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1
Payer, Tilman. "Modelling extreme wind speeds." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-67547.
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Conan, Boris. "Wind resource accessment in complex terrain by wind tunnel modelling." Phd thesis, Université d'Orléans, 2012. http://tel.archives-ouvertes.fr/tel-00843645.
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To benefit from strong winds, an increasing number of wind turbines are placed in complex terrains. But complex terrains means complex flows and difficult wind resource assessment. This study proposed to use wind tunnel modelling to evaluate the wind in a complex topography. The goal of this study is to evaluate the possibilities of wind resources assessment by wind tunnel modelling and to quantify the important modelling parameters. The lower part of the atmosphere, the atmospheric boundary layer (ABL) is defined by a velocity and a turbulence gradient. The ABL is reproduced in the wind tunnel by placing obstacles and roughness elements of different size representative to the type of terrain desired. The flow produced in the wind tunnel is validated against field data and a wise choice of the obstacles is discussed to reproduce the desired wind profile. The right reproduction of the inflow conditions is found to be the most important parameter to reproduce. The choice of the area to reproduce around a site in usually difficult to make in order to keep a low scaling factor and to account for the surrounding topography. A series of tests on simplified hills helps the experimentalist in this choice by enlightening the longitudinal and vertical extension of the wake downstream different hills shapes. Finally, two complex topographies are studied in two wind tunnels, the Bolund hill in Denmark and the Alaiz mountain in Spain. The results are giving good results, 5 to 10 %, for predicting the wind speed but more scatter is observed for the modelling of the turbulence, up to 100 %. The laboratory simulation of atmospheric flows proves to be a demanding but reliable tool for the prediction of the mean wind speed in complex terrain.
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Alisar, Ibrahim. "Stochastic Modelling Of Wind Energy Generation." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614930/index.pdf.
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In this thesis work, electricty generation modeling of the wind energy -one type of the
renewable energy sources- is studied. The wind energy characteristics and the distribution of
wind speed in a specific region is also examined. In addition, the power curves of the wind
turbines are introduced and the relationship between the wind speed and wind power is
explained. The generation characteristics of the wind turbines from various types of
producers are also investigated. In this study, the main wind power forecasting methods are
presented and the advantages and disadvantages of the methods are analyzed. The physical
approaches, statistical methods and the Artificial Neural Network (ANN) methods are
introduced. The parameters that affect the capacity factor, the total energy generation and the
payback period are examined. In addition, the wind turbine models and their effect on the
total energy generation with different wind data from various sites are explained. As a part
of this study, a MATLAB-based software about wind speed and energy modelling and
payback period calculation has been developed. In order to simplify the calculation process,
a Graphical User Interface (GUI) has been designed. In addition, a simple wind energy
persistence model for wind power plant operator in the intra-day market has been developed.
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Poushpas, Saman. "Wind farm simulation modelling and control." Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27911.
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The increasing trend towards large-scale deployment of wind energy imposes numerous operational challenges regarding large integration of wind power to the transmission system including the maintenance of system stability due to the uncertain nature of wind power. Thus, the traditional way of operating and controlling wind turbines and wind power plants are becoming less acceptable. Furthermore, wind power plants are progressively being subjected to the Transmission network operators (TSO's) regulations and are required to operate as a single controllable unit, similar to the conventional power plants, to provide active power regulation. To provide such a functionality, wind turbines in a wind farm must provide more flexible output power control in a quick and safe operating manner. Additionally, the operation of the wind turbines must be coordinated so as to operate the whole wind power plant as a single controllable entity. The main goal of this thesis is to generate a wind farm Simulink model that captures all the essential dynamics for the wind farm controller design and load analysis. To achieve this main aim, a mathematic wind farm model has been developed which offers sufficiently fast simulation for iterative controller design task, and contains a suitable wind-field model that provides a suitable representation of the wind-field and wake propagation through the wind farm. The wind farm controller design with the objectives of primary frequency response and power optimisation has also been investigated.
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Haglund, El Gaidi Sebastian. "Partially Parabolic Wind Turbine Flow Modelling." Thesis, KTH, Mekanik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-226309.
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Climate change is an evermore urging existential treat to the human enterprise. Mean temperature and greenhouse gas emissions have in-creased exponentially since the industrial revolution. But solutions are also mushrooming with exponential pace. Renewable energy technologies, such as wind and solar power, are deployed like never before and their costs have decreased significantly. In order to allow for further transformation of the energy system these technologies must be refined and optimised. In wind energy one important field with high potential of refinement is aerodynamics. The aerodynamics of wind turbines constitutes one challenging research frontier in aerodynamics today. In this study, a novel approach for calculating wind turbine flow is developed. The approach is based on the partially parabolic Navier-Stokes equations, which can be solved computationally with higher efficiency as compared to the fully elliptic version. The modelling of wind turbine thrust is done using actuator-disk theory and the torque is modelled by application of the Joukowsky rotor. A validation of the developed model and force implementation is conducted using four different validation cases. In order to provide value for industrial wind energy projects, the model must be extended to account for turbulence (and terrain in case of onshore projects). Possible candidates for turbulence modelling are parabolic k-ε and explicit Reynolds stress turbulence models. The terrain could possibly be incorporated consistently with the used projection method by altering the finite difference grid layout.
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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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Maldonado, Jose Miguel. "MODELLING WIND FLOW THROUGHCANOPIES SYSTEMS USING OPENFOAM." Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-15461.
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The most proper emplacements for set a wind farm are already taken or cannot be used forenvironmental causes. So in order to check the viability of the complex terrain locations whichare still available Computational Fluid Dynamics tools are used. As the commercial codes arenot flexible enough and very expensive, an open software will be used OpenFOAM.OpenFOAM needs a code for accomplish the simulation; this code is programmed in C++. Theterrain roughness, the Coriolis force and the gravity force were developed, so the next step willbe to include the effect of canopies systems in the flow simulations.Although it could be considered as roughness, it is suggested to add a forest canopy model inorder to forecast the behaviour of the wind flow over the forests.Along this document it will be shown the process followed in order to insert the canopiessystems in the CFD software. This achievement has two mains goals: Pre-processing tool which will insert the canopy parameters in the mesh of thedomain. This application will situate the forest along the studied case. The second goal is to develop a solver which take into account the effect caused by thecanopy.Once both of them are made, as there is no software which includes this kind of obstacles inthe airflow, the results just can be checked by an experimental research but that experiment issuggested as future work because it is out of this thesis. So it will be checked that the canopyparameters are uploaded to the case, and that the airflow is disturbed in a consequently wayby any forest.
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zafar, syed hammad. "Modelling and control of large wind turbine." Thesis, Karlstads universitet, Avdelningen för fysik och elektroteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-30703.
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In order to make the wind energy an economical alternative for energy production, upscaling of turbine to 10 - 15MW may be necessary to reduce the overall cost of energy production. This production target requires a considerable increase in the turbine size and placing the turbines at high wind speed locations. But increase in turbine size also increases the uneven load distribution across the turbine structure. Therefore an efficient load reduction technique is necessary to increase the turbine reliability in high wind speed locations. Variable speed wind turbine offers most desirable load reduction through actively pitch angle control of turbine blades. Research has shown that the Individual Pitch Control (IPC) is most promising option for turbine load reduction. This thesis work is focused on modelling of a large wind turbine and implementation of a new mutlivariable control concept for turbine load reduction. A detailed mathematical model is designed which includes turbine blade and tower dynamics and a proposed Linear Quadratic Gaussian (LQG) algorithm is implemented for Individual Pitch Control (IPC) loop of wind turbine. Proposed model in this thesis work is derived from the previous turbine model used in ECN with additional tower dynamics. My contribution in turbine modelling portion is to linearize the equations of motion to form a statespace model and to implement LQG algorithm for turbine active load reduction. This proposed method is compared with the previous control technique used in ECN for turbine fatigue load reduction to measure the overall efficiency of the proposed technique. Fatigue load has major effect on the turbine working age. In quantitative way, proposed LGQ design offers 8-10% approx. more fatigue load reduction in comparison with the previous design. In simple convention, decrease in turbine fatigue load increases the turbine age. This 8 - 10% fatigue load reduction offers 8 - 10% minimum increase in turbine working age which means that if a turbine works for 20 years in total for energy production, this proposed technique will add 2 extra years into the turbine working life. This age increase has major economic impact to make the wind turbine a viable alternative for energy production.
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Chane, Kon Laurent. "Wind erosion modelling of stockpiles and embankments." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408520.
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Renström, Joakim. "Modelling of ice throws from wind turbines." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-251292.
