Rozprawy doktorskie: „Wind turbines- Structural engineering”

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Fégeant, Olivier. "Noise from wind turbines." Doctoral thesis, KTH, Byggnader och installationer, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3100.

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A rapid growth of installed wind power capacity is expectedin the next few years. However, the siting of wind turbines ona large scale raises concerns about their environmental impact,notably with respect to noise. To this end, variable speed windturbines offer a promising solution for applications in denselypopulated areas like the European countries, as this designwould enable an efficient utilisation of the masking effect dueto ambient noise. In rural and recreational areas where windturbines are sited, the ambient noise originates from theaction of wind on the vegetation and about the listener's ear(pseudo-noise). It shows a wind speed dependence similar tothat of the noise from a variable speed wind turbine and cantherefore mask the latter for a wide range of conditions.However, a problem inherent to the design of these machines istheir proclivity to pure tone generation, because of theenhanced difficulty of avoiding structural resonances in themechanical parts. Pure tones are deemed highly annoying and areseverely regulated by most noise policies. In relation to thisproblem, the vibration transmission of structure-borne sound tothe tower of the turbine is investigated, in particular whenthe tower is stiffened at its upper end. Furthermore, sincenoise annoyance due to wind turbine is mostly a masking issue,the wind-related sources of ambient noise are studied and theirmasking potentials assessed. With this aim, prediction modelsfor wind-induced vegetation noise and pseudo-noise have beendeveloped. Finally, closely related to the effect of masking,is the difficulty, regularly encountered by local authoritiesand wind farm developers, to measure noise immission from windturbines. A new measurement technique has thus been developedin the course of this work. Through improving thesignal-to-noise ratio between wind turbine noise and ambientnoise, the new technique yields more accurate measurementresults. Keywords: Masking, vibration transmission, diffraction,ambient noise, pseudo-noise, cylindrical shell, perturbationmethods, structural mobility, acoustic outdoor measurement. QC 20100616

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Nguyen-Sy, Lam. "The theoretical modelling of circular shallow foundation for offshore wind turbines." Thesis, University of Oxford, 2005. http://ora.ox.ac.uk/objects/uuid:fa4000fb-8de6-4093-b528-3e60d774dea0.

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Currently, much research is being directed at alternative energy sources to supply power for modern life of today and the future. One of the most promising sources is wind energy which can provide electrical power using wind turbines. The increase in the use of this type of energy requires greater consideration of design, installation and especially the cost of offshore wind turbines. This thesis will discuss the modelling of a novel type of shallow foundation for wind turbines under combined loads. The footing considered in this research is a circular caisson, which can be installed by the suction technique. The combined loads applied to this footing will be in three-dimensional space, with six degrees of freedom of external forces due to environmental conditions. At the same time, during the process of building up the model for a caisson, the theoretical analyses for shallow circular flat footing and spudcans also are established with the same principle. The responses of the soil will be considered in both elastic and plastic stages of behaviour, by using the framework of continuous plasticity based on thermodynamic principles. During this investigation, it is necessary to compare the numerical results with available experimental data to estimate suitable values of factors required to model each type of soil. There are five main goals of development of the model. Firstly, a new expression for plasticity theory which includes an experimentally determined single yield function is used to model the effects of combined cyclic loading of a circular footing on the behaviour of both sand and clay. This formulation based on thermodynamics allows the derivation of plastic solutions which automatically obey the laws of thermodynamics without any further assumptions. A result of this advantage is that non-associate plasticity, which is known to be a proper approximation for geotechnical material behaviour, is obtained logically and naturally. A FORTRAN source code called ISIS has been written as a tool for numerical analysis. Secondly, since there are some characteristics of the geometric shape and installation method which are quite different from that of spudcans and circular flat footing, another objective of this study is to adapt the current model which has been developed in ISIS for spudcans to the specific needs of caissons. The third goal of this research is the simulation of continuous loading history and a smooth transition in the stress-strain relationship from elastic to plastic behaviour. The model is developed from a single-yield-surface model to a continuous plasticity model (with an infinite number of yield surfaces) and then is discretized to a multiple-yield-surface model which can be implemented by numerical calculation to be able to capture with reasonable precision the hysteretic response of a foundation under cyclic loading. This can not be described by a conventional single-yield-surface model. Fourthly, as a method to simplify the numerical difficulties arising from the calculation process, a rate-dependent solution will be introduced. This modification is implemented by changing the dissipation function derived from the second law of thermodynamics. Finally, in order to control the model to capture the real behaviour, many parameters are proposed. A parametric study will be implemented to show the effects of these parameters on the solution.

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Folster, Kaylee. "Influence of geometry on the dynamic behaviour of steel tubular towers for onshore wind turbines." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25282.

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South Africa has recently experienced challenges regarding electricity consumption and availability. As part of the country's Integrated Resource Plan, these challenges are to be addressed. This involves a 20 year plan which aims to increase electricity supply capacity as well as reduce the reliance on coal power as part of the global trend to become more environmentally friendly. Wind power, specifically, is to account for a large portion of the renewable energy that is expected to become available by 2030. This results in the need for the understanding of wind turbine design by South African engineers. The dynamic analysis of wind turbine structures, is of particular interest to Civil Engineers. Wind turbine towers are recently of the monopole or tubular type tower, predominantly constructed of either concrete or steel or a combination of both. Steel tubular towers above a height of 80m are generally not recommended for wind turbines owing to cost concerns as well as difficulties in meeting dynamic behaviour requirements. Concrete towers and steel-concrete hybrid towers are recommended for this height regime. The aim of this study was to assess the prospective use of steel tubular towers of varying geometric shape for wind turbines with tower heights of 80m or greater. The study focussed on the analysis of natural frequency and assessing the applicability of steel tubular towers of geometric shapes that have not been previously explored or reported. The turbine of choice for this study was the Vestas V112 3MW type as this is one of the most commonly used and more efficient turbines for towers of this height regime. The results of this study showed that steel monopole towers of heights of 80m and more are still viable options for wind turbine towers. Various geometric tower cases of heights varying from 80m to 120m, produced acceptable fundamental natural frequencies within the allowable frequency range for a Vestas V112 3MW turbine.

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Gwon, Tae gyun. "Structural Analyses of Wind Turbine Tower for 3 kW Horizontal Axis Wind Turbine." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/600.

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Structure analyses of a steel tower for Cal Poly's 3 kW small wind turbine is presented. First, some general design aspects of the wind turbine tower are discussed: types, heights, and some other factors that can be considered for the design of wind turbine tower. Then, Cal Poly's wind turbine tower design is presented, highlighting its main design features. Secondly, structure analysis for Cal Poly's wind turbine tower is discussed and presented. The loads that are specific to the wind turbine system and the tower are explained. The loads for the static analysis of the tower were calculated as well. The majority of the structure analysis of the tower was performed using the finite element method (FEM). Using Abaqus, commercial FEM software, both static and dynamic structural analyses were performed. A simplified finite element model that represents the wind turbine tower was created using beam, shell, and inertia elements. An ultimate load condition was applied to check the stress level of the tower in the static analysis. For the dynamic analysis, the frequency extraction was performed in order to obtain the natural frequencies and the mode shapes of the tower. Using the results, the response spectrum analysis and the transient dynamic analysis, which are based on the modal superposition method, were performed in order to see the structure's response for earthquakes that are likely to happen at the wind turbine installation site.

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Moss, Andrew M. "Analysis of a Gravity Hinge System for Wind Turbines." Cleveland State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=csu1624479290234317.

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Rastegar, Damoon. "Modification of Aeroelastic Model for Vertical Axes Wind Turbines." Thesis, Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-3388.

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In wind turbines, flow pressure variations on the air-structure interface cause aerodynamic forces. Consequently the structure deforms and starts to move. The interaction between aerodynamic forces and structural deformations mainly concerns aeroelasticity. Since these two are coupled, they have to be considered simultaneously in cases which the deformations are not negligible in comparison to the other geometric dimensions. The purpose of this work is to improve the simulation model of a vertical axis wind turbine by modifying the structural model from undamped Euler-Bernoulli beam theory with lumped mass matrix to the more advanced Timoshenko beam theory with consistent mass matrix plus an additional damping term. The bending of the beam is then unified with longitudinal and torsional deformations based on a fixed shape cross-section assumption and the Saint-Venant torsion theory. The whole work has been carried out by implementing the finite element method using MATLAB code and implanting it in a previously developed package as a complement. Finally the results have been verified by qualitative comparisons with alternative simulations.

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Di, Pietro Joshua (Joshua Michael). "Structural analysis and design of floating wind turbine systems." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/50575.

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Thesis (S.M. in Mechanical Engineering and Naval Architecture and Marine Engineering)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. Includes bibliographical references (p. 139-140). As oil supply rates approach potential maximums and the global detrimental effects of carbon emitting energy technology are becoming more comprehensively understood, the world is searching for environmentally benign energy technology which can be reliably and economically harvested. Deep water offshore wind is a vast, reliable and potentially economical energy source which remains globally untapped. In order to harvest this resource, potential floating turbine systems must be analyzed and designed for economic production and deployment, reliable operation, and adequate service life. The Laboratory of Ship and Platform Flow (LSPF) has created trusted hydrodynamic modeling software used to perform a Pareto Optimization which resulted in an optimized Floating Wind Turbine (FWT) design which is a Tension Leg Platform (TLP); hereto called MIT TLP-1. This thesis details the structural design aspects of Floating Wind Turbines (FWT) in a rationally based optimization approach for incorporation into existing LSPF hydrodynamic optimization approaches. A steel structural design is created based on the geometry and loading of the MIT TLP-1 for a 10m significant wave height. The design is based on similar system analysis, classic linear structural theory, American Bureau of Shipping rules and American Petroleum Institute recommended practices. The design is verified using Finite Element Analysis (FEA). The results of this work show that the MIT TLP-1 design is technically feasible from a structural integrity, performance and producibility standpoint. by Joshua Di Pietro. S.M.in Mechanical Engineering and Naval Architecture and Marine Engineering

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Al-Khudairi, Othman. "Structural performance of horizontal axis wind turbine blade." Thesis, Kingston University, 2014. http://eprints.kingston.ac.uk/32197/.

