CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / A constÃncia dos ventos brasileiros, e a necessidade de amenizar a demanda das grandes cidades encontraram na energia eÃlica uma forte parceira. Como uma alternativa na produÃÃo de energia elÃtrica, condomÃnios e prÃdios modernos, alÃm de algumas aplicaÃÃes rurais, tÃm recorrido Ãs turbinas eÃlicas de pequeno porte como uma alternativa para sanar suas necessidades. Contudo, a maioria da tecnologia encontrada no mercado à importada e nÃo foi desenvolvida exclusivamente para aplicaÃÃes no Brasil. A ferramenta mais importante na aerodinÃmica experimental à o tÃnel de vento. Experimentos controlados em escala fornecem um grande nÃmero de dados confiÃveis, alÃm de fornecer seguranÃa a quem o manuseia. Dada a sua importÃncia, este trabalho tem como objetivo o desenvolvimento, a prototipagem, e conhecer o comportamento de um rotor de turbina eÃlica em escala sujeito a testes em tÃnel de vento e comparar os resultados obtidos com os presentes na literatura para um protÃtipo em escala real. Para tanto, faz necessÃrio o uso de tÃcnicas de correÃÃo de efeitos de bloqueio de tÃnel de vento. Foi projetado e fabricado 4 conjuntos de rotores com valores de velocidade especÃfica de ponta de 6 atà 9 (λp=6, 7, 8 e 9). Os testes foram conduzidos em um tÃnel de vento onde foram coletados dados de velocidade de escoamento livre, velocidade de escoamento com a turbina em operaÃÃo, alÃm de medidas de velocidade angular e torque gerado pelas pÃs, com a finalidade de conhecer a curva de potÃncia de cada rotor. Foi observado que em situaÃÃes de escoamento em que as rotaÃÃes nÃo sejam representativas (o suficiente para atingir valores superiores ao intervalo de λ entre 3 e 5,6), indica-se um projeto com λp=6. Jà em situaÃÃes nas quais os valores de λ oscilam entre 4,7 e 7,3, λp=7 mostrou-se mais eficiente. Jà λp=9 mostrou-se nÃo vantajoso em comparaÃÃo aos demais projetos. Ao comparar os dados obtidos neste trabalho com os da literatura e do BEM, pode-se afirmar que o estudo de turbinas eÃlicas em tÃnel de vento à bastante confiÃvel. / The constancy of Brazilian winds and the need to mitigate the demand of large cities have found in wind energy a strong partner. As an alternative for the production of electrical power, modern buildings and condominiums, plus some rural applications, have resorted to small wind turbines as an alternative to solve your needs. However, most of the technology found in the market is imported and has not been developed exclusively for applications in Brazil. The most important tool in experimental aerodynamics is the wind tunnel. Scale controlled experiments provide a large number of reliable data, besides providing security to those who handle. Given its importance, this paper aims at the development, prototyping, and understands the behavior of a wind turbine rotor scale subjected to wind tunnel tests and compares the results with those in the literature for a prototype scale real. Therefore, it required the use of correction techniques blockage effects of the wind tunnel. It was designed and manufactured 4 sets of rotors with values specific tip speed of 6 to 9 (λp=6, 7, 8 e 9). The tests were conducted in a wind tunnel where velocity data free stream, stream velocity with the turbine in operation, and angular speed and torque generated by the blades, was collected in order to know the curve of each rotor. It was observed that in situations where the flow speeds are not representative enough to reach the higher values of λ range between 3 and 5,6, indicates a design with λp=6. Already in situations where the values of λ ranging between 4,7 and 7,3, λp=7 proved to be more efficient. Have λp=9 proved to be no advantage in comparison to other projects. By comparing the data obtained in this work with the literature and the BEM, it can be stated that the study of wind turbines in a wind tunnel is quite reliable.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-09-12T18:09:24Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) UMA METODOLOGIA PARA ANÁLISE DE COMPORTAMENTO ESTRUTURAL DE COMPONENTES DE AEROGERADORES.pdf: 2234628 bytes, checksum: c801a59ec85918d199458eb62c41c451 (MD5) / Made available in DSpace on 2016-09-12T18:09:25Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) UMA METODOLOGIA PARA ANÁLISE DE COMPORTAMENTO ESTRUTURAL DE COMPONENTES DE AEROGERADORES.pdf: 2234628 bytes, checksum: c801a59ec85918d199458eb62c41c451 (MD5) Previous issue date: 2016-01-29 / Simulações computacionais do comportamento dinâmico dos modernos aerogeradores constituem-se em informação técnica estratégica muito empregada e, cada vez mais valorizada, nas etapas de projeto e certificação de uma nova máquina para o cada vez mais concorrido mercado global de energia eólica. Essas simulações são realizadas com o emprego de complexos sistemas computacionais que demandam do usuário expertise em vários campos de conhecimento técnico das engenharias. Este trabalho objetiva apresentar e testar uma metodologia para investigar