A evolução do uso da energia eólica nas últimas décadas está diretamente relacionada ao desenvolvimento da tecnologia empregada na conversão e projeto das instalações. A viabilização de uma instalação eólica de grande porte depende da avaliação correta do potencial eólico. A fim de avaliar a capacidade de conversão de energia cinética do vento em torque, é fundamental a modelagem da esteira aerodinâmica das turbinas eólicas. Este trabalho apresenta um estudo sobre a esteira aerodinâmica formada por uma turbina eólica dimensionada conforme a teoria de otimização de Betz. Para tanto, realiza-se inicialmente uma pesquisa sobre a evolução da transformação da energia contida no vento em energia mecânica e métodos de análise adotados. Para modelagem da esteira, realiza-se a simulação numérica do escoamento sobre uma turbina de eixo horizontal empregando o Método de Volumes Finitos. Através do uso da Dinâmica dos Fluidos Computacional são resolvidas as Equações de Navier-Stokes com Médias de Reynolds (RANS) e a utilização dos modelos de turbulência k-, k- RNG, k- e k- SST. Para a solução das equações é utilizado o programa ANSYS-CFX. Define-se o perfil NACA 4412 como perfil aerodinâmico para projeto das pás da turbina, e modela-se a turbina através da teoria de dimensionamento ótimo de Betz. O domínio, discretizado em um número finito de volumes de controle, possui duas regiões distintas, uma estática e outra rotacional, representado o rotor da turbina. Inicialmente são apresentadas simulações com os diferentes modelos de turbulência e definido o modelo que apresenta os melhores resultados, o k- SST. Para o modelo escolhido são realizadas simulações incluindo estudos com a turbina inclinada em relação à direção de incidência do vento, para verificar a alteração no perfil da esteira gerada e na capacidade da turbina em transformar a energia do vento em Torque. Os resultados obtidos para os campos de velocidade e pressão são comparados com os de outros autores e mostraram-se coerentes, indicando que a simulação feita é capaz de representar o fenômeno analisado. / The evolution of the use of the wind energy in recent decades is directly related to the technology in the facilities conversion and design. The feasibility of a large wind farm depends on the correct assessment of wind potential. To evaluate the capacity of converting wind kinetic energy in torque, it is essential to model the wake aerodynamics of wind turbines. This paper presents a study on the aerodynamic wake formed by a wind turbine sized according to the Betz optimization theory. For this, initially it is performed a research on the evolution of the energy contained in wind into mechanical energy and the adopted analysis methods. For wake modeling, a horizontal axis wind turbine flow numerical simulation is done using the Finite Volume Method. Using the Computational Fluid Dynamics, the Reynolds Averaged Navier-Stokes equations are solved with the use of the k-, k- RNG, k- e k- SST turbulence models and using the software ANSYS-CFX. It is defined the NACA 4412 profile as aerodynamic profile for turbine blades and the turbine is modeled using the Betz optimization theory. The domain, discretized into a finite number of control volumes, has two distinct regions, one static and one rotational, represented the turbine rotor. Initially the simulations with different turbulence models are presented and the model k- SST is defined as the model that gives best results. For the chosen model, simulations are performed, including studies on the turbine yawed with respect to the wind incidence direction, to verify the profile change in the generated wake and turbine capacity to convert wind energy into torque. The obtained results for the velocity and pressure fields are compared to other authors are very consistent, indicating that the proposed simulation is capable of representing the analyzed phenomenon.