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The power output from a wind turbine is proportional to rotor swept area and as a result in the past 30 years continuous effort has been made to design larger blades. In this period, the blade length has been increased about 10 times since 1980s to present time. With the longest blade currently measuring more than 100m in length, wind turbine blade designers and manufacturers face enormous challenges to encounter the effect of increased weight and other loads on fatigue durability of the blade. Wind turbine blades are mainly made from glass fibre reinforced plastic (GFRP) composite. materials. As a result, in the design of various parts of wind turbine blades such as the shear web, spar cap and the aerofoil the fatigue behaviour of F RP materials is required. The performance of these parts as well as the adhesively bonded joint under fatigue loading is crucial for structural integrity of a long lasting blade. During operation, delamination can initiate and propagate shortening blade life; hence, characterisation of failure envelope of GFRP laminates under different loading mode is necessary. In this regard in this project, quasi-static tests were carried out to find mode 1, mode 11 and mixed mode I/11 delamination fracture toughness using DCB, ENF and MMB tests and the fracture envelope was established for various mode mixity. In the next stage, the stress-lifetime (S-N) diagrams of the GFRP was studied. Fatigue-life experiments on three different types of loading, i.e. tension-tension at R=0.1, 0.5, tension- compression at R=-1 and compression-compression at R=2 and R=10 were performed. From the results of S-N diagrams, the constant life diagrams (CLD) for 90 degree and 0 degree fibre directions were constructed. CLD diagrams are useful for prediction of fatigue lifetime for loading condition that no experimental data available. The analysis of delamination crack propagation under cyclic loading was next area of the research. The onset life and propagation delamination crack grth of 0//0 interface of GR P laminate in mode I loading using DCB specimens was investigated and the Gm. from the onset life test was determined. From the fitted curve to mode I experimental propagation data the Paris’ law coefficient for the laminated GFRP in mode I was determined. The mode II fatigue crack growth in laminated 0//0 GFRP material was also investigated using ENF specimens. The fatigue behaviour in this mode is analysed based on application of Paris’ law as a function of energy release rate for mode II loading. From the fitted curve to experimental data, the Paris’ law coefficient for the laminated GFRP in mode II was determined. The effect of fatigue delamination growth on fracture surface was studied by fractography analysis of SEM images of fracture surfaces. Studying the behaviour of GFRP under cyclic loading and delamination under static and dynamic load led to full-scale testing of wind turbine blade to establish damage tolerance of the blade under cyclic loading. The sensitivity of wind turbine blade to damage has considerable interest for turbine operators and manufacturers. For full-scale fatigue testing, calibration test and modal analysis of a 45.7m blade has been done and moment-strain diagram and natural frequencies of the blade were obtained. Next, the blade sensitivity to damage under fatigue loading was investigated. The blade has been damaged intentionally by initially inserting a crack of 0.2m between the shear web and spar cap and later it was extended to 1m. The effect of these damages on the modal shape, natural frequencies and strains at various locations of the blade were investigated. The damaged blade fatigue tested, the structural integrity and growth of damage were monitored, and the results were discussed. Finally for the improvement of delamination resistance for joints between spar beam and aero-shell stitching method was used. T-beam and box beam joint were chosen as the platform for testing the stitching effect on the delamination. Various pattern of stitching was applied and the optimum pattern was determined.

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Alhajali, Abdallah. "Analysis of existing offshore structures considering structural damage to investigate a vertical axis wind tower." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.

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The most common offshore structures are the Jackets which are tools used to extract the oil and natural gas in relative low water depth particularly exist in Adriatic Sea and a lot of them have been constructed in the last 50 years. When the offshore oil and gas resources exhaust, these structures must be replaced to another region containing underground resources or removed if reaching the design life, furthermore, another solution can be considered: changing life of the future working of these platforms by applying renewable energy and alternating them into offshore wind towers. This thesis proposes to study and examine the stiffness matrix of an existing Jacket which consider damaged components for reliability analysis of offshore installations. In this research it was used the 8-step simplified methodology which includes several step to analyze the ability of the offshore jacket structure to examine if it is tolerable to endure the effect of wind or wave loads (environmental forces) more than usual by simulating a minimizing of the stiffness matrix using several random cases which they are ten cases, firstly minimizing in the x direction ( 5 cases) and lastly in y direction and then comparing each of these cases with the original case .It was presented two of the most critical cases to show the effect of each step one in x direction and the other in y direction consequently. At the end it is showed that even the structure jacket is 50 years old it is standable and bearable to face some reduction of its stiffness

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Cantoni, Lorenzo. "Load Control Aerodynamics in Offshore Wind Turbines." Thesis, KTH, Kraft- och värmeteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291417.

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Due to the increase of rotor size in horizontal axis wind turbine (HAWT) during the past 25 years in order to achieve higher power output, all wind turbine components and blades in particular, have to withstand higher structural loads. This upscalingproblem could be solved by applying technologies capable of reducing aerodynamic loads the rotor has to withstand, either with passive or active control solutions. These control devices and techniques can reduce the fatigue load upon the blades up to 40% and therefore less maintenance is needed, resulting in an important money savings for the wind farm manager. This project consists in a study of load control techniques for offshore wind turbines from an aerodynamic and aeroelastic point ofview, with the aim to assess a cost effective, robust and reliable solution which could operate maintenance free in quite hostile environments. The first part of this study involves 2D and 3D aerodynamic and aeroelastic simulations to validate the computational model with experimental data and to analyze the interaction between the fluid and the structure. The second part of this study is an assessment of the unsteady aerodynamic loads produced by a wind gust over the blades and to verify how a trailing edge flap would influence the aerodynamic control parameters for the selected wind turbine blade. På grund av ökningen av rotorstorleken hos horisontella vindturbiner (HAWT) under de senaste 25 åren, en design som har uppstod för att uppnå högre effekt, måste alla vindkraftkomponenter och blad stå emot högre strukturella belastningar. Detta uppskalningsproblem kan lösas genom att använda metoder som kan minska aerodynamiska belastningar som rotorn måste tåla, antingen med passiva eller aktiva styrlösningar. Dessa kontrollanordningar och tekniker kan minska utmattningsbelastningen på bladen med upp till 40 % och därför behövs mindre underhåll, vilket resulterar i viktiga besparingar för vindkraftsägaren. Detta projekt består av en studie av lastkontrolltekniker för havsbaserade vindkraftverk ur en aerodynamisk och aeroelastisk synvinkel, i syfte att bedöma en kostnadseffektiv, robust och pålitlig lösning som kan fungera underhållsfri i tuffa miljöer. Den första delen av denna studie involverar 2D- och 3D-aerodynamiska och aeroelastiska simuleringar för att validera beräkningsmodellen med experimentella data och för att analysera interaktionen mellan fluiden och strukturen. Den andra delen av denna studie är en bedömning av de ojämna aerodynamiska belastningarna som produceras av ett vindkast över bladen och för att verifiera hur en bakkantklaff skulle påverka de aerodynamiska styrparametrarna för det valda vindturbinbladet.

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Korobenko, Artem. "Advanced Fluid--Structure Interaction Techniques in Application to Horizontal and Vertical Axis Wind Turbines." Thesis, University of California, San Diego, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3670451.

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During the last several decades engineers and scientists put significant effort into developing reliable and efficient wind turbines. As a wind power production demands grow, the wind energy research and development need to be enhanced with high-precision methods and tools. These include time-dependent, full-scale, complex-geometry advanced computational simulations at large-scale. Those, computational analysis of wind turbines, including fluid-structure interaction simulations (FSI) at full scale is important for accurate and reliable modeling, as well as blade failure prediction and design optimization. In current dissertation the FSI framework is applied to most challenging class of problems, such as large scale horizontal axis wind turbines and vertical axis wind turbines. The governing equations for aerodynamics and structural mechanics together with coupled formulation are explained in details. The simulations are performed for different wind turbine designs, operational conditions and validated against field-test and wind tunnel experimental data.

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Nel, Emma. "Design and analysis of small scale wind turbine support structures." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71848.

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Thesis (MScEng)--Stellenbosch University, 2012 ENGLISH ABSTRACT: A technology that has advanced immeasurably as a result of the necessity for green energy production is the harnessing of wind energy. One of the most important aspects of a wind turbine is its supporting structure. The tower of a wind turbine needs to be sufficiently reliable and structurally sound to ensure that the design life of the wind turbine machine is unaffected. The tower also needs to be of the correct height to ensure that the full potential of energy capture is realised. The supporting structure of a wind turbine constitutes up to as much as 30% of the total costs of a wind turbine. The most common wind turbine supporting structures seen worldwide today are Steel Monopole Towers. The large cost proportion of the tower compels the industry to investigate the most feasible alternative supporting tower structures and thus prompted the research developed in this thesis. In this thesis the focus is on small scale wind turbines (<50kW), more specifically, a 3kW Wind Turbine. The proposed alternative design the support structures of small scale wind turbines to the presently used Steel Monopole tower was a Steel Lattice tower. Both a Steel Lattice and Steel Monopole Tower was designed for a 3kW Wind Turbine using rational design methods determined from pertinent sections of the South African design codes. The Tower designs needed to incorporate the details of the element connections, so as to encompass all of the cost parameters accurately. The foundation design of each of the towers was also required from the point of view of cost analysis completeness, and ended up playing a critical role in the feasibility analysis. To validate the design methods, the two towers were modelled in the finite element package Strand7 and a number of different analyses were performed on the two towers. The analyses included linear static, nonlinear static, natural frequency and harmonic frequency analyses. The towers were assessed for a number of different load case combinations and were examined in terms of stress states, mass participation factors and deflections, to mention a few, for the worst loading combination cases that were encountered. Once a final design was reached for both the Steel Lattice and Steel Monopole Towers, each element from which they were made was assessed from a structural viewpoint to determine manufacturing and construction costs. The cost analysis was conducted by means of asking a number of leading construction companies for unit prices for each of the identified elements to be assessed. The fabrication and construction of each of the Towers was then compared to determine which one was more feasible, in terms of each design aspect considered as well as looking at the complete end product. It was found that the Steel Lattice Tower was more feasible from the points of view of fabrication, and construction, as well as having a far more cost effective foundation. This was a positive conclusion from the perspective of the proposal for a more feasible alternative to the presently used Steel Monopole Towers. The outcome of the research conducted here could certainly prove to be worth considering from a wind farm development perspective, with particular focus on the up and coming Wind Industry developments in South Africa. AFRIKAANSE OPSOMMING: As gevolg van die noodsaaklikheid vir die produksie van volhoubare energie is ŉ tegnologie wat met rasse skrede vooruitgegaan het die vir die benutting van windenergie. Een van die belangrikste aspekte van 'n windturbine is die ondersteunende struktuur. Die toring van 'n windturbine moet funksioneel en struktureel betroubaar wees om te verseker dat die ontwerpleeftyd van die windturbine masjien nie nadelig beïnvloed word nie. Die toring moet ook die regte hoogte wees om te verseker dat die volle potensiaal van die wind energie in meganiese energie omgesit word. Die koste van die ondersteunende struktuur van 'n windturbine verteenwoordig tot 30% van die totale koste van 'n windturbine. Die mees algemene vorm van ondersteunende strukture vir windturbines wat vandag wêreldwyd teëgekom word, is die van 'n enkel staal buisvormige toring. Die groot koste‐komponent van die toring dwing die industrie om ondersoek in te stel na die mees koste effektiewe prakties uitvoerbare alternatief vir die ondersteunende toring struktuur. Hierdie aspek van die struktuur konseptualisering het gelei tot die navorsing wat in hierdie tesis onderneem is. Die fokus van die navorsing is op klein skaal windturbines (<50kW), en meer spesifiek op 'n 3kW windturbine model. Die alternatiewe ontwerp wat ontwikkel is vir klein skaal wind turbines se ondersteunende structure, is 'n staal vakwerk toring as alternatief vir die staal buisvormige toring. Beide 'n staal vakwerk en staal buisvormige toring vir 'n 3kW wind turbine is ontwerp deur rasionele ontwerp metodes. Die toepaslike gedeeltes van die Suid‐Afrikaanse ontwerp kodes is hiervoor gebruik. Die ontwerp vir die toring moet die besonderhede van die element verbindings in ag neem en die nodige koste parameters moet akkuraat bepaal word. Die ontwerp van die fondament van elke toring is ook noodsaaklik vir die volledigheid van die koste‐ontleding en dit speel ook 'n kritieke rol in die gangbaarheid analise. Om die ontwerp metodes te bevestig, is die twee tipes torings in die eindige element pakket, Strand7, gemodelleer en 'n aantal verskillende ontledings vir die twee torings is uitgevoer. Die ontledings sluit lineêr en nie‐lineêr statiese ontledings asook natuurlike frekwensie en dinamiese ontledings onder harmoniese belastings in. Die torings is vir 'n aantal verskillende lasgevalkombinasies ondersoek en in die spannings toestande, massadeelname faktore en defleksies vir die ergste laskombinasie gevalle wat ondervind is, is geassesseer. Sodra 'n finale ontwerp vir beide die staal vakwerk en staal buisvormige toring voltooi is, is elke element beoordeel uit 'n strukturele en materiaal oogpunt om die kostes daarvan te bepaal. Die koste‐analise is baseer op data wat voorsien is deur 'n aantal vooraanstaande konstruksiemaatskappye op 'n prys per eenheid basis vir elk van die geïdentifiseerde elemente wat geassesseer moes word. Die vervaardiging en konstruksie van elke toring is dan vergelyk om te bepaal watter een die mees haalbaar is, in terme van elke toepaslike ontwerpsaspek en deur ook die volledige eindproduk te evalueer. Daar is bevind dat die staal vakwerk toring uit die oogpunt van vervaardiging en konstruksie, asook as gevolg van 'n meer koste‐effektiewe fondament, die voorkeur alternatief verteenwoordig het. Dit was 'n positiewe gevolgtrekking uit die oogpunt van die soeke na 'n ander alternatief as die buisvormige staal torings wat tans algemeen in gebruik is. Die uitkoms van hierdie navorsing verdien oorweging uit ŉ windplaas ontwikkelingsperspektief, met ŉ spesifieke fokus op die opkomende ontwikkelinge in die wind energie industrie in Suid‐Afrika.