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As the wind energy sector expands into areas with colder climate, the problem with ice throw will increase. Due to a rotor diameter of more than 120 meters for a typical modern turbine with an effect of 3.3 MW, the separated ice fragment will get a high initial velocity, and therefore, they will also be thrown a long distance. Ice throw might therefore be a large safety risk for the people, who are staying in surrounding areas to wind turbines. A ballistic ice throw model has been developed to be able to investigate how far the ice fragments can be thrown from a wind turbine. The work was divided into two parts, one sensitivity analysis and one real case study. In the sensitivity analysis, the influence of eight important parameters was investigated. The results from this part show that changes in the parameters initial radius and angle position, and mass and shape of the ice fragments have a significant influence on the throwing distance both lateral and downwind. The wind speed has only a significant influence on the downwind throwing distance, but this is quite large. A maximum throwing distance of 239 meters downwind the wind turbine was achieved with U=20 m/s, r=55 m and θ=45°. While including the lift force, a maximum downwind distance of 350 meter was achieved. However, the uncertainties about the shape of the ice fragment make these results quite uncertain. In the real case study, ice throws were simulated by letting the ice throw model run with modeled meteorological data for a wind farm in northern Sweden. The wind farm consists of 60 wind turbines, and the probability for that an ice fragment will land in a square of 1*1m was calculated around each turbine. To be able to calculate this probability, a Monte Carlo analysis was necessary in which a large number of ice fragments were separated. The result shows a large correlation between the landing positions of the ice fragments and the wind direction. Due to the fact that the wind farm is located in a complex terrain, the shape and density of the probability field vary among different parts of the farm. Especially in the southern part of the wind farm, the probability field will have the highest density and largest extension to the northeast of the turbines due to a prevailing wind direction during ice throw events from southwest.När vindkraftssektorn expanderar till områden med ett kallare klimat, kommer problemet med nedisade vindkraftverk och iskast att öka. Moderna vindkraftverk kan ha en typisk effekt på 3.3 MW och en rotordiameter på över 120 meter, vilket resulterar i att de ivägkastade isbitarna skulle kunna få en initialhastighet på 90 m/s. Det skulle även resultera i att isbitarna kastas iväg en lång sträcka från kraftverket, vilket i kombination med den höga initialhastigheten skulle kunna bli en stor säkerhetsrisk för de personer som vistas i områdena närmast runt vindkraftverken. En ballisisk iskastmodel utvecklades för att beräkna hur långt från vinkraftverket isbitarna kan kastas. Arbetet delades upp i två delar, en känslighetsanalys och en verklig fallstudie. I känslighetsanalysen undersöktes åtta viktiga parametrars inflytande på iskastet. Resultatet från den visar på att ändringar i parametrarna isbitens massa och form samt seperations positionen på bladet och bladets vinkel hade störst inverkan på kastlängden. En maximal kastlängd nedströms vindkraftverket på 239 meter erhölls för U=20m/s, θ=45° och r=55m. När lyftkraften inkluderades ökade kastlängden nedströms till 350 meter, dock är osäkerheten i isbitarnas form stor, vilket gör dessa resultat osäkra. I den verkliga fallstudien simulerades iskast genom att iskastmodellen kördes med modellerad meteorologisk data från en vindkraftspark i norra Svergie. Vinkraftsparken innehöll 60 turbiner och sannolikheten för att en isbit ska landa i en ruta på 1*1m beräknades runt varje turbin. För att kunna beräkna sannolikheten användes en Monte Carlo analys där ett stort antal isbitar skickades iväg. Resultatet visade på att korrelationen var stor mellan sannolikheten för att en isbit ska landa i en ruta på 1 m² och vindriktningen. Eftersom vindkraftsparken var belägen i ett område med en komplex terräng varierade formen och intensiteten på sannolikhetsområdena mellan olika delar av parken. Speciellt i parkens södra del är sannolikhetsområdet för vindkraftsverken mer utbrett i nordostlig riktning på grund av att sydvästliga vindar är vanligast då iskast förekommer.
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Stangroom, Paul. "CFD modelling of wind flow over terrain." Thesis, University of Nottingham, 2004. http://eprints.nottingham.ac.uk/10112/.
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The aim of this project is to show the capabilities of a RANS based numerical model in accurately analysing wind flow over real terrain regions, and assess its usage for wind energy applications. The main reasons this type of model is not widely used in the wind energy industry are due to the computational cost and the expertise required to operate such a model. These factors are assessed and various setups of the model are examined to consider the accuracy attained. The modelling process is also automated to reduce necessary user input in the process. The models performance is tested over a number of terrain types: Flat terrain (with surface roughness), an axisymmetric hill and a real terrain region (the Askervein hill). Primary consideration is given to velocity speed-up predictions which are paramount when considering the energy availability in the wind. A number of turbulence models have been tested for each terrain region to assess the improved accuracy obtained by using a more complicated CFD setup. The mesh discretisation has also been analysed for sensitivity to change, providing a comprehensive analysis of wind flow over Askervein. The CFD setup process is automated to reduce the time taken in setting up a model and increase the speed of providing a full wind field assessment for all wind directions, and allowing determination of average yearly values of velocity. This improves the access to such models for non-expert users and improves the availability of the model to wind energy developers siting farms in complex terrain regions. The model is shown to perform well for all terrain and roughness types. The turbulence properties are not well modelled, and that is a known limitation of this model type. The project demonstrates the advantages of CFD models for wind energy applications through the presented results and successful automation of the process.
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Hall, Phillip. "Numerical modelling of wind-induced lake circulation." Thesis, University of Birmingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511642.
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The main objective of this study was to develop a stable numerical model capable of simulating the three-dimensional steady-state wind-driven circulation in a lake. Firstly, the relevant differential equations were derived from the Navier-Stokes equations by making certain simplifying assumptions. After comparing some standard finite difference schemes the decision was made to base the method of solution upon the alternating direction implicit technique. The depth- and layer-averaged equations were then expressed in a finite difference form before proceeding to solve the resulting sets of simultaneous equations by Gaussian elimination and back substitution. A step-like finite difference grid representation of the lake bed was used initially, before a more refined approach was adopted. The model also developed from a two-dimensional, vertical cross-section of the lake, to three dimensions, thus simulating the circulation throughout the entire lake. A field measurement programme was undertaken on Esthwaite Water, a small lake in the Lake District, and these measurements were used in comparisons with the numerically predicted results, to assess the models performance. Finally, the sensitivity of the results to some of the main model parameters was investigated by several series of simulations of the circulation in Esthwaite Water under various conditions.
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Olauson, Jon. "Modelling Wind Power for Grid Integration Studies." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302837.
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When wind power and other intermittent renewable energy (IRE) sources begin to supply a significant part of the load, concerns are often raised about the inherent intermittency and unpredictability of these sources. In order to study the impact from higher IRE penetration levels on the power system, integration studies are regularly performed. The model package presented and evaluated in Papers I–IV provides a comprehensive methodology for simulating realistic time series of wind generation and forecasts for such studies. The most important conclusion from these papers is that models based on coarse meteorological datasets give very accurate results, especially in combination with statistical post-processing. Advantages with our approach include a physical coupling to the weather and wind farm characteristics, over 30 year long, 5-minute resolution time series, freely and globally available input data and computational times in the order of minutes. In this thesis, I make the argument that our approach is generally preferable to using purely statistical models or linear scaling of historical measurements. In the variability studies in Papers V–VII, several IRE sources were considered. An important conclusion is that these sources and the load have very different variability characteristics in different frequency bands. Depending on the magnitudes and correlations of these fluctuation, different time scales will become more or less challenging to balance. With a suitable mix of renewables, there will be little or no increase in the needs for balancing on the seasonal and diurnal timescales, even for a fully renewable Nordic power system. Fluctuations with periods between a few days and a few months are dominant for wind power and net load fluctuations of this type will increase strongly for high penetrations of IRE, no matter how the sources are combined. According to our studies, higher capacity factors, more offshore wind power and overproduction/curtailment would be beneficial for the power system.
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Hannah, Paul. "Application of wind modelling techniques in complex terrain." Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272741.
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Ekenbäck, Andreas. "Numerical modelling of ENAs from stellar wind interactions." Doctoral thesis, Institutet för rymdfysik (IRF), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1804.
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Energetic neutral atoms (ENAs) are produced whenever a stellar wind encounters a neutral atmosphere. If a stellar wind proton comes sufficiently close to a neutral a charge-exchange reaction may take place, transforming the proton into an ENA. Unaffected by magnetic and electric fields, ENAs provide an opportunity for global imaging of stellar wind interactions.
This thesis presents methods and results of numerical modelling of stellar wind interactions. In particular it treats in depth production of ENAs at comets, Mars and the extrasolar planet HD 209458b.
Sufficiently accurate numerical models of stellar wind interactions require extensive computations. Parallel computing has therefore been used throughout the work, both for fluid and particle simulations of space plasmas. This thesis describes the use of a general simulation tool, providing parallel computing for space plasma simulations.
