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1
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.
Testo completoAbstract (sommario):
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.<br>QC 20100616
2
Fégeant, Olivier. "Noise from wind turbines /." Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3100.
Testo completo
3
Horikiri, Kana. "Aerodynamics of wind turbines." Thesis, Queen Mary, University of London, 2011. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1881.
Testo completoAbstract (sommario):
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.
4
Dunbabin, Penny. "Noise from wind turbines." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/14768.
Testo completoAbstract (sommario):
This thesis is an investigation into the nature of aerodynamic noise emitted by wind turbine blades as they rotate. The main aims of this work were a follows: 1. to give an account of theoretical and experimental work on aerodynamic noise emission from aerofoils, 2. to examine experimental data from a variety of different wind turbines, and to extract from these comparisons information about the influence of different blade design parameters on noise emission, 3. to examine experimentally the influence of tip angle of attack on noise using a new method, 4. to use the information gleaned from (1) and (2) to write a noise prediction program which can be used for any design of horizontal axis wind turbine operating under any reasonable conditions, 5. to compare the predictions with experimental data. The first three chapters consist of background information, concerning the development of wind farms, the noise regulations with which they must comply and the theory of aerodynamic noise emission. The following four chapters contain new work, the principal findings being: 1. Comparisons of experimental noise data from different designs of wind turbines indicate that low frequency noise (less than 250 Hz) is the most sensitive to tip speed, while frequencies between 250 and 630 Hz are less affected, and frequencies in the kHz range are almost unaffected by tip speed. This conflicts with existing noise prediction codes. 2. Noise may increase slightly with tip angle of attack, but this is not pronounced for modern blades with sharp trailing edges. However, there is a significant reduction in high frequency noise (above 1.5 kHz) as the tip angle of attack is reduced in constant winds. In addition, for the turbine studied, a broad aerodynamic peak centred on 630 Hz was observed when the tip angle of attack was reduced. 3. A rotor noise prediction code has been written, which gives accurate results over a range of tip speeds.
5
Farr, Thomas D. "The effects of atmospheric and wake turbulence on wind turbines and wind turbine wakes." Thesis, University of Surrey, 2015. http://epubs.surrey.ac.uk/807177/.
Testo completoAbstract (sommario):
Wind tunnel studies using model wind turbines have been used to investigate the effects and characteristics of neutral and unstable atmospheric boundary layers on their operation and wake behaviour. Wind turbine arrays have also been arranged to observe the effect of wake interaction. Single-point two-component and two-point single-component velocity measurements have been made using laser Doppler anemometry in conjunction with cold-wire anemometry to interrogate the modelled boundary layer. The manufacture and installation of a second traverse mechanism in the wind tunnel was necessary to perform the two-point measurements, along with the development of laboratory software for control and data analysis. In order to allow for measurements of turbine performance, a current sensor was developed so that correlations could be made between velocity and torque fluctuations. Investigation of larger arrays, up to 12 turbines, required the production of additional turbines and installation and subsequent integration of the associated control systems. Measurements made in the neutral flow conditions show that there is an increasing correlation between the upstream turbulence and torque fluctuations with proximity to the turbine, especially in the wake of another turbine where the flow is rapidly evolving. Two-point velocity measurements, with a lateral separation, have shown that there is little effect of the turbine on the correlation of the flow over the rotor disc. Analysis of data from this type of measurement also shows that in an array of four aligned turbines, the spatial structures reach an equilibrium state and are of larger size after the second turbine. Furthermore, the velocity-torque correlation magnitude decreases after the first turbine, but then increases with distance through the array owing to the increased correlation over the rotor disc, although not to the level observed for the first turbine. The turbulence approaching the first turbine behaves in a frozen-flow manner, but this is not true for the second and subsequent turbines, although the idea of convection time still applies. Measurements made in the modelled unstable atmospheric boundary layer show that the length and time scales are changed in the flow, in addition to the alteration of the profiles of mean velocity and Reynolds stresses. The increased turbulence caused by the convective boundary layer increases the rate of wake deficit recovery and does not result in the same spatial structures as the neutral conditions. Temperature effects are of secondary importance with regard to wake and turbine behaviour, with the main driving force behind the performance being the increased turbulence levels.
6
Moor, Gary Duncan. "Optimization of wind energy transfer using wind turbines." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53542.
Testo completoAbstract (sommario):
Thesis (MScIng)--Stellenbosch University, 2003.<br>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.<br>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.
7
Eriksson, Petersen Lovisa. "The impact of wind conditions on wind turbines." Thesis, KTH, Energiteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192535.