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Vesel, Richard W. Jr. "Aero-Structural Optimization of a 5 MW Wind Turbine Rotor." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1331134966.

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Ahlström, Anders. "Aerolastic simulation of wind turbine dynamics." Doctoral thesis, KTH, Mekanik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-157.

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The work in this thesis deals with the development of an aeroelastic simulation tool for horizontal axis wind turbine applications. Horizontal axis wind turbines can experience significant time varying aerodynamic loads, potentially causing adverse effects on structures, mechanical components, and power production. The needs for computational and experimental procedures for investigating aeroelastic stability and dynamic response have increased as wind turbines become lighter and more flexible. A finite element model for simulation of the dynamic response of horizontal axis wind turbines has been developed. The developed model uses the commercial finite element system MSC.Marc, focused on nonlinear design and analysis, to predict the structural response. The aerodynamic model, used to transform the wind flow field to loads on the blades, is a Blade-Element/Momentum model. The aerodynamic code is developed by The Swedish Defence Research Agency (FOI, previously named FFA) and is a state-of-the-art code incorporating a number of extensions to the Blade-Element/Momentum formulation. The software SOSIS-W, developed by Teknikgruppen AB was used to generate wind time series for modelling different wind conditions. The method is general, and different configurations of the structural model and various type of wind conditions can be simulated. The model is primarily intended for use as a research tool when influences of specific dynamic effects are investigated. Verification results are presented and discussed for an extensively tested Danwin 180 kW stall-controlled wind turbine. Code predictions of mechanical loads, fatigue and spectral properties, obtained at different conditions, have been compared with measurements. A comparison is also made between measured and calculated loads for the Tjæreborg 2 MW wind turbine during emergency braking of the rotor. The simulated results correspond well to measured data. QC 20100826

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Horsthemke, Hagen Wolfgang. "An approach to multi-objective life cycle cost optimization of wind turbine tower structures." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85839.

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Thesis (MEng)-- Stellenbosch University, 2013. ENGLISH ABSTRACT: Support tower structures of Wind Energy Conversion Systems (WECS) are major cost items and by means of integrated design and optimization, the Life-Cycle Cost (LCC) can be reduced substantially. In this thesis, Horizontal Axis Wind Turbine (HAWTs) tower structures are investigated by means of a technique or tool that can bene t in decision making related situations to reduce the LCC of such WECS support towers from inception to disposal. Often, during the conceptual design phase a certain level of uncertainty or fuzziness exists and plays a role. The central focus in this project is on lattice type towers; however an account on tapered, tubular monopole towers is given as well. The problem is identi ed to be of a multi-objective nature, where a variety of criteria or objectives that are identi ed play a role in the possible reduction of the total LCC of the structure. The study also entails the delineation and discussion of the factors and components that a ect the LCC of a steel structure. The decision maker has control over only a few of these factors and components as identi ed, and these can be formulated by means of an objective to be minimized (or maximized in several other cases). Some of the objectives are incommensurable and others are commensurable with each other. In other words, several of these objectives either `compete' or don't `compete' against each other, respectively. The investigation resulted in the development of a multi-objective LCC optimization using the λ-formulation (or min-max formulation) as the objective aggregating approach for the four objectives identi ed (varied during analysis for sensitivity checks). The objectives are user-de ned in terms of membership functions that grade the degree of membership from total acceptance to total rejection by means of boundary values. This formulation is Non-Pareto based and the decision maker obtains the best trade-o or best compromise solution. The detailed discussion around these objectives is included in the literature study. The objectives in the multi-objective study are weight, cost, perimeter and nodal deflections, and a weighting of the objectives is possible but this is excluded from this study. A Genetic Algorithm (GA), coded in MATLAB, is implemented as the optimization tool or technique. The algorithm uses a quadratic penalty function approach and a natively written Finite Element Analysis (FEA) tool is used for the response model in the tness evaluation process, where the performance for stability, capacity and overall deflections of an individual in the population is quanti ed. A GA has the advantage that it operates on an entire population of individuals using basic principles such as genetics, crossover, mutation, selection and survival of the ttest from biology and Darwinian principles. GAs are very robust and e ective global search methods that can be applied to most elds of study. GAs have previously been e ectively applied in structural, single objective optimization (structural weight) problems. The GA is adopted and modi ed and veri ed with results on academic problems obtained from literature. Satisfactory performance was observed, although room for improvement is identi ed. A case study on a full scale model is performed, using circular hollow sections and equal leg angle sections. These are commonly used steel profi les for lattice type towers. The results obtained are as expected. The structural mass was used as a measure to compare the results. A heavier structure is obtained using the equal leg angle sections compared to the CHS structure with a di fference of up to 20% in weight. The best compromise solutions are feasible and near optimal, given the conditions of the equally weighted objectives in this study. The membership function defi nition and boundary value determination still remains a key issue when using fuzzy logic to incorporate the preference information of the decision maker. AFRIKAANSE OPSOMMING: Toringstrukture van windturbines is belangrike kostekomponente van `n windkragopwekking stelsel. Deur middel van geï ntegreerde ontwerp en optimalisering kan die lewensikluskoste aansienlik verminder word. In hierdie tesis word horisontale-as windturbinetoringstrukture ondersoek. Deur middel van `n tegniek of hulpmiddel wat kan baat vind by besluitneming situasies, word die lewensiklus-koste van sodanige windturbine ondersteuning torings vanaf voorgebruik-fase tot lewenseinde-fase verminder. Dikwels, tydens die konseptuele ontwerp-fase, speel `n sekere vlak van onsekerheid of verwarring ook `n rol. Die sentrale fokus in hierdie projek is op staal vakwerk tipe torings gelê. `n Vereenvoudigde ontleeding van buisvormige torings is ook benader. Die probleem is van multikriteria aard, waar `n verskeidenheid van kriterie of doelwitte ge denti seer was. Hulle speel `n rol in die moontlike vermindering van die totale lewensiklus-koste van die struktuur. Die studie behels ook die bespreking en afbakening van die faktore en komponente wat die lewensiklus-koste van 'n staal struktuur bepaal. Die besluitnemer het slegs beheer oor sekere van hierdie faktore en komponente, en hierdie word deur middel van `n saamgevoegde doel-funksie gede neer wat dan geminimeer word. Sommige van die doelfunksies kompeteer met mekaar en sommige kompeteer nie met mekaar nie. Die ondersoek het gelei tot die ontwikkeling van `n multikriteria lewensiklus-koste optimalisering met behulp van die λ-formulering (of min-max formulering). Hierdie is `n tegniek wat die kriterie in vorm van `n verteenwoordigende doel-funksie saamvoeg. Daar is vier doelwitte wat geï denti seer was. Die gebruiker de nieer spesiale, lineêre doel-funksies wat van totale aanvaarding tot totale verwerping streek. Dit word deur middel van randwaardes gedoen. Hierdie formulering is nie Pareto gebaseer nie, en die besluitnemer verkry die `best trade-off ' of die beste kompromis oplossing. Die detailleerde bespreking rondom hierdie doelwitte is in die literatuurstudie ingesluit. Die doelwitte wat in die multikriteria studie gebruik word is gewig, koste, omtrek van die snitpro el en strukturêle defleksie. `n Gewig kan aan elke kriterium toegeken word, maar dit word van hierdie studie uitgesluit. `n Genetiese algoritme (GA), geï mplementeer in MATLAB, word as die optimalisering instrument en tegniek gebruik. Die algoritme gebruik `n kwadratiese `straf-funksie' en `n MATLAB Eindige Element Analise (EEA) word gebruik vir die gedragsmodel in die `fi ksheid' evalueringsproses. Die prestasie vir stabiliteit, kapasiteit en algehele verlegging van `n individu in die GA bevolking word daardeur gekwanti seer. `n GA het die voordeel, dat dit met `n hele bevolking van individue werk. Dit is gebaseer op beginsels van genetika en Darwin se beginsels. GAs is baie stabiel en ook e ektiewe globale soek metodes wat van toepassing in verskillende studierigtings is. GAs is al e ektief toegepas in strukturêle optimalisering (veral strukturêle gewig optimalisiering). Die GA in hierdie studie was aangepas en die gedrag en prestasie is bevestig met resultate van akademiese probleme uit die literatuur. Bevredigende prestasie is waargeneem, maar ruimte vir verbetering is ook geï denti seer. `n Gevallestudie oor `n grootskaal model is uitgevoer, en die gebruik van ronde holpro ele en gelykbenige hoekpro ele is uitgevoer. Dit is algemeen gebruikte staalpro ele vir vakwerk tipe torings. Die resultate wat verkry is, is soos verwag. Die strukturêle massa is gebruik as `n maatstaf om die resultate te vergelyk. `n Swaarder struktuur is die resultaat wanneer gelykbenige hoekpro ele gebruik word in vergelyking met die ronde holpro el struktuur. `n Verskil tot 20% in gewig is waargeneem. Die beste kompromis oplossing is haalbaar en naby-optimaal, gegewe die omstandighede van die gelyk geweegde doelfunksies in hierdie studie. Die doel-funksie de nisie, die voorkeur van die besluitnemer en die bepaling van die randwaardes bly steeds `n belangrike kwessie by die gebruik van hierdie benadering.

