Most of the modern wind turbines are based on doubly fed induction generators (DFIG), with a back to back power converter connecting the rotor to the network. It is known that voltage dips at the stator terminals can cause overcurrents in the rotor windings, which could threaten the converter integrity. In order to protect the converter, several strategies have been proposed in technical literature, requiring in some cases the converter deactivation, which disables the control that the converter has over the power transference between the generator and the system. This last is not a desirable behavior since it can put on risk the voltage stability of the electric system. It is the aim of this dissertation to introduce and compare five of those protection strategies, through the computational simulation of their performance in case of balanced voltage dips. In order to achieve this, the electromagnetic dynamic model of the DFIG was theoretically developed, as well as the models of the strategies of interest. Subsequently, the computational model of the system was assembled in the software Matlabs Simulink to finally perform the desired simulations and its corresponding analysis. / A maioria das turbinas eólicas modernas é baseada em geradores de indução duplamente alimentados (GIDE), com um back to back conversor de energia que liga o rotor para a rede. Sabe-se que as quedas de tensão nos terminais do estator podem causar sobrecorrentes nos enrolamentos do rotor, que podem ameaçar a integridade do conversor. A fim de proteger o conversor, várias estratégias têm sido propostas na literatura técnica, exigindo, em alguns casos, a desativação do conversor, o qual desativa o controlo do conversor, que possui ao longo da transferência de energia entre o gerador e o sistema. Este último não é um comportamento desejável, uma vez que pode colocar em risco a estabilidade de tensão do sistema elétrico. É o objetivo desta dissertação apresentar e comparar cinco dessas estratégias de proteção, através da simulação computacional de seu desempenho em caso de quedas de tensão equilibrada. A fim de alcançar este objetivo, o modelo dinâmico eletromagnética do DFIG teoricamente foi desenvolvido, bem como os modelos das estratégias de interesse. Subsequentemente, o modelo computacional do sistema foi montado no software Simulink do Matlab para finalmente executar as simulações desejadas e sua análise correspondente.

Esse trabalho propõe a investigação da geometria dos contornos internos de eixos vazados para aerogeradores quando aplicados mandris com diferentes diâmetros ao longo de seu comprimento no forjamento incremental em matriz aberta. Tem-se por finalidade a fabricação de um mandril que proporcione à peça forjada formato mais perto do formato final proposto. Foram estudados através do uso de simulações numéricas computacionais com o software Simufact.forming 12 e ensaios com o material modelo plasticina possíveis geometrias de mandris, variando a angulação na região de troca de diâmetros ao longo do comprimento entre 0˚, 30˚ e 60˚, e analisados o comportamento do escoamento do material na região. Com o processo simulatório concluído, foi produzido o mandril que apresentou melhor desempenho e foram realizados testes práticos. No total, duas peças foram forjadas e analisados seus resultados. A geometria proposta da peça foi alcançada, confirmando a escolha da cinemática do processo. A temperatura do mandril foi aferida e comparada com a temperatura durante a simulação, onde no último passe, a medida foi 720°C e a simulada em torno de 620°C. As forças de forjamento apresentaram diferença entre a simulação e forjado na média de 7,6%. / This work proposes the investigation of the internal contour of hollow shafts for wind turbines when applied mandrels with different diameters along its length in incremental open-die forging. It is intended to manufacture a mandrel to provide a forged part closer to the final proposed geometry. Studies were conducted using the numerical computer simulations software Simufact.forming 12 and models of plasticine aiming possible mandrel geometries, varying the angle of the different-diameters region along the length between 0˚, 30˚ and 60˚ and analyzed the behavior of the material flow in the region. As the simulation process was concluded, the mandrel with the best performance was produced and practical tests were performed. In total, two workpieces were forged and analyzed its results. The proposed geometry was achieved, confirming the choice of process kinematics. The temperature of the mandrel was measured and compared with the temperature during the simulation at the last pass, the measurement resulted in 720°C and the simulated around 620°C. The forging forces showed differences between simulation and forging of an average of 7.6%.