o comportamento estrutural de componentes de aerogeradores. O estudo de caso é desenvolvido com um aerogerador modelo do tipo Velocidade Varável Pitch Variável de 2 MW disponível em um código aeroelástico, GL Bladed que será utilizado nas simulações dinâmicas dos principais estados operacionais (operação normal, partida, parada normal, parada de emergência) e não operacionais (estado ocioso, estado estacionário) do aerogerador para obter as forças e momentos tridimensionais que serão transmitidas para toda a estrutura do aerogerador. Uma ferramenta de CAD (Solidworks) é utilizada para representar em 3D o modelo do aerogerador completo, considerando-se duas situações para a sua estrutura de sustentação: torre de aço e torre de concreto armado. Em seguida, os modelos geométricos são exportados para uma ferramenta de elementos finitos (COMSOL Multiphysics) visando realizar simulações numéricas da resposta estrutural dos modelos através de verificação das tensões e deslocamentos produzidos. A ferramenta de elementos finitos é alimentada pelos cenários mais críticos identificados, dentre os elencados pela IEC 61400-1. Ao se comparar os resultados obtidos pela solução do modelo de elementos finitos para todas as condições simuladas, verificou-se que nenhum dos valores de tensões máximas de Von-Mises sofridas pelas torres de aço e de concreto atingiu o valor das suas respectivas tensões de cálculo. Este resultado evidencia que tanto o modelo da torre de aço quanto ao de concreto resistiriam aos piores cenários de forças e momentos tridimensionais. Observaram-se concentrações de tensões nas regiões de descontinuidade geométricas da estrutura das torres. Por outro lado, os deslocamentos máximos obtidos para as torres foram analisados para verificar o aspecto da flexibilidade da estrutura de sustentação. Por fim, analisou-se o comportamento estrutural dos modelos das torres de aço e de concreto armado em regime estacionário, sob a ação da velocidade básica do vento (velocidade extrema) da região de interesse. Este estudo de caso demonstrou a aplicabilidade da metodologia proposta para análise do comportamento estrutural de componentes de aerogeradores. Sugere-se a aplicação da mesma para outros componentes da máquina visando demonstrar a robustez do método proposto. / Computational simulations of the dynamic behavior of modern wind turbines provide technical strategic information very much employed and, increasingly valued during the design stages and certification of a new wind turbine for the increasingly competitive global wind energy market. These simulations are performed with the use of complex computational systems that require user experience in several technical expertise fields of engineering. This work seeks to present and test a methodology in order to investigate the structural behavior of wind turbine components. The case study is performed with a 2 MW Variable Speed Variable Pitch (VSVP) wind turbine model available in an aeroelastic code, GL Bladed where dynamic simulations of the main operational (normal operation, start-up, normal stop, emergency stop) and non-operational (idling and parked state) states of the wind turbine are performed in order to obtain the tridimensional forces and moments transmitted to the whole turbine structure. A CAD tool (Solidworks) is employed to represent the complete wind turbine model in 3D, considering two situations for the support system: steel tower and reinforced concrete tower. The geometric models are exported to a finite element tool (COMSOL Multiphysics) with the aim of simulating numerically their structural behavior by observing the stresses and displacement produced. The finite element tool is fed with the most critical scenarios identified, among others given by IEC 61400-1. When the results of the solution given by the finite element model for all the simulated conditions were compared, it was observed that the maximum von Mises stresses produced in each of the towers did not reach the respective calculated stress value. This result proves that both concrete and steel towers resisted the worst scenarios of tridimensional forces and moments. Stress concentrations were identified in the discontinuity regions of the tower structures. On the other hand, the maximum displacements produced on the towers were analyzed with the aim of verifying the flexibility aspect of the support structure. Finally, the influence of extreme wind on the structural models of the steel and reinforced concrete tower model were analyzed under the rotor parked mode at the region of interest. The case study demonstrated the applicability of the proposed methodology for analyzing the integrity of wind turbine components. It is recommended that this methodology is applied for other wind turbine components in order to demonstrate the robustness of the proposed method.