Dissertations / Theses: 'Wind turbine'

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Mitchell, Andrew J. "Wind Turbine Noise." Thesis, University of Canterbury. Mechanical Engineering, 2004. http://hdl.handle.net/10092/6622.

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The objectives of this thesis were (i) to investigate the main sources and paths of noise on modern utility size wind turbines; (ii) to explore methods of reducing the noise; (iii) to assess our current ability to accurately predict and measure wind turbine noise. The accomplishment of these objectives would enable quieter wind turbines to be developed and allow them to be located near residential dwellings with greater confidence that the noise would not be a nuisance. A comprehensive review of the current literature was carried out and the findings were used as a basis for the investigative work conducted. It was found that wind turbine noise could be classed as either aerodynamically produced noise or mechanically produced noise. Aerodynamically produced noise on wind turbines arises mainly from the interaction of the flow over the blade with the surrounding air. Mechanically produced noise arises from a number of sources such as the gearbox, generator and hydraulic pumps. The noise can be radiated directly from the noisy component (airborne) and / or transferred through the structure of the turbine and radiated elsewhere (structure-borne) such as the tower. The prototype Windflow 500 wind turbine near to Christchurch was used for the majority of the investigative work carried out, and to assess the predictions made. The main radiators of noise from the turbine were identified as the blades (86 – 90% of the total sound power), the tower (initially 8 – 12% but later reduced to ~4% of the total sound power), and the nacelle cladding (1% of the total sound power). A prominent tone in the sound power spectrum from the turbine was observed in the 315 Hz 1/3 octave band. This was shown to be predominantly caused by gear meshing in the second stage of the gearbox at 311 Hz. The presence of the tone was significant because under commonly used standards a tonal penalty would be applied to the measured sound pressure level from the turbine to account for the extra annoyance caused by the tone. This in turn would mean that any potential wind farms would need to be sited further from residential dwellings than would otherwise be necessary in order to comply with noise regulations. Investigations were carried out that addressed the noise radiated from each of the main contributors outlined above. The sound power level radiated from the tower was found to be effectively reduced by attaching rubber tiles at strategic locations inside the tower. Noise radiated from the nacelle was reduced with a combination of acoustic insulation and acoustic absorption inside the nacelle. An investigation into the gearbox noise was also carried out. Attempts to reduce the tonal noise caused by gear meshing were made with little success but the investigation provided a good basis upon which to conduct further work. Preliminary investigations into both structure-borne and aerodynamically generated blade noise were carried out. The structure-borne blade noise investigation showed that the blades readily vibrated at a range of frequencies, the result being that structurally transmitted noise radiated from the blades was likely to be present at high levels. Research showed that the structure-borne noise radiated from the blades could be significantly reduced by partially filling the internal cavity of the blades with foam. The investigation of aerodynamically produced noise was carried out on a section of Windflow 500 blade in the low noise wind tunnel at the University of Canterbury. The tests showed that the blade generated noise at a range of frequencies including those in the 315 Hz 1/3 octave band. This suggested that the tonal noise measured from the blades was not only due to structurally transmitted noise from the gearbox but was also contributed to by aerodynamically produced noise. It was found that the noise from the blade section could be reduced by up to 4.5 dB at certain frequencies by attaching serrated strips to the trailing edge of the aerofoil. Empirical equations for prediction of wind turbine sound power levels were evaluated and found to be in good agreement with measured data. It was found that accurate spectral predictions of the sound power level were much more difficult. However given spectral data for a turbine, it was found that accurate predictions of the noise propagation from the turbine could be made, taking into account meteorological effects and the effect of complex topography. It was found that the CONCAWE propagation model was well suited to the prediction of noise propagation from wind turbines because of its superior handling of meteorological effects. In an investigation carried out which modelled the Gebbies Pass site of the Windflow 500 it was found that the CONCAWE model could predict sound pressure levels from the turbine to within 2 dB at distances of up to 1400 m. Further work in the area of wind turbine noise should be focused on the reduction of blade noise. This is especially relevant to the Windflow 500 since blade noise was found to be by far the largest contributor to total noise radiated from the turbine. Acoustic treatments elsewhere would therefore produce only small reductions in the total sound power emitted by the turbine.

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Lynum, Susanne. "Wind turbine wake meandering." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22400.