Este trabalho apresenta a avaliação experimental em túnel aerodinâmico de características de dois aerogeradores de pequeno porte com cinco pás. Para isso, utilizando-se prototipagem 3D, construíram-se dois modelos em escala reduzida, os quais foram avaliados primeiramente utilizando-se Pás Ótimas de Betz e depois Pás Ótimas de Betz Modificadas. Antes de se avaliar o equipamento determinou-se a distribuição de velocidades na seção transversal do túnel com o auxílio de um tubo de Pitot. Com o perfil de velocidades do túnel conhecido, determina-se o torque estático do protótipo com o uso de um torquímetro digital acoplado ao eixo do equipamento, que registrou todas as leituras para as faixas de velocidade de 1 m/s até 9,88 m/s. Também com o torquímetro avalia-se a influência da posição angular das pás no torque medido. Para tanto, elas são projetadas móveis no hub, o que possibilitou variar sua angulação em relação ao escoamento, mudando assim o ângulo de ataque e, por conseguinte o torque produzido. Empregou-se um foto tacômetro para medir a rotação do modelo em giro livre. Com os dados obtidos, determina-se a curva de torque estático e a curva de RPM em função da velocidade incidente. Através da determinação experimental do perfil de velocidade incidente e do perfil de velocidade na esteira aerodinâmica de cada turbina é avaliada a variação da quantidade de movimento do escoamento e determinada a potência extraída pelos rotores em rotação livre. Este estudo visa contribuir com o projeto de um aerogerador real, prevendo as características aerodinâmicas que o equipamento apresentará se construído com o presente layout. Com os dados analisados se faz uma previsão para as curvas de potência dos protótipos. Os resultados experimentais de torque e potência demonstram boa aproximação com os resultados obtidos por avaliação analítica pelo método do elemento de pá. A prototipagem 3D administrada se mostrou eficaz traduzindo realismo e excelente custo-benefício. A turbina construída com Pás Ótimas de Betz apresentou torque estático 17,8% superior à construída com as Pás Modificadas e extraiu 22% a mais de potência do escoamento de ar. / This paper presents the experimental evaluation in wind tunnel of two small wind turbines features five blades. Therefore, using 3D prototyping, two models were built on a reduced scale, which were first evaluated using Optimal Blade Betz and Optimal Blade Betz Modified. Prior to evaluating the distribution machine at speeds determined in the tunnel cross-section with the aid of a Pitot tube. With the known tunnel velocity profile, determines the static torque of the prototype with the use of a digital torquimeter coupled to the machine axis, which recorded all the readings for the speed range of 1 m/s to 9,88 m/s. Also with the torquimeter evaluates the influence of the angular position of the blades in the measured torque. Therefore, it is mobile designed in the hub, allowing vary their angle in the outflow, thereby changing the angle of attack and therefore the torque produced. Employed a photo tachometer for measuring the rotation of the model in free spin. With the data, determines the static torque curve and RPM curve as a function of incident speed. Through experimental determination of the incident velocity profile and the velocity profile in the aerodynamic wake of each turbine is evaluated the variation of the amount of movement of the flow and determined the power extracted by the rotor in free rotation. This study aims to contribute to the design of a real wind turbine informing the aerodynamic characteristics of the equipment shall be constructed with this layout. With the data analyzed to make a prediction for the prototype power curves. The experimental results demonstrate torque and power good approximation to the results obtained by evaluation by analytical element of the paddle method. The turbine constructed with Optimal Betz Blades presented static torque 17,8% higher than constructed with the Modified Blades and extracted 22% more power air outflow.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Esta dissertaÃÃo implementa uma planta de uma unidade de bombeamento suprida por eletricidade a partir da energia eÃlica, para viabilizar a extraÃÃo da Ãgua de poÃos. Instalada na EstaÃÃo de Engenharia de Pesca no Campus do Pici situado na Universidade Federal do Cearà (UFC), em Fortaleza - CE, Brasil. A unidade dispÃe de um aerogerador (1 kW-220 Vca), um controlador de carga, um sistema de bombeamento de Ãgua a partir de poÃo atà um reservatÃrio elevado. A energia elÃtrica para o acionamento do sistema de bombeamento pode ser fornecida pelo tanto pelo aerogerador quanto atravÃs da rede elÃtrica convencional. Outro aspecto enriquecedor do trabalho foi o desenvolvimento de uma tubulaÃÃo configurÃvel em que à possÃvel submeter à bomba a diversas cargas hidrÃulicas, para fins de realizaÃÃo dos testes operacionais. A planta desenvolvida foi capaz de bombear, em mÃdia, 4.318 L/dia de Ãgua com o valor mÃximo 10.698 L/dia a uma velocidade de vento mÃdia de 3,84 m/s. Os rendimentos mÃdios alcanÃados foram 10% (eÃlico/hidrÃulico) e 41% (elÃtrico /hidrÃulico) para uma velocidade de 6,5 m/s. Os ensaios realizados demonstraram baixa robustez do aerogerador utilizado, comprometendo, dessa forma, a disponibilidade operacional e a confiabilidade do equipamento. SÃo sugeridos aÃÃes para garantir a viabilidade da unidade usada no bombeamento de Ãgua acionada por aerogerador de pequeno porte.