Testo completoAbstract (sommario):
The world is facing global warming and the challenge to reduce greenhouse gas emissions. Wind power is a renewable source of energy with no greenhouse gas emissions when operating. Therefore, it could contribute in this challenge. Vattenfall is a Swedish energy company that invests in the wind power business and have many wind turbines in operation. On behalf of Vattenfall this study has been performed with the aim to find how wind conditions affect wind turbines and how it is correlated to amount of alarms, time loss, energy availability and time availability in a wind turbine. Improving this knowledge will be an advantage when making investments in wind turbines and their maintenance. A statistical analysis was conducted in order to examine correlations of wind speed and turbulence intensity with the number of alarms, time loss, energy availability and time availability of a turbine. A case study of Lillgrund, an offshore park in Sweden, was performed since the park layout is tightly spaced and hence interesting in sense of turbulence intensity. Lillgrund suffered to a lot of blade vibration alarms and therefore these alarms were investigated deeper in terms of the wind conditions one hour, one day and one week before the alarm occurred. Four additional parks with other turbine types and manufacturers than Lillgrund’s were also included in the correlation analysis. The amount of alarms per year of each turbine was examined in order to compare this with the failure curve of a wind turbine. The purpose was to see if the wear-out period had started earlier for turbines with certain wind conditions but unfortunately the turbines were not old enough to draw a conclusion. The analysis resulted in positive correlations for high turbulence and high amount of alarms and blade vibration alarms for the Siemens SWT-2.3-93 turbines investigated while there were no clear correlations for time loss, energy availability and time availability. Also, the other turbine types had no strong correlations for the investigated parameters. From the results it can be concluded that there are no strong correlations for the wind conditions investigated and energy availability and time availability. It can also be said that the amount of alarms in Siemens SWT-2.3-93 turbines increases with higher turbulence. Hence, alarms do not influence the energy availability noticeably for this type of turbine.<br>Världen står inför en global uppvärmning och utmaningen att minska utsläppen av växthusgaser. Vindkraft är en förnybar energikälla utan utsläpp av växthusgaser vid drift som skulle kunna bidra positivt i denna utmaning. Vattenfall är ett svenskt energiföretag som investerar i vindkraftsverksamhet och äger många vindkraftverk. Denna studie genomförts på uppdrag av Vattenfall med syfte att finna hur vindförhållanden påverkar vindkraftverk och hur de är korrelerade till mängden av alarm, tidsförlust, energitillgänglighet och tidstillgänglighet i ett vindkraftverk. Att förbättra denna kunskap kommer att vara en fördel när investeringar i vindkraftverk och deras underhåll görs. En statistisk analys genomfördes för att undersöka korrelationer av vindhastighet och turbulensintensitet med antalet alarm, tidsförlust, energitillgänglighet och tidstillgänglighet hos en turbin. En studie av Lillgrund, en havsbaserad park i Sverige, genomfördes då parkens turbiner är placerade tätt intill varandra och därmed ger ett intressant perspektiv på turbulensintensitet. Lillgrund har en stor mängd bladvibrationsalarm och därför har dessa alarm undersökts djupare när det gäller vindförhållandena en timme, en dag och en vecka innan alarmet inträffade. Ytterligare fyra parker med andra turbintyper och tillverkare än Lillgrunds ingick i korrelationsanalysen. Mängden alarm per år för varje turbin undersöktes för att jämföra detta med felintensitetskurvan för ett vindkraftverk. Syftet var att se om utslitningsperioden hade börjat tidigare för turbiner med vissa vindförhållanden men tyvärr var de studerade turbinerna inte tillräckligt gamla för att dra slutsatser kring detta. Analysen resulterade i positiva korrelationer för hög turbulens och hög mängd av alarm och bladvibrationsalarm för de undersökta Siemens SWT-2.3-93-turbinerna medan det inte fanns några tydliga korrelationer för tidsförlust, energitillgänglighet och tidstillgänglighet. Även de andra turbintyperna saknade starka samband för de undersökta parametrarna. Av resultaten kan slutsatsen dras att det inte finns några starka samband för de undersökta vindförhållandena och energitillgängligheten och tidstillgängligheten. Det kan också sägas att mängden alarm i Siemens SWT-2.3-93-turbiner ökar med högre turbulensintensitet. Därför påverkar inte alarm energitillgängligheten märkbart för denna typ av turbin.
8
Lee, Donghoon. "Multi-flexible-body analysis for applications to wind turbine control design." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04052004-180040/unrestricted/lee%5Fdonghoon%5F200312%5Fphd.pdf.
Testo completo
9
Zhang, Zijun Kusiak Andrew. "Wind turbine vibration study a data driven methodology /." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/454.