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In this master thesis the meandering of the wake of a three bladed horizontal axis model wind turbine has been studied. Measurements have been conducted by the use of four hot-wire probes located at multiple nearby points in the wake at X/D = 1, 3 and 5 downstream the model wind turbine. The meandering has been studied based on the location of the tip vortices shed by the turbine blades. The experiments were conducted in the wind tunnel at NTNU at the Department of Energy and Process Engineering. The aim of the study was to see the effect on the meandering of the wake of the model turbine when placed in an incoming flow with turbulence intensity typical for atmospheric turbulence, compared to an incoming flow with a low turbulence intensity round 0.3 %. The atmospheric turbulence was generated by inserting a grid in the inlet to the test section in the wind tunnel. The grid generated a turbulence intensity round 5.5 % and integral length scales of Luuz = 3.1E-2 m and Luux = 6.5E-2 m at the position of the model wind turbine in the tunnel. The performance of the model turbine in both incoming flows was calculated based on measurements of the thrust and torque acting on the turbine in a free stream velocity of 10 m/s. The greatest deviation in the performance curve was found at the top of the curve; however the difference between the two cases was minor. Initial measurements with a single hot-wire probe was conducted in the wake of the turbine to locate the tip vortices. Based on these results, the location to conduct the multiple hot-wire measurements was decided. Already at this stage the effect of the grid turbulence was evident due to the smeared out energy in the flow in the wake caused by diffusion and mixing. The tip speed ratio (TSR) of the model wind turbine was 6 in the case without grid generated turbulence, and 7 in the case with grid turbulence during the final measurements in the wake. The effect of the change in TSR was evaluated, and it was found that new measurements were not needed. The normal stress based on the velocity measurements in the wake were phase averaged according to the position of the turbine blade using Matlab. When comparing these results with the normal stress calculated directly from the time series, it was found that the tip vortices had merged together or broken up at all measurement point except at X/D = 1 downstream the turbine without grid generated turbulence. Using power spectral density function (PSD) the observations were confirmed.The tip vortices was not equally distributed within the wake and were located 30°, 128° and 224° at respectively z/R =1.12, 1.15 and 1.20. Their diameters were found to be 1.8E-2 m, 1.35E-2 m, 2.7E-2 m in z direction. The location of the peak in the normal stress tended to meander a bit back and forth, mainly directed towards the rotor center, with a distance from 4.5E-3 m to 1.8E-2 m, and in the streamwise direction with a total distance of 6.17E-2 m. The tip vortices seem to meander individually within the wake, and not with the same distance.Based on the results and observations conducted throughout this study, new measurements should be conducted at a shorter distance to the turbine rotor to be able to compare the meandering of the wake for the two different incoming flows.

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Chinchore, Asmita C. "Computational Study of Savonius Wind Turbine." Cleveland State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=csu1389795972.

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Chaath, Alaaeddin. "Improving the Design of Wind Turbine Plants : Future Design of Wind Turbine Plants." Thesis, Högskolan i Halmstad, Energivetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-31084.

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Applying the new ideas developed by the present study on the current design of WTP can lead to satisfactory results and give flexibility in terms of producing more electrical power during periods of low/medium wind velocity. The innovative ideas and methods included in the present work reveal the features of the future renewable energy designs that could, in the few coming years, revolutionize the field of wind turbine designs worldwide. Also, increase the capacity factor significantly, since the application of these ideas in areas where wind class II and III blows have proven to be very effective. Especially, when compares the result of new ideas with the current wind turbine designs. Testing the innovative ideas regarding the future wind turbines on a current WTP achieved a good results in increasing electric energy production over the year. For example applies the new ideas on a WTP model Enercon (E-101) will achieve an annual increase around 20% of electric power generation (wind class II, Cp = 36), i.e. when wind speed is ranging from 0-10 m/s (Level C – option 02) the production improved at the highest value, reaching up to +46%. Also, in Level B the generation of electricity witnessed an increase up to 10% when the wind velocity being always between level C with a minimum of 10 meters per second and Level A (Level A is the maximum output value, which is changing from one turbine type to the other).

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

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

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Farr, Thomas D. "The effects of atmospheric and wake turbulence on wind turbines and wind turbine wakes." Thesis, University of Surrey, 2015. http://epubs.surrey.ac.uk/807177/.

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Wind tunnel studies using model wind turbines have been used to investigate the effects and characteristics of neutral and unstable atmospheric boundary layers on their operation and wake behaviour. Wind turbine arrays have also been arranged to observe the effect of wake interaction. Single-point two-component and two-point single-component velocity measurements have been made using laser Doppler anemometry in conjunction with cold-wire anemometry to interrogate the modelled boundary layer. The manufacture and installation of a second traverse mechanism in the wind tunnel was necessary to perform the two-point measurements, along with the development of laboratory software for control and data analysis. In order to allow for measurements of turbine performance, a current sensor was developed so that correlations could be made between velocity and torque fluctuations. Investigation of larger arrays, up to 12 turbines, required the production of additional turbines and installation and subsequent integration of the associated control systems. Measurements made in the neutral flow conditions show that there is an increasing correlation between the upstream turbulence and torque fluctuations with proximity to the turbine, especially in the wake of another turbine where the flow is rapidly evolving. Two-point velocity measurements, with a lateral separation, have shown that there is little effect of the turbine on the correlation of the flow over the rotor disc. Analysis of data from this type of measurement also shows that in an array of four aligned turbines, the spatial structures reach an equilibrium state and are of larger size after the second turbine. Furthermore, the velocity-torque correlation magnitude decreases after the first turbine, but then increases with distance through the array owing to the increased correlation over the rotor disc, although not to the level observed for the first turbine. The turbulence approaching the first turbine behaves in a frozen-flow manner, but this is not true for the second and subsequent turbines, although the idea of convection time still applies. Measurements made in the modelled unstable atmospheric boundary layer show that the length and time scales are changed in the flow, in addition to the alteration of the profiles of mean velocity and Reynolds stresses. The increased turbulence caused by the convective boundary layer increases the rate of wake deficit recovery and does not result in the same spatial structures as the neutral conditions. Temperature effects are of secondary importance with regard to wake and turbine behaviour, with the main driving force behind the performance being the increased turbulence levels.