Made available in DSpace on 2017-07-10T15:14:31Z (GMT). No. of bitstreams: 1 DissertacaoRobersonParizotto.pdf: 2503168 bytes, checksum: db5f1a0599dffdd5ab378e0d828d8f19 (MD5) Previous issue date: 2014-02-21 / This project aimed to install a water pumping system with wind generator and evaluation of the performance of the same field, considering the availability of wind energy on site. The system was composed of a small wind turbine Horizontal axis Greatwatt the brand mounted on a self-supporting tower and a water pump from SHURflo brand model 8000, it was installed on CASA (Center for Analysis of Alternative Systems) project. Data on the local wind speed, the power generated by the wind turbine and the water flow pumped by the motor pump were collected. With these data it was possible to determine the wind energy in place, the energy generated by the wind turbine, the wind turbine performance and the relationship between energy generated and the pump flow. Thus, by determining the best times of incidence of wind where it was possible to evaluate the best time range for wind power generation and performance of the pump under the action of different levels of wind speed system. / Este projeto teve como objetivo a instalação de um sistema de bombeamento d água com gerador eólico e avaliação do desempenho do mesmo em campo, considerando a disponibilidade de energia eólica no local. O sistema foi composto de um aerogerador de pequeno porte de eixo horizontal da marca Greatwatt instalado sobre uma torre autoportante e uma bomba d água da marca SHURflo modelo 8000, o mesmo foi instalado no projeto CASA (Centro de Analises de Sistemas Alternativos). Foram coletados dados de velocidade do vento no local, a energia gerada pelo aerogerador e a vazão d água bombeada pela moto bomba. Com esses dados foi possível determinar a energia eólica no local, a energia gerada pelo aerogerador, o rendimento do aerogerador e a relação entre a energia gerada e a vazão da bomba. Com isso determinou-se os horários de melhor incidência de vento onde foi possível avaliar a melhor faixa de horário para geração de energia eólica e o desempenho do sistema de bombeamento sob a ação de diferentes patamares de velocidade do vento.

Cette thèse de doctorat propose une méthodologie d’identification et de quantification du gisement éolien dans un contexte insulaire caractérisé par une topographie complexe et une forte pression sur l’usage des sols, puis elle l’applique au cas de l’île de La Réunion. Notre approche est interdisciplinaire, faisant appel tour à tour au droit, à la géographie, à la statistique et à la physique pour quantifier le gisement éolien à l’île de La Réunion, puis à l’économie pour évaluer le coût d’exploitation de ce gisement et définir des politiques publiques de soutien à la production d’électricité éolienne. La première partie de la thèse évalue l’impact du cadre réglementaire foncier sur le potentiel éolien en termes de puissance éolienne crête installable à La Réunion. Ce cadre réglementaire est défini en termes de scenarios décrivant les enjeux sociaux et environnementaux propres à l’installation de capacités éoliennes à l’île de La Réunion. Une approche basée sur les Systèmes d’Information Géographique est développée pour identifier la répartition spatiale des sites éoliens accessibles en fonction de l’évolution du cadre juridique foncier à La Réunion. La deuxième partie de la thèse vise à quantifier le gisement éolien sur les sites accessibles du point de vue règlementaire. La thèse expose la méthodologie d’étude de la distribution jointe de la distribution de la vitesse et de la direction horizontales du vent basée sur une analyse des variations saisonnières et journalières, et identifie les différents régimes de vent en vigueur à La Réunion. Elle justifie le recours au modèle paramétrique de Weibull dans un cadre probabiliste et montre l’intérêt d’utiliser un mélange de distributions de Weibull conditionnelles à la direction du vent, pour quantifier le potentiel éolien d’un site, par rapport au modèle conventionnel de Weibull à deux paramètres. La thèse présente également une méthodologie de construction de l’information géographique concernant les obstacles au sol, nécessaire pour profiler le cisaillement vertical du vent à La Réunion. Elle propose ensuite deux méthodes de prévision spatiale de la ressource éolienne permettant de l’évaluer à partir des observations réalisées aux stations météorologiques disponibles et utilise ces méthodes pour modéliser l’évolution spatiale de la moyenne et du coefficient de variation empiriques de la vitesse du vent. La dernière partie de notre thèse présente une méthode d’évaluation croisée de la politique réglementaire et de la politique de subvention de l’électricité éolienne par le biais de systèmes de tarifs de rachat garantis. Pour chaque scénario de politique réglementaire, on identifie les éoliennes qui sont économiquement profitables dans le cadre de la politique publique de subvention de l’éolien pratiquée à La Réunion. Pour chaque scénario réglementaire, on évalue également le niveau du tarif de rachat garanti de l’électricité éolienne permettant d’atteindre les objectifs publics de développement de l’éolien à La Réunion, ce qui permet de chiffrer le montant du subventionnement public nécessaire pour atteindre ces objectifs. / This doctoral thesis proposes a methodology to identify and quantify the wind power resource in a context characterized by a complex topography and a strong competition for land use, and then it applies it to the case of Reunion island. Our approach is interdisciplinary by using in turn law, geography, statistics and physics to quantify the wind power resource in Reunion Island, then economics to cost the mining of this deposit and to formulate public policies to support wind power generation. The first part of the thesis assesses the impact of land regulatory framework on the wind power resource defined in terms of installable peak power. This regulatory framework is defined in terms of scenarios depicting the social and environmental challenges associated with wind power generation in Reunion Island. A methodology based on Geographic Information Systems is developed to identify the spatial distribution of installable wind farms and to assess the impact of an evolution of land legal framework in Reunion. The second part of the thesis aims at quantifying the wind power on sites accessible from a regulatory point of view. The thesis presents a methodology to study the joint distribution of horizontal wind speed and direction based on the analysis of its seasonal and daily variations, and identifies the different wind regimes in force in Reunion. The thesis supports the use of Weibull distribution model on ground of probability theory, and provides evidence of superiority of using a mixture of Weibull distributions conditional on wind direction to quantify the wind power resource of an accessible site with respect to the use of the conventional marginal two parameters Weibull model. The thesis also provides a methodology to construct the geographical information regarding ground obstacles necessary for profiling the vertical wind shear profile in Reunion. Then, the thesis proposes two spatial prediction methods to assess the spatial distribution of wind resource allowing its estimation from the observations recorded at the available weather stations, and uses these methods to model the spatial evolution of the wind speed mean and variation coefficient. The last part of the thesis provides a method to cross assess the regulatory public policy and the public subsidy policy for wind power generation through feed-in-tariff schemes. For each regulatory scenario, we identify the wind power plants which are profitable under existing feed-in-tariff schemes. For each regulatory scenario, we also evaluate the level at which the feed-in-tariff must be set to reach public objectives of wind power development in Reunion, which allows to assess the amount of public subsidy needed to achieve these objectives.