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10
Homola, Matthew Carl. "Atmospheric icing on wind turbines." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-15209.
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11
Linde, Børge. "Motion of floating wind turbines." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11593.
Testo completoAbstract (sommario):
Motion of floating wind turbines has been studied. A literature study on different concepts and what tools are available for simulating them is presented. Marintek’s simulation software SIMO is used for time simulations. In the calculations, the hydrodynamic forces, mooring line forces and aerodynamic forces from the tower and rotor are taken into account. In addition a pitch control algorithm is used for the rotor blades. Results are compared to available experimental results from model tests. The structure studied is a 5 MW version of the Hywind concept.
12
Moore, Ian F. "Inertial response from wind turbines." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/42939/.
Testo completoAbstract (sommario):
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.
13
Cotton, Ian. "Lightning protection of wind turbines." Thesis, University of Manchester, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578062.
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14
Andrawus, Jesse A. "Maintenance optimisation for wind turbines." Thesis, Robert Gordon University, 2008. http://hdl.handle.net/10059/268.
Testo completoAbstract (sommario):
Wind is becoming an increasingly important source of energy for countries that ratify to reduce the emission of greenhouse gases and mitigate the effects of global warming. Investments in wind farms are affected by inter-related assets and stakeholders’ requirements. These requirements demand a well-founded Asset Management (AM) frame-work which is currently lacking in the wind industry. Drawing from processes, tools and techniques of AM in other industries, a structured model for AM in the wind industry is developed. The model divulges that maintenance is indispensable to the core business objectives of the wind industry. However, the common maintenance strategies applied to wind turbines are inadequate to support the current commercial drivers of the wind industry. Consequently, a hybrid approach to the selection of a suitable maintenance strategy is developed. The approach is used in a case study to demonstrate its practical application. Suitable Condition-Based Maintenance activities for wind turbines are determined. Maintenance optimisation is a means to determine the most cost-effective maintenance strategy. Field failure and maintenance data of wind turbines are collected and analysed using two quantitative maintenance optimisation techniques; Modelling System Failures (MSF) and Delay-Time Maintenance Model (DTMM). The MSF permits the evaluation of life-data samples and enables the design and simulation of a system’s model to determine optimum maintenance activities. Maximum Likelihood Estimation is used to estimate the shape (β) and scale (η) parameters of the Weibull distribution for critical components and subsystems of the wind turbines. Reliability Block Diagrams are designed using the estimated β and η to model the failures of the wind turbines and of a selected wind farm. The models are simulated to assess and optimise the reliability, availability and maintainability of the wind turbine and the farm. The DTMM examines equipment failure patterns by taking into account failure consequences, inspection time and cost in order to determine optimum inspection intervals. Defects rate (α) and mean delay-time (1/γ) of components and subsystems within the wind turbine are estimated. Optimal inspection intervals for critical subsystems of the wind turbine are then determined.
15
Waltham, M. R. "Sailwing vertical axis wind turbines." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316334.
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16
Spinato, Fabio. "The reliability of wind turbines." Thesis, Durham University, 2008. http://etheses.dur.ac.uk/1918/.
Testo completoAbstract (sommario):
The residual scepticism surrounding the installation of wind turbines, is mainly due to the perceived lack of reliability and expense of these energy converters. Because of the commercial significance of reliability, few sources of such data are publicly available, with the result that knowledge of the true reliabihty of wind turbines is fragmentary and sometimes anecdotal, even among operators and professionals in the wind energy industry.
17
Botha, Paul Cedric. "The siting of wind turbines." Master's thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/8288.
Testo completoAbstract (sommario):
Bibliography: leaves 73-82.<br>In September 1984, Guy Roberts completed a report on the cost of wind energy in South Africa. His results showed that wind-energy in South Africa was uneconomical, but they suggest that at locations with higher wind speeds, the cost of wind power would approach the South African grid electricity cost. Knowing that locations with high annual average wind speeds would make the most suitable wind turbine sites, it was decided to investigate the wind enhancement, due to localized topography in such areas. Existing available wind data, together with previous studies on the South African wind energy potential suggested that the site worthy of investigation was in the vicinity of Cape Agulhas. A number of methods of ascertaining the wind potential over a given region were considered for investigating the area of interest. The two readily available techniques, physical and numerical modeling, were chosen to investigate the topographical wind enhancement. Previous work done on the siting of wind turbines using physical modeling was investigated prior to proceeding with the construction of and experimentation with a scale model. The utilization of two modeling techniques enabled the direct comparison of results.