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Uma alternativa para minimizar os problemas energÃticos utilizando fontes renovÃveis de energia, à a microgeraÃÃo distribuÃda em meios urbanos. Neste ambiente onde os ventos sÃo turbulentos e irregulares, as turbinas eÃlicas de eixo vertical apresentam uma eficiÃncia muito prÃxima Ãs turbinas eÃlicas de eixo horizontal, com a vantagem de possuÃrem baixas vibraÃÃes, por trabalharem com baixas rotaÃÃes. Assim, com o objetivo de explorar esta tecnologia de eixo vertical, este trabalho apresenta um sistema eÃlico de conversÃo de energia utilizando uma turbina de eixo vertical de 1500 watts. Inicialmente à proposta uma topologia composta por dois estÃgios de conversÃo, sendo o primeiro um retificador trifÃsico semicontrolado em alta frequÃncia (RTSCAF) e o segundo estÃgio um conversor Buck convencional, onde todo o controle à feito de forma analÃgica. Buscando melhorias com relaÃÃo ao rendimento e tamanho, à proposta em seguida uma segunda topologia, onde o conversor Buck convencional à substituÃdo por um conversor Buck intercalado sÃncrono, com controle totalmente digital. Para todos os conversores, foram realizadas as anÃlises qualitativa e quantitativa, sendo realizado tambÃm o projeto dos componentes e dos controladores. Ao final sÃo apresentados os resultados de simulaÃÃo onde se verifica uma distorÃÃo harmÃnica total (DHT) na corrente de entrada de aproximadamente 18,5% para ambas as topologias, e observa-se uma diminuiÃÃo de 30% na corrente eficaz que circula no banco de capacitores do barramento cc ao utilizar o conversor Buck intercalado sÃncrono, na segunda topologia. O protÃtipo experimental de 1500 watts da primeira topologia foi testado e apresentou um rendimento de 91% para potÃncia nominal. / An option to minimize the energetic problems using renewable energy sources is the distributed micro generation in urban areas. In this kind of environment, where the winds are not regular ande turbulent, the efficiencies from vertical axis wind turbines are comparable to those ones from horizontal axis wind turbines, with the additional vantage of producing low mechanical vibrations at low rotation speeds. Thus, in order to explore this technology, this work presents a wind energy conversion system using a 1.5 kW vertical axis wind turbine. Firstly, a two power conversion stages topology is proposed, the first stage is a high frequency, semi controlled, three phase rectifier and the second stage is a classical Buck converter, the proposed topology is controlled by an analog control system. Secondly, in order to achieve size and efficiency improvements, a second topology is proposed, where the classic Buck converter is substituted by a synchronous, interleaved Buck converter, this second topology is fully digitally controlled. For both topologies, qualitative and quantitative analyses have been realized as well as its control systems have been design. Finally, simulation results are presented for both topologies, where an 18.5% input current total harmonic distortion can be verified for both topologies and, a 30% reduction of rms current trough dc link capacitors is verified for the second topology. A 1.5 kW prototype, based on the first proposed topology, was built and tested, achieving a full power efficiency of 91%.

The installed capacity of European Offshore Wind Turbines (OWT) is likely to rise from the 2014 value of 7GW to 150GW in 2030. However maintenance of OWT is facing unprecedented challenges and cost 35% of lifetime costs. This will be equivalent to £14billion/year by 2030 if current OWT maintenance schemes are not changed. However the complexities around OWT operation require tools and systems to optimise OWT maintenance. The design of optimal OWT maintenance requires failure analysis of over 10,000 components in OWT for which there is little published work relating to performance and failure. In this work, inspection reports of over 400 wind turbine gearboxes (source: Stork Technical Services) and SCADA data (source: Shetland Aerogenerators Ltd) were studied to identify issues with performance and failures in wind turbines. A modified framework of Failure Mode Effects and Criticality Analysis (i.e. FMECA+) was designed to analyse failures according to the unique requirements of OWT maintenance planners. The FMECA+ framework enables analysis and prediction of failures for varied root causes, and determines their consequences over short and long periods of time. A software tool has been developed around FMECA+ framework that enables prediction of component level failures for varied root causes. The tool currently stores over 800 such instances. The need to develop a FMECA+ based Enterprise Resource Planning tool has been identified and preliminary results obtained from its development have been shown. Such a software package will routinely manage OWT data, predict failures in components, manage resources and plan an optimal maintenance. This will solve some big problems that OWT maintenance planners currently face. This will also support the use of SCADA and condition monitoring data in planning OWT maintenance, something which has been difficult to manage for a long time.