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Hu, Yu. "Improvement of the structural response of steel tubular wind turbine towers by means of stiffeners." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6227/.

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In the thesis the structural response of steel tubular wind turbine towers with various design configurations is analysed using FEM modelling. First, a structural response simulation model was validated by comparison with the existing experimental data. This was then followed with a mesh density sensitivity analysis to obtain the optimum element size. Based on this outcome, towers of various heights between 50-250m are considered and investigated with three different design options as follows: (i) thick walled tower with internal horizontal stiffening rings, (ii) thick walled tower without stiffening rings and (iii) thin walled tower with stiffening rings. Based on this analysis, weight reduction ratios are examined in relation to the horizontal sway and von Mises stress increase ratios in order to identify a more efficient design approach between reducing the wall thickness and adopting internal stiffeners. All studied design solutions satisfy the strength and serviceability requirements as specified by the design codes of practice.

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Alessi, Lorenzo. "Design of wind tower in existing offshore platforms." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.

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Jackets are the most common structures in the Adriatic Sea for extracting natural gas. These structural typologies are suitable for relative low water depth (around 250m) and flat sandy sea floors. Most of them have been built in the last 50 years. When the underground source finishes, these structures should be moved to another location or removed if they reached their design life. Nevertheless, another solution might be considered: change the future working life of these platforms by involving renewable energy and transforming them into offshore wind towers. The present research proposal aims to investigate the possibility of converting actual structures for gas extraction to offshore platforms for wind turbine towers.

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Perry, Dylan R. "AERODYNAMIC DESIGN AND STRUCTURAL ANALYSIS PROCEDURE FOR SMALL HORIZONTAL-AXIS WIND TURBINE ROTOR BLADE." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1375.

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This project accomplished two correlated goals of designing a new rotor blade to be used with the Cal Poly Wind Power Research Center, as well as defining the methodology required for the aerodynamic analysis of an optimized blade, the procedure required for generation of an accurate CAD model for the new blade geometry, and structural integrity verification procedure for the new blade via finite element analysis under several operating scenarios. The new rotor blades were designed to perform at peak efficiency at a much lower wind speed than the current CPWPRC rotor blades and incorporated a FEA verification process which was not performed on the earlier rotor blade design. Since the wind characteristics relative to the location of the CPWPRC are essentially unchanging the most viable option, in regards to generating power for longer periods of time, is to redesign the HAWT rotor to capture more of the wind energy available. To achieve this, the swept area of the rotor was increased, suitable airfoils were utilized, and the new rotor blades were optimized to maximize their performance under the CPWPRC location’s wind conditions. With an increased magnitude of wind energy being captured the aerodynamic loading on the rotor blades simultaneously increased which necessitated a structural analysis step to be implemented, both with classical hand calculations and with the assistance of an adequate FEA program, to ensure the new rotor blades did not fail under normal or extreme wind conditions. With the completion of this project the new rotor blade designed and analyzed in this report may be finalized and refined in order to be incorporated into the CPWPRC system in the future or the methodology defined throughout this project may be used to design an entirely different aerodynamically optimized rotor blade, including a CAD model and FEA structural integrity verification, as well.

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Nicholson, John Corbett. "Design of wind turbine tower and foundation systems: optimization approach." Thesis, University of Iowa, 2011. https://ir.uiowa.edu/etd/1042.

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A renewed commitment in the United States and abroad to electricity from renewable resources, such as wind, along with the recent deployment of very large turbines that rise to new heights, makes obtaining the most efficient and safe designs of the structures that support them ever more important. Towards this goal, the present research seeks to understand how optimization concepts and Microsoft Excel's optimization capabilities can be used in the design of wind turbine towers and foundations. Additionally, this research expands on the work of previous researchers to study how considering the tower and foundation as an integral system, where tower support conditions are not perfectly rigid, affects the optimal design. Specifically, optimization problems are formulated and solved with and without taking into account the effect of deflections, resulting from the foundation's rotational and horizontal stiffness, on natural frequency calculations. The general methodology used to transcribe the design of wind turbine towers and foundations into an optimization problem includes: 1) collecting information on design requirements and parameter values 2) deciding how to analyze the structure 3) formulating the optimization problem 4) implementation using Microsoft Excel. Key assumptions include: 1) use of an equivalent lumped mass method for estimating natural frequency 2) International Electrotechnical Commission (IEC) 61400-1 extreme loading condition controls design (i.e. fatigue loading condition is not considered) 3) extreme loads are obtained from manufacturer provided structural load document that satisfies loading cases outlined in IEC 61400-1 4) wind forces on the tower are calculated in accordance with IEC 61400-1 5) optimization variables are continuous. The sum of the tower material and fabrication cost and the total foundation cost is taken as the objective function. Important conclusions from this work include: 1) optimization concepts and Microsoft Excel's optimization capabilities can be used to obtain reasonable conceptual level designs and cost estimates 2) detailed designs and cost estimates could be achieved using a solver capable of handling discrete optimization problems 3) considering the tower and foundation as an integral system results in a more expensive, but safer, design 4) for the assumed parameter values, the constraint on the tower's natural frequency was found to control the tower design and the bearing capacity constraint was found to control the foundation design 5) relaxing or tightening the limit on the natural frequency will result in the greatest benefit or penalty, respectively, on the optimum solution.

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Lee, Jin Woo. "Multi-level Decoupled Optimization of Wind Turbine Structures Using Coefficients of Approximating Functions as Design Variables." University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1501003238831086.

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Horikiri, Kana. "Aerodynamics of wind turbines." Thesis, Queen Mary, University of London, 2011. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1881.

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The study of rotor blade aerodynamic performances of wind tur- bine has been presented in this thesis. This study was focused on aero- dynamic effects changed by blade surface distribution as well as grid solution along the airfoil. The details of numerical calculation from Fluent were described to help predict accurate blade performance for comparison and discussion with available data. The direct surface curvature distribution blade design method for two-dimensional airfoil sections for wind turbine rotors have been dis- cussed with the attentions to Euler equation, velocity diagram and the factors which affect wind turbine performance and applied to design a blade geometry close to an existing wind turbine blade, Eppler387, in order to argue that the blade surface drawn by direct surface curvature distribution blade design method contributes aerodynamic efficiency. The FLUENT calculation of NACA63-215V showed that the aero- dynamic characteristics agreed well with the available experimental data at lower angles of attack although it was discontinuities in the surface curvature distributions between 0.7 and 0.8 in x/c. The dis- continuities were so small that the blade performance could not be affected. The design of Eppler 387 blade performed to reduce drag force. The discontinuities of surface distributionmatched the curve of the pressure coefficients. It was found in the curvature distribution that the leading edge pressure side had difficulties to connect to Bezier curve and also the trailing edge circle was never be tangent to the lines of trailing edge pressure and suction sides due to programming difficulties.

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Bedon, Gabriele. "Aero-Structural Optimization of Vertical Axis Wind Turbines." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424493.

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This Thesis focuses on the aero-structural simulation and optimization of Darrieus Vertical Axis Wind Turbines. Aerodynamic simulation tools based on different techniques are developed, improved with respect to state-of-art tools, and validated against experimental data. The main considered approaches are based on the Blade Element Momentum, Vortex, two- and three-dimensional Unsteady Reynolds-Averaged Navier-Stokes (URANS) Computational Fluid Dynamics (CFD) models. The models are developed keeping in mind the final coupling with an optimization algorithm, therefore with particular emphasis on the computational effort and simulation robustness. A structural simulation tool based on the Euler-Bernoulli beam theory is also developed and validated against experimental data to perform an efficient aero-structural simulation. The validated models are coupled with an optimization algorithm under certain constraints to create an iterative loop able to produce improved designs. Different applications are considered based on the most relevant research topics and real case scenarios. The particular case of a floating Troposkien Vertical Axis Wind Turbine is analysed by improving the baseline aerodynamic design for the 5 MW rotor developed in the FP7 DeepWind project and evaluating the aerodynamic performance under rotor tilted conditions for the 1 kW demonstrator. The airfoil shape for the blade of a 500 kW H-rotor is also subjected to an optimization analysis with the aim to increase the aerodynamic production, obtaining a new geometry different from literature design. Finally, the aerodynamic and structural simulation tools are coupled to perform a complete aero-structural optimization of blade shape and chord distribution for a 500 kW Troposkien rotor. Both aerodynamic production and rotor stress are targeted in the routine and new blade shapes are found and discussed. The Thesis results, beside the increased performance with respect to the baseline case, prove that iterative loops, obtained by coupling a fast simulation tool and an optimization algorithm, can be adopted in the design and test phase of Darrieus Vertical Axis Wind Turbines, by providing the designer an advanced insight on the aerodynamic and structural phenomena experienced by these complex machines. Questa Tesi ha come oggetto la simulazione e l'ottimizzazione aero-strutturale di Turbine Eoliche ad Asse Verticale Darrieus. Strumenti per la simulazione aerodinamica basati su differenti tecniche sono sviluppati, migliorati rispetto allo stato dell'arte, e validati rispetto a dati sperimentali. I principali approcci considerati sono basati sui modelli Blade-Element Momentum, Vortex e Unsteady Reynolds-Averaged Navier-Stokes (URANS) Computational Fluid Dynamics (CFD) bi- e tri-dimensionali. I modelli sono sviluppati tenendo a mente l'accoppiamento con un algoritmo di ottimizzazione, quindi con particolare enfasi sullo sforzo computazionale e sulla robustezza della simulazione. Uno strumento di simulazione strutturale basato sulla teoria della trave di Eulero-Bernoulli è, in aggiunta, sviluppato e validato rispetto a dati sperimentali per effettuare una efficiente simulazione aero-strutturale. I modelli validati sono accoppiati con un algoritmo di ottimizzazione per la creazione di un ciclo per l'ottenimento di configurazioni migliorate. Differenti applicazioni sono considerate, basate sui temi di ricerca più rilevati e scenari reali. Il caso particolare di una Turbina Eolica ad Asse Verticale Troposkiana è stato considerato al fine di migliorare la configurazione aerodinamica di base di un rotore da 5 MW sviluppato nell'ambito del progetto FP7 DeepWind e di valutare le prestazioni aerodinamiche del dimostratore da 1 kW con rotore inclinato. La forma del profilo per la pala di un rotore ad H da 500 kW è oggetto anch'essa di un'attività di ottimizzazione finalizzata all'aumento della produzione aerodinamica, ottenendo una nuova geometria completamente differente da quelle disponibili in letterature. Infine, gli strumenti di simulazione aerodinamica e strutturale sono accoppiati per condurre una completa ottimizzazione aero-strutturale della forma della pala e della distribuzione di corda per un rotore Troposkiano da 500 kW. Sia la produzione aerodinamica che lo stato tensionale sono considerati come obiettivi e nuove forme palari sono individuate e discusse. I risultati della Tesi, oltre all'incremento di prestazioni rispetto alle geometrie di base, provano che i cicli iterativi, ottenuti tramite l'accoppiamento di un veloce strumento di simulazione e un algoritmo di ottimizzazione, possono essere adottati nella progettazione e test di Turbine Eoliche ad Asse Verticale Darrieus, fornendo al progettista un avanzato strumento di analisi dei fenomeni aerodinamici e strutturali agenti in queste complesse macchine.