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Pearson, Charlie. "Vertical axis wind turbine acoustics." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245256.

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Increasing awareness of the issues of climate change and sustainable energy use has led to growing levels of interest in small-scale, decentralised power generation. Small-scale wind power has seen significant growth in the last ten years, partly due to the political support for renewable energy and the introduction of Feed In Tariffs, which pay home owners for generating their own electricity. Due to their ability to respond quickly to changing wind conditions, small-scale vertical axis wind turbines (VAWTs) have been proposed as an efficient solution for deployment in built up areas, where the wind is more gusty in nature. If VAWTs are erected in built up areas they will be inherently close to people; consequently, public acceptance of the turbines is essential. One common obstacle to the installation of wind turbines is noise annoyance, so it is important to make the VAWT rotors as quiet as possible. To date, very little work has been undertaken to investigate the sources of noise on VAWTs. The primary aim of this study was therefore to gather experimental data of the noise from various VAWT rotor configurations, for a range of operating conditions. Experimental measurements were carried out using the phased acoustic array in the closed section Markham wind tunnel at Cambridge University Engineering Department. Beamforming was used in conjunction with analysis of the measured sound spectra in order to locate and identify the noise sources on the VAWT rotors. Initial comparisons of the spectra from the model rotor and a full-scale rotor showed good qualitative agreement, suggesting that the conclusions from the experiments would be transferable to real VAWT rotors. One clear feature observed in both sets of spectra was a broadband peak around 1-2kHz, which spectral scaling methods demonstrated was due to laminar boundary layer tonal noise. Application of boundary layer trips to the inner surfaces of the blades on the model rotor was found to eliminate this noise source, and reduced the amplitude of the spectra by up to 10dB in the region of the broadband peak. This method could easily be applied to a full-scale rotor and should result in measurable noise reductions. At low tip speed ratios (TSR) the blades on a VAWT experience dynamic stall and it was found that this led to significant noise radiation from the upstream half of the rotor. As the TSR was increased the dominant source was seen to move to the downstream half of the rotor; this noise was thought to be due to the interaction of the blades in the downstream half of the rotor with the wake from the blades in the upstream half. It was suggested that blade wake interaction is the dominant noise source in the typical range of peak performance for the full-scale QR5 rotor. Different solidity rotors were investigated by using 2-, 3- and 4-bladed rotors and it was found that increasing the solidity had a similar effect to increasing the TSR. This is due to the fact that the induction factor, which governs the deflection of the flow through the rotor, is a function of both the rotor solidity and the TSR. With a large body of experimental data for validation, it was possible to investigate computational noise prediction methods. A harmonic model was developed that aimed to predict the sound radiated by periodic fluctuations in the blade loads. This model was shown to agree with similar models derived by other authors, but to make accurate predictions very high resolution input data was required. Since such high resolution blade loading data is unlikely to be available, and due to the dominance of stochastic sources, the harmonic model was not an especially useful predictive tool. However, it was used to investigate the importance of the near-field components of the sound radiated by the wind tunnel model to the acoustic array. It was shown that the near-field terms were significant over a wide range of frequencies, and the total spectrum was always greater than that of the far-field component. This implied that the noise levels measured by the acoustic array represented an upper bound on the sound radiated to the far-field, and hence that the latter would also be dominated by stochastic components. An alternative application of the harmonic model, which attempted to determine the blade loading harmonics from the harmonics in the sound field was proposed. This inversion method utilised a novel convex optimisation technique that was found to generate good solutions in the simulated test cases, even in the presence of significant random noise. The method was found to be insensitive at low frequencies, which made it ineffective for inverting the real microphone data, although this was shown to be at least partly due to the limitations imposed by the array size. In addition to the harmonic models, an empirical noise prediction method using the spectral scaling laws derived by \citet*{Brooks_1989} was trialled, and was found to be capable of making predictions that were in agreement with the measured data. The model was shown to be sensitive to the exact choice of turbulence parameters used and was also found to require good quality aerodynamic data to make accurate noise predictions. If such data were available however, it is expected that this empirical model would be able to make useful predictions of the noise radiated by a VAWT rotor.

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Worasinchai, Supakit. "Small wind turbine starting behaviour." Thesis, Durham University, 2012. http://etheses.dur.ac.uk/4436/.

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Small wind turbines that operate in low-wind environments are prone to suffer performance degradation as they often fail to accelerate to a steady, power-producing condition. The behaviour during this process is called “starting behaviour” and it is the subject of this present work. This thesis evaluates potential benefits that can be obtained from the improvement of starting behaviour, investigates, in particular, small wind turbine starting behaviour (both horizontal- and vertical-axis), and presents aerofoil performance characteristics (both steady and unsteady) needed for the analysis. All of the investigations were conducted using a new set of aerodynamic performance data of six aerofoils (NACA0012, SG6043, SD7062, DU06-W-200, S1223, and S1223B). All of the data were obtained at flow conditions that small wind turbine blades have to operate with during the startup - low Reynolds number (from 65000 to 150000), high angle of attack (through 360◦), and high reduced frequency (from 0.05 to 0.20). In order to obtain accurate aerodynamic data at high incidences, a series of CFD simulations were undertaken to illustrate effects of wall proximity and to determine test section sizes that offer minimum proximity effects. A study was carried out on the entire horizontal-axis wind turbine generation system to understand its starting characteristics and to estimate potential benefits of improved starting. Comparisons of three different blade configurations reveal that the use of mixed-aerofoil blades leads to a significant increase in starting capability. The improved starting capability effectively reduces the time that the turbine takes to reach its power-extraction period and, hence, an increase in overall energy yield. The increase can be as high as 40%. Investigations into H-Darriues turbine self-starting capability were made through the analogy between the aerofoil in Darrieus motion and flapping-wing flow mechanisms. The investigations reveal that the unsteadiness associated with the rotor is key to predicting its starting behaviour and the accurate prediction can be made when this transient aerofoil behaviour is correctly modelled. The investigations based upon the analogy also indicate that the unsteadiness can be exploited to promote the turbine ability to self-start. Aerodynamically, this exploitation is related to the rotor geometry itself.