No description available.

To maximize the effectiveness of the rapidly increasing capacity of installed wind energy resources, new models must be developed that are capable of more nuanced control of each wind turbine so that each device is more responsive to inflow events. Models used to plan wind turbine arrays and control behavior of devices within the farm currently make questionable estimates of the incoming atmospheric flow and update turbine configurations infrequently. As a result, wind turbines often operate at diminished capacities, especially in arrays where wind turbine wakes interact and inflow conditions are far from ideal. New turbine control and wake prediction models must be developed to tune individual devices and make accurate power predictions. To that end, wind tunnel experiments are conducted detailing the turbulent flow in the wake of a wind turbine in a model-scale array. The proper orthogonal decomposition (POD) is applied to characterize the spatial evolution of structures in the wake. Mode bases from distinct downstream locations are reconciled through a secondary decomposition, called double proper orthogonal decomposition (DPOD), indicating that modes of common rank in the wake share an ordered set of sub-modal projections whose organization delineates underlying wake structures and spatial evolution. The doubly truncated basis of sub-modal structures represents a reduction to 0.015% of the total degrees of freedom of the wind turbine wake. Low-order representations of the Reynolds stress tensor are made using only the most dominant DPOD modes, corrected to account for energy excluded from the truncated basis with a tensor of constant coefficients defined to rescale the low-order representation of the stresses to match the original statistics. Data from the wind turbine wake are contrasted against simulation data from a fully-developed channel flow, illuminating a range of anisotropic states of turbulence. Complexity of flow descriptions resulting from truncated POD bases is suppressed in severe basis truncations, exaggerating anisotropy of the modeled flow and, in extreme cases, can lead to the loss of three dimensionality. Constant corrections to the low-order descriptions of the Reynolds stress tensor reduce the root-mean-square error between low-order descriptions of the flow and the full statistics as much as 40% and, in some cases, reintroduce three-dimensionality to severe truncations of POD bases. Low-dimensional models are constructed by coupling the evolution of the dynamic mode coefficients through their respective time derivatives and successfully account for non-linear mode interaction. Deviation between time derivatives of mode coefficients and their least-squares fit is amplified in numerical integration of the system, leading to unstable long-time solutions. Periodic recalibration of the dynamical system is undertaken by limiting the integration time and using a virtual sensor upstream of the wind turbine actuator disk in to read the effective inflow velocity. A series of open-loop transfer functions are designed to inform the low-order dynamical system of the flow incident to the wind turbine rotor. Validation data shows that the model tuned to the inflow reproduces dynamic mode coefficients with little to no error given a sufficiently small interval between instances of recalibration. The reduced-order model makes accurate predictions of the wake when informed of turbulent inflow events. The modeling scheme represents a viable path for continuous time feedback and control that may be used to selectively tune a wind turbine in the effort to maximize power output of large wind farms.

Renewable energy technology has received much attention over recent years. The depletion of known fossil fuel reserves and the volatility of international fuel prices require that society looks beyond the current coal-dominated electricity generation methods. Wind energy is an internationally well-established technology with large markets in major countries around the world, such as the USA and Germany. South Africa has the potential to generate large amounts of electricity from the wind because of the strength of the country’s wind resource. The long coast line and open areas are ideal for the exploitation of wind energy. A wind farm project has been proposed for development near the town of Jeffrey’s Bay, in the Eastern Cape. The proposed project involves the construction and installation of a 15MW wind farm, consisting of 6-10 turbines standing 120m tall, over an area of 20ha.There are indirect costs and benefits (externalities) associated with a wind farm project and it is important that projects such as these are evaluated from a social standpoint. The aim of this study was to determine the compensation required by residents for siting a wind farm in their area. This compensation was then used as a component of an overall evaluation of the project.