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Moore, Ian F. "Inertial response from wind turbines." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/42939/.

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Wind power is an essential part of the strategy to address challenges facing the energy sector. Operation of the electricity network in 2020 will require higher levels of response and reserve from generation. The provision of inertial response from wind turbines was investigated. A model was developed for the simulation of frequency on the mainland UK system, including a simplified model for a synchronous generator to represent Full Power Converter turbines. Two different methods of inertia response, the step method and the inertia coupling method, were modelled and introduced into the turbine torque speed control. Simulations illustrated the effects on primary frequency control for a high penetration of wind turbines. Results are shown for different demand levels with generation losses of 1320GW and 1800GW. A comparison of the inertia functions is included and the effect of wind speed and the constant speed region of the maximum power extraction curve. For the scenarios modelled only a small change in turbine output was required for inertia response (0.02p.u). Without inertia response a large increase in synchronous plant response was needed. A test rig was constructed consisting of a Full Power Converter bridge and a synchronous generator driven by a dc machine. Power converters were designed and constructed by the candidate. Vector control of both the generator converter and grid converter was implemented on a dedicated control platform. The inertia coupling function was implemented and a test frequency deviation injected to represent a load generation imbalance. Results compared closely to those from the model and demonstrated the capability to closely couple turbine speed to system frequency with adjustment of the response via a filter if desired. The experimental work confirmed the adequacy of the simplified generator model and further confirmed the possibility of using inertia response. The inertia coupling function was considered suitable for use for the UK system.

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Moor, Gary Duncan. "Optimization of wind energy transfer using wind turbines." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53542.

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Thesis (MScIng)--Stellenbosch University, 2003. ENGLISH ABSTRACT: The effect of topography and terrain on wind is examined in order to ensure that the wind turbine positioning will encourage a greater availability of wind energy to it. Maximum power point tracking methods are presented whereby the loading on the wind turbine is controlled to ensure that the maximum available energy from the wind is captured. The wind turbine system is modelled and used in simulations to evaluate the three proposed maximum power point trackers, named anemometer control, calculation control and constant step control for the purpose of this thesis. An additional analog system is also created whereby the complete wind turbine system is able to be simulated. An inverter is used to replicate the generator and the loading is controlled using an active rectifier since this will be used on the practical system. The results from the simulations and analog system are presented whereby one of the trackers is shown to be inadequate and the other two trackers are shown to be close to ideal. The appeal of the calculation method is in the redundancy of an anemometer making it attractive to less expensive, small-scale systems. AFRIKAANSE OPSOMMING: Die invloed van die topografie en die terrein op die dinamika van wind word ondersoek om sodoende te verseker dat die posisionering van wind turbienes 'n beter effektiwiteit van wind energie oordrag sal bewerkstellig. Maksimum drywingspunt volger metodes word bespreek sodat die lading op die wind turbiene beheer kan word om sodoende te verseker dat die maksimum wind energie oorgedra kan word. Die wind turbiene stelsel word gemodeleer en geimplimenteer om die drie voorgestelde maksimum drywingspount volgers te evalueer, naamlik windspoedbeheer, berekening-beheer en konstantestap-beheer vir die doeleindes van hierdie tesis. 'n Adissionele analoog stelsel is ontwerp waarmee die volledige wind turbiene stelsel gesimuleer kan word. 'n Omsetter word gebruik om die generator na te boots en die belading word beheer deur middel van 'n aktiewe gelykrigter soos gebruik 'n praktese stelsel. Resultate van die simulasies en die analog stelsel is verskaf om te bewys dat een van die volg-metodes onvoldoende volging bewerkstellig, en die ander twee nabyaan ideale volging bewerkstellig. Dit is getoon dat die berekening metode meer aantreklik is vir kleinskaal stelsels, aangesien 'n windspoedsensor onnodig is.

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Li, Jiale. "ANALYTICAL FATIGUE DAMAGE CALCULATION FOR WIND TURBINE SUPPORT STRUCTURE." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1364832753.

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Tracy, Christopher (Christopher Henry). "Parametric design of floating wind turbines." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40877.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. Includes bibliographical references. As the price of energy increases and wind turbine technology matures, it is evident that cost effective designs for floating wind turbines are needed. The next frontier for wind power is the ocean, yet development in near shore waters has been slowed by aesthetic concerns of coastal residents. Going further offshore eliminates these aesthetic concerns and has the additional advantage of stronger and more consistent winds. However, the vast majority of promising locations beyond the view of land are in sufficiently deep water to make building a rigid structure to the ocean floor economically infeasible. Cost effective floating structures are needed to enable wind farm installation in deep water and increase the world's installed base of renewable energy. This thesis presents a parametric approach to the design of these floating structures for offshore wind turbines. It starts with the relevant design concepts from the offshore oil gas industry and presents appropriate combinations of structures and mooring systems that meet the requirements for a generic five mega watt wind turbine. The results of the parametric study are a number of designs that show Pareto fronts for mean square acceleration of the turbine versus multiple cost drivers for the offshore structure. These cost drivers include displacement of the floating structure and total mooring line tension. by Christopher Tracy. S.M.

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Luypaert, Thomas (Thomas J. ). "Flexible dynamics of floating wind turbines." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70441.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. "February 2012." Cataloged from PDF version of thesis. Includes bibliographical references (p. 84-86). This work presents Tower Flex, a structural dynamics model for a coupled analysis of offshore floating wind turbines consisting of a tower, a floating platform and a mooring system. In this multi-body, linear frequency-domain model, the tower is represented as a series of uniform Timoshenko beams connected to each other. The deflections of the tower are solved analytically in each beam while the mass, damping and stiffness coming from the rotor, the floating platform and the mooring lines are taken into account via generalized boundary conditions. Tower Flex is used for the evaluation of a 3MW offshore floating wind turbine mounted on a Tension Leg Platform (TLP). Natural frequencies, motion responses and fatigue damage are analyzed to illustrate the features of Tower Flex and assess the performance of the proposed design. by Thomas Luypaert. S.M.

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Casanovas, Carlos (Casanovas Bermejo). "Advanced controls for floating wind turbines." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92149.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. Cataloged from PDF version of thesis. Includes bibliographical references (pages 64-65). Floating Offshore Wind Turbines (FOWT) is a technology that stands to spearhead the rapid growth of the offshore wind energy sector and allow the exploration of vast high quality wind resources over coastal and offshore areas with intermediate and large water depths. This generates the need for a new generation of Wind Turbine control systems that take into account the added complexity of the dynamics and wave-induced motions of the specific floater. The present work presents a simulation study of advanced controls for Tension Leg Platform (TLP) FOWT that attempts to enhance the power output of the Wind Turbine by conversion of the surge kinetic energy of the TLP into wind energy. The public access data of the NREL 5MW offshore wind turbine have been used to perform the study. After establishing a theoretical upper bound for the possible wave energy extraction using frequency-domain methods, a time-domain state-space dynamic model of the FOWT with coupled dynamics of platform surge motion and turbine rotation has been developed that includes both a simplified model of the turbine aerodynamics and the floater surge hydrodynamics. This simulation model has then been used to implement advanced controls that maximize energy extraction by the Wind Turbine in the below rated power region. The proposed controllers are variations of a Linear-Quadratic Regulator (LQR), considering both a steady-state case and a non-stationary, finite horizon LQR case. The latter requires wave-elevation forecasting to be implemented and therefore two different forecasting algorithms have also been developed according to existing literature. While the wave-induced annual energy yield enhancement of the studied FOWT in the two considered locations is small (around 0.02% the baseline annual energy yield of the studied turbine in the two locations) the study is not exhaustive and other FOWT topologies might achieve better results. The present results clearly indicate, however, that the existing correlation between strong wind and waves makes FOWTs a sub-optimal choice as energy extraction mechanism for ocean wave energy harvesting. by Carlos Casanovas. S.M.

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Zhang, Yu Ph D. Massachusetts Institute of Technology Department of Mechanical Engineering. "Wave loads on offshore wind turbines." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100344.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. Cataloged from PDF version of thesis. Includes bibliographical references (page 65). Ocean energy is one of the most important sources of alternative energy and offshore floating wind turbines are considered viable and economical means of harnessing ocean energy. The accurate prediction of nonlinear hydrodynamic wave loads and the resulting nonlinear motion and tether tension is of crucial importance in the design of floating wind turbines. A new theoretical framework is presented for analyzing hydrodynamic forces on floating bodies which is potentially applicable in a wide range of problems in ocean engineering. The total fluid force acting on a floating body is obtained by the time rate of change of the impulse of the velocity potential flow around the body. This new model called Fluid Impulse Theory is used to address the nonlinear hydrodynamic wave loads and the resulting nonlinear responses of floating wind turbine for various wave conditions in a highly efficient and robust manner in time domain. A three-dimensional time domain hydrodynamic wave-body interaction computational solver is developed in the frame work of a boundary element method based on the transient free-surface Green-function. By applying a numerical treatment that takes the free-surface boundary conditions linearized at the incident wave surface and takes the body boundary condition satisfied on the instantaneous underwater surface of the moving body, it simulates a potential flow in conjunction with the Fluid Impulse Theory for nonlinear wave-body interaction problems of large amplitude waves and motions in time domain. Several results are presented from the application of the Fluid Impulse Theory to the extreme and fatigue wave load model: the time domain analysis of nonlinear dynamic response of floating wind turbine for extreme wave events and the time domain analysis of nonlinear wave load for an irregular sea state followed by a power spectral density analysis. by Yu Zhang. S.M.