18
Peesapati, Vidyadhar. "Lightning protection of wind turbines." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/lightning-protection-of-wind-turbines(e710c763-840e-4b76-b7a5-0d006c4e0983).html.
Testo completoAbstract (sommario):
Wind turbines are the largest contributor to renewable energy both in Britain and the rest of Europe. With a rise in the installed capacity and an increase in offshore wind energy due to governments green targets by 2020, there has been a large development in new wind turbines for optimized performance. The present thesis deals with the uncertainties in regards to the lightning phenomenon on wind turbines with emphasis on the rotor blades. Rotor blades are the most expensive part to replace in the event of lightning related damage. The research presents results based on lightning data analysis on wind turbines, backed up by finite element analysis testing of wind turbine systems. The final chapters include the testing and improving of lightning protection systems installed on modern day rotor blades. The first part of the thesis deals with the theoretical understanding of the lightning phenomenon and its effect on wind turbine systems. The core work of the research begins with the analysis of lightning data collected over Nysted wind farm and different wind turbines installed over the world. The data analysis helps in identifying the parts of the wind turbine that are at high risk to lightning attachment and related damage. The peak current levels of the lightning strikes seen on the wind turbine are compared with those in modern day lightning standards, and show that historic data in the standards are not an exact match to the real case scenarios. The lightning data analysis also sheds light into the importance of upward initiated lightning, which will become important for large wind turbines, especially in their new offshore environment. A full scale 3D FEA model of a wind turbine, with lightning protection systems installed in its rotor blades, is subjected to electrical stresses to find likely attachment points in regards to upward initiated lightning, and these results are later compared to those found in the data analysis. The second half of the thesis deals with the testing of new materials and prototype blades, to be introduced to reduce their radar cross section. The new materials include a large amount of carbon content which affects the efficiency of the lightning protection system. High voltage and high current tests backed up with finite element analysis have been performed to find how these new materials affect the performance of the lightning protection system. The results indicate that further work needs to be done before these new materials can be integrated into the blade, as they increase the risk of lightning related damage to the blade.
19
Pang, Zhongyuan. "Dynamic models for wind turbines." Thesis, Pang, Zhongyuan (2014) Dynamic models for wind turbines. Other thesis, Murdoch University, 2014. https://researchrepository.murdoch.edu.au/id/eprint/23213/.
Testo completoAbstract (sommario):
With the increase of wind power capacity, wind energy is now becoming an essential part of energy production system. High wind power penetration may increase the instability of grid due to the characteristic of wind. Fortunately, with the development of power electronics, it is possible to provide a relatively stable energy production by applying power electronics to wind turbine.
Due to the complexity of wind turbine, a generic dynamic model of wind turbine can be helpful. The objective of the work is to develop a general wind turbine models that can be used for investigations.
The report had tracked the theory of wind turbine and its development, three different kinds of wind turbine are included, which are fixed speed wind turbine, variable slip wind turbine and doubly-fed induction generator wind turbine. Fundamental working theory and a model built by Matlab was provided for each of technology.
Assessment for the models was done to prove that it has the ability to reflect the characteristic of wind turbine. Despite from that, the models were done in three phase, so it has the ability to do with load flow analysis or grid stability.
20
Běťáková, Vendula. "Visual preferences for wind turbines." Doctoral thesis, Česká zemědělská univerzita v Praze, 2016. http://www.nusl.cz/ntk/nusl-261409.
Testo completoAbstract (sommario):
This dissertation is a selection of three papers focused on visual preference of wind turbines. Visual impact presents the connectivity of the articles, whereas each one deals with the topic from different perspective. First paper "Wind turbines location: How many and how far?" analyses in detail the characteristics of wind turbines themselves, i.e. their number and distance from observer or vantage point in relation to landscape quality. Second paper "How education orientation affects attitudes toward wind energy and wind farms: implications for the planning process" concentrates on respondents´ characteristics, in particular educational orientation, general attitude, occurrence of WTs in respondents´ vicinity and willingness to live close to WTs. Whereas first two papers use same assessment method to analyse differences of WTs perception from different point of view, the third paper "Futuristic Wind Power Systems Suitable as Artistic Sculptures" presents review of WTs appearance in general and proposals of possible future look as an alternative to traditional wind turbines.
21
Zhang, Zijun. "Performance optimization of wind turbines." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3024.
Testo completoAbstract (sommario):
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.
22
Ndzukuma, Sibusiso. "Statistical tools for wind energy generation." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1020627.
