turbine. This project has resulted in some of the studied locations being interesting candidates for

The main objective of this Mater Thesis is to study which is the effect of using Active Flow Control techniques on the aerodynamics of a wind turbine aerofoil. The study is performed over a NACA 4418 aerofoil, a common blade’s root aerofoil with a quite simple shape to avoid strange interactions between upper and lower generated vortices. The simulations are performed at low Reynolds numbers due to the limited computational resources and time. The cases studied are performed at a fixed 10o angle of attack and the parameters changed to study their effect are slot location, jet angle, jet velocity ratio and two different techniques, suction and injection. The mesh is generated via a MATLAB semi-automatic script and with GMSH. Then, the mesh obtained is simulated using OpenFoam integrated solvers. The results are analysed using ParaView and self – developed MATLAB scripts. The idea of having a semi – automatic mesh generator is to have a really quick tool to vary the aerofoil used or the angle of attack and have the new mesh in few seconds. The work process is based on simulating a base case to get the aerodynamics of the aerofoil without AFC usage, then, taking the results from base case, place the slot and define the AFC to be used and see how much does the AFC usage improve the aerodynamics of the aerofoil and which is the effect on the trailing edge’s vortex shedding. The results showed that suction is the easiest AFC of the two studied to be simulated, as there are no values which can cause strange phenomenon. On the other hand, the usage of injection needs to be carefully defined to avoid a premature detachment of the boundary layer and the consequences derived from it.

The reliability requirements of wind turbine (WT) components have increased significantly in recent years in the search for a lower impact on the cost of energy. In addition, the trend towards larger WTs installed in offshore locations has significantly increased the cost of repair of the components. In the wind industry, therefore, condition monitoring is crucial for maximum availability. In this work, without using specific tailored devices for condition monitoring but only increasing the sampling frequency in the already available sensors of the SCADA system, a data-driven multi-fault diagnosis strategy is contributed. The advanced WT benchmark proposed by [1] is used. That is a 5 MW modern WT simulated with the FAST [2] software and subject to various actuators and sensors faults of different type. The measurement noise at each sensor is modeled as a Gaussian white noise. First, the SCADA measurements are pre-processed and feature transformation based on multiway principal component analysis (MPCA) is realized. Then, 10-fold cross validation support vector machines (SVM) based classification is applied. In this work, SVMs were used as a first choice for fault detection as they have proven their robustness for some particular faults [3-5] but never accomplished, to the authors’ knowledge, at the same time the detection and classification of all the proposed faults taken into account in this work. To this end, the choice of the features as well as the selection of data are of primary importance. Simulation results show that all studied faults are detected and classified with an overall accuracy of 98%. Finally, it is noteworthy that the prediction speed allows this strategy to be deployed for real-time condition monitoring in WTs., Postprint (published version)

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 s

Copyright 2016 AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing., Lifting line vortex models have been widely used to predict flow fields around wind turbine rotors. Such models are known to be deficient in modelling flow fields close to the blades due to the assumption that blade vorticity is concentrated on a line and consequently the influences of blade geometry are not well captured. The present study thoroughly assessed the errors arising from this approximation by prescribing the bound circulation as a boundary condition on the flow using a lifting line free-wake vortex approach. The bound circulation prescribed to free-wake vortex model was calculated from two independent sources using (1) experimental results from SPIV and (2) data generated from a 3D panel free-wake vortex approach, where the blade geometry is fully modelled. The axial and tangential flow fields around the blades from the lifting line vortex model were then compared with those directly produced by SPIV and the 3D panel model. The comparison was carried out for different radial locations across the blade span. The study revealed the cumulative probability error distributions in lifting line model estimations for the local aerofoil flow field under both 3D rotating and 2D non-rotating conditions. It was found that the errors in a 3D rotating environment are considerably larger than those for a wing of infinite span in 2D flow. Finally, a method based on the Cassini ovals theory is presented for defining regions around rotating blades for which the lifting line model is unreliable for estimating the flow fields., Peer Reviewed, Postprint (published version)

Realizar el diseño aerodinámico de las palas de un mini aerogenerador de eje horizontal (diámetro aprox ~1 m) usando la teoría de BEM (Blade Element Momentum) y el estudio del ‘wind lens’ para mejorar la eficiencia. Además se realizará un prototipo de las palas., El objeto de este proyecto es adquirir conocimientos sobre el diseño aerodinámico de las palas de un aerogenerador con ‘wind lens’. Usando la teoría de BEM (‘Blade Element Momentum’) modificada por eluso de‘wind lens’.También serealizó un prototipo de la pala para materializar el diseño y poner en práctica conocimientos básicos de fabricación.

