The work presented in this thesis aims at investigating the attachment of lightning flashes to wind turbines. Modern wind turbines are highly exposed to lightning strikes, due to the increase of their height and the rotation of the blades. Upward lightning is the dominant mechanism of lightning strikes to them. Therefore, this study evaluates the initiation of the initial upward leader discharge and the process of lightning attachment of dart leaders taking place prior to the first return stroke in upward flashes. This work extends the self-consistent leader inception and propagation model (SLIM) to evaluate the lightning attachment of dart and dart-stepped leaders to grounded objects. SLIM was originally proposed to evaluate the lightning attachment of stepped leaders. Unlike the well-studied lightning attachment of stepped leaders, upward connecting leaders initiated in response to dart and dart-stepped leaders develop under a significantly faster change of the ambient electric field. Additionally, these connecting leaders could develop in warm air pre-conditioned by the previous strokes in the same flash. An analytical expression to evaluate the charge required to thermalize the connecting leader per unit length is also developed in the extended model. This model is validated through the analysis of three attachment events recorded in rocket-triggered lightning experiments. Good agreement between the predicted properties of the upward leaders and the measurements has been found. The model is utilized to evaluate the different conditions where connecting leaders can develop prior to the return strokes in upward lightning. The extended model of SLIM is also applied to study the interception of lightning dart leaders by upward connecting leaders initiated from wind turbines. The evaluation considers the influence of the return stroke peak current, the blade rotation and wind on the attachment of lightning dart leaders to wind turbines. The probability of lightning strikes to the receptors along the blade and on the nacelle is calculated for upward lightning flashes. It is shown that the lightning attachment of dart leaders is a mechanism that can explain the lightning damages to the inboard region of the blades (more than 10 meters from the tip) and the nacelle of wind turbines. Furthermore, the critical stabilization electric field required to initiate upward lightning from wind turbines is evaluated for both ‘self-initiated’ and ‘other-triggered’ upward flashes. The calculation shows that the stabilization electric field of an operating wind turbine periodically changes due to the rotation of its blades.  The initiation of upward lightning is greatly facilitated by the electric field change produced by nearby lightning events. However, the rate of rise of the electric field only has a weak impact on the stabilization electric field. The evaluation of the stabilization electric field provides essential information needed for the estimation of the incidence of upward lightning to wind turbines. / <p>QC 20161201</p>

This report describes how a new and modern monitoring system is crea- ted for a wind turbine. Elvira Vind AB is a company that has an old operating surveillance system manufactured in 1992. A need has arisen with the owner of the company and are looking for a simple and smooth system that monitors the situation in a wind turbine. Therefore, a system is created that can transmit data wireless- ly through a GSM-module. The system must be able to sense temperature, vibration and sound levels. Also a camera has to take a picture when it de- tects vibration and display the values of the sensors in a web site. The system must also be powered during a power failure, therefore a voltage regulator and a charging circuit was made in the circuit board. The goal of this project is to create a sensor-based monitoring system for a wind turbine and to see the sensor readings wirelessly and displayed in a web site. The report describes how the electronic circuit board has been created and which methods have been used for each sensor in this project. There is also a description of how to use the system for both software and hardware. / Övervakningssystem för vindkraftverk

Esta dissertação aborda o desenvolvimento de um método numérico para a análise de forças e momentos aerodinâmicos em turbinas eólicas fixas e flutuantes no domínio do tempo, utilizando a teoria da quantidade de movimento do elemento de pá (Blade Element Momentum Theory, BEMT) em C++. As pás são divididas em segmentos menores, onde a influência da turbina no fluxo é realizada através do cálculo de fatores de indução. Cada segmento é considerado como um aerofólio bidimensional, sendo possível estimar forças e momentos através de coeficientes para asas infinitas. A teoria da quantidade de movimento do elemento de pá, embora conceitualmente simples, é usualmente empregada com algumas correções em suas equações para se ajustar aos resultados experimentais. A inclusão de turbinas flutuantes é realizada através do movimento de corpo rígido da plataforma, que tem um impacto direto no cálculo aerodinâmico. Por não ser o objetivo deste trabalho, as equações de movimento são calculadas através de uma fonte externa e posteriormente colocadas como dado de entrada do código, simplificando assim a análise e excluindo uma fonte potencial de erro na verificação. O caso de estudo é a turbina do projeto Offshore Code Comparison Collaboration Continuation (OC4), a qual é analisada como uma turbina fixa e flutuante, utilizando uma plataforma semi-submersível. Os resultados das forças e momentos aerodinâmicos do software FAST do Laboratório Nacional de Energias Renováveis (National Renewable Energy Laboratory, NREL) são comparados ao código desenvolvido, mostrando excelente concordância para todos os casos analisados. / This dissertation addresses the development of a numerical method for the analysis of aerodynamic forces and moments of fixed and floating wind turbines in time domain, using the Blade Element Moment Theory (BEMT) written in C++. The blades are divided into smaller segments, where the influence of the turbine in the flow is performed through the calculation of induction factors. Each segment is considered as a two-dimensional airfoil, and it is possible to estimate forces and moments through coefficients for infinite wings. The Blade Element Moment Theory, though conceptually simple, is usually employed with some corrections in its equations to fit experimental results. The inclusion of floating turbines is performed through the rigid body motion of the platform, which has a direct impact on the aerodynamic calculation. Since it is not the objective of this work, the equations of movement are calculated through an external source and then placed as input data of the code, thus simplifying analysis and excluding a potential source of error in verification. The case of study is the turbine of the Offshore Code Comparison Collaboration Continuation (OC4) project, which is analyzed either as a fixed or a floating turbine, using a semi-submersible platform. The results of aerodynamic forces and moments from FAST software of the National Renewable Energy Laboratory (NREL) are compared to the developed code, showing excellent agreement for all cases analyzed.