Testo completoAbstract (sommario):
In this study we conduct wind resource assessment to evaluate the annual energy production of a wind turbine. To estimate energy production of a wind turbine over a period of time, the power characteristics of the wind turbine are integrated with the probabilities of the wind speed expected at a chosen site. The first data set was obtained from a wind farm in Denmark. We propose several probability density functions to model the distribution of the wind speed. We use techniques from nonlinear regression analysis to model the power curve of a wind turbine. The best fit distribution model is assessed by performing numeric goodness–of–fit measures and graphical analyses. Johnson’s bounded (SB) distribution provides the best fit model with the smallest Kolmogorov–Smirnov (K-S) test statistic . 15. The four parameter logistic nonlinear regression (4PL) model is determined to provide the best fit to the power curve data, according to the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC). The estimated annual energy yield is compared to the actual production of the wind turbine. Our models underestimate the actual energy production by a 1 difference. In Chapter Six we conduct data processing, analyses and comparison of wind speed distributions using a data set obtained from a measuring wind mast mounted in Humansdorp, Eastern Cape. The expected annual energy production is estimated by using the certified power curve as provided by the manufacturer of the wind turbine under study. The commonly used Weibull distribution is determined to provide the best fit distribution model to our selected models. The annual energy yield is estimated at 7.33 GWh, with a capacity factor of 41.8 percent.
23
Veldkamp, Herman Frederik. "Chances in wind energy : a probabilistic approach to wind turbine fatigue design /." [Delft] : DUWIND Delft Univ. Wind Energy Research Inst, 2006. http://www.gbv.de/dms/bs/toc/520167805.pdf.
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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.
Testo completoAbstract (sommario):
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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Santos, Richard A. "Damage mitigating control for wind turbines." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3256394.
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Wisznia, Roman. "Condition Monitoring of Offshore Wind Turbines." Thesis, KTH, Kraft- och värmeteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-118455.
Testo completoAbstract (sommario):
The growing interest around offshore wind power, providing at the same time better wind conditions and fewer visual or environmental impacts, has lead many energy suppliers to consider the installation of offshore wind farms. However, the marine environment makes the installation and maintenance of wind turbines much more complicated, raising the capital and operation costs to an undesirable level and preventing the fast progression of this technology worldwide. Availability of offshore wind turbines varies between 65 and 90% depending on location, whereas onshore turbines range between 95 and 98% in most cases. In 2009, the ETI launched a research project aiming to improve economical efficiency of offshore wind farms by increasing their availability and decreasing their maintenance costs (partly through replacing corrective maintenance by preventive maintenance). This project named “Inflow” involves the development of a condition monitoring system, a system designed to monitor the state of different wind turbine components, and to analyze this data in order to determine the wind turbines overall condition at any given time, as well as its potential system ailments This paper describes two different approaches to perform the condition monitoring of offshore wind farms, the first one involves thresholds-based analysis, while the other involves pattern recognition.
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Drew, Daniel. "Analysis tools for urban wind turbines." Thesis, University of Reading, 2011. http://centaur.reading.ac.uk/35837/.
Testo completoAbstract (sommario):
With the UK seeking to increase the contribution of microgeneration, the number of small wind turbines installed in urban areas has increased. However, a wide-spread experience is that urban located turbines have generated considerably less energy than anticipated. This thesis demonstrates that poor turbine placement, due to inadequacies in commonly used wind resource modelling and assessment techniques, has played a large part in this disappointing outcome. The current site assessment tools estimate a turbine's performance at a potential site using a method developed for large scale wind energy projects in rural areas. Using data measured at 91 Met Office weather stations across the UK and a rooftop site in London, this thesis shows that when applied in urban areas, this method can lead to large errors in the predicted energy production of a small wind turbine. The magnitude of these errors is such that the tools cannot consistently identify the economic viability of a turbine/site combination. This is largely due to a simplified representation of the site's wind resource. By not considering the decelaration of the wind by friction, there are large errors in the predictions of a site's annual mean wind speed. Across the sites there is a mean error of over 40% and 18% for the DECC wind speed database and the Carbon Trust tool respectively. Furthermore, analysis of data collected at the roof top site shows that due to high levels of turbulence in urban areas, a Weibull distribution does not provide a sufficient representation of the temporal variability of a site's wind resource. 1 Subsequently the thesis develops an improved, more reliable means of predicting mean wind speed at urban sites by considering interactions between the flow and the morphology of built-up areas in more detail than has been possible previously. When applied to the Greater London area the model shows that turbines generally perform better towards the outskirts of the city, however there are some sites with good wind resource close to the city centre with low aerodynamic roughness.
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Crabtree, Christopher James. "Condition monitoring techniques for wind turbines." Thesis, Durham University, 2011. http://etheses.dur.ac.uk/652/.