Small wind turbines that operate in low-wind environments are prone to suffer performance degradation as they often fail to accelerate to a steady, power-producing condition. The behaviour during this process is called “starting behaviour” and it is the subject of this present work. This thesis evaluates potential benefits that can be obtained from the improvement of starting behaviour, investigates, in particular, small wind turbine starting behaviour (both horizontal- and vertical-axis), and presents aerofoil performance characteristics (both steady and unsteady) needed for the analysis. All of the investigations were conducted using a new set of aerodynamic performance data of six aerofoils (NACA0012, SG6043, SD7062, DU06-W-200, S1223, and S1223B). All of the data were obtained at flow conditions that small wind turbine blades have to operate with during the startup - low Reynolds number (from 65000 to 150000), high angle of attack (through 360◦), and high reduced frequency (from 0.05 to 0.20). In order to obtain accurate aerodynamic data at high incidences, a series of CFD simulations were undertaken to illustrate effects of wall proximity and to determine test section sizes that offer minimum proximity effects. A study was carried out on the entire horizontal-axis wind turbine generation system to understand its starting characteristics and to estimate potential benefits of improved starting. Comparisons of three different blade configurations reveal that the use of mixed-aerofoil blades leads to a significant increase in starting capability. The improved starting capability effectively reduces the time that the turbine takes to reach its power-extraction period and, hence, an increase in overall energy yield. The increase can be as high as 40%. Investigations into H-Darriues turbine self-starting capability were made through the analogy between the aerofoil in Darrieus motion and flapping-wing flow mechanisms. The investigations reveal that the unsteadiness associated with the rotor is key to predicting its starting behaviour and the accurate prediction can be made when this transient aerofoil behaviour is correctly modelled. The investigations based upon the analogy also indicate that the unsteadiness can be exploited to promote the turbine ability to self-start. Aerodynamically, this exploitation is related to the rotor geometry itself.

Alliant flexibilité de contrôle et bon rendement, les Machines Synchrone à Double Excitation (MSDE) sont de plus en plus investiguées pour diverses applications de petites et moyennes puissances et rarement pour des applications de fortes puissances. Cette thèse a pour objectif l’étude d’un Générateur Synchrone à Double Excitation (GSDE) de forte puissance. Un modèle de comportement a été établi. Des méthodes analytiques et semi-analytiques ont été utilisées pour la modélisation multi-physique de la machine. Ce modèle a été validé, dans un premier temps, par comparaison aux résultats d’un modèle éléments finis.Comparé à un Générateur Synchrone à Pôles Saillants (GSPS), le GSDE offre des solutions plus intéressantes énergétiquement et économiquement, que ce soit en fonctionnement à vitesse constante ou à vitesse variable. Dans le cadre d’un fonctionnement en générateur éolien, l’augmentation du nombre d’encoche par pôle et par phase et l’augmentation de la fréquence d’alimentation contribuent à l’amélioration des performances de la GSDE. Cependant il faudrait tenir compte des impacts sur l’électronique de puissance et le multiplicateur mécanique. En plus, la distribution de Weibull et le bon choix de la plage utile de variation de la vitesse du vent, jouent un rôle important sur le dimensionnement optimal du générateur éolien.Un prototype de GSDE d’une puissance d’1MVA a été dimensionné, optimisé et fabriqué. Tout d’abord, le prototype a servi à la validation du modèle multi-physique. En plus la réalisation des essais sur deux étapes (avant et après le collage des aimants permanents) a montré l’apport énergétique du GSDE par rapport au GSPS / The use of Hybrid Excitation Synchronous Machine (HESM) can widely be extended to any size of power applications in regards to its high efficiency and simplicity of flux control. The aim of this thesis consists to analyze different design constraints and develop optimization processes of a Hybrid Excitation Synchronous Generator (HESG).Analytical and lumped models were used with reasonable level of accuracy and minimum computation time. The model has been validated by comparing the result to those achieved by FEM.The study shows the technical and economical advantages of the use of HESG compare to the conventional Salient Pole Synchronous Generator (SPSG). The comparison between the two generator topologies was considered for constant and variable speed applications such as wind energy. The influence of several parameters such as frequency and the number of slot per pole and per phase was investigated. For the case of wind energy application the study shows the importance of Weibull distribution and the speed range when looking for the optimized generator.In order to validate the multi-physics model, a 1MVA HESG was considered and a prototype produced. To highlight the advantages and performances of HESG generator a test program was carried out into steps. A first set of tests have been made before bounding the permanent magnets and the second set of tests have been made after bounding the permanent magnets