The thesis presents estimations of the magnitude and morphology of the ENA production at comets and HD 209458b. It compares the results obtained with observations and analyzes them in the light of ENA production at similar objects. Also, simulated ENA images for Mars were produced and compared to observations.
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Green, Duncan R. R. "Modelling the wake flow of large wind turbines." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/27795.
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To provide power on a national scale, a large number of windmills will have to be deployed in wind farms or arrays because the output of individual machines is relatively small. Within an array, some windmills will be faced with the wakes generated by others. This interaction leads to a loss of power relative to upwind turbines and changes in the wind loading across the turbine blades.
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Boulanger, Isabelle. "Lillgrund Wind Farm Modelling and Reactive Power Control." Thesis, KTH, Elektriska energisystem, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119256.
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The installation of wind power plant has significantly increased since several years due to the recent necessity of creating renewable and clean energy sources. Before the accomplishment of a wind power project many pre-studies are required in order to verify the possibility of integrating a wind power plant in the electrical network. The creation of models in different software and their simulation can bring the insurance of a secure operation that meets the numerous requirements imposed by the electrical system. Hence, this Master thesis work consists in the creation of a wind turbine model. This model represents the turbines installed at Lillgrund wind farm, the biggest wind power plant in Sweden. The objectives of this project are to first develop an accurate model of the wind turbines installed at Lillgrund wind farm and further to use it in different kinds of simulations. Those simulations test the wind turbine operating according to different control modes. Also, a power quality analysis is carried out studying in particular two power quality phenomena, namely, the response to voltage sags and the harmonic distortion. The model is created in the software PSCAD that enables the dynamic and static simulations of electromagnetic and electromechanical systems. The model of the wind turbine contains the electrical machine, the power electronics (converters), and the controls of the wind turbine. Especially, three different control modes, e.g., voltage control, reactive power control and power factor control, are implemented, tested and compared. The model is tested according to different cases of voltage sag and the study verifies the fault-ride through capability of the turbine. Moreover, a harmonics analysis is done. Eventually the work concludes about two power quality parameters.
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Scheurich, Frank. "Modelling the aerodynamics of vertical-axis wind turbines." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2897/.
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The current generation of wind turbines that are being deployed around the world features, almost exclusively, a three-bladed rotor with a horizontal-axis configuration. In recent years, however, a resurgence of interest in the vertical-axis wind turbine configuration has been prompted by some of its inherent advantages over horizontal-axis rotors, particularly in flow conditions that are typical of the urban environment. The accurate modelling of the aerodynamics of vertical-axis wind turbines poses a significant challenge. The cyclic motion of the turbine induces large variations in the angle of attack on the blades during each rotor revolution that result in significant unsteadiness in their aerodynamic loading. In addition, aerodynamic interactions occur between the blades of the turbine and the wake that is generated by the rotor. Interactions between the blades of the turbine and, in particular, tip vortices that were trailed in previous revolutions produce impulsive variations in the blade aerodynamic loading, but these interactions are notoriously difficult to simulate accurately. This dissertation describes the application of a simulation tool, the Vorticity Transport Model (VTM), to the prediction of the aerodynamic performance of three different vertical-axis wind turbines - one with straight blades, another with curved blades and a third with a helically twisted blade configuration - when their rotors are operated in three different conditions. These operating conditions were chosen to be representative of the flow conditions that a vertical-axis wind turbine is likely to encounter in the urban environment. Results of simulations are shown for each of the three different turbine configurations when the rotor is operated in oblique flow, in other words when the wind vector is non-perpendicular to the axis of rotation of the rotor, and also when subjected to unsteady wind. The performance of the straight-bladed turbine when it is influenced by the wake of another rotor is also discussed. The capability of the VTM to simulate the flow surrounding vertical-axis wind turbines has been enhanced by a dynamic stall model that was implemented in the course of this research in order to account for the effects of large, transient variations of the angle of attack on the aerodynamic loading on the turbine blades. It is demonstrated that helical blade twist reduces the oscillation of the power coefficient that is an inherent feature of turbines with non-twisted blades. It is also found that the variation in the blade aerodynamic loading that is caused by the continuous variation of the angle of attack on the blades during each revolution is much larger, and thus far more significant, than that which is induced by an unsteady wind or by an interaction with the wake that is produced by another rotor. Furthermore, it is shown that a vertical-axis turbine that is operated in oblique flow can, potentially, produce a higher power coefficient compared to the operation in conditions in which the wind vector is perpendicular to the axis of rotation, when the ratio between the height of the turbine and the radius of the rotor is sufficiently low.
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Mumtaz, Majid. "Harmonic domain modelling of wind-based micro-grids." Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3800/.
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Power quality problems have been identified with wind generation sites and their connection with the distribution network. The main aim of this research is to put forward and develop models for the conventional components in a power system, but with provision for the representation of wind farms. To develop the necessary tools and computational methods that can be embedded in programmes in such a way that economic and security assessments can be carried out on present and future wind-based networks that are likely to be highly decentralised in future. The goal has been accomplished using MATLAB programming and the 'power library' tools.
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Fritzell, Julius. "Sound propagation modelling with applications to wind turbines." Thesis, KTH, Mekanik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-260322.
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Wind power is a rapidly increasing resource of electrical power world-wide. With the increasing number of wind turbines installed one major concern is the noise they generate. Sometimes already built wind turbines have to be put down or down-regulated, when certain noise levels are exceeded, resulting in economical and environmental losses. Therefore, accurate sound propagation calculations would be beneficial already in a planning stage of a wind farm. A model that can account for varying wind speeds and complex terrains could therefore be of great importance when future wind farms are planned. In this report an extended version of the classical wave equation that allows for variations in wind speed and terrain is derived which can be used to solve complex terrain and wind settings. The equation are solved with the use of Fourier transforms and Chebyshev polynomials and a numerical code is developed. The numerical code is evaluated against test cases where analytical and simple solutions exist. Tests with no wind for both totally free propagation and with a ground surface is evaluated in both 2D and 3D settings. For these simple cases the developed code shows good agreement to analytical solutions if the computational domain is sufficiently large. More advanced test cases with wind and terrain is not evaluated in this report and needs further validation. If the sound pressure needs to be calculated for a large area, and if the frequency is high, the developed model has problems regarding computational time and memory. These problems could be solved by further development of the numerical code or by using other solution methods.
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Arnold, Robert John. "Mathematical modelling of wind effects on closed lakes /." Title page, contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09pha758.pdf.
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Aljadiri, R. T. "Modelling and design of electrostatic based wind energy harvester." Thesis, Coventry University, 2014. http://curve.coventry.ac.uk/open/items/9ee6a6e1-bd1d-4717-b48d-ee48fefb4657/1.
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Wireless sensor networks and portable electronic devices, such as mobile phones, media players, digital cameras and iPods, require local electric power supplies. Although these devices are operational all the time, they consume just a few milli-or micro-watts. This means energy harvesting from the environment is an attractive option for powering these devices. Mechanical energy harvesters can use electromagnet, electrostatic or piezoelectric approaches. Of these, electrostatic devices are found to be the most suitable approach for harvesting mechanical energy since they are compact, sensitive to low level mechanical energy, easier to integrate in small scale systems, not requiring smart materials, simple to fabricate, inexpensive and simply structured using less circuitry. Most of electrostatic harvesters proposed in previous studies use mechanical vibration. However, only a few studies have investigated harvesting rotational mechanical energy. The objective of this thesis is to investigate the possibility of harvesting rotational mechanical energy from wind using the electrostatic approach. The proposal involves capturing wind energy using a micro wind turbine then converting it into usable electrical energy. This work first considers general design considerations and the design procedure that must be followed to construct a suitable electrostatic based wind energy harvester. Second, it describes the operating principles of various parts needed to design a novel efficient electrostatic harvesting system. The new harvester consists of a micro wind turbine, a gearbox, a multi-pole variable capacitor or capacitor array, an LC to LC energy transfer circuit, a capacitance sensing system and a microcontroller. The harvesting process has three main steps. First, wind energy is captured and converted into mechanical power using the micro wind turbine. Second, mechanical power is converted into electrical power using the variable capacitor in three phases: pre-charge, harvest and reset. Third, the electrical energy is processed and stored in a Lithium ion battery. The proposed harvester was simulated using Matlab/Simulink to study energy transfer throughout the three energy harvesting phases. Energy analysis was then carried out to study the effect of varying the structure of the multi-pole capacitor on the amount of harvested energy. Results from the simulation for capacitance variation from 2.5 nF to 0.6 nF indicated that an eight-pole variable capacitor can produce 29.43 μJ/sec at a wind speed of 10 m/sec, while a capacitor array of the same capacitance variation with 10 capacitors in the array can produce 295 μJ/sec at a wind speed of 10 m/sec. The results of experiments were carried out to test wind harvesting using a two-pole capacitor proved that the proposed harvester is capable of powering an RF transmitter to transmit wind speed information wirelessly.