Testo completoAbstract (sommario):
This thesis focuses on practical condition monitoring of wind turbines. With offshore wind playing an increasing part in UK electricity generation, prompt fault detection leading to preventative maintenance is gaining in importance. This work describes the development of a condition monitoring test rig and the innovation and application of signal processing techniques for the detection of faults in non-stationary signals. Work is supported throughout by information from wind turbine operators and their experiences of variable speed, variable load wind turbines in the field. Experimental work is carried out on a condition monitoring test rig comprising a wound rotor induction generator, gearbox and DC driving motor. The test rig operates at variable speed and allows the implementation of a number of fault-like conditions including rotor electrical asymmetry, shaft mass unbalance and gear tooth failure. Test rig instrumentation was significantly developed during this research and both electrical and mechanical condition signals are monitored. A signal processing algorithm was developed based on experience with analysis techniques and their relationship with the characteristics of a wind turbine. The algorithm is based on Fourier analysis and allows the analysis of fault-related speed-dependent frequencies within non-stationary signals such as those encountered on a wind turbine. The detection of different faults is discussed and conclusions drawn on the applicability of frequency tracking algorithms. The newly developed algorithm is compared with a published method to establish its advantages and limitations.
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Wilkinson, Michael Richard. "Condition Monitoring for Offshore Wind Turbines." Thesis, University of Newcastle Upon Tyne, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492117.
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Goodfellow, David. "Variable speed operation of wind turbines." Thesis, University of Leicester, 1986. http://hdl.handle.net/2381/7822.
Testo completoAbstract (sommario):
This work describes a control system in which a cycloconverter is connected between the secondary windings of a three phase induction machine and the a. c. mains supply to give variable speed sub- and super –synchronously. In order to control the system smoothly in an asynchronous mode a secondary emf signal generator has been designed, which enables the cycloconverter to operate in synchronism with the emf induced in the secondary windings of the machine. A computer programme has been written which calculates the required firing angles for the cycloconverter to produce secondary current in phase with the secondary emf in the machine. An electronic system has been built which ensures that these firing angles are used by the cycloconverter during actual operation. A cycloconverter has been built, using an effective six phases of mains supply, and has been successfully operated over a range of 20% about synchronous speed in both generating and motoring modes. Results show the ability of the cycloconverter to drive the machine up from standstill as a motor to just below 20% subsynchronous speed. An on-line computer simulation of a wind turbine has been developed which enables an assessment of variable speed generation applied to wind turbines to be achieved. This simulation, in connection with a d. c. machine and thyristor controller, can be used to drive the shaft of the induction machine and assess operation of the cycloconverter control scheme under actual wind turbine operating conditions.
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Roynarin, Wirachai. "Optimisation of vertical axis wind turbines." Thesis, Northumbria University, 2004. http://nrl.northumbria.ac.uk/1655/.
Testo completoAbstract (sommario):
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/.
Testo completoAbstract (sommario):
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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Tracy, Christopher (Christopher Henry). "Parametric design of floating wind turbines." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40877.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.<br>Includes bibliographical references.<br>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.<br>by Christopher Tracy.<br>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.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.<br>"February 2012." Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 84-86).<br>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.<br>by Thomas Luypaert.<br>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.
Testo completoAbstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 64-65).<br>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.<br>by Carlos Casanovas.<br>S.M.
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Gomez-Iradi, Sugoi. "CFD for Horizontal Axis Wind Turbines." Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511051.
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Dymock, Ben R. "Urban wind turbines : a feasibility study." Thesis, London South Bank University, 2017. http://researchopen.lsbu.ac.uk/1864/.