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Velliyur, Ramachandran Krishna Guha. "An Aeroacoustic Analysis of Wind Turbines." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1293650904.

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Lee, Kwang Hyun. "Responses of floating wind turbines to wind and wave excitation." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33564.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005. Includes bibliographical references (leaf 55). The use of wind power has recently emerged as a promising alternative to conventional electricity generation. However, space requirements and public pressure to place unsightly wind turbines out of visual range make it desirable to move large wind farms offshore and into deeper coastal waters. A necessary step for the deployment of wind turbines into deeper waters is the development of floating platform systems. This thesis will present a general technical description of two concept designs for floating wind turbine systems, and make a preliminary evaluation of their performance in wind and waves. A new approach to computing the nonlinear wave excitation is also presented. by Kwang Hyun Lee. S.M.

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Oliver, Andrew G. "Air jet vortex generators for wind turbines." Thesis, City University London, 1997. http://openaccess.city.ac.uk/8384/.

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Air jet vortex generators are a boundary layer control device and as such can effect a significant delay to the stall of an aerofoil. They can also reattach a separated flow, as long as the angle of attack is less than the air jets 'on' stall angle. A wind tunnel model was built and tested and then modified to incorporate air jets. The air jets increased CL max by 55% and reduced the drag throughout the incidence range, a, for the chosen blowing pressure of 1 p. s. i. (6900Pa). By varying the air supply so that the jets operate between 'off' and fully 'on' a whole family bf aerofoil L/D characteristics could be derived. The blade set of a 150 kW stall regulated wind turbine was then modified with air jet vortex generators and tested at full scale. This was done primarily to increase its energy yield by reducing energy loss in the region of the power curve 'knee', but also to allow a degree of power regulation in high wind speeds. The air supply in this demonstration was supplied by a fan mounted on, and rotating with, the rotor. Full-scale trials demonstrated that air jets can indeed be used to straighten the power curve prior to rated wind speed. This important result means that a stall regulated machine can be made to behave in the same way as a pitch controlled machine without having to pitch the blades. Of the two air jet configurations tested in the wind tunnel, the second had an improved L/D characteristic and required less mass flow, even though the physical change was minor. This indicates that further optimisation of air jets may be achieved. Further wind tunnel testing showed that it should be possible to eliminate the fan used in the full scale trials and use one of two 'passive' blowing techniques. It was shown that the air jets can be supplied by air at atmospheric pressure due to the suction on the upper surface of the aerofoil which is sufficient to pull air through the jet exits and create vortices. However, to achieve an optimised air jet configuration and to investigate the possibilities of using passive blowing, air jet vortex generators will need to be modelled numerically, so that this innovative concept can be brought to market quickly.

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Roynarin, Wirachai. "Optimisation of vertical axis wind turbines." Thesis, Northumbria University, 2004. http://nrl.northumbria.ac.uk/1655/.

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A practical Vertical Axis Wind Turbine (VAWTs) based on a Darrieus rotor has been designed and tested and found to be capable of self-starting at wind speeds above 4m/s. The self-start feature has been achieved by replacing the usual symmetrical aerofoil blade in the VAWT rotor and by using a concentric Savonius rotor or semi-cylinder turbine. A computer program was produced to compute the power coefficient versus tip speed ratio characteristics of a selected aerofoil profile employed in a VAWT. The program accounts for chord length, pitch angle, number of blades, and rotor radius at any wind speed. The published data from 40 aerofoil sections were assessed, taking into account the two main criteria — self-starting and efficiency. Computational fluid dynamics software (ANSYS, Flotran) has been used to investigate the lift and drag performance of a NACA 66-212 and NACA 4421 aerofoils in order to check the computer program predictions. Excellent agreement was obtained for the static aerofoil assessment, but only after special ICEM Computational Fluid Dynamics (CFD) meshing interface routines were utilised. However, agreement between the theoretical and published results was not good for the rotating aerofoils in a VAWT. Thus, further CFD work was not pursued and in preference, an experimental route was initiated. In the first series of wind tunnel tests involving three candidate profiles, good agreement was found between the experimental results and the mathematical models. The aerofoils chosen were the NACA 661-212, the 51223 and the Clark-Y standard aerofoils. A number of prototype VAWTs were fabricated and tested for the influence of the blade pitch angle, the chord length ratio, with 2 or 3 blades. The aerofoil surfaces were made from aluminium sheet with a standard surface finish. The prototype designs were tested in the Northumbria University low speed wind tunnel facility - the models were 0.4 m. high with a 0.4 m diameter. The torque versus wind speed characteristics were recorded and analysed. The S 1223 profile was found to be self-starting with high efficiency. This model generated a high power coefficient of about 0.3 at a tip speed ratio of 1.2. The second series of tests were carried out in field sites in the UK with a 2 m diameter straight—bladed Darrieus rotor prototype with 3 blades using the S1223 blade section. Three field trials were undertaken in the UK to produce realistic performance characteristics for wind conditions of 4-10 m/s. The maximum power coefficient of this machine was found to be 0.18 at a tip speed ratio of 1.2. In addition, an alternative semi-cylinder turbine combined with a Darrieus rotor was fabricated and tested in the UK. It demonstrated the advantage that it could self-start at lower wind speeds, that is 3m/s but delivers approximately 50% less power than that obtained from the first proposed design. A final phase of testing was carried out with an enlarged and modified 3 m diameter prototype installed at a shrimp farm in Thailand to demonstrate how the unit could be used to replace an equivalent 2 HP 2-stroke diesel engine and hence eliminate its inherent emission pollution problems. A Savonius rotor was fitted to the prototype to improve self-start capabilities at a wind speed of 4 m/s for a practical application which by its nature required a high starting torque. The designs are easy to fabricate, low cost, pollution free and have been demonstrated to be ideal for applications in developing countries where there are sufficient wind resources.

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Tong, Xin. "Control of large offshore wind turbines." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/99841/.

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Several control strategies are proposed to improve overall performances of conventional (geared equipped) and hydrostatic offshore wind turbines. Firstly, to maximise energy capture of a conventional turbine, an adaptive torque control technique is proposed through simplifying the conventional extremum seeking control algorithm. Simulations are conducted on the popular National Renewable Energy Laboratory (NREL) monopile 5-MW baseline turbine. The results demonstrate that the simplified ESC algorithms are quite effective in maximising power generation. Secondly, a TMD (tuned mass damper) system is configured to mitigate loads on a monopile turbine tower whose vibrations are typically dominated by its first mode. TMD parameters are obtained via H2 optimisation based on a spatially discretised tower-TMD model. The optimal TMDs are assessed through simulations using the NREL monopile 5-MW baseline model and achieve substantial tower load reductions. In some cases it is necessary to damp tower vibrations induced by multiple modes and it is well-known that a single TMD is lack of robustness. Thus a control strategy is developed to suppress wind turbine’s vibrations (due to multiple modes) using multiple groups of TMDs. The simulation studies demonstrate the superiority of the proposed methods over traditional ones. Thirdly, the NREL 5-MW baseline turbine model is transformed into a hydrostatic wind turbine (HWT). An H∞ loop-shaping torque controller and a light detection and ranging-based linear-parameter-varying anti-windup pitch controller are designed for the HWT. The tests on a monopile HWT model indicate good tracking behaviours of the torque controller and much improved performances of the linear-parameter-varying pitch controller over a gain-scheduled PI pitch controller. Finally, the hydraulic reservoir of a barge HWT is made into a bidirectional-tuned- liquid-column-damper (BTLCD) to suppress barge pitch and roll motions. The simulation results validate the effectiveness of the optimal BTLCD reservoir in reducing the tower loads and power fluctuations.

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Rossander, Morgan. "Electromechanics of Vertical Axis Wind Turbines." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331844.

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Wind power is an established mean of clean energy production and the modern horizontal axis wind turbine has become a common sight. The need for maintenance is high and future wind turbines may need to be improved to enable more remote and offshore locations. Vertical axis wind turbines have possible benefits, such as higher reliability, less noise and lower centre of gravity. This thesis focuses on electromechanical interaction in the straight bladed Darrieus rotor (H-rotor) concept studied at Uppsala University. One of the challenges with vertical axis technology is the oscillating aerodynamic forces. A force measurement setup has been implemented to capture the forces on a three-bladed 12 kW open site prototype. The normal force showed good agreement with simulations. An aerodynamic torque could be estimated from the system. The total electrical torque in the generator was determined from electrical measurements. Both torque estimations lacked the expected aerodynamic ripple at three times per revolution. The even torque detected is an important result and more studies are required to confirm and understand it. The force measurement was also used to study the loads on the turbine in parked conditions. It was discovered that there is a strong dependence on wind direction and that there is a positive torque on the turbine at stand still. The results can assist to determine the best parking strategies for an H-rotor turbine. The studied concept also features diode rectification of the voltage from the permanent magnet synchronous generator. Diodes are considered a cheap and robust solution for rectification at the drawback of inducing ripple in the torque and output voltage. The propagation of the torque ripple was measured on the prototype and studied with simulations and analytical expressions. One key conclusion was that the mechanical driveline of the turbine is an effective filter of the diode induced torque ripple. A critical speed controller was implemented on the prototype. The controller was based on optimal torque control and according to the experiments and the simulations it was able to avoid a rotational speed span. Finally, the optimal torque control was evaluated for multiple turbines with diode rectification to a common DC-link. The setup can potentially reduce the overall complexity of wind farms. The simulations suggest that stability of the system can be obtained by controlling the DC-link load as a semi constant voltage. The thesis is based on nine papers of which six are treated in the thesis summary.

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Zhang, Zijun. "Performance optimization of wind turbines." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3024.

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Improving performance of wind turbines through effective control strategies to reduce the power generation cost is highly desired by the wind industry. The majority of the literature on performance of wind turbines has focused on models derived from principles versed in physics. Physics-based models are usually complex and not accurate due to the fact that wind turbines involve mechanical, electrical, and software components. These components interact with each other and are subjected to variable loads introduced by the wind as well as the rotating elements of the wind turbine. Recent advances in data acquisition systems allow collection of large volumes of wind energy data. Although the prime purpose of data collection is monitoring conditions of wind turbines, the collected data offers a golden opportunity to address most challenging issues of wind turbine systems. In this dissertation, data mining is applied to construct accurate models based on the turbine collected data. To solve the data-driven models, evolutionary computation algorithms are applied. As data-driven based models are non-parametric, the evolutionary computation approach makes an ideal solution tool. Optimizing wind turbines with different objectives is studied to accomplish different research goals. Two research directions of wind turbines performance are pursued, optimizing a wind turbine performance and optimizing a wind farm performance. The goal of single wind turbine optimization is to improve wind turbine efficiency and its life-cycle. The performance optimization of a wind farm is to minimize the total cost of operating a wind farm based on the computed turbine scheduling strategies. The methodology presented in the dissertation is applicable to processes besides wind industry.