There are definitely many reasons for choosing off-grid wind power systems. Few key ones involve the positive enhancement of societies, economies and natural environments. From a project developers’ perspective these systems provide a large potential market, which can cover a wide range of applications with relatively reasonable costs.  In spite of this, many challenges may interfere with the diffusion and the success of such systems. In the report we discuss the various factors affecting  the implementation of off-grid wind power systems and demonstrate some of the challenges project developers may be facing during the planning stage. Some of these include the acceptance of stakeholders (local inhabitants in particular) and the securing of the financing of the projects.  Another noted challenge lying outside the control of project developers was found to be the absence of encouraging policies and incentives. As a conclusion the thesis provides a set of self-interpreted recommendations along with a flow chart. The concluded summary indicates some key factors that project developers should be aware of and careful when dealing with, these which include: The choice of the site, verification of projects’ economics along with the securing of a convenient finance. The recommendations also point out the great advantage in having local developers as these tend to be more capable in building relations with the local citizens and politicians.

Tilting the nacelle of a wind turbine modifies entrainment into the wind plant and impacts total efficiency. Extreme angles can produce flying and crashing wakes where the wake either disrupts entertainment from the undisturbed flow above or is decimated on the ground. The effect of tilt angle on downstream wake behavior was investigated in a series of wind tunnel experiments. Scale model turbines with a hub height and diameter of 12 cm were arranged in a Cartesian array comprised of four rows of three turbines each. Nacelle tilt was varied in the third row from -15° to 15° in chosen 5° increments. Stereo PIV measurements of the instantaneous velocity field were recorded at four locations for each angle. Tilted wakes are described in terms of the average streamwise velocity field, wall-normal velocity field, Reynolds stresses, and mean vertical transport of kinetic energy. Conditional sampling is used to quantify the importance of sweep vs. ejection events and thus downwards vs. upwards momentum transfer. Additionally, wake center displacement and changes in net power are presented and compared to existing models. The results demonstrate large variations in wake velocity and vertical displacement with enhanced vertical energy and momentum transfer for negative tilt angles. Simulation models accurately predict wake deflection while analytic models deviate considerably highlighting the difficulties in describing tilt phenomena. Negative angles successfully produce crashing wakes and improve the availability of kinetic energy thereby improving the power output of the wind plant.