Esta dissertação descreve um simulador em tempo real para aplicação em testes de reguladores de velocidade de hidrelétricas. O simulador é implementado num hardware que permite a conexão física de todos os sinais que o regulador teria na usina. As dimensões e o perfil hidráulico da usina, dados das máquinas e unidade de força hidráulica são inseridos através de tabelas de fácil entendimento pelo usuário Os transientes hidráulicos no conduto forçado são simulados usando o método das características e levam em conta a influência da turbina. A unidade hidráulica e os atuadores são modelados incluindo suas não-linearidades. Além dos testes de fábrica, este simulador pode ser utilizado para análise preliminar de transientes hidráulicos, treinamento de operadores e como plataforma de testes para novas estratégias de controle da turbina. / This work describes a real-time simulator to be used in hydroturbine speed governor tests. The simulator is implemented using a hardware configuration which allows the physical connection to the governor under test like it would be in the hydropower plant. The conduit dimensions, hydraulic scheme, machine and hydraulic power unit data are inserted into the simulator by user friendly input tables. The hydraulic transients in the penstock are simulated using the method of characteristics and take into account the turbine influence. The electrohydraulic interface, servomotor and hydraulic power unit are simulated including the nonlinearities of valves and servomotors. Besides the factory tests, this simulator can also be applied for a preliminary analysis of hydraulic transients, operator training and platform for testing new turbine control strategies.

Electricity demand is rapidly increasing with growth of population, development of technologies and electrically intensive industries. Also, emerging climate change concerns compel governments to seek environmentally friendly ways to produce electricity such as wind energy systems. In 2018, the wind energy reached 600 GW total capacity globally. However, this corresponds to only about 6% of global electricity demand and there is a need to increase wind energy penetration in electricity grids. One way to enhance the competitiveness of wind energy is to improve its reliability and availability and reduce associated maintenance costs. This study utilizes a database entitled “Wind Monitor and Evaluation Program (WMEP)” to investigate, model and improve wind turbine reliability and availability. The WMEP database consists of maintenance data of 575 wind turbines in Germany during 1989-2008. It is unique as it includes details of turbine model and size, affected subsystem and component, cause of failure, date and time of maintenance, location, and energy production from the wind turbines. Additional parameters such as climatic regions, geography number of previous failures and mean annual wind speed are added to the database in this study. In this research, two metrics are considered and developed such as time-to-failure or failure rate and time-to-repair or downtime for reliability and availability, respectively. This study investigated failure causes, effects and criticalities of wind turbine subsystems and components, assessed the risk factors impacting wind turbine reliability, modeled the reliability of wind turbines based on assessed risk factors, and predicted the cost of wind turbine failures under various operational and environmental conditions. A well-established reliability assessment technique - Failure Modes, Effects and Criticality Analysis is applied on the WMEP maintenance data from 109 wind turbines and three different climatic regions to understand the impacts of climate and wind turbine design type on wind turbine reliability and availability. First, climatic region impacts on identical wind turbine failures are investigated, then impacts of wind turbine design type are examined for the same climatic region. Furthermore, we compared the results of this investigation with results from previous FMECA studies which neglected impacts of climatic region and turbine design type in section 5.4. Two-step cluster and survival analyses are used to determine risk factors that affect wind turbine reliability. Six operational and environmental factors are considered for this approach, namely capacity factor (CF), wind turbine design type, number of previous failures (NOPF), geographical location, climatic region and mean annual wind speed (MAWS). Data are classified as frequent (time-to-failure<40 days) and non-frequent (time-to-failure>80 days) failures and we identified 615 operations listing all these factor and energy production from 21 wind turbines in the WMEP data base. These factors are examined for their impact on wind turbine reliability and results are compared. In addition, wind turbine reliability is modeled by machine learning methods, namely logistic regression (LR) and artificial neural network (ANN), using the considered 615 operations. The objective of this investigation is to model and predict probability of frequently-failing wind turbines based on wind turbines’ known operational and environmental conditions. The models are evaluated and cross validated with 10-fold cross validation and prediction performances and compared with other algorithms such as k-nearest neighbor and support vector machines. Also, prediction performances of LR and ANN are discussed along with their easiness to interpret and share with others. Lastly, using data from 753 operations, a decision support tool for predicting cost of wind turbine failures is developed. The tool development includes machine learning application for estimating probability of failures in 60 days of operation and time-to-repair probabilities for divisions of 0-8hrs, 8-16hrs, 16-24hrs and more than 1 day based on operational and environmental conditions of wind turbines. Prediction for cost of wind turbine failures for 60 days of operation is calculated using assumed costs from time-to-repair divisions. The decision support tool can be updated by the user’s discretion on the cost of failures. This study provides a better understanding of wind turbine failures by investigating associated risk factors, modeling wind turbine reliability and predicting the future cost of failures by applying state-of-the art reliability and data analysis techniques. Wind energy developers and operators can be guided by this study in improving the reliability of wind turbines. Also, wind energy investors, operators and maintenance service managers can predict the cost of wind turbine failures with the decision support tool provided in this study.