The target of this project is to continue the work started in a previous project, studying and optimizing the aerodynamics of flat back airfoils, which are used for wind turbine applications, through numerical simulations., Update the available literature on current flat back airfoils.Continue the optimization of flatback surfaces obtained from conventional sections and develop completely new designs with the objective of obtaining better aerodynamic characteristics than conventional airfoils.

Consolidar i ampliar els coneixements en termodinàmica, transferència de calor, dinàmica de fluids computacional, aerodinàmica, etc. en genral i eficiència energètica en particular. Desenvolupar un treball d'aplicació al disseny en àmbits propis de la enginyeria en general i la optimizació energètica en particular., Anàlisi previ d'antecedents i state of the art. Desenvolupament de les eines de simulació numèrica necessàries. Obtenció de resultats i propostes d'optimització en el disseny. Conclusions.

The main objective is intended to be the experimental investigation in wind tunnel to determine the structure of the real flow in a fixed Savonius wind turbine. A secondary objective of this experimental study will be to obtain the aerodynamic performance of studied wind turbine and also information about velocity field around the rotor., Due to its principle of operation and the continuous variation of flow angle with respect to blades, strong unsteady effects including separation and vortex shedding are observed in a Savonius wind turbine . The flow analysis helps to qualify the design of the wind turbine and to assess the quality of numerical simulations, data concerning the mechanism of torque creation, the vortex structure downstream of the rotor and aerodynamic performance. The experimental investigation in wind tunnel is carried out using flow visualization technique.The main tasks will be:- State of the art of efficient wind turbines- Theoretical study of a Savonius wind turbine- Study of the different available geometries of Savonius to the wind tunnel- Choose the best experimental method for the flow visualization and learn how to use it- Design and construction of the Savonius wind turbine model and the test bench- Experimental running- Results analysis

El present treball consisteix en l’estudi de l’energia eòlica marina a partir de parcs eòlics offshore. Es centra en el seus principis fonamentals des de un punt de vista teòric. Posteriorment s’estudia des de un punt de vista comparatiu amb les diferents energies alternatives, tan renovables com no renovables (impacte ambiental, impacte econòmic i impacte energètic). Es comprova l’evolució tecnològica que ha anat patint la tecnologia offshore al llarg dels anys. El projecte continua amb una breu explicació dels parcs offshore més importants que hi ha actualment al món. Finalment s’arriba a la última part del projecte on es dur a terme un estudi per al disseny, i posterior, avaluació econòmica (viabilitat) d’un parc eòlic offshore.

This project consists in the study of vertical axis turbines, which in opposition to classical horizontal axis turbines have their axis of rotation perpendicular to the fluid (air/water) direction. These kinds of turbines have some advantages like their reduced size, allowing their installation in urban environments. Moreover, vertical axis turbines do not need a yaw pointing system, as they can rotate with independence of the fluid direction, which reduce their maintenance cost. ANSYS Fluent has been used as Computational Fluid Dynamics (CFD) software, providing simulated results with enough accuracy and reliability into this approach to vertical axis turbines. The project begins with an introduction to turbines, showing the main differences between horizontal and vertical axis turbines. After that, the configuration process of Fluent is detailed, as well as the theoretical development that relates the power coefficient with the tip speed ratio of the turbine. A study about the validation of the results has been done, consisting in a mesh and time independence study. Several simulations have been done in order to obtain the optimum configuration of the turbine. The turbine parameters that have been studied are: blade chord, airfoil type, number of blades and turbine radius. The modification of each parameter is aimed to obtain the maximum efficiency of the turbine. Furthermore, a comparison between wind and tidal turbines is described. Finally the conclusions and future work are presented., Este proyecto consiste en el estudio de turbinas de eje vertical, las cuales a diferencia de las turbinas de eje horizontal clásicas tienen su eje de rotación perpendicular a la dirección del fluido (aire / agua). Entre las ventajas de este tipo de turbinas destaca la posibilidad de instalarlas en entornos urbanos gracias a su reducido tamaño. Así mismo las turbinas de eje vertical no necesitan un sistema de apuntamiento ya que pueden girar con independencia de la dirección del fluido, reduciéndose su coste de mantenimiento. ANSYS Fluent se ha utilizado como software de Dinámica de Fluidos Computacional (CFD), para la realización de simulaciones con la suficiente precisión y fiabilidad en esta aproximación a las turbinas de eje vertical. El proyecto se inicia con una introducción a las turbinas, mostrando las principales diferencias entre las turbinas de eje horizontal y vertical. A continuación se detalla el proceso de configuración de Fluent, así como el desarrollo teórico que relaciona el coeficiente de potencia con el parámetro TSR (Tip Speed Ratio). Se ha procedido a la realización de un estudio de independencia del mallado y del muestreo temporal en Fluent, a fin de proceder a la validación de los resultados obtenidos. Se han llevado a cabo varias simulaciones con el fin de obtener la configuración óptima de la turbina. Los parámetros de la turbina que han sido objeto de estudio han sido: cuerda de la pala, tipo de perfil aerodinámico, número de palas y el radio de la turbina. Las modificaciones realizadas sobre cada parámetro están enfocadas a la obtención de la máxima eficiencia de la turbina. Además, se presenta una comparación entre turbinas de viento y marinas. Finalmente se presentan las conclusiones y trabajo futuro que se podría realizar.