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Barcons, Roca Jordi. "A downscaling methodology for microscale wind modelling and forecasting." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/461606.
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Near-surface wind fields are typically obtained from mesoscale Numerical Weather Prediction (NWP) models. These models describe the physics and dynamics of atmospheric phenomena with characteristic dimensions spanning from several hundreds down to few kilometres. Operational configurations use horizontal grid resolutions insufficient to capture flow effects over complex terrains. These effects are relevant for applications that include wind resource evaluation, wind power forecast, or simulation of wind-driven hazardous phenomena such as wildfire spreading or atmospheric dispersion of pollutants and toxic substances. In these applications, some mesoscale-to-microscale downscaling strategy turns necessary.
Traditionally, high-resolution near-surface winds have been obtained by diagnostic models. However, these models fail in representing flow phenomena such as recirculation behind obstacles, vortex shedding or surface boundary layer profiles. The increase in computational power is extending rapidly the use of Computational Fluid Dynamics (CFD) models the dynamical NWP-CFD model coupling methodologies allow capturing physical phenomena that are not implicit in the simpler mass-consistent models. However, the computational cost of CFD models still precludes the use of dynamical downscaling strategies in operational weather forecast. Therefore, although the ABL flow is intrinsically dynamic, operational high-resolution wind modelling below the mesoscale range should be headed towards less computationally intensive physical-statistical methodologies.
This Ph.D. thesis proposes a novel downscaling methodology for wind field characterisation and forecast. The downscaling is based on a model chain, which considers a NWP, a CFD model, and the methodologies to couple both models physically-statistically. The Ph.D. focuses on three main objectives:
1) This first study evaluates the ability of WRF-3DVar and LAPS to assimilate surface automatic weather stations for the mesoscale model initialisation. Results show different assimilation patterns; 3DVar shows unrealistic large-scale features missing in representing the inhomogeneous nature of the near-surface fields; LAPS reproduces small-scale features and provides an initial condition much consistent with observations. The validation shows that high-resolution WRF forecasts initialized with LAPS analyses improve substantially the forecasted wind fields.
2) The second objective faces the Alya-CFDWind (CFD-RANS) model simulation of diurnal cycles to circumvent part of the limitations of the neutral atmosphere assumption. These transient simulations provide a suitable framework to incorporate atmospheric stability considerations in the downscaling. As a test case, a wind resource assessment incorporating this capability shows promising results and substantially improves the annual energy production with respect to the neutral stratified assumption.
3) The third objective focuses on the development of the downscaling strategy. The methodology combines a domain segmentation technique with the use of transfer functions. This strategy preserves the mesoscale pattern and incorporates the unresolved mesoscale model sub-grid terrain forcing effects from pre-computed microscale simulations. Finally, the downscaling is successfully applied to simulate atmospheric CO2 dispersal from a limnic eruption occurred at Lake Nyos (Cameroon) in 1986.
The fulfilment of these objectives has resulted in an efficient and operationally affordable downscaling methodology designed as a NWP model post-process tool for wind field characterisation and forecast. At present, the methodology is ready to be implemented at the Meteorological Service of Catalonia (SMC) operational setup as a prototype for its validation and evaluation.Els camps de vent pròxims a la superfície es solen obtenir a partir de models numèrics de predicció meteorològica mesoescalar (Numerical Weather Prediction: NWP). Aquests models descriuen la física i la dinàmica de fenòmens atmosfèrics amb extensions que van des de diversos centenars fins a pocs quilòmetres. En configuracions operacionals, aquests models treballen a resolucions insuficients per capturar els efectes que exerceixen orografies complexes sobre el flux. Aquests efectes poden ser rellevants per aplicacions com l'avaluació i previsió del recurs eòlic o la simulació de fenòmens perillosos deguts al vent, com la propagació d'incendis forestals o la dispersió atmosfèrica de substàncies tòxiques. Per aquestes aplicacions, és necessària una estratègia de downscaling mesoescala-microescala. Tradicionalment, els vents en alta resolució s'obtenen mitjançant models de diagnòstic. Aquests models, però, no són capaços de representar fenòmens com els de la recirculació darrere d'obstacles o els perfils de vent en la capa límit atmosfèrica. Gràcies a l'increment del poder computacional, l'ús de models Computational Fluid Dynamics (CFD) s'està estenent ràpidament. Les metodologies per acoblar dinàmicament models mesoescalars i CFD permeten capturar fenòmens físics que no són resolts per models més simples. Tanmateix, el cost computacional dels CFD n'impedeix l'ús en predicció operacional. Per tant, tot i que la capa límit atmosfèrica és intrínsecament dinàmica, la modelització eòlica operativa en alta resolució ha d'enfocar-se en mètodes computacionalment menys exigents, com per exemple, mètodes estadístics o físic-estadístics. Aquesta tesi doctoral proposa una nova metodologia per a la caracterització i pronòstic del vent en alta resolució. El downscaling es basa en una cadena de models; un model mesoescalar, un model microescalar CFD, i les metodologies per l'acoblament físic-estadístic. El doctorat es centra en tres objectius principals: 1) S'avalua la capacitat d'assimilar estacions meteorològiques automàtiques en superfície de WRF-3DVar i LAPS, per a la inicialització del model mesoescalar WRF. Els resultats mostren patrons d'assimilació diferents; el 3DVar mostra característiques de gran escala sense representar la naturalesa no homogènia dels camps superficials; el LAPS reprodueix característiques de petita escala i proporciona una condició inicial coherent amb les observacions. La validació mostra que les prediccions del model WRF inicialitzades amb els anàlisis de LAPS milloren substancialment els camps de vent pronosticats. 2) S'afronta la simulació de cicles diaris amb Alya-CFDWind (CFD-RANS) per tal de pal·liar part de les limitacions provinents de l'assumpció d'atmosfera neutra. Aquestes simulacions transitòries proporcionen un marc adequat per incorporar consideracions tèrmiques degudes a l'estratificació atmosfèrica. Els resultats de l'avaluació del recurs eòlic en un enclau a l'estat Puebla (Mèxic) són prometedors i substancialment millors que els obtinguts amb l'assumpció d'estratificació neutra. 3) Es desenvolupa l'estratègia de downscaling. La metodologia combina una tècnica de segmentació de dominis amb l'ús de funcions de transferència. Aquesta estratègia demostra la capacitat de preservar el patró mesoescalar i d'incorporar els efectes microescalars no resolts pel model mesoescalar gràcies a CFD pre-correguts. Finalment, el downscaling s'aplica amb èxit en la simulació de dispersió atmosfèrica de CO2 procedent d'una erupció límnica al Llac Nyos (Camerun, 1986). El compliment d'aquests objectius ha donat com a resultat una metodologia de downscaling eficient i operacionalment assumible, dissenyada com a post-procés del model mesoescalar i que permet la caracterització i el pronòstic del camp de vents. Actualment, la metodologia està preparada per ser implementada al Servei Meteorològic de Catalunya com a prototip per a la seva validació i avaluació.
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Skittides, Christina. "Statistical modelling of wind energy using Principal Component Analysis." Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/2930.
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The statistical method of Principal Component Analysis (PCA) is developed here from a time-series analysis method used in nonlinear dynamical systems to a forecasting tool and a Measure-Correlate-Predict (MCP) and then applied to wind speed data from a set of Met. Office stations from Scotland. PCA for time-series analysis is a method to separate coherent information from noise of measurements arising from some underlying dynamics and can then be used to describe the underlying dynamics. In the first step, this thesis shows that wind speed measurements from one or more weather stations can be interpreted as measurements originating from some coherent underlying dynamics, amenable to PCA time series analysis. In a second step, the PCA method was used to capture the underlying time-invariant short-term dynamics from an anemometer. These were then used to predict or forecast the wind speeds from some hours ahead to a day ahead. Benchmarking the PCA prediction against persistence, it could be shown that PCA outperforms persistence consistently for forecasting horizons longer than around 8 hours ahead. In the third stage, the PCA method was extended to the MCP problem (PCA-MCP) by which a short set of concurrent data from two sites is used to build a transfer function for the wind speed and direction from one (reference) site to the other (target) site, and then apply that transfer function for a longer period of data from the reference site to predict the expected wind speed and direction at the target site. Different to currently used MCP methods which treat the target site wind speed as the independent variable and the reference site wind speed as the dependent variable, the PCA-MCP does not impose that link but treats the two sites as joint observables from the same underlying coherent dynamics plus some independent variability for each site. PCA then extracts the joint coherent dynamics. A key development step was then to extend the identification of the joint dynamics description into a transfer function in which the expected values at the target site could be inferred from the available measurements at the reference site using the joint dynamics. This extended PCA-MCP was applied to a set of Met. Office data from Scotland and benchmarked a standard linear regression MCP method. For the majority of cases, the error of the resource prediction in terms of wind speed and wind direction distributions at the target site was found to be between 10% and 50% of that made using the standard linear regression. The target mean absolute error was also found to be only the 29% of the linear regression one.