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Paul, Bryan. "Analytical And Experimental Study Of Monitoring For Chain-Like Nonlinear Dynamic Systems." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5686.

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Inverse analysis of nonlinear dynamic systems is an important area of research in the ?eld of structural health monitoring for civil engineering structures. Structural damage usually involves localized nonlinear behaviors of dynamic systems that evolve into different classes of nonlinearity as well as change system parameter values. Numerous parametric modal analysis techniques (e.g., eigensystem realization algorithm and subspace identification method) have been developed for system identification of multi-degree-of-freedom dynamic systems. However, those methods are usually limited to linear systems and known for poor sensitivity to localized damage. On the other hand, non-parametric identification methods (e.g., artificial neural networks) are advantageous to identify time-varying nonlinear systems due to unpredictable damage. However, physical interpretation of non-parametric identification results is not as straightforward as those of the parametric methods. In this study, the Multidegree-of-Freedom Restoring Force Method (MRFM) is employed as a semi-parametric nonlinear identification method to take the advantages of both the parametric and non-parametric identification methods. The MRFM is validated using two realistic experimental nonlinear dynamic tests: (i) large-scale shake table tests using building models with different foundation types, and (ii) impact test using wind blades. The large-scale shake table test was conducted at Tongji University using 1:10 scale 12-story reinforced concrete building models tested on three different foundations, including pile, box and fixed foundation. The nonlinear dynamic signatures of the building models collected from the shake table tests were processed using MRFM (i) to investigate the effects of foundation types on nonlinear behavior of the superstructure and (ii) to detect localized damage during the shake table tests. Secondly, the MRFM was applied to investigate the applicability of this method to wind turbine blades. Results are promising, showing a high level of nonlinearity of the system and how the MRFM can be applied to wind-turbine blades. Future studies were planned for the comparison of physical characteristic of this blade with blades created made of other material. M.S. Masters Civil, Environmental, and Construction Engineering Engineering and Computer Science Civil Engineering; Structures and Geotechnical Engineering

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Ahmadi, Mehran. "Analysis and Study of Floating Offshore Wind Turbines." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1376643304.

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Shawler, James R. "Engineering aerodynamics of horizontal axis wind turbines (HAWTs)." Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/7629.

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This thesis comprises two main original contributions. The first concerns the aeroelastic modelling of a large-scale prototype wind turbine undertaken specifically to explain experimentally observed mechanical instabilities. The second explores the aerodynamic aspect of turbine modelling in greater detail since this is the main identified technical challenge, this process makes use of detailed largescale wind tunnel test data from NREL for model validation purposes. The MS4 prototype wind turbine was modelled using ADAMS/WT software, the aerodynamic model was provided by the NREL AERODYN subroutines. The drivetrain instability of the machine of 0.75Hz was reproduced by the computer simulation. The causes of the instability were found to be negative aerodynamic damping, complex blade bending modes caused by the blade design and rapid yawing and tilting inducing Coriolis forces in the rotor structure. Accurate analysis of the aerodynamic forces acting on the MS4 was not possible because of the lack of detailed data available and the complicated aeroelastic response of its flexible structure. Theoretical comparisons with the results from the NREL wind tunnel tests were made using several different engineering aerodynamic models (including those used with AERODYN). It was found that blade element aerofoil data had a controlling influence on the blade forces predicted through theory. The effect of inflow models was found to be marginal at lower tip speed ratios and to decrease with decreasing tip speed ratio. Experimental blade forces at low tip speed ratios were found to be defined by gross 3 dimensional effects and the use of 2 dimensional aerofoil data led to inaccurate prediction of blade forces. The use of a stall delay model improved results but was not convincing. Yawed flow predictions were again controlled by the blade element aerofoil data used, use of a stall delay model again improved results in a steady state fashion. A dynamic stall model also improved results but the phasing of results towards the blade root was questionable and may be caused by unsuitable time constants or the influence of the delayed stall effect.

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Simley, Eric J. "Wind Speed Preview Measurement and Estimation for Feedforward Control of Wind Turbines." Thesis, University of Colorado at Boulder, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3721887.

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Wind turbines typically rely on feedback controllers to maximize power capture in below-rated conditions and regulate rotor speed during above-rated operation. However, measurements of the approaching wind provided by Light Detection and Ranging (lidar) can be used as part of a preview-based, or feedforward, control system in order to improve rotor speed regulation and reduce structural loads. But the effectiveness of preview-based control depends on how accurately lidar can measure the wind that will interact with the turbine. In this thesis, lidar measurement error is determined using a statistical frequency-domain wind field model including wind evolution, or the change in turbulent wind speeds between the time they are measured and when they reach the turbine. Parameters of the National Renewable Energy Laboratory (NREL) 5-MW reference turbine model are used to determine measurement error for a hub-mounted circularly-scanning lidar scenario, based on commercially-available technology, designed to estimate rotor effective uniform and shear wind speed components. By combining the wind field model, lidar model, and turbine parameters, the optimal lidar scan radius and preview distance that yield the minimum mean square measurement error, as well as the resulting minimum achievable error, are found for a variety of wind conditions. With optimized scan scenarios, it is found that relatively low measurement error can be achieved, but the attainable measurement error largely depends on the wind conditions. In addition, the impact of the induction zone, the region upstream of the turbine where the approaching wind speeds are reduced, as well as turbine yaw error on measurement quality is analyzed. In order to minimize the mean square measurement error, an optimal measurement prefilter is employed, which depends on statistics of the correlation between the preview measurements and the wind that interacts with the turbine. However, because the wind speeds encountered by the turbine are unknown, a Kalman filter-based wind speed estimator is developed that relies on turbine sensor outputs. Using simulated lidar measurements in conjunction with wind speed estimator outputs based on aeroelastic simulations of the NREL 5-MW turbine model, it is shown how the optimal prefilter can adapt to varying degrees of measurement quality.

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Feitosa, Evaraldo Alencar Do Nacimento. "Parametric resonance in horizontal axis wind turbines." Thesis, University of Southampton, 1989. https://eprints.soton.ac.uk/52253/.

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Regions of parametric resonance are predicted for the flexible blades of Horizontal Axis Wind Turbines subjected to periodic parametric loading due to gravity. The mathematical model consists of rigid blade flapping, rigid blade lagging and shaft torsion degrees of freedom. A hypothetical hinge offset, flapping and lagging stiffnesses, and aerodynamic loading are considered in the model. Also, hinge inclination which induces stiffness coupling is included in the analysis. The equations of motion (Mathieu/Hill's equations) are investigated using the Harmonic Balance Method for the determination of the main parametric resonance. The analysis has been carried out with the support of the computer algebra system REDUCE. Particular attention is given to: the importance of aerodynamic terms; the influence of coning angle; the influence of the flapping and lagging stiffnesses and the influence of the hinge inclination. The size and position of these regions of instability are significantly affected by these factors. Experimental results are presented from wind tunnel tests in which a Horizontal Axis Wind Turbine model of 1.82m diameter with flexible blades was investigated. The experimental results show clearly some regions of parametric resonance

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Zhao, Songling. "Observer-Based Fault Diagnosis of Wind Turbines." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1308064070.

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Lupton, Richard. "Frequency-domain modelling of floating wind turbines." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/252880.

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The development of new types of offshore wind turbine on floating platforms requires the development of new approaches to modelling the combined platform-turbine system. In this thesis a linearised frequency-domain approach is developed which gives fast but approximate results: linearised models of the structural dynamics, hydrodynamics, aerodynamics and control system dynamics are brought together to find the overall response of the floating wind turbine to harmonic wind and wave loading. Initially, a nonlinear flexible multibody dynamics code is developed and verified, which is then used to provide reference nonlinear simulation results. The structural dynamics of a wind turbine on a moving platform are shown to be nonlinear, but for realistic conditions the effects are small. An approximate analysis of the second-order response of floating cylinders to hydrodynamic loads suggests slow drift motion may be relatively small for floating wind turbines, compared to other floating offshore structures. The aerodynamic loads are linearised using both harmonic and tangent linearisation approaches; the harmonic linearisation gives improved results when stall occurs. The wake dynamics can also be included. The control system behaviour is linearised using the same method, which works well when the wind speed is far from the rated wind speed; close to the rated wind speed the nonlinearity is stronger, but further improvement should be possible. These sub-models are combined to give a simple but complete model of a floating wind turbine, with flexible blades and a flexible tower, but neglecting the control system behaviour, wake dynamics and nonlinear hydrodynamic loads. For the OC3-Hywind turbine, the accuracy of the results is assessed by comparison to nonlinear time-domain simulations using the commercial code Bladed. Peak-peak errors of less than 5 % are achievable for many harmonic wind and wave inputs, but certain conditions lead to larger errors. The effect of including linearised control system behaviour is demonstrated for a subset of conditions. Overall, the results are promising but more work is needed for practical application.

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Hajiabady, Siavash. "Integrated condition monitoring of industrial wind turbines." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8121/.

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The continuous growth in wind turbine power ratings and numbers has led to increased demands in inspection and maintenance due to the more significant financial and operational consequences of unexpected wind turbine failure. The fact that wind farms are commonly located at remote sites with potentially poor accessibility means it is necessary to reduce the need for corrective maintenance through evolution to preventive and prognostic maintenance activities. Prognostic repair schedules can be employed in order to optimise maintenance and contribute to the minimisation of the overall operational costs of wind farms. The present study presents the development and qualitative evaluation of remote condition monitoring methodologies for the evaluation of the wind turbine power electronics and gearboxes. The failures of power converter and gearbox components result in significant wind turbine downtime and associated repair costs. Effective condition monitoring can enable the timely diagnosis of faults in order to prevent unexpected failures and loss of electricity production, contributing towards a noteworthy increase the reliability, availability, maintainability and safety (RAMS) of wind farms. Within this study two customised test rigs have been employed to simulate various of faults and assess the capability of RCM in diagnosing this fault effectively. In addition, field measurements have been carried out and correlated to the findings of the test rig experiments. In this study, it has been possible to identify these variables qualitatively, but the quantitative investigation is still pending and will be most likely the subject of several future studies in this field. The present thesis provides a compact summary of the analysis of the key findings of the experimental work performed within the context of the OPTIMUS FP7 European collaborative project.