Integration of large amount of wind energy in an interconnected power system creates concerns about secure, reliable and economical operation of the entire power system. So it becomes very necessary to investigate the impacts of wind power infeed on the dynamic behavior of the power system. This paper presents the impacts of large amount of wind power in feed on the rotor oscillatory stability. Wind turbine generator types currently employed in wind farms, optimal location of the wind farms in the interconnected power system, reliable optimal dispatch of the wind power and the degree of tie line congestion have been thoroughly investigated. Kundur's two area network model has been utilized to study the mentioned impacts on the overall system using MATLAB/Simulink. Some of the key results show that the damping characteristics of the wind farms critically depend on the location of interconnection in the network and the optimal wind energy dispatch. Increasing the penetration of the wind energy generally improves the damping of the inter area oscillations. Moreover, reducing stress on the weak tie lines also improves the inter area mode of oscillation. So with the investigation of these impacts this study is helpful for the planning of new wind power projects., Peer Reviewed, Postprint (published version)

El objeto de este estudio es adquirir conocimientos sobre los perfiles flatback y con ellos generar y optimizar un nuevo diseño de perfil de este tipo. Estos perfiles, que tienen un potencial uso en las palas de los aerogeneradores, reemplazarían a los perfiles gruesos que son usados en la raíz de cada pala del aerogenerador y presentan deficiencias aerodinámicas debido a su gran espesor, Collect available literature on current flat back airfoils.Study conventional airfoils used in current wind turbines blade design and characterise its aerodynamic properties.Obtain flat back airfoils from this conventional sections and optimise them to obtain better aerodynamic characteristics.

La generación de energía eléctrica a partir de energía cinética procedente del viento ha cobrado importancia, en los últimos años, debido al aumento de la demanda energética global y a la creciente sensibilización medioambiental. En este contexto, el estudio aerodinámico juega un papel fundamental estimando la producción energética anual. El presente trabajo contiene toda la información necesaria para implementar un método de cálculo de fuerzas aerodinámicas. El uso de un modelo no estacionario (Beddoes-Leishman) supone una mejora sustancial en el modelo original, formado por la combinación de la teoría de disco actuador y elemento de pala (BEM). Las limitaciones propias del modelo original motivan a estudiar nuevos modelos complementarios que aparecen para corregir dichas limitaciones. Tras la realización de un código de cálculo en Matlab, los resultados son validados mediante una comparativa de resultados analíticos y experimentales obtenidos sobre el modelo de turbina de TUDelft. Los resultados son positivos, por lo que el programa realizado puede ser utilizado de manera satisfactoria en la estimación de fuerzas aerodinámicas., Energy harvesting from wind’s kinetics energy has emerged as a major theme in recent years due to rising energy demand and growing environmental awareness. In this context, the aerodynamic study plays an important role estimating the annual energy yield. The present work contains all the information necessary to implement a calculation method for the aerodynamic forces. An unsteady model (Beddoes-Leishman) represents a substantial improvement in the original model based on the combined Momentum and Blade Element Theory (BEM). The inherent limitations of the original method motivate us to study new complementary models which make possible to correct such limitations. Following the development of a calculation code in Matlab, the results are validated by a comparison between simulation and experimental results obtained on the TUDelft wind turbine. The results are positive and the code can either be used on its own as a complementary tool in the estimation of forces.