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Maljaars, Marianne Dina. "Modelling the wind transport of sand over wet surfaces." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq21694.pdf.
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Caliao, Nolan D. "Modelling and Control of a Fully RatedConverter Wind Turbine." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504789.
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The research investigated the capability of fully rated converter wind turbines (FCWT) to meet the fault ride through requirement of the Grid Codes and their potential to improve network damping. A FCWT using an induction generator was modelled in detail in a manner suitable for large system studies. The GB Grid Code voltage sag duration curve was used to demonstrate the capability of the FCWT to meet the fault ride through requirement. Small signal analysis of the FCWT connected to a large power system was undertaken. The dynamic behaviour of the FCWT was investigated using eigenvalue analysis. Transient stability studies were also undertaken - to compliment the small-signal stability studies. Eigenvalue analysis was undertaken to determine the influence of the network short circuit level on the networks dominant eigenvalues. It was shown that the strength of the transmission system does not influence the dynamic behaviour ofthe generator of the FCWT. The impact of FSIG and FCWT wind generators on the GB network was investigated. It was shown that adding more FSIG generation improves the damping of the network whilst adding more FCWT generation reduces damping. A power system oscillation damping controller (PDC) for a FCWT was shown to improve network damping.
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Wang, Tongguang. "Unsteady aerodynamic modelling of horizontal axis wind turbine performance." Thesis, University of Glasgow, 1999. http://theses.gla.ac.uk/4039/.
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The present work presents a study of unsteady aerodynamic modelling of horizontal axis wind turbine performance. The unsteady aspects addressed in this work include effects of variations in turbine inflow velocity due to operation in yawed flow, in the atmospheric boundary layer, in a wind tunnel, and due to the tower wake. In each case, the basis for the analysis is a prescribed wake vortex model, the development and enhancement of which has been the main focus of the work. A high resolution model has been developed to meet the requirement for adequate representation of the tower shadow effects. A near wake dynamic model has been enhanced with appropriate modifications and integrated into the prescribed wake scheme to produce a hybrid method capable of predicting the detailed high resolution unsteady response in the tower shadow region. The azimuthal interval used within the shadow region can be reduced to 0.5° whilst the computational cost introduced by the high resolution near wake model is almost negligible. A low order source panel method and the prescribed wake model have been combined into a coupled scheme capable of assessing the basic effect of wind tunnel walls on wind turbine flow and performance. The wind tunnel walls are discretised into a series of panels on which source singularities are placed. The source strengths are related to the turbine bound and wake vorticities via their induced velocities. The geometry of the turbine wake is obtained by superposition of the contribution of the disturbance velocities due to the source panels upon the prescribed wake. This new wake structure modifies the wind turbine aerodynamic performance in turn.
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Abdulqadir, Sherwan Ahmed. "Turbulence modelling for horizontal axis wind turbine rotor blades." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/turbulence-modeling-for-horizontal-axis-wind-turbine-rotor-blades(2536b213-3a0c-4977-ac39-916a9fce98d2).html.
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This Thesis aims to assess the reliability of turbulence models in predicting the flow fields around the horizontal axis wind turbine (HAWT) rotor blades and also to improve our understanding of the aerodynamics of the flow field around the blades. The simulations are validated against data from the NREL/NASA Phase VI wind turbine experiments. The simulations encompass the use of fourteen turbulence models including low-and high-Reynolds-number, linear and non-linear eddy-viscosity models and Reynolds stress models. The numerical procedure is based on the finite-volume discretization of the 3D unsteady Reynolds-Averaged Navier-Stokes equations in an inertial reference frame with the sliding mesh technique to follow the motion of the rotor blades. Comparisons of power coefficient, normalised thrust, local surface pressure coefficients (CP) and the radial variation of the section average of normal force coefficients with published experimental data over a range of tip-speed ratios, lead to the identification of the turbulence models that can reliably reproduce the values of the key performance indicators. The main contributions of this study are in establishing which RANS models can produce quantitatively reliable simulations of wind turbine flows and in presenting the flow evolution over a range of operating conditions. At low (relative to the blade tip speed) wind speeds the flow over the blade surfaces remains attached and all RANS models return the correct values of key performance coefficients. At higher wind speeds there is circumferential flow separation over the downwind surface of the blade, which eventually spreads over the entire surface, Moreover, within the separation bubble the centrifugal force pumps the flow outwards, which at the higher wind speeds suppresses the formation of the classical tip vortices. More refined RANS models which do not rely on the linear effective viscosity approximation generally lead to more reliable predictions over this range of higher wind speeds. In particular the Gibson-Launder version of the Reynolds stress transport model and the high-Re versions of the Lien et al non-linear k-ε produce consistently reliable simulations over the entire range of wind speeds. By contrast some popular linear effective viscosity models, like the SST (k-ω) and the v^2-f, perform the poorest over this complex flow range. Finally all RANS models are also able to predict the dominant (lowest) frequency of the pressure fluctuations and the non-linear effective viscosity models, the Launder and Shima version of RSM and the SST are also able to return some of the higher frequencies measured.
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Soraghan, Conaill Eoin. "Aerodynamic modelling and control of vertical axis wind turbines." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23210.
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Designing a structure which harnesses energy from the wind offshore is a radically different design challenge compared to that which the industry standard three-blade Danish model horizontal axis wind turbine (HAWT) has evolved to serve. Vertical axis wind turbines (VAWTs) may prove to be suitable candidates for the offshore sector due to the potential to locate heavy and complex mechanical components near the water surface providing ease of access and a low centre of gravity. Unlike their horizontal-axis counterparts, VAWT designs have not benefited from forty years of intense research and development. Therefore many challenges lie ahead for VAWT technology but lessons can be drawn from the development of HAWT technology. The main aims of this thesis are to create a design tool capable of investigating the performance of large scale, variable pitch VAWTs and to provide analyses of rotor design and control systems that would align utility scale VAWTs with aerodynamic performance and operational flexibility of state of the art HAWTs. The design tool developed is based on the double multiple streamtube (DMS) adaptation of blade element momentum theory and it incorporates tip loss effects, flow curvature, dynamic stall, flow expansion and variable pitch. Validation demonstrates good estimation of local wind flow conditions and aerodynamic performance for both fixed pitch and variable pitch rotors. The model has been developed to investigate in particular V-rotor performance and the potential of variable pitch for VAWTs. A contribution is made to DMS modelling, which involves capturing the effects of varying degrees of streamtube expansion occurring along the blade. This contribution is referred to as fanning and is particularly significant when implementing or designing pitch regimes. Three novel investigations are provided that contribute to fixed pitch VAWT rotor design and control. Firstly, a method for applying lift to drag ratio to VAWTs is introduced, which accounts for azimuthal variation in aerodynamic performance. Secondly, the impact of wind shear on V-rotor rotor design is analysed. Thirdly, a solution for smoothing power fluctuations from aggregated VAWTs is proposed, which is based on controlling the phase of each rotor so peaks in individual generated power do not occur simultaneously. A holistic approach to the way in which cyclic variable pitch can benefit VAWT operation is provided. Five control objectives are identified that span the entire operating envelope for any wind turbine, namely providing high torque during start-up, maximising power coefficient in below rated conditions, alleviating cyclic loading, power limiting in above rated conditions and aerodynamic braking in extremely high winds. Two test case turbines are designed, a similarly rated H-rotor and V-rotor, and for each turbine and each objective, a cyclic pitch regime is developed and analysed.
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Dinwoodie, Iain. "Modelling the operation and maintenance of offshore wind farms." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24845.