Testo completoAbstract (sommario):
There is an existing body of research into noise, vibration and wind regime concerns associated with urban wind turbines demonstrating the detrimental effects of these topics on the energy yield potential and therefore financial worth of an installation. Much of the research has focused on wind regime assessment and optimum roof top placement via CFD modeling offering generalised guidelines showing a potential for wind power to contribute towards lowering London's CO2 emissions. Unfortunately, without benefiting from appropriate planning assessment, a number of early urban turbines failed and have risked irreversibly tarnishing the concept. Hitherto no studies have been specifically conducted on the urban potential of building integrated wind turbines. As integration is bespoke, typically determined by the architecture, it is unknown whether existing guidelines for roof mounted wind turbines could be directly applied. It is probable that each installation would merit its own assessment and analysis procedure. This study aims to investigate the differences between roof mounted and building integrated turbines in terms of assessment, operation and urban potential. In response to these differences it is intended to demonstrate how a successful installation can be achieved. Comparisons between two urban sites, one smaller, roof mounted HAWT and one larger, building integrated HAWT have been made via noise, vibration, CFD and atmospheric data recorded and analysed over two years to build a comprehensive understanding of the inherent urban issues. The prospect of successfully situating an urban turbine is complex in nature and considering the high installation costs and high level of design and engineering required to do so it is imperative that their energy yield provide a satisfactory return on investment and efficient supply of power without adversely impacting upon the surrounding environment or themselves. This study concludes that a multifaceted approach is necessary to achieve an efficient building integrated turbine, comprised of: (i) accurate local noise surveys to establish the local acoustic environment to inform acceptable turbine operating ranges, (ii) specific noise modeling of manufacturer provided data or, where none is available, acoustic testing of the proposed turbine across all applicable wind speed ranges, (iii) comprehensive vibration assessment, not only of the turbine tower/system but also of the turbine housing and any lower residential floors to ensure no natural frequencies will be excited and to prevent any vibration transmission via appropriate mounting, isolation or damping where necessary, (iv) the acquirement of site specific wind data to inform architectural design, turbine selection and placement. If monitoring at hub height is not possible it has been found that it may be acceptable to monitor in close proximity and then extrapolate the results using CFD analysis and wind profile methods, (v) CFD modeling of the surrounding topography, the turbine mount and/or enclosure. These areas are discussed with potential areas of noise and vibration control and turbine optimisation, specific to the case studies, investigated. Further to the aforementioned study an investigation into a new method of assessing noise and vibration levels associated with average anemometry recorded wind speeds has been presented so as to attain average levels per wind speed bin without being skewed by impulsive gusts.
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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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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.
Testo completoAbstract (sommario):
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.<br>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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Floridia, Daniele. "Hybrid foundations for offshore wind turbines." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3284/.
Testo completoAbstract (sommario):
Nowadays offshore wind turbines represents a valid answer for energy production but with an increasing in costs mainly due to foundation technology required. Hybrid foundations composed by suction caissons over which is welded a tower supporting the nacelle and the blades allows a strong costs reduction. Here a monopod configuration is studied in a sandy soil in a 10 m water depth. Bearing capacity, sliding resistance and pull-out resistance are evaluated. In a second part the installation process occurring in four steps is analysed. considering also the effect of stress enhancement due to frictional forces opposing to penetration growing at skirt sides both inside and outside. In a three dimensional finite element model using Straus7 the soil non-linearity is considered in an approximate way through an iterative procedure using the Yokota empirical decay curves.
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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.
Testo completoAbstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (page 65).<br>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.<br>by Yu Zhang.<br>S.M.
42
Poole, Sean. "The development of a segmented variable pitch small horizontal axis wind turbine with active pitch control." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1020583.
Testo completoAbstract (sommario):
Small scale wind turbines operating in an urban environment produce dismal amounts of power when compared to their expected output [1-4]. This is largely due to the gusty wind conditions found in an urban environment, coupled with the fact that the wind turbines are not designed for these conditions. A new concept of a Segmented Variable Pitch (SVP) wind turbine has been proposed, which has a strong possibility to perform well in gusty and variable wind conditions. This dissertation explains the concept of a SVP wind turbine in more detail and shows analytical and experimental results relating to this concept. Also, the potential benefits of the proposed concept are mentioned. The results from this dissertation show that this concept has potential with promising results on possible turbine blade aerofoil configurations. Scaled model tests were completed and although further design optimisation is required, the tests showed good potential for the SVP concept. Lastly a proof-of-concept full scale model was manufactured and tested to prove scalability to full size from concept models. Along with the proof-of-concept full scale model, a wireless control system (to control the blade segments) was developed and tested.
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Clohessy, Chantelle May. "Evaluation of noise levels of micro-wind turbines using a randomised experiment." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1015974.
Testo completoAbstract (sommario):
One of the biggest environmental concerns of a wind turbine is the wind turbine noise (Prospathopoulos and Voutsinas, 2007). This study assesses the noise impacts of wind turbines on the environment by comparing the micro-wind turbine noise to traditional accepted surrounding sounds. The collection of the sound level data was done by using a randomised experiment. The sound level data was then fitted to a General Linear Model to determine the relationship between the sound levels generated at a given site to the time of day, wind speed, wind direction and distance from the sound source. An additional study was conducted to determine the relationship between wind speed and the sound levels of wind turbines. The distribution of frequency components of wind turbine sound was also determined.
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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.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005.<br>Includes bibliographical references (leaf 55).<br>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.<br>by Kwang Hyun Lee.<br>S.M.
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Ross, Ian J. "Wind tunnel blockage corrections : an application to vertical-axis wind turbines /." Dayton, Ohio : University of Dayton, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271306622.