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Loland, Kari Medby. "Wind Turbine in Yawed Operation." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13437.

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The task of this project was to investigate the near wake, performance characteristics and yaw moment on a model wind turbine. The test turbine is a horizontal axis three bladed machine with a rotor diameter of 0.9 meter. Initially it is an upwind turbine, but was used for downwind measurements as well by rotating the blades and the entire construction 180^0. For the wake measurements the tip speed ratio was set to be TSR=3, TSR=6 and TSR=9 to describe the different regimes; partly stalled, optimal operation and partly propeller operation. Two different yaw angles, 0^0 and 30^0, was also explored for the near wake measurements. The velocity field was measured at X/D=1, as well as X/D=4 for TSR=6 and the two yaw angles; X/D being the number of rotor diameters downstream from the rotor plane. The performance characteristics and yaw moment were measured for yaw angles 0^0, 10^0, 20^0 and 30^0, and with tip speed ratios from 1 to 11. The power and thrust coefficients were found to decrease with increasing yaw angle. This is due to the reduced projected rotor area and reduced effective wind velocity component interacting with the turbine blades. The loss in power due to the yaw angle of the turbine is approximately 6% for yawAngle=10^0 and 40% for yawAngle=30^0 with upstream configuration. For downstream setup the reduction in power due to the yaw angle was 5.2% and 38% for yawAngle=10^0 and yawAngle=30^0 respectively. The near wake velocity field was strongly influenced by tip speed ratio and yaw angle. At TSR=3 the outer parts of the wake had a velocity close to the freestream velocity. Therefore much of the flow passes through without interacting with the rotor blades. For TSR=6 the velocity deficit was close to uniform in the wake. Most of the turbine blades operate efficiently at the design condition, and gives the peak in the power coefficient curve at this TSR. When TSR=9 the inner part of the blades experience negative angle of attack and provide energy to the wind instead of subtracting it. The outer parts of the blade operate more efficiently, but due to the inner part working as a propeller the power coefficient is low. The thrust coefficient is high for this operating condition. When the turbine is operating in yawed condition, the wake width is reduced and shifted towards the yawed direction. At downstream distance X/D=4 for TSR=6 the wake deficit becomes more uniform for both yawAngle=0^0 and yawAngle=30^0. For the downstream configuration the yaw moment was generally stable at more operating conditions than the upstream setup. Common for both configurations was that the yaw moment tended to rotate the rotor plane out of the wind at low tip speed ratios and yaw angles. The downwind turbine got a stabilizing moment for a lower tip speed ratio than the upwind turbine for all yaw angles. Both upwind and downwind turbine setup had an unconditionally stable yaw moment for yawAngle=30^0.

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Wilmshurst, Stephen Michael Brand. "Wind turbine performance and dynamics." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236111.

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The work described in the dissertation consists of various experimental investigations involving a 5 metre diameter horizontal-axis wind turbine at the Cambridge field test site and a model wind turbine in the low-speed wind tunnel at the Central Electricity Research Laboratories. The first chapter is introductory, summarising previous work by the author's research group and placing the present work in its wider context. The second chapter describes measurements and analysis of the problem of tower shadow for a downwind turbine - the 5m machine - including the use of a streamlined fairing to alleviate the problem. There follow three chapters relating to the broad area of wind turbine performance. The first of these reports how power measurements made in two different ways have been used to define the performance of the 5m machine, giving results in good agreement with theoretical predictions. The next discussed the use of blade-mounted spoilers as a control mechanism and describes experiments which have been carried out with spoilers of a simple design. Chapter 5 concerns the subject of control strategies. Both computer simulation and experimental results are presented for several different operating strategies, with particular attention to the impact on power production. The final chapter describes work carried out in a wind tunnel using a small model turbine. A comprehensive investigation of the model's wake has been undertaken and is analysed with reference to blade loading, ambient turbulence and downstream development.

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Plumley, Charles. "The smart rotor wind turbine." Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25483.