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There are ambitious plans for renewable energy sources to provide a significant contribution to the future energy mix. The huge potential capacity and relative maturity compared to other offshore technologies has resulted in a strong commercial focus on offshore wind, particularly in Europe. However, costs of offshore wind remain significantly higher than conventional generation approaches as well as onshore wind. Reducing the cost associated with operations and maintenance of offshore wind remains a key challenge in decreasing lifetime cost of energy and achieving cost parity with alternative generation technologies. The combination of nascent turbine and infrastructure design, moving into more challenging sea state and wind environments and the highly commercial nature of the industry has prevented the maintenance costs of offshore wind being adequately reduced through early operating experience alone. In order to accelerate the reduction of costs and critically to understand the uncertainty associated with future sites and novel operating strategies, it is necessary to simulate maintenance operations. This thesis has developed an offshore wind operations and maintenance expenditure model and specified a decision support methodology for this purpose. The models enable the quantification of the influence of cost drivers for current and future offshore wind farms and provide an improved understanding of the uncertainty associated with operating decisions. Using the developed models, a detailed sensitivity analysis of the influence on lifetime costs from operational climate, failure behaviour, wind farm configuration and external cost drivers has been carried out to provide new insights on the industry. Operational climate and failure behaviour are identified as the critical cost drivers and sources of uncertainty currently. In addition, a detailed analysis of operational strategies for major repairs that involve the use of high cost, specialist vessels has been carried out for the first time, identifying the strengths and weaknesses of different strategies. Finally, a case study demonstrating how decision support models can be used to determine the optimal strategy choices for operators and reduce uncertainty has been performed. The analysis in this thesis provides new insights on the industry and the developed methodologies have the potential to deliver significant financial savings in the future.
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Wang, Lin. "Nonlinear aeroelastic modelling of large wind turbine composite blades." Thesis, University of Central Lancashire, 2015. http://clok.uclan.ac.uk/12129/.
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The increasing size and flexibility of large wind turbine blades introduces significant aeroelastic effects, which are caused by fluid-structure interaction. These effects might result in aeroelastic instability problems, such as edgewise instability and flutter, which can be devastating to the blades and the wind turbine. Therefore, developing a reliable and efficient aeroelastic model to investigate the aeroelasticity characterisation of large wind turbine blades is crucial in the development of large wind turbines. There are several aeroelastic models available today for wind turbine blades. Almost all of them are linear models based on assumption of small blade deflections, and do not take account of large deflection effects on modelling responses and loads. However, with the increasing size and flexibility of large wind turbine blades, this assumption is not valid anymore because the blades often experience large deflections, which introduce significant geometric nonlinearities. Additionally, existing cross-sectional analysis models, which are used to extract cross-sectional properties of wind turbine composite blades for aeroelastic modelling, are either time-consuming or inaccurate. This thesis aims to provide a reliable and efficient aeroelastic modelling of large wind turbine blades through developing 1) a cross-sectional model, which can extract cross-sectional properties of wind turbine composite blades in a reliable and efficient way; and 2) a nonlinear aeroelastic model, which is capable of handling large blade deflections. In this thesis, a cross-sectional analysis model for calculating the cross-sectional properties of composite blades has been developed by incorporating classical lamination theory (CLT) with extended Bredt-Batho shear flow theory (EBSFT). The model considers the shear web effects and warping effects of composite blades and thus greatly improves the accuracy of torsional stiffness calculation. It also avoids complicated post-processing of force-displacement data from computationally expensive 3D finite-element analysis (FEA) and thus considerably improves the computational efficiency. A MATLAB program was developed to verify the accuracy and efficiency of the cross-sectional analysis model, and a series of benchmark calculation tests were undertaken. The results show that good agreement is achieved comparing with the data from experiment and FEA, and improved accuracy of torsional stiffness calculation due to consideration of the shear web effects is observed comparing with an existing cross-sectional analysis code PreComp. Additionally, a nonlinear aeroelastic model for large wind turbine blades has been developed by combining 1) a blade structural model, which is based on a mixed-form formulation of geometrically exact beam theory (GEBT), taking account of geometric nonlinearities; and 2) a blade load model, which takes account of gravity loads, centrifugal loads and aerodynamic loads. The aerodynamic loads are calculated based on combining the blade element momentum (BEM) model and the Beddoes-Leishman (BL) dynamic stall model. The nonlinear aeroelastic model takes account of large blade deflections and thus greatly improves the accuracy of aeroelastic analysis of wind turbine blades. The nonlinear aeroelastic model was implemented in COMSOL Multiphysics, and a series of benchmark calculation tests were undertaken. The results show that good agreement is achieved when compared with experimental data, and its capability of handling large deflections is demonstrated. After the validation, the nonlinear aeroelastic model was applied to the aeroelastic simulation of the parked WindPACT 1.5MW wind turbine blade and to the stability analysis of the blade. Reduced flapwise deflection from the nonlinear aeroelastic model is observed compared to the linear aeroelastic code FAST. The calculated damping ratio of the edgewise mode is much lower than the calculated damping ratio of the flapwise mode, indicating that edgewise instability is more likely to occur than flapwise instability. It is also demonstrated that improper rotor rotational speeds can result in edgewise instability.
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Christie, Elizabeth Katherine. "Numerical modelling of morphological impacts of offshore wind farms." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2005580/.
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Demand for renewable energy resources to reduce greenhouse gases for EU targets, has led to a recent rapid development of Offshore Wind Farms (OWF). As OWFs become larger and multiple sites are developed, it becomes increasingly important to determine the wind farms impact on the coastal environment for design and planning. It is well established that the wind turbine monopiles at OWFs modify the flow in the localised area of the structure, to create a complex 3D flow structure, which ultimately results in scour hole formation. This present research aims to determine the impact of an OWF at both the localised and coastal scale through large scale modelling with the structures represented as islands in the mesh. This method is thought to be an improvement on the typical method of representing the structures as a resistance term in the grid, as it is able to capture some of the complex flow at the structure. The TELEMAC modelling package is used, with the hydrodynamics determined by the TELEMAC-3D module, the waves by the TOMAWAC module, and sediment transport by the SISYPHE module. Validation of the model at the structure showed good agreement with empirical data in the near field of the structure. Tidal flows are well predicted across the water depth, whilst scour formation is well predicted in front of the pile, there are areas of accretion in the wake which are unexpected. The large scale impact of the wind farm on coastal processes was assessed and compared over two wind farm sites, representing different coastal environments. The Burbo Bank wind farm is situated in a coastal bay, whereas Scroby Sands OWF is an open coast site. In both cases the wind farm was seen to block the flow and influence the large scale coastal sediment pathways. At Burbo Bank the wind farm enabled stirring of sediment into suspension, and influenced the sediment transport over the south east corner of Liverpool Bay. The Scroby Sands wind farm was found to reduce the sediment flux magnitude in the vicinity of the array. The long term morphological impact is also determined for the Burbo Bank OWF over a year period, with a morphological acceleration factor. Two methods are compared for generation of a set of representative waves, based on frequency of occurrence and wave energy. Both methods indicate that over a year period the wind farm has a large influence on sediment transport pathways, and increases sediment flux across the Great Burbo Flats. Maximum scour depth predictions at the structures showed good agreement with empirical formula. The pattern of scour for the representative waves based on frequency of occurrence, fits well with measured scour at the wind farm array.
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Yan, Juan. "Advanced Gaussian process modelling for probabilistic wind power forecasting." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709864.
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The demand for more sustainable social and economic development has resulted in a rapid growth in wind power generation largely due to the highly available of wind resource worldwide. Despite that various approaches have been proposed to improve the accuracy and to overcome the uncertainties associated with traditional wind power methods, the stochastic nature of wind still remains the most challenging issue. A temporally local Gaussian process (TLGP) for time series forecasting is proposed to enhance the time varying adaptation and overcome the computation complexity problem. The iterative techniques are employed to achieve multi-step forecasting. Statistical analysis of the application results in real wind farms shows that the method generates smaller residuals which better follows Gaussian distribution. Such a method overcomes the strict assumption made in standard Gaussian process and reduces the computation complexity involved. Further, the uncertainty propagation for iterative multi-step forecasting is analysed based on Taylor expansion. The key finding is that TLGP not only gives better accuracy but also is less sensitive to the multi-step uncertainty propagation. The probability of successful predictions in each confidence region of multi-step TLGP better fits a Gaussian distribution. Under some unique circumstances such as ramping events, the nearby local data will contribute little to predict new generations. A hybrid Gaussian process (HGP) is proposed, combining both recently collected data and historical similar patterns. The application of HGP to real wind farm shows improved prediction accuracy and response swiftness. In addition to accurate forecasting, efficient modelling and calculation techniques are investigated. Meta heuristic methods for nonlinear optimization have been studied and TLBO is deployed. Furthermore, efficient matrix operation is achieved by combining proper matrix decomposition and least square solution methods. Therefore, advanced Gaussian process modelling for probabilistic wind power forecasting under different circumstances is accomplished.
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Rashid, Laith S. "Impact modelling of offshore wind farms on marine radars." Thesis, University of Manchester, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677838.
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Guo, Xuewen. "An assessment of mesoscale wind modelling techniques in complex terrain." Thesis, University of East Anglia, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327952.
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Roberts, E. C. "Energy simulation of climatic wind tunnel plant." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/7250.