In order to accurately model large, advanced and efficient wind turbines, more reliable and realistic aerodynamic simulation tools are needed. In this project a code to compute the aerodynamics of a Horizontal Axis Wind Turbine is developed. The formulation is based on Prandtl's lifting line theory and assuming a helical prescribed wake of the rotor. To develop this code, another code to compute the wing aerodynamics based in Prandtl's lifting line is developed. This wing code is also explained and validated in this project. Furthermore, the formulation of the numerical lifting line and its adaptation to compute the wing and rotor aerodynamics is presented. The HAWT code is expected to predict the tangential and normal forces to the rotor plane and the results coming from numerical and experimental comparisons are presented. Finally, further code improvements are suggested

This project aims to study the performance of the Rutland 504 micro wind turbine by means of a numerical simulation, and by implementing an experimental analysis.The numerical approach allows the computation of the aerodynamic efficiency of the rotor, understood as the power that can be extracted from the wind and converted into mechanical energy. This study is based on the Blade Element Momentum Theory using the two dimensional features of the wind turbine blade’s aerofoil. On the other hand, the experimental study is accomplished in order to measure the electrical power provided to a battery. Measures of the wind speed, the rotational speed of the rotor, and the current and voltage provided to a 12 V battery allows the evaluation of the total efficiency of the Rutland 504, understood as the electrical power generated from the total power available in the wind.

The flow around the blade of a horizontal axis wind turbine wind tunnel model, operating at its optimal tip speed ratio in axial flow, has been investigated by means of stereoscopic particle image velocimetry (SPIV). The aim was to assess the possibility of measuring the loads impinged on the blade, using the acquired velocity field and its spatial derivatives. Thus, the three-dimensional (3D) velocity field and the pressure distribution surrounding the blade, as well as the aerodynamic loads, responsible for thrust and torque, were obtained with a non-intrusive method. The SPIV equipment was mounted on a traverse system and provided with phase-locked velocity planes perpendicular to the blade axis, scanning the blade from the root to the tip, at a fixed azimuthal position. The obtained velocity fields were used to estimate the pressure distribution and the aerodynamic loads on each plane, using a 3D formulation. Finally, these results were compared and discussed with similar results obtained computationally with a panel method model, showing good consistency. In the future, the proposed methodology could be used to study relevant topics such as active load control techniques, rotational augmentation, dynamic stall phenomena and the aerodynamics of small wind turbines operating at low Re numbers, among others. The processed and averaged flow fields from the experimental SPIV data are made available online to the reader. See appendix for description of the files., Peer Reviewed, Postprint (published version)

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

Peer Reviewed, Postprint (author's final draft)

One of the challenges of the wind energy community today is to improve the existing background on the aerodynamic phenomena of a Horizontal Axis Wind Turbine (HAWT), the prediction of the wind speed distribution on the rotor plane, and the estimation of the design loads. This dissertation aims at contributing to the fulfillment of these objectives. In this way, this study assessed the feasibility of measuring the loads exerted on a HAWT blade by means of Stereoscopic Particle Image Velocimetry (SPIV), which is a non intrusive technique that provides with the whole 3D velocity field in a plane. Thus, with this PIV-Loads method, the velocity and pressure fields, as well as the resultant aerodynamic forces around a section of the blade, would be available simultaneously, without the need of modifying the model or disturbing the flow. In order to achieve this goal progressively, the PIV-Loads method, based in a Momentum Equation contour-based approach, was firstly validated using DNS data, both for a laminar unsteady flow case, as for a velocity averaged turbulent flow. Secondly, the method was tested in the wind tunnel with a bidimensional problem, measuring forces in a stationary flat plate, for different angles of attack (with laminar and turbulent flow conditions). The force estimation results were compared with those provided by a high sensitive balance. Finally, the PIV-Loads method was applied to a HAWT model working both in axial and yaw flow conditions, measuring forces on a rotating blade for steady and unsteady cases. Final load calculations were compared with those resulting from a numerical simulation based in the Panel method approach. Bringing the project to completion, the near vortex wake of a HAWT was characterized by means of Time Resolved PIV. Regarding the PIV-Loads methodology, load predictions are more reliable if the integration path does not cross a shear layer or a boundary layer. In addition, it is neither recommended to neglect the third velo, Postprint (published version)

Offshore wind power technologies are still developing. Floating systems represent the future of wind energy as they provide sites with better wind characteristics. Nowadays they are under intensive study and experimentation, with, for example, the large Denmark investment or the FORWARD project in Japan. The aim of this thesis is the verification of an existing numerical model of a small offshore floating wind turbine: PIGAL, a project of Politecnico di Torino. First of all, the existing model is going to be explained. This numerical model concerns the modelling of hydrodynamic, aerodynamic, mechanical and mooring forces. The verification of the model is going to be done comparing it with the adaptation of the model and experimental data of another small floating wind turbine. The validation of the numerical model is important for the development of larger machines. Afterwards, it is going to be considered the optimization of blades to match the wind conditions of the experimentation., Outgoing