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The smart rotor is an upgrade to the wind turbine rotor that facilitates active modification of the blade aerodynamics, thus allowing enhanced control of the rotor loads. In this thesis a number of research areas relating to the smart rotor are explored and advanced. The synthesised wind field spatial and temporal requirements are assessed, suggesting the current guidelines, of less than 5m spatial and 10Hz temporal resolutions, are more than adequate. Also regarding the wind field, it is shown that the smart rotor provides the greatest percentage benefits when there is high wind shear, but low turbulence intensity. An analytical approach to selecting the chord-width of trailing edge flaps, based on thin aerofoil theory, is presented. Demonstrating a trade-off between flap size, flap actuator requirements and load reductions. The unsteady aerodynamics of trailing edge flaps and their modelling in Bladed is also considered, showing only a limited requirement to develop the aerodynamic code. A comparison of individual pitch and smart rotor controllers shows that both methods can achieve similar load reductions. The main benefit of using a smart rotor system is the lower pitch motion. The smart rotor is also shown to reduce pitch motion by supplementing collective pitch control. The trade between pitch actuator requirements, load reductions and the cost of smart rotor control, is therefore considered the defining factor in valuing the smart rotor, rather than purely load reductions. Finally, a fault scenario of a single jammed flap is detected and corrected for. With results suggesting that even unreliable systems can achieve a significant lifetime fatigue load reduction. These studies are conducted using a methodical process detailed in this thesis, such that future researchers may build upon this work. Access to the models and code developed are provided in the appendix.

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Martin, Heather Rae. "Development of a Scale Model Wind Turbine for Testing of Offshore Floating Wind Turbine Systems." Fogler Library, University of Maine, 2011. http://www.library.umaine.edu/theses/pdf/MartinH2011.pdf.

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Papagiannis, Michail. "WIND TURBINE FOUNDATIONS IN CLAY : Technical and economic considerations for proposals for wind turbine foundations." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-353397.

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This thesis approaches the problem of the cost-efficient wind turbine foundation on an onshore site of clayey soil characteristics. The given soil stratigraphy includes a layer of clay and two sands of different density. The characteristics of the soil and the water level that were used as input come from a site in Peloponissos, Greece. The applied wind, static and seismic loads on this study were resolved with the German DIN standards, and other related research and European standards. The safety factors were adjusted for wind turbines. For the pile solution, after the bearing and overturning adequacy against the horizontal and vertical loads was proven with the calculation of the DIN equations, then the model was inserted in the Pfahl program using DIN 4017 equations to calculate settlements. Firstly, a shallow foundation of various dimensions in the clay layer over the water level with all the necessary checks was considered. Afterward, a deep foundation solution of a single bored pile, with reinforcement steel casing, of various diameters was investigated. The different foundation solutions were assessed and compared on a technical and economic basis. As a conclusion, the 0.70 meter diameter single pile was chosen as the best solution because it needs only a few days for construction, and it is the most cost-efficient. The chosen circular footing was of a diameter of 10 meters and 1.5 meter raft thickness, but proved unfeasible because of high excavations costs. The checks on the DIN standards and Eurocode that set the boundaries for the design in the two cases were recognised and possible future work goals were discussed.

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Mason, Jesse Cheyenne. "On improving wind-turbine hub-height wind-speed forecasts." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46558.

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Pitchford, Corey. "Impedance-Based Structural Health Monitoring of Wind Turbine Blades." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/34946.

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Wind power is a fast-growing source of non-polluting, renewable energy with vast potential. However, current wind technology must be improved before the potential of wind power can be fully realized. One of the key components in improving wind turbines is their blades. Blade failure is very costly because blade failure can damage other blades, the wind turbine itself, and possibly other wind turbines. A successful structural health monitoring (SHM) system incorporated into wind turbines could extend blade life and allow for less conservative designs. Impedance-based SHM is a method which has shown promise on a wide variety of structures. The technique utilizes small piezoceramic (PZT) patches attached to a structure as self-sensing actuators to both excite the structure with high-frequency excitations, and monitor any changes in structural mechanical impedance. By monitoring the electrical impedance of the PZT, assessments can be made about the integrity of the mechanical structure. Recent advances in hardware systems with onboard computing, including actuation and sensing, computational algorithms, and wireless telemetry, have improved the accessibility of the impedance method for in-field measurements. The feasibility of implementing impedance-based SHM on wind turbine blades is investigated in this work. Experimentation was performed to determine the capability of the method to detect damage on blades. First, tests were run to detect both indirect and actual forms of damage on a section of an actual wind turbine blade provided by Sandia National Laboratories. Additional tests were run on the same blade section using a high-frequency response function method of SHM for comparison. Finally, based on the results of the initial testing, the impedance method was utilized in an attempt to detect damage during a fatigue test of an experimental wind turbine blade at the National Renewable Energy Laboratoryâ s National Wind Technology Center.
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Lynch, Charles Eric. "Advanced CFD methods for wind turbine analysis." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39491.