The trend of future wind farms moving further offshore requires much higher reliability for each wind turbine in order to reduce maintenance cost. The drive-train system and power electronic converter system have been identified as critical sub-assemblies that are subject to higher failure rates than the other sub-assemblies in a wind turbine. Modern condition monitoring techniques may help schedule the maintenance and reduce downtime. However, when it comes to offshore wind turbines, it is more crucial to reduce the failure rates (or reduce the stresses) for the wind turbines during operation since the harsh weather and a frequently inaccessible environment will dramatically reduce their availability once a failure happens. This research examines the mechanical, electrical and thermal stresses in the sub-assemblies of a doubly-fed induction generator (DFIG) wind turbine and how to reduce them by improved control strategies. The DFIG control system (the rotor-side and the grid-side converter control) as well as the wind turbine control system are well established. The interactions of these control systems have been investigated. This research examines several further strategies to reduce the mechanical and electrical stresses. The control system's coordination with the protection schemes (crowbar and dc-chopper) during a grid fault is presented as well. An electro-thermal model of the power converter has been developed to integrate with the DFIG wind turbine model, for the evaluation of the thermal stresses under different operating states and control schemes. The main contributions of this thesis are twofold. A first contribution is made by providing all the control loops with well-tuned controllers in a more integrated methodology. The dynamics of these controllers are determined from their mathematical models to minimize the interference between different control-loops and also to reduce the electrical transients. This thesis proposes a coordination strategy for the damping control, pitch control and crowbar protection which significantly reduces the mechanical oscillations. On the other hand, an integrated model of the wind turbine and converter electro-thermal system is established that can illustrate the performance integration with different control strategies.

Wind energy is one of the fastest-growing renewable energy technologies, and horizontal axis wind turbines (HAWT) have been the most common device to convert wind kinetic energy into electrical energy. As the capacities of wind turbines and scales of wind farm constructions are rapidly increasing over time, environmental impacts of wind energy are becoming more relevant and raising more attention than ever before. One of the major environmental concerns is noise emission from wind energy facilities, especially low-frequency noise and infrasound that allegedly cause so-called wind turbine syndrome. Therefore, a numerical simulation program capable to predict low-frequency noise and infrasound emission from wind turbines is a useful tool to aid future wind energy development. In this study of this thesis, a computer program named TDRIP (Time Domain Rotor Infrasound Prediction) is developed based on acoustic analogy theories. Farassat’s formulation 1A, a solution to Ffowcs Williams-Hawkings (FW-H) equation, is implemented in the TDRIP program to compute aerodynamically generated sound. The advantage of this program is its capability to simultaneously compute infrasound emission of multiple wind turbines in time domain, which is a challenging task for other aerodynamic noise prediction methods. The developed program is validated against results obtained from computational fluid dynamics (CFD) simulations. The program is then used to compute aerodynamic noise emitted from wind turbine rotors. The effects of wind direction, wind turbine siting, and phase of wind turbine rotation on consequent aerodynamic noise are investigated. Results of aerodynamic noise computation imply that wind turbine siting configuration or wind turbine phase adjustment can help reducing noise level at certain locations, which make the program ideal to be integrated into wind farm siting or control tools.