This study examines the potential effects of Brexit on the wind power industry within the UK. It became apparent that in order to reach the objective that the approach of the research needed to be broadened as it was found that Brexit has potential effects in many areas of the UK's electricity industry, including the import and export of electricity and the associated fuels used in the generation of electricity. It was found that in the event of a hard Brexit, one with no deal, that the UK's physical connections by undersea cables with the EU may be disrupted. There is a raft of legislation within the Internal Energy Market (IEM) governing this issue that will need a complete rewrite should the UK be forced to leave the IEM. Consideration was given to the effect of Brexit on the three main traditional methods used to generate electricity in the UK, coal, gas and nuclear power and how wind powered energy could be used to fill any shortfall directly or indirectly caused by Brexit. The UK Government has pledged to eradicate the use of coal in generating electricity by 2025 so the study considered only the short term effect of this. For gas, the UK is a net importer, albeit mainly from outside the EU, so the implications of Brexit on gas fired generation of electricity were discussed and found to be negligible. For nuclear powered electricity generation the implications were found to be more serious. The UK would have to resign its membership of Euratom, the European Atomic Agency Community. The potential implications of this include, limited access to nuclear fuel, and reduced participation into nuclear research carried out by the EU. The scope of Euratom also includes a large variety of areas including the safeguarding of nuclear materials in storage and in transit along with radiation protection. Plans by two Japanese companies to build new nuclear power stations in the UK have been shelved with Brexit adding to the uncertainty of their viability. It was found that the combined implications of the above could result in a shortfall in the medium term provision of electricity within the UK. Finally it was discussed whether or not wind powered energy could fill this void and it was found that the UK Government could overcome the deficiency by encouraging investment in wind power by increasing the value of their Contract for Difference, CfD,  auctions.

The dynamics of a tether cable for a flying wind generator, employed to generate electricity by utilising the high velocity jet-stream winds in the troposphere, is analysed. A non-linear mathematical model for the study of the dynamics of the cable is described by a partial differential equation, which is solved analytically without damping. For unsteady and damped states, ordinary differential equations are obtained by adopting a discrete analysis approach, which are solved numerically with the aid of MATLAB software. Solutions are found for a range of lumped masses to represent the cable and each solution is verified against a previous case. Likewise, the result for the three masses is checked against the cable using a single lumped mass. The analysis is extended to seven discrete masses. This research highlights the dynamic behaviour of the cable subjected to wind gusts on the rotors and it also represents an appreciable input to the flying wind generator concept. The dynamic behaviour of the cable is critical for a flying electric generator. / Master of Engineering (Hons)

<p>This thesis aims to determine what CSR issues stakeholders in the wind power industry careabout and how stakeholders want to be involved in these issues. The objective is furthermoreto test and improve the theory of stakeholder involvement – the normative idea thatstakeholder management should strive for maximum stakeholder involvement.The study is carried out using a case study, o2, an important actor in the wind power industryin Sweden. Five stakeholder groups are included in the study, customers, capital providers, inthe form of a major bank and a private equity company, NGO’s and lastly regulators.The study contributes directly to the stakeholder management practices in the wind powerindustry by giving guidance on how to prioritize among different stakeholder groups as wellas to the untested theory of stakeholder involvement by applying the theory to a real casestudy.The result of the study suggests that stakeholders value environmentally related CSR issuesmore than socially related CSR issues. In particular the issues of emissions and flora & faunaare classified as the most important CSR issues for the wind power industry to manage.Furthermore, the theory of stakeholder involvement is shown to be misleading for thestakeholders closest to the company, the once with a direct contractual stake (customers andcapital providers). However, it is shown to be directly applicable, and useful, to thestakeholders more external to the company (NGO’s and regulators).</p>

<p>Nowadays, due to global warming and the depletion of petroleum reserves, renewable energies have gained special prominence. At the moment, wind energy is the most successful renewable energy resource, and the technology to convert this wind energy into electricity has been very developed. As a consequence, the costs per kWh of generation have decreased and it has become a competitive alternative for conventional fossil-fuel power plants to generate electricity.However, a lot of factors and variables are involved in wind power generation. In the first part of this document, some of this factors like the Betz limit, the classification of wind turbines and its components, and the power curve of a wind turbine are explained.In the second part, the performance of a real wind farm is studied. The wind farm is called Es Milà, and it is located in an island called Minorca, in Spain.Firstly, a description of this wind farm and the energy and electricity in Minorca is made.Then, with meteorological and power data of 2007 a thorough study of its performance is completed. In this study, first of all some meteorological aspects like wind direction, wind velocity and its distribution are discussed.After that, the study focuses on electricity production, looking at the power curve, at the expected and the real production, and trying to explain a little of the reactive power.</p>