On August 5, 2010 the U.S. Department of Energy (DOE) has designated the Center for Ocean Energy Technology (COET) at Florida Atlantic University (FAU) as a national center for ocean energy research and development of prototypes for open-ocean power generation. Maintenance on ocean-based machinery can be very costly. To avoid unnecessary maintenance it is necessary to monitor the condition of each machine in order to predict problems. This kind of prognostic health monitoring (PHM) requires a condition-based maintenance (CBM) system that supports diagnostic and prognostic analysis of large amounts of data. Research in this field led to the creation of ISO13374 and the development of a standard open-architecture for machine condition monitoring. This thesis explores an implementation of such a system for ocean-based machinery using this framework and current open-standard technologies. / by Mark Bowren. / Thesis (M.S.C.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

This thesis describes a method to detect, localize and identify a faulty bearing in a rotating machine using narrow band envelope analysis across an array of accelerometers. This technique is developed as part of the machine monitoring system of an ocean turbine. A rudimentary mathematical model is introduced to provide an understanding of the physics governing the vibrations caused by a bearing with a raceway defect. This method is then used to detect a faulty bearing in two setups : on a lathe and in a dynamometer. / by Nicholas Waters. / Thesis (M.S.C.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

On August 5, 2010 the U.S. Department of Energy (DOE) has designated the Center for Ocean Energy Technology (COET) at Florida Atlantic University (FAU) as a national center for ocean energy research and development. Their focus is the research and development of open-ocean current systems and associated infrastructure needed to development and testing prototypes. The generation of power is achieved by using a specialized electric generator with a rotor called a turbine. As with all machines, the turbines will need maintenance and replacement as they near the end of their lifecycle. This prognostic health monitoring (PHM) requires data to be collected, stored, and analyzed in order to maximize the lifespan, reduce downtime and predict when failure is eminent. This thesis explores the use of a data gateway which will separate high level software with low level hardware including sensors and actuators. The gateway will v standardize and store the data collected from various sensors with different speeds, formats, and interfaces allowing an easy and uniform transition to a database system for analysis. / by Joseph. Gundel. / Thesis (M.S.C.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

This work incorporates previous work done by Guerra and the application of fluid dynamics. The structure attached to the turbine will cause unsteady fluctuations in the flow, and ultimately affect the acoustic pressure. The work of Guerra is based on a lot of assumptions and simplifications to the geometry of the turbine and structure. This work takes the geometry of the actual turbine, and uses computational fluid dynamic software to numerically model the flow around the turbine structure. Varying the angle of the attack altered the results, and as the angle increased the noise levels along with the sound pulse, and unsteady loading increased. Increasing the number of blades and reducing the chord length both reduced the unsteady loading. / by Renee' Lippert. / Thesis (M.S.C.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Thesis. 1978. Ocean E.--Massachusetts Institute of Technology. Dept. of Ocean Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / Ocean E.