abstract: An airborne, tethered, multi-rotor wind turbine, effectively a rotorcraft kite, provides one platform for accessing the energy in high altitude winds. The craft is maintained at altitude by its rotors operating in autorotation, and its equilibrium attitude and dynamic performance are affected by the aerodynamic rotor forces, which in turn are affected by the orientation and motion of the craft. The aerodynamic performance of such rotors can vary significantly depending on orientation, influencing the efficiency of the system. This thesis analyzes the aerodynamic performance of an autorotating rotor through a range of angles of attack covering those experienced by a typical autogyro through that of a horizontal-axis wind turbine. To study the behavior of such rotors, an analytical model using the blade element theory coupled with momentum theory was developed. The model uses a rigid-rotor assumption and is nominally limited to cases of small induced inflow angle and constant induced velocity. The model allows for linear twist. In order to validate the model, several rotors -- off-the-shelf model-aircraft propellers -- were tested in a low speed wind tunnel. Custom built mounts allowed rotor angles of attack from 0 to 90 degrees in the test section, providing data for lift, drag, thrust, horizontal force, and angular velocity. Experimental results showed increasing thrust and angular velocity with rising pitch angles, whereas the in-plane horizontal force peaked and dropped after a certain value. The analytical results revealed a disagreement with the experimental trends, especially at high pitch angles. The discrepancy was attributed to the rotor operating in turbulent wake and vortex ring states at high pitch angles, where momentum theory has proven to be invalid. Also, aerodynamic design constants, which are not precisely known for the test propellers, have an underlying effect on the analytical model. The developments of the thesis suggest that a different analytical model may be needed for high rotor angles of attack. However, adding a term for resisting torque to the model gives analytical results that are similar to the experimental values. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2019

Orientador: André Luiz Andreoli / Resumo: As fontes renováveis de energia apresentam-se como solução para problemas relacionados ao aumento da demanda por energia elétrica e crescimento dos níveis de emissão de gás carbônico, uma vez que são não poluentes, limpas e abundantes. Aproveitamentos eólicos se mostram como uma das mais promissoras fontes de energia renovável, e por essa razão as pesquisas envolvendo este tipo de aproveitamento têm despertado grande interesse na comunidade científica. Este trabalho apresenta o desenvolvimento de um emulador de turbina eólica (ETE), uma ferramenta de apoio às investigações experimentais capaz de reproduzir o comportamento mecânico dinâmico de uma turbina eólica através de uma malha de controle digital em configuração de hardware-in-the-loop atuando sobre um acionamento eletrônico de uma máquina de indução Operando como fonte de força motriz, o ETE torna mais fácil a avaliação dinâmica de geradores e seus sistemas de controle associados voltados às aplicações envolvendo energia eólica. A pesquisa apresenta uma revisão bibliográfica sobre o estado da arte, a modelagem e a implementação experimental de um emulador de turbina eólica utilizando um motor de indução trifásico (MIT) acionado por um inversor de frequência. Para isso, é implementado um controle em malha fechada de conjugado e velocidade. Este controle faz com que o acionamento eletromecânico representado pelo MIT e inversor de frequência apresente em seu eixo o comportamento de uma turbina eólica conforme os parâmetros... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

Motivation "Am stetig steigenden Anteil der erneuerbaren Energien, der auf der einen Seite durch die ehrgeizigen Ziele der Politik forciert und auf der anderen Seite durch wirtschaftliche Interessen beflügelt wird, stellt die Windenergie den größten und aussichtsreichsten Bestandteil dar (BMU 2012). Setzt sich der gegenwärtige Trend fort, so ist in den nächsten Jahren mit Multimegawattanlagen im mehrstelligen Megawattbereich zu rechnen."