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Villalobos, Jara Felipe Alberto. "Model testing of foundations for offshore wind turbines." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:438cfe69-c8d4-4630-ab0b-482da5ea2839.

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Suction caissons are a new foundation option for offshore wind turbines. This thesis is focussed on the behaviour of suction caisson foundations in sand and in clay during installation, and under subsequent vertical and combined moment-lateral loadings. The research is based on extensive experimental work carried out using model scaled caissons. The analysis of the results allowed the determination of parameters for hyperplasticity models. Model caissons were vertically loaded in loose and dense sands to study in service states and plastic behaviour. Bearing capacity increased with the length of the caisson skirt. The bearing capacity formulation showed that the angle of friction mobilised was close to the critical state value for loose sands and close to those of peak values due to dilation for dense sands. The vertical load increased, though at a lower rate than during initial penetration, after large plastic displacements occurred. A hardening law formulation including this observed behaviour is suggested. In sand the installation of caissons by suction showed a drastic reduction in the net vertical load required to penetrate the caisson into the ground compared with that required to install caissons by pushing. This occurred due to the hydraulic gradients created by the suction. The theoretical formulations of the yield surface and flow rule were calibrated from the results of moment loading tests under low constant vertical loads. The fact that caissons exhibit moment capacity under tension loads was considered in the yield surface formulation. Results from symmetric and non symmetric cyclic moment loading tests showed that Masing’s rules were obeyed. Fully drained conditions, partially drained and undrained conditions were studied. Caisson rotation velocities scaled in the laboratory to represent those in the field induced undrained response for relevant periods of wave loading, a wide range of seabed permeabilities and prototype caisson dimensions. Under undrained conditions and low constant vertical loads the moment capacity of suction caissons was very small. Under partially drained conditions the moment capacity decreased with the increase of excess pore pressure. In clay, vertical cyclic loading around a mean vertical load of zero showed that in the short term the negative excess pore pressures generated during suction installation reduced vertical displacements. The yield surface and the flow rule were determined from moment swipe and constant vertical load tests. The moment capacity was found to depend on the ratio between the preload Vo and the ultimate bearing capacity Vu. Gapping response was observed during cyclic moment loading tests, but starting at smaller normalised rotations than in the field. The hysteresis loop shape obtained during gapping cannot be reproduced by means of the Masing’s rules.

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Dadashnialehi, Ehsan. "Modeling And Control of Variable Speed Wind Turbines." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1356372607.

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Wahlström, Niklas, and Oscar Gabrielsson. "Additive Manufacturing Applications for Wind Turbines." Thesis, KTH, Maskinkonstruktion (Inst.), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209654.

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Additive manufacturing (AM), also known as 3D-printing is an automated manufacturing process in which the component is built layer upon layer from a predefined 3D computer model. In contrast to conventional manufacturing processes where a vast volume of material is wasted due to machining, AM only uses the material that the component consists of. In addition to material savings, the method has a number of potential benefits. Two of these are (1) a large design freedom which enables the production of complex geometries and (2) a reduced compexity in supply chain as parts can be printed on-demand rather than be kept in stock. This master thesis has been performed at Vattenfall Wind Power and aims to investigate the feasibility to reproduce and/or to refurbish one or two spare parts on a wind turbine by AM and if it can introduce any practical benefits. Components with a high failure rate and/or with an suitible design for AM have been investigated. A rotating union or fluid rotary joint (FRJ) was selected for further analysis. A comprehensive background study has been conducted. A current status of metal AM is described as well as a comparison between conventional and additive processes. Furthermore, current and future applications for AM witihin the wind turbine industry are presented. The mehodology "reverse engineering", main components in a wind power plant including the fluid rotary joint as well as fluid dynamics are also treated in the background study. As a part of the process, a fluid rotary joint with worse historical failure data was disassembled and examined. In order to find other design solutions that contributes to a better and more reliable operation, another better performing fluid roraty joint was investigated. Since detail drawings and material information are missing for the examined units, reverse engineering has been carried out to gather details of the designs. A concept for the first unit has been developed, in which improved design solutions has been introduced and a number of changes have been implemented in order to minimize material consumption and to adapt the design for AM. The concept has been evaluated by the use of numerical methods. Costs and build time have also been estimated for the developed concept. This project has illustated that it is feasable to manufacture spare parts by the use of AM. The developed concept demonstrates several improvements that are not possible to achieve with conventional manufacturing processes. Nevertheless, a number of limitations such as insufficient build volume, costs as well as time cosuming engineering effort and post-proccessing methods are present for AM. These restrictions, in combination with lack of 3D-models, limits the possibility to make use of the technology. However, the future looks bright, if the technology continues to develop and if subcontractors are willing to adapt to AM it will probably have a major breakthrough within the windpower industry. Additiv tillverkning, "additive manufacturing" (AM) eller 3D-printing är en automatiserad tillverkningsmetod där komponenten byggs lager för lager från en fördefinierad 3D datormodell. Till skillnad från konventionella tillverkningsmetoder där en stor mängd material ofta bearbetas bort, använder AM nästintill endast det material som komponenten består utav. Förutom materialbesparingar, har metoden ett flertal andra potentiella fördelar. Två av dessa är (1) en stor designfrihet vilket möjliggör produktion av komplexa geometrier och (2) en möjlighet till en förenklad logistikkedja eftersom komponenter kan tillverkas vid behov istället för att lagerföras. Detta examensarbete har utförts på Vattenfall Vindkraft och har till syfte att undersöka om det är möjligt att tillverka och/eller reparera en eller två reservdelar genom AM och om det i så fall kan införa några praktiska fördelar. En kartläggning av komponenter med hög felfrekvens och/eller som kan vara lämpade för AM har genomförts. Av dessa har en roterande oljekoppling även kallad roterskarv valts ut för vidare analys. En omfattande bakgrundsstudie har utförts. En nulägesorientering inom området AM för metaller redogörs, här redovisas även en generell jämförelse mellan konventionella och additiva tillverkningsmetoder. Vidare behandlas aktuella och framtida användningsområden för AM inom vindkraftsindustrin. I bakgrundsstudien behandlas också arbetssättet "reverse engineering", huvudkomponenter i ett vindkraftsverk inklusive roterskarven samt flödesdynamik. Under arbetets gång har en roterskarv med sämre driftshistorik undersökts. I syfte att finna andra konstruktionslösningar som bidrar till en säkrare drift har en bättre presenterande enhet från en annan tillverkare granskats. Då viss detaljteknisk data och konstruktionsunderlag saknas för de undersökta enheterna har "reverse engineering" tillämpats. Ett koncept har sedan utvecklats för den första enheten där förbättrade konstruktionslösningar har introducerats samtidigt som en rad konstruktionsförändringar har gjorts i syfte att minimera materialåtgången och samtidigt anpassa enheten för AM. Konceptet har sedan evaluerats med hjälp av numeriska beräkningsmetoder. För det givna konceptet har även kostnad och byggtid uppskattats. Arbetet visar på att det är möjligt att ta fram reservdelar till vindkraftverk med hjälp av AM. Det framtagna konceptet visar på ett flertal förbättringar som inte kan uppnås med konventionella tillverkningsmetoder. Emellertid finns det en rad begränsningar såsom otillräcklig byggvolym, kostnader och tidskrävande ingenjörsmässigt arbete och efterbehandlingsmetoder. Dessa förbehåll i kombination med avsaknad av 3D-modeller begränsar möjligheterna att nyttja tekniken i dagsläget. Framtiden ser dock ljus ut, om tekniken fortsätter att utvecklas samtidigt som underleverantörer är villiga att nyttja denna teknik kan AM få ett stort genombrott i vindkraftsindustrin.

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D'Ambrosio, Marco, and Marco Medaglia. "Vertical Axis Wind Turbines: History, Technology and Applications." Thesis, Halmstad University, Halmstad University, School of Business and Engineering (SET), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-4986.

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In this Master Thesis a review of different type of vertical axis wind turbines (VAWT) and a preliminary investigation of a new kind of VAWT are presented.After an introduction about the historical background of wind power, the report deals with a more accurate analysis of the main type of VAWT, showing their characteristics and their operations. The aerodynamics of the wind turbines and a review of different type on generators that can be used to connect the wind mill to the electricity grid are reported as well.Several statistics are also presented, in order to explain how the importance of the wind energy has grown up during the last decades and also to show that this development of the market of wind power creates new opportunity also for VAWT, that are less used than the horizontal axis wind turbine (HAWT).In the end of 2009 a new kind of vertical axis wind turbine, a giromill 3 blades type, has been built in Falkenberg, by the Swedish company VerticalWind. The tower of this wind turbine is made by wood, in order to get a cheaper and more environment friendly structure, and a direct driven synchronous multipole with permanent magnents generator is located at its bottom. This 200 kW VAWT represents the intermediate step between the 12 kW prototype, built in collaboration with the Uppsala University, and the common Swedish commercial size of 2 MW, which is the goal of the company.A preliminary investigation of the characteristics of this VAWT has been done, focusing in particular on the value of the frequency of resonance of the tower, an important value that must be never reached during the operative phase in order to avoid serious damage to all the structure, and on the power curve, used to evaluate the coefficient of power (Cp) of the turbine. The results of this investigation and the steps followed to get them are reported. Moreover a energy production analysis of the turbine has been done using WindPro, as well as a comparison with and older type on commercial VAWT.

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Zavvos, Aristeidis. "Structural optimisation of permanent magnet direct drive generators for 5MW wind turbines." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8299.

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This thesis focuses on permanent magnet "direct drive" electrical generators for wind turbines with large power output. A variety of such generator topologies is reviewed, tested and optimised in an attempt to increase their potential as commercial concepts for the wind industry. Direct drive electrical generators offer a reliable alternative to gearbox drivetrains. This novel technology reduces energy loses thus allowing more energy to be yield from the wind and decreases the maintenance cost at the same time. A fundamental issue for these generators is their large size which makes them difficult to manufacture, transport and assembly. A number of structural designs have been suggested in the literature in an attempt to minimise this attribute. A set of design tools are set out in an attempt to investigate the structural stiffness of the different permanent magnet direct drive generator topologies against a number of structural stresses that apply to such wind turbine energy converters. Optimisation techniques, both analytical and structural, are also developed for minimising the total mass of a variety of "directly driven" machines with power output of 5MW or greater. Conventional and promising generator designs are modelled and optimised with the use of these optimisation techniques. The topologies under examination are then compared in terms of structural mass, stiffness and cost. As the number of wind turbine manufactures who adopt the direct drive concept increases, it is important to outline the unique characteristics of the different topologies and increase their manufacturing potential. Discussions and conclusions will provide an indication of the design solutions that could help decrease the mass and cost of such machines.

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Ross, Ian Jonathan. "Wind Tunnel Blockage Corrections: An Application to Vertical-Axis Wind Turbines." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271306622.

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