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The Climatic Wind Tunnel (CWT) is a facility used by the motor industry to test vehicles under climatic extremes without the need for expensive overseas test programs. This work focuses on the application of computer simulation to the Heating Ventilation and Air Conditioning (HVAC) plant that makes up a CWT facility. The objective being to reduce its operational costs through the identification of energy saving operational strategies. When in operation the CWT has a peak power consumption of 3MW. The implementation of any measures that would reduce this peak load would give rise to considerable savings in the operating costs of the facility. Computer simulation is an accepted technique for the study of systems operating under varying load conditions. Simulation allows rapid analysis of different strategies for operating plant and the effectiveness of achieving the desired effect without compromising the buildings performance. Models for the components of the CWT have been developed and coded in Neutral Model Format. These models have then been linked together in a modular simulation environment to give a model of the complete plant. The CWT plant naturally decomposesin to four major subsystems these being the test chamber, the soakroom, air make-up and refrigeration system. Models of all the primary and secondary HVAC plant are described as is how they constitute the systems that make up the CWT. Validation tests for individual components as well as for the systems have been carried out. To illustrate the potential of the application of computer simulation into finding improved modes of operation that would reduce the energy consumption of the facility, four studies have been carried out. The studies involve the possibility of scheduling the operation of condenser fans as a function of refrigeration load and outside ambient temperature, methods for the pre-test conditioning of a vehicle, a reduction in the secondary refrigerant flow temperature and an increase in the thickness of the insulated panels from which the facility is constructed. The studies carried out showed that there was potential for moderate energy savings to be made in the operation of the facility and that extended simulation runs would allow for the in-depth assessment of a large range of possible modes of plant operation in order to identify the areas where the greatest savings are possible.
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STERMASI, ADRIST. "Offshore wind energy in the Adriatic Sea: Modelling of the microscale wind field and short-term forecast of wind power potential." Doctoral thesis, Università Politecnica delle Marche, 2015. http://hdl.handle.net/11566/242945.
Full textAbstract:
Studying wind energy is still a challenge. Many arguments are involved in this field such as
environmental sustainability, infrastructures, economics and many others, has to find the
equilibrium and coexist together for the further development of this technology. The P.O.W.E.R.E.D
project, part of the IPA-PROGRAMME deal with these issues concerning the Adriatic basin.
Numerical and experimental evaluation of wind energy resources is assigned to Università
Politecnica delle Marche. Two maps of different spatial resolutions of one and three kilometers
respectively, for one and five years are produced using the PSU/NCAR mesoscale MM5 (fifth
generation) in hind-casting.
The existing meteorological network data's are used as single point monitor the inter area so
experimental data will be available for different uses. Further more a forecasting system will be
available for the possible wind farms. For the expansion of wind energy to new markets for the
Adriatic Basin poses a challenge into estimating this resource for the whole area. An accurate
climatic description relies on a comprehensive regional observation network, characteristic often not
available on emerging markets, and generally not extensive on established markets. In these cases
the use of Mesoscale modeling can provide a large-scale analysis with regional features. Considering
existing limitations, this approach can be used to support an initial ranking and selection of sites for
wind farm projects.
Initial large-scale conditions are obtained from the Reanalysis database, which contains global
meteorological observations, covering over 30 years at 1° km spatial resolution. An initial large-scale
analysis of 3 km of spatial resolution is conducted for the study of the climatology of the Adriatic
region for 5 consecutive years; from 2008 to 2012 describing the average conditions in across a
desired area. In a second time, a finest resolution wind map of 1 km is obtained in order to better
understand the evolution of the climatology near the costs.
The simulation of the regional wind climate is conducted using the Mesoscale Modeling (MM5). This
modeling system calculates the dynamics and thermodynamics of the atmosphere in limited areas,
and is currently developed and employed at several universities and research centers worldwide.
Through the process of downscaling the Reanalysis data is used to describe the initial conditions for
the desired area, allowing the MM5 to calculate in great detail the effects of local features over the
large-scale conditions.
In order to assess the limitations of this approach, several validation efforts are conducted over
different areas, providing an overview of the benefits of this methodology for wind energy
estimation.
The results generated from such a method can be used to represent the wind resource distribution
over an area of interest for a wind farms projects, and data points can be obtained in order to
represent time-series and vertical profiles for a specific area. However, as with any numerical
simulation, the limitations of this approach should be carefully considered on a case-per-case
analysis, and its results should be used as an additional aid to initial studies and green-field
procurement.
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Campos-Arriaga, Liliana. "Wind energy in the built environment : a design analysis using CFD and wind tunnel modelling approach." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10806/.
Full textAbstract:
Renewable energies are a critical element for reducing greenhouse gases emissions and achieving a sustainable development. Until recently, building integration of renewable sources was focused on solar technologies. Nevertheless,building integrated wind turbines can and must be part of the solution to the global energy challenge. This research investigated the potential of integrating small vertical wind turbines between medium-rise buildings. Wind velocities were measured around 7 fifteenstorey towers. The measurements were carried out for nine different configurations,using a boundary layer wind tunnel and computational fluid dynamics (CFD) simulations. Computed and measured results showed reasonable agreement. The differences were more apparent at ground level. It was established that building orientation and the separation between buildings defines to a great extent the wind environment around buildings. It was found that a distance between buildings of 15 metres and an orientation of θ=260˚ produced the higher augmentation factors. This configuration produced up to 17,812kWh in a typical Nottingham UK year, using six vertical wind turbines of 2.5kW each. Results suggested that the use of CFD as a visualisation tool is extremely useful at design stages in projects involving the integration of wind turbines. Nevertheless, the results of CFD simulations are highly dependent on the type of roughness modification applied to the wall functions, the choice of the turbulence model and the modelling of the inlet wind velocity profile. Because servicing buildings accounts for around half of the UK’s total energy consumption, the need to reduce the consumption of fossil fuels is central to good building design. That is why the architectural practice must respond professionally by delivering buildings that successfully integrate wind energy technologies, which can only be achieved if the designer actively engages with the environmental design principles and improves his understanding of building physics.
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Lange, Bernhard. "Modelling the marine boundary layer for offshore wind power utilisation." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966278410.
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Wu, Feng. "Modelling and control of wind and wave energy conversion systems." Thesis, University of Birmingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525483.
Full textAbstract:
The modelling and control of wind and wave energy conversion systems is carried out in this thesis. The thesis comprises two parts. The first part is focused on the modelling and control of wind conversion system while the second part is on the modelling and control of wave energy conversion system (WEe). In the first part, the small signal stability of the \\lind turbine (\VT) with doubly fed induction generator (DFIG) and the WT with direct-drive permanent magnet generator (DDPMG) an: analysed using detailed models. A parameter tuning algorithm and a nonlinear controller are proposed, respectively, to improve dynamic performance of WT with DFIG. The impacts of WT with DFIG, WT with DDPMG and WT the induction generator (lG) on power system transient stability are compared. In the second part, a new coordinate transformation is proposed for the model of Archimedes wave swing (A WS) based WEe system, the transformed model is compatible with the power system dynamic analysis. The controllers for A WS based WEe are designed so as to extract maximum power from the wave, output constant power and maintain the terminal voltage. The application of battery energy storage in smoothing the output power of WEe system is studied.
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Homer, Jeffrey R. "Physics-based control-oriented modelling for floating offshore wind turbines." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54891.
Full textAbstract:
As offshore wind technology advances, floating wind turbines are becoming larger and moving further offshore, where wind is stronger and more consistent. Despite the increased potential for energy capture, wind turbines in these environments are susceptible to large platform motions, which in turn can lead to fatigue loading and shortened life, as well as harmful power fluctuations. To minimize these ill effects, it is possible to use advanced, multi-objective control schemes to minimize harmful motions, reject disturbances, and maximize power capture. Synthesis of such controllers requires simple but accurate models that reflect all of the pertinent dynamics of the system, while maintaining a reasonably low degree of complexity.
In this thesis, we present a simplified, control-oriented model for floating offshore wind turbines that contains as many as six platform degrees of freedom, and two drivetrain degrees of freedom. The model is derived from first principles and, as such, can be manipulated by its real physical parameters while maintaining accuracy across the highly non-linear operating range of floating wind turbine systems. We validate the proposed model against advanced simulation software FAST, and show that it is extremely accurate at predicting major dynamics of the floating wind turbine system.
Furthermore, the proposed model can be used to generate equilibrium points and linear state-space models at any operating point. Included in the linear model is the wave disturbance matrix, which can be used to accommodate for wave disturbance in advanced control schemes either through disturbance rejection or feedforward techniques. The linear model is compared to other available linear models and shows drastically improved accuracy, due to the presence of the wave disturbance matrix.