Testo completoAbstract (sommario):
Thesis (M.S. in Aerospace Engineering) -- University of Dayton.<br>Title from PDF t.p. (viewed 06/22/10). Advisor: Aaron Altman. Includes bibliographical references (p. 101-104). Available online via the OhioLINK ETD Center.
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Poole, Sean Nichola. "Optimisation of a mini horizontal axis wind turbine to increase energy yield during short duration wind variations." Thesis, Nelson Mandela Metropolitan University, 2017. http://hdl.handle.net/10948/7036.
Testo completoAbstract (sommario):
The typical methodology for analytically designing a wind turbine blade is by means of blade element momentum (BEM) theory, whereby the aerofoil angle of attack is optimized to achieve a maximum lift-to-drag ratio. This research aims to show that an alternative optimisation methodology could yield better results, especially in gusty and turbulent wind conditions. This alternative method looks at increasing the aerofoil Reynolds number by increasing the aerofoil chord length. The increased Reynolds number generally increases the e_ectiveness of the aerofoil which would result in a higher or similar lift-to-drag ratio (even at the decreased angle of attacked require to maintain the turbine thrust coe_cient). The bene_t of this design is a atter power curve which causes the turbine to be less sensitive to uctuating winds. Also, the turbine has more torque at startup, allowing for operatation in lower wind speeds. This research is assumed to only be applicable to small wind turbines which operated in a low Reynolds number regime (<500 000), where Reynolds number manipulation is most advantageous.
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Walsh, Justin M. "Composite material bend-twist coupling for wind turbine blade applications." Laramie, Wyo. : University of Wyoming, 2009. http://proquest.umi.com/pqdweb?did=1965523621&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Testo completo
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Newey, Kerryn Brett. "The development of an optimised rotor software design tool to improve performance of small horizontal axis wind turbines." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1009431.
Testo completoAbstract (sommario):
Horizontal axis wind turbines are by far the most common and well understood forms of wind turbine. Typically a large amount of research and development has been invested in the technology of large scale wind turbines. Unfortunately, development of small machines (rotor diameter smaller than 10 metres) has not been as forthcoming. The advantages of small turbines are that they are accessible to the individual consumer and they are a very attractive project for the home builder. The disadvantage of small turbines is that due to the negative influence of economies of scale, they tend to be costly in relation to their power output and suffer from a long-term return on investment. Furthermore, trends in the wind industry have shown that smaller machines tend to be relatively simple devices that have been developed with very little research and development. As a result, small turbines can be inefficient, unreliable and expensive to maintain. In many cases rotor design is less than optimal, with very little blade refinement. This is especially critical for small rotors due to low Reynolds Number operation. Further exacerbating the problem is that the rotors are typically not well matched to the generator. In many cases the machines are not suited to the wind speed range in which they are designed to operate, reducing the financial viability due to poor performance. It is envisaged that by applying optimising techniques and automating some of the design complexities into a software design tool, more cost-effective and viable machines can be developed that will deliver improved performance and therefore become more financially viable.
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Halliday, J. A. "Wind meteorology and the integration of electricity generated by wind turbines." Thesis, University of Strathclyde, 1988. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21325.
Testo completoAbstract (sommario):
The generation of electricity using wind turbines is now widespread and commercially viable. There are two aspects of wind energy which are critically important. Firstly, the evaluation of the wind resource, both on nationally and on a local scale. Secondly, the integration of electricity generated by wind turbines into existing electricity grids without reducing the reliability of supply or reducing the overall economic efficiency of the system. This thesis examines both these aspects. Chapters 3 and 4 are concerned with the large scale utilisation of wind energy. Chapter 3 discusses the suitability for wind energy evaluation of the data held by the UK Meteorological office, describes the results of a detailed examination of over 130 station-years of hourly data, and recommends areas of further study as well as a UK standard for site description. Chapter 4 describes a computer model used to examine the effects of integrating wind-generated electricity into the CEGB National Grid and the results obtained with it. The relative importance of dispersal of wind turbines, load and wind forecasting, variation of turbine characteristics and inter-annual variability of wind speed is determined. Chapters 5 and 6 are concerned with a detailed evaluation of thewind energy potential on the Shetland island group. Chapter 5 describes the planning, testing and installation of two hill-top monitoring stations on Shetland and the results found. Chapter 6 describes the development of a computer model of the Shetland Power Station, which is used to examine how the introduction of wind turbines would affect the operation of the power station and the maximum energy penetration possible before power cuts occur. Both chapters conclude with detailed recommendations which will be of worldwide use as the wind energy potential of other diesel-fuelled grids is determined.
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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.
Testo completo