The paper describes the market environment in the field of wind energy. Its aim is to evaluate a concrete investment project of a wind turbine from an investor's point of view. The investor assesses a potential construction of a wind turbine through considering experts's judgments. As an example, three different variations of financing were chosen. On each of these variations standard methods of effectiveness evaluation were applied

The earliest design of a wind power system with multiple rotors on a single support structure dates back to the late 1800s. Such a system called a Multi-Rotor Wind Turbine (MRWT) was proposed by several researchers due to its perceived advantages over a single-rotor wind turbine. As turbine size increases, power produced by a rotor tends to scale up as the square of its diameter, as opposed to rotor weight which varies as its cube. So, several smaller rotors will weigh and cost less than one large rotor producing the same power. MRWTs offer several advantages such as better distribution of loads, better logistics of the components and scope for standardization. The MRWT system can also continue operation even if some of the rotors fail. However, MRWTs require a complex support structure to connect the rotors to the tower and an arrangement to yaw them into the wind. A recent study involving a scaling model for a three-rotor MRWT system estimates a cost saving of 13.1% as compared to the NREL 5 MW single-rotor model. A triangular truss type support structure for the MRWT model is designed and its preliminary static analysis is performed in that study. This thesis is a continuation of that study where the scaling model is extended to include MRWT systems having two to seven rotors. A systematic design method is developed for modeling any MRWT support structure for two to seven rotors for the given 5 MW configuration. The structure consists of frames and cables and the design constraints for the static analysis are stress, deflection and buckling. A dynamic analysis of the MRWT solution is also carried out to verify that the structure can withstand loads induced at varying wind conditions and design load cases – especially steady, turbulent and extreme wind conditions. Some special cases for the three-rotor MRWT system, such as use of two-bladed rotors, direct-drive machines, analysis for zero wind loads, load analysis for each of the assembly stages are also discussed. Finally, as the support structure design for the three and seven-rotor models is the main focus of the thesis, the scaling model is validated by comparing these models with similar turbines having rated power corresponding to the rotors used in the models.

System specifications and testing model for increasing the rated power output, rotor diameter, hub height, and maximum tip speed of horizontal axis wind turbines is designed and implemented on the system advisor model simulator. Its performance is tested on offshore wind turbine’s direct-drive and single stage-low speed generators. Although this simulator produces impressive results, it has some limitations in the operation of wind turbines. The terrain and topography of wind turbines are not considered in the simulation process. It also does not assess the electrical transients and physical stress of wind turbine components. Despite its limitations, four large offshore wind turbines and wind farms have been successfully simulated. It is found that the 9 MW, 10 MW, 11 MW and their respective wind farms generate more energy and better capacity factor on the direct-drive than single stage-low speed generator. Furthermore, a rectangular layout of 20 wind turbines considerably impacted the excellent performance of this generator on the wind farms. Another notable outcome of the study is that higher system specifications do not always generate feasible results for wind turbines despite favourable weather conditions. For the Vestas 8 MW wind turbine, the viable percentages for increasing the size of its rated power output, rotor diameter, hub height and maximum tip speed is only 12.5%, 25% and 37.5%. The viability of these three upgrades has been confirmed by suitable graphs of power curves and feasible energy production results. Thus, these percentages confirm an 8 MW wind turbine’s attainable design limits for generating realistic energy production and capacity factor. On the contrary, a 50% increase in the above four system specifications yielded unviable capacity factor and energy production results. This is because this upgrade is too high to work successfully on the current wind turbine technology. Furthermore, the shape of the power curve from the 50% specifications is not the typical curve for wind turbines. It has been observed that increasing the value of maximum tip speed beyond 143 m/s and the rotor diameter beyond 246 m give rise to an unusual power curve. Concerning wind speed for high energy production, an average daily minimum and maximum wind speed of 4.58 m/s and 15.08 m/s yielded good results. Given the prevailing trend of designing large wind turbines, findings in this study are particularly helpful in understanding how capacity factor, energy production and energy losses are affected by the size of system specifications. Not only that, but these findings also have fundamental concepts that can be used to optimize the design of large offshore wind turbines. The study is equally valuable for determining suitable weather conditions and wind power potential for large offshore wind farm sites. / Dissertation (MEng (Electrical Engineering))--University of Pretoria, 2020. / Electrical, Electronic and Computer Engineering / MEng (Electrical Engineering) / Unrestricted