Finally, using the linear model, we develop four different controllers of increasing complexity, including a multi-objective PID controller, an LQR controller, a disturbance-rejecting H∞ controller, and a feedforward H∞ controller. We show through simulation that the controllers that use the wave disturbance information reduce harmful motions and regulate power better than those that do not, and reinforce the notion that multi-objective control is necessary for the success of floating offshore wind turbines.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Kumaraperumal, K. Ayyapan N. "Modelling and measurement of wind-driven rain on building facades." Thesis, Glasgow Caledonian University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517932.
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Walshe, John D. "CFD modelling of wind flow over complex and rough terrain." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/7827.
Full textAbstract:
A model has been developed using the general-purpose Navier-Stokes solver CFX4 to simulate Atmospheric Boundary Layer flow over complex terrain. This model has been validated against the measured data from the Askervein Hill experiment, and has been shown to perform well. The CFD model is also compared to the WAsP linear model of wind flow over topography, and a significant improvement is noted for flow over complex topography. Boundary conditions, gridding issues and sensitivity to other solver parameters have all been investigated. An advanced roughness model has been developed to simulate flow over forest canopies, using a resistive body force within the canopy volume. The model is validated against measured data for simple 2D cases, and for a complex 3D case over real topography. The model is shown to give a more physically realistic profile for the wind speed in and just above forest canopies than the standard roughness length model used in most CFD simulations. An automated methodology for setting up CFD simulations using the models described has been developed. A custom pre-processing package to implement this has been written, to enable the use of the CFD methodology in a commercial environment.
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Cockerill, Timothy Thomas. "Cost modelling of offshore wind energy systems in northern Europe." Thesis, University of Sunderland, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420744.
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Koçyigit, Müsteyde Baduna. "Numerical modelling of wind-induced circulation in lakes and reservoirs." Thesis, Cardiff University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412516.
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Carey, P. S. "Direct wind tunnel modelling of natural ventilation for design purposes." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422325.
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Jaen, Sola Pablo. "Advanced structural modelling and design of wind turbine electrical generators." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28677.
Full textAbstract:
This thesis concentrates on direct drive electrical generators for wind energy applications. A variety of wind turbine configurations and generator topologies are reviewed. Direct drive renewable energy converters introduce a low speed, high torque input into the electrical machine. Due to this, these generators have to be larger and more robust than their high speed counterparts. With very large airgap closing forces, a very stiff structure capable of withstanding the stress is necessary. As a result very heavy machines, with structural ('inactive') material dominating the electromagnetically 'active' material are designed. In this thesis a stiffness approach is introduced which combines electromagnetic stiffness and structural stiffness for different modes of deflection. This is used to minimise mass of the generator by trading stiffness of rotor and stator structures. Design tools are presented, validated and utilised to model lightweight supporting structures ('inactive material') for high torque radial flux permanent magnet synchronous generators. Different structural layouts are statically studied, compared and optimised. Making use of low density materials, such as composites, a simplified generator structure is designed and contrasted with its optimised steel counterpart. As a rotating piece machinery forming part of a bigger and more complex machine, electrical generators are subject to dynamic and external forces coming from the wind turbine rotor. The optimised steel design is looked at from a dynamic viewpoint. Discussions and conclusions highlight the potential design solutions that can be adopted to minimise the mass and therefore the cost of these machines.
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Stannard, Nick. "Generator design for, and modelling of, small-scale wind turbines." Thesis, Durham University, 2008. http://etheses.dur.ac.uk/1846/.
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Beuckelaers, William. "Numerical modelling of laterally loaded piles for offshore wind turbines." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:9feba16c-fc8e-464e-8928-3ca3a7a9fb73.
Full textAbstract:
The offshore wind market has grown rapidly over recent years. The most widely used foundation type for offshore wind turbines is the monopile. Current design guidance for monopile foundations dates back to the 1950s and 1960s and was originally developed for the oil and gas industry, where both the pile dimensions as well as the design load conditions are different than for offshore wind. The PISA project was aimed at investigating the behaviour of monopile foundations and reducing the conservatism in design. The project used state of the art numerical modelling, which was validated through a field testing campaign. The numerical modelling was focused on capturing the monotonic response of the foundation to failure. The field testing provided valuable additional data for the rate effects and the cyclic behaviour of monopile foundations. Data analysis methods are presented to accurately interpret the foundation response. The data analysis is focused on capturing the ground level foundation response as well as the pile behaviour below ground. Additionally, the cyclic behaviour is analysed in detail. These results are used as a basis for the development of numerical models for capturing the observed behaviour in the field tests. This thesis outlines plasticity models which are integrated in a generalised Winkler model. The model development makes use of the Hyperplasticity framework. These numerical models include: (1) the kinematic hardening model to capture plastic unloading; (2) the rate effect model to capture increased foundation capacity with increasing load rate; (3) the ratcheting model to capture accumulated rotation under cyclic loading; (4) the combined rate and ratcheting model and (5) the gapping model to capture gapping on the active side of the pile. Each of the models is calibrated to the PISA eld tests illustrating the capabilities and limitations of the models for capturing the eld test response. Finally, the kinematic hardening model is integrated in software to calculate the dynamic behaviour of an operating wind turbine. Integrating more accurate soil-structure interaction models could lead to improved predictions of the turbine behaviour and reduce the cost of monopiles.
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Wu, JenHao. "Reliability analysis for small wind turbines using Bayesian hierarchical modelling." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/29015.
Full textAbstract:
In this thesis, the reliability of small wind turbines is studied. Both conventional reliability analysis methods and the novel Bayesian models (Bayesian Hierarchical Modelling (BHM)) are used to analyse the reliability performance of the Gaia-Wind turbines / assemblies and components of the Gaia-Wind turbine. In Chapter 2, a simple failure mode and effect analysis (FMEA) is conducted. An approximated risk priority number (RPN) is calculated for each failure mode and assembly. The assembly that is identified to have the highest RPN is the "Rotor and Blade Assembly". As for the failure modes, "Blade Split" and "Generator Failure" failure modes are identified to have the highest RPNs. In Chapter 3, the conventional methods including the Kaplan-Meier Analysis, Weibull Plot Analysis, Homogeneous Poisson Process (HPP) Analysis, and Crow-AMSAA (Non-Homogeneous Poisson Process (NHPP)) Analysis are used to study the reliability performance of the generic turbine and the critical assemblies based on the approximated RPNs. By using these conventional methods, the L10 life can be approximated (Kaplan-Meier), the main failure modes of an assembly can be identified (Weibull Plot Analysis), the annual failure rate can be estimated (HPP), and the number of future failures can be predicted (NHPP). These methods have been implemented in a novel on-line interactive platform, named ReliaOS (Chapter 7), which effectively facilitates the process of converting the information in the warranty record to the meaningful reliability information. Three novel BHM models are proposed and implemented in WinBUGS (an open source software), namely the repair model, the environmental model, and the informative prior framework, (Chapter 5 and Chapter 6). The repair model is used to quantify the repair effectiveness of a generic repair action. The model is applied on both the turbine level as well as the component level. At the turbine level, the annual failure rate of the generic turbine is predicted to be 0:159 per turbine per year at the first year. Individual turbines can be categorised into different quality levels ("Good", "Good- Normal", "Normal", "Normal-Bad", and "Bad") based on the predicted annual failure rate values. At the component level, "Blade split", "Cracked Frame", and "Generator Failure" failure modes are studied. These are the most critical failure modes for "Rotor and Blade Assembly", "Tower, Foundation, and Nacelle", and "Generator" assemblies respectively. "Cracked Frame" failure mode is predicted to have the lowest characteristic life and a slightly increasing failure rate trend. The repair effectiveness of the "Cracked Frame" failure mode is identified to be slightly ineffective. The environmental model quantifies the influence of three environmental covariates, i.e. AverageWind Speed (AWS), Turbulence Intensity (TI), and Terrain Slope (TS). These environmental covariates are all identified to have negative impact to the reliability of the generic turbine, where TI and AWS have more pronounced impact than TS. The informative prior BHM framework offers a way of quantifying the reliability of the drivetrain frame (which corresponds to the "Cracked Frame" failure mode) in a situation where zero failure instance is recorded for the new drivetrain frame design. This is achieved by jointly considering the simulation results from SOLIDWORKS as the prior information into the BHM model. This thesis strives to understand the reliability performance of the Gaia-Wind small wind turbine from different perspectives, i.e. the generic turbine, individual turbines, and the components, by the use of conventional methods and the proposed BHM models. The novel on-line reliability platform, ReliaOS, mitigates the difficulties in converting the information in the data to the reliability information for the end users. It is believed that the proposed BHM models and the ReliaOS on-line reliability analysis platform will improve the reliability analysis of small-wind turbines.