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Horizontal-axis wind turbines operate in a complex, inherently unsteady aerodynamic environment. The flow over the blades is dominated by 3-D effects, particularly during stall, which is accompanied by massive flow separation and vortex shedding. There is always bluff-body shedding from the turbine nacelle and support structure which interacts with the rotor wake. In addition, the high aspect ratios of wind turbine blades make them very flexible, leading to substantial aeroelastic deformation of the blades, altering the aerodynamics. Finally, when situated in a wind farm, turbines must operate in the unsteady wake of upstream neighbors. Though computational fluid dynamics (CFD) has made significant inroads as a research tool, simple, inexpensive methods, such as blade element momentum theory, are still the workhorses in wind turbine design and aeroelasticity applications. These methods are unable to accurately predict rotor loads near the edges of the operating envelope. In this work, a range of unstructured grid CFD techniques for predicting wind turbine loads and aeroelasticity has been developed and applied to the NREL Unsteady Aerodynamics Experiment Phase VI rotor. First, a kd-tree based nearest neighbor search algorithm was used to improve the computational efficiency of an approximate unsteady actuator blade method. This method was then shown to predict root and tip vortex locations and strengths similar to an overset method, but without the computational expense of modeling the blade surfaces. A hybrid Reynolds-averaged Navier-Stokes / Large Eddy Simulation (HRLES) turbulence model was extended to an unstructured grid framework and demonstrated to improve predictions of unsteady loading and shedding frequency in massively separated cases. For aeroelastic predictions, a methodology for tight coupling between an unstructured CFD solver and a computational structural dynamics tool was developed. Finally, time-accurate overset rotor simulations of a complete turbine---blades, nacelle, and tower---were conducted using both RANS and HRLES turbulence models. The HRLES model was able to accurately predict rotor loads when stalled. In yawed flow, excellent correlations of mean blade loads with experimental data were obtained across the span, and wake asymmetry and unsteadiness were also well-predicted.

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Friman, Manne. "Directivity of sound from wind turbines : A study on the horizontal sound radiation pattern from a wind turbine." Thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-48926.

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In the present paper, a study on the directivity of sound from a wind turbine has been conducted. The aim of the study is to investigate the horizontal sound radiation pattern through a field study compared to a noise prediction. The benefit of the results may be used to optimize the output effect from the wind turbine while the guidelines for noise levels at nearby residential areas still are met. The complete directivity pattern around the wind turbine was investigated by performing emission measurements around the wind turbine from a method described in IEC 61400-11 Wind turbine generator systems – Part 11: Acoustic noise measurement technique. Furthermore, the dominant sound source from the wind turbine, the turbulent boundary layer trailing edge noise, and the frequency range where it is dominating has also been scrutinized. The results show that the dipole character of the trailing edge noise has an impact on the entire horizontal radiation pattern from the wind turbine. From a field study it was found that there was a distinguishable directivity of the sound. On a distance of 125 m from the wind turbine the sound pressure level in the crosswind direction of the wind turbine is close to 3 dBA less than the sound pressure level in the downwind direction of the wind turbine when the wind speed is 8 m/s at a height of 10 m. The difference between other directions compared to the downwind direction is less significant. This could be utilized to optimize the power output, however the difference in sound level is relatively small but the advantage for power output have to be quantified before a conclusion of the benefits can be made.

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18

Medici, Davide. "Wind turbine wakes : controland vortex shedding." Licentiate thesis, KTH, Mechanics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-361.

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Wind tunnel studies of the wake behind a model wind turbine have been made in order to get a better understanding of wake development as well as the possibility to predict the power output from downstream turbines working in the wake of an upstream one. Both two-component hot-wire anemometry as well as particle image velocimetry (PIV) have been used to map the flow field. All three velocity components were measured both for the turbine rotor normal to the oncoming flow as well as with the turbine inclined to the free stream direction (the yaw angle was varied from 0 to 30 degrees). The measurements showed, as expected, a wake rotation in the opposite direction to that of the turbine. A yawed turbine is found to clearly deflect the wake flow to the side showing the potential of controlling the wake position by yawing the turbine. The power output of a yawed turbine was found to vary nearly as the square of the cosine of the yaw angle. The possibility to use active wake control by yawing an upstream turbine was evaluated and was shown to have a potential to increase the power output significantly for certain configurations. An unexpected feature of the flow was that spectra from the time signals showed the appearance of a low frequency fluctuation both in the wake and in the flow outside. This fluctuation was found both with and without free stream turbulence and also with a yawed turbine. The non-dimensional frequency (Strouhal number) was independent of the free-stream velocity and turbulence level but increases with the yaw angle. However the low frequency fluctuations were only observed when the tip speed ratio (or equivalently the drag coefficient) was high. This is in agreement with the idea that the turbine shed structures as a bluff body. It is hypothesized that the observed meandering of wakes in field measurements is due to this shedding.

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19

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

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

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20

Höyland, Jörg. "Challenges for large wind turbine blades." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13545.

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With global climate problems receiving increasingly international political attention,most European nations are looking for sources of renewable energy. Wind turbines area promising source of renewable energy and their numbers have steadily increasedsince the introduction of the modern wind turbine in the 1970s. The largest units todayhave a rated power of 7 MW and blades ranging up to 62.5 m in length. Offshore windturbines have access to stronger winds with less turbulence, thereby increasing theenergy output of each unit. Offshore turbines will also have a lesser environmentalimpact than onshore turbines. It is believed that the development of offshore wind turbineswill encourage the development of even longer blades. The main spar geometry of a 100 m wind turbine blade was established in order to evaluatehow the use of carbon and glass fiber composites would affect the design. A hybridsolution using UD carbon fiber for global stiffness and ±45° glass fiber plies for bucklingresistance was also developed. The ultimate loads were calculated for blades with pitchcontrol and blades experiencing failure of pitch control during the 1-year and 50-yearextreme gust. The DNV-OS-J102 standard for wind turbines was used in the calculationof safety factors for both loads and material strength criteria. The distribution of ±45°anti-buckling plies by buckling analysis is extremely time consuming and therefore aprogram for automatic ply distribution was developed. The Matlab program interactedwith the FEM software Abaqus, defining input files and extracting results, and proved tobe highly efficient. The results from the FEM analyses were combined with a simple costmodel in order to evaluate both the weight and cost of the different spar solutions. Important weight reductions can be obtained by optimizing the performance of the composite laminate in the spar. Several sub-models of the 100 m spar were created withthe aim of optimizing the spar’s buckling performance. The angle and distribution ofboth the ±45° and UD plies were systematically altered in order to increase the bucklingload. The introduction of ply homogenization and core material in the flange was alsoevaluated and yielded the largest increases of buckling load. The results from the optimizedsub-models were implemented in a 100 m spar and found to decrease theamount of ±45° plies by 50 %. A 6 m scaled main spar of glass fiber composite was produced by resin infusion. Thespar was tested in a 4-point bending test and designed to fail by buckling of the topflange. In order to control the location of the buckling failure, an artificial imperfectionwas introduced in the middle of the top flange during manufacturing. The imperfectionis representative for imperfections found during manufacturing of wind turbine spars. Inaddition to measuring force and global deflection, 25 strain gages were installed tomonitor the spar. Finally, a FEM analysis of the 6 m spar was developed and correlated with the experimentalresults. By implementing the imperfection in the compression spar and the useof non-linear analysis, the strain patterns from the test results were successfully reproduced

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Babu, Thennarasu Ganesh, and Annamalai Muralidharan Hemanth Kumar. "Transportation Excellence for Wind Turbine Nacelle." Thesis, KTH, Industriell produktion, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103012.

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With the growing demand of renewable wind energy, logistics and operations associated with a wind turbine makes for compelling study and analysis. The study entails understanding of transporting a wind turbine nacelle from Denmark till Australia. The methods of transporting the wind turbine nacelle and the modes of transportation that are currently in use have been studied. Factors that are detrimental to efficient shipping have been reviewed with existing literature and analysed for a wind turbine nacelle. The two key factors that influence transportation namely humidity and G-force have been identified. Simple and cost effective solutions such as use of insulation material, use of desiccants to overcome the effects of humidity, use of shock absorber pallets to reduce shock and vibration have been proposed. For the damages caused to a wind turbine nacelle due to random causes, some suggestions to prevent such damages have also been provided.

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22

Ivanell, Stefan S. A. "Numerical computations of wind turbine wakes." Licentiate thesis, Stockholm : Royal Institute of Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-316.

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23

Schmidt, Michael Frank. "Economic optimization of wind turbine design." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19740.

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24

Bailly, Cyril. "Wind turbine dynamic - application to foundations." Thesis, KTH, Bro- och stålbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145160.

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These latest years, the green energy is highlighted and new technologies appeared. It is the case for wind turbines. The aim of latest developments has been to increase the power output. The use of new material enables the design of wind turbine with an impressive height, more and more flexible, inducing significant dynamic forces. However, several problems have been encountered on the connection between the foundation and the tower, which threaten the entire integrity of the structure. The initial lifetime could be impacted. The first aims of the master thesis are to understand the dynamic behavior of a wind turbine, determine the resultant forces at the foundation in order to explain the issues encountered at the foundation level on site, and compare these results with the resultant forces given by the wind turbine manufacturer. Indeed, the constructor transmits to the civil engineer one or more resultants forces without justifications in order to design the foundation. These loads are often issued from extreme load case. The analysis of the serviceability limit state is not well realized. It is this resultant force in operation which must be determined in this master thesis. After having presented the history of wind turbines, the different parts and the model use for the wind; the blade element model is used to calculate the forces of the wind on the rotor. These forces calculated from the theory used are eventually compared with the provider data. The turbulence component of the wind on the tower is evaluated by a spectral method and a fluid structure interaction with the software Abaqus. The inertial effects of the tower are calculated in order to give an order of magnitude of the resultant load on the foundations. This knowledge enables to analyze the connection in serviceability limit state which is another aim of the study. An analysis of the connection is done in order to get an idea of the risks. In particular, the punching resistance and the stability of the structure are verified.

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Kopp, Duncan Rath. "Foundations for an offshore wind turbine." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/60766.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 75-76).
Worldwide energy demand is growing rapidly, and there is great interest in reducing the current reliance on fossil fuels for uses such as power generation, transportation, and manufacturing. Renewable energy sources, such as solar and wind, are abundant but have very low power densities. The US is in the process of approving its first offshore wind farm, located in Nantucket Sound. Geotechnical factors will play a large role in the development of offshore wind projects due to the high cost contribution from foundations, and the high loads associated with storm conditions. Offshore wind turbine foundations provide unique design challenges. First, various foundation alternatives exist, so it is important that an appropriate cost-effective foundation type be selected. Second, the loads and soil conditions will vary for each location. Therefore, it is important to ensure the foundation can adequately support vertical and horizontal loads. Finally, each turbine manufacturer has unique deflection and rotation criteria. Therefore, the foundation should perform within those tolerances, even under worst-case loading. This thesis considers the performance of a monopile foundation under typical vertical and horizontal storm loading conditions. Capacity, deflection, and rotation of a proposed monopile foundation are calculated by various methods to simulate the design procedure. The results show that very stiff foundations are required to keep pile head movements within design tolerances.
by Duncan Rath Kopp.
M.Eng.

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26

Hunter-Jones, Bridget I. "Redesign of a wind turbine hub." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92187.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 27).
The current designs of wind turbine hubs contain many faults. The slew ring bearing that connects the blade to the hub takes on a large bending moment that in many cases causes the joints to fail and the blade to break off. The design of the hub is very large, heavy, and expensive to machine. The objective of this research is to reappraise the existing design of wind turbine hub and to suggest an alternative design, which does not have the design faults that are currently found. Drawings and sketches are presented along with all necessary calculations for the current and new wind turbine hub. The proposed redesign of the hub will have a bearing pack that will distribute the load of the blade and a new hub which is lighter, less complex, and simple to machine. This new design will be much safer than the current design and will produce more reliable wind turbines.
by Bridget I. Hunter-Jones.
S.B.

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27

Deters, Christian. "Intelligent assembly of wind turbine hubs." Thesis, King's College London (University of London), 2014. https://kclpure.kcl.ac.uk/portal/en/theses/intelligent-assembly-of-wind-turbine-hubs(fa88b634-aa36-4e71-bd12-62352873ca93).html.

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The fast growing wind turbine industry is expected to play a major role in solving our energy needs in the future. At present turbine manufacturing is performed mostly manually. Due to market growth the economical peak point is reached where an automated assembly concept can be introduced. This thesis focuses on the assembly of the wind turbine hub, in particular, on the bolt tightening process for the wind turbine bearing assembly, contributing to EU project COSMOS. Within this industrial research project, bolt tightening has been identified as an important research problem and the control strategies derived in this PhD thesis contributed to the activities of COSMOS. A wind turbine hub has three bearings which are assembled using multiple bolts (in current wind turbines, this can be up to 128 bolts). With the need to conform to stringent safety requirements and with the aim to produce long-lasting systems, the desired clamping force between the nut and a counteracting flange needs to be accurately and reliably achieved as a result of the tightening process. This thesis analyses the bolt tightening process divided into several tightening stages, with each stage addressing particular control and safety problems. The introduced fuzzy control architecture makes use of membership functions combined with linguistic rules to set the control target (which are specific torque and angle levels for the investigated wind turbine assembly process) to ensure that the desired clamping force is reached successfully and accurately. The control results (step response of the final control values and final clamping force) have been compared to more traditional control paradigms, including the proportional-integral-derivative (PID) controller. Experiments have shown that the accuracy improved and the standard deviation of the Fuzzy controller is more than 4 times lower than the one achieved using the PID controller. The bolt system has been further analysed and a numerical state space model has been identified using an experimental identification method. The found model has been used to identify suitable control gains for a proportional-integral (PI) control strategy and were then fine-tuned using an online learning process based on a genetic algorithm (GA). Error detection and avoidance is another important aspect when assembling safety-critical systems such as wind turbines. This PhD study introduces an error detection mechanism that is active during the bolt tightening process and integrated with the fuzzy control architecture used for bolt tightening. This is achieved by defining additional membership functions and linguistic rules for error detection. The error detection mechanism is based on a logic based approach terminating the tightening process when critical control parameters are exceeded.

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Kim, Yusik. "Wind turbine aerodynamics in freestream turbulence." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/360372/.

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Topics in wind turbine aerodynamics are reviewed. These include the effect of freestrearn turbulence all the flows over wind turbine blades; dynamic stall phenomenon; and rotational augmentation. The advantages of numerical studies on these topics are highlighted and large-eddy simulation (LES) is selected to overcome the defects for other numerical approaches, e.g. Reynolds Average Navier-Stokes (RANS) , all such applications

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29

Kleusberg, Elektra. "Wind turbine simulations using spectral elements." Licentiate thesis, KTH, Stabilitet, Transition, Kontroll, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-207630.

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Understanding the flow around wind turbines is a highly relevant research question due to the increased interest in harvesting energy from renewable sources. This thesis approaches the topic by means of numerical simulations using the actuator line method and the incompressible Navier–Stokes equations in the spectral element code Nek5000. The aim is to gain enhanced understanding of the wind turbine wake structure and wind turbine wake interaction. A verification study of the method and implementation is performed against the finite volume solver EllipSys3D using two types of turbines, an idealized constant circulation turbine and the Tjæreborg turbine. It is shown that Nek5000 requires significantly lower resolution to accurately compute the wake development, however, at the cost of a smaller time step.The constant circulation turbine is investigated further with the goal of establishing guidelines for the use of the actuator line method in spectral element codes, where the mesh is inherently non-equidistant and currently used guidelines of force distribution based on Gaussian kernels are difficult to apply. It is shown that Nek5000 requires a larger kernel width in the fixed frame of reference to remove numerical instabilities. Further, the impact of different Gaussian widths on the wake development is investigated in the rotating frame of reference, showing that the convection velocity and the breakdown of the spiral tip and root vortices are dependent on the Gaussian width. In the second part, the flow around single and multiple wind-turbine setups at different operating conditions is investigated and compared with experimental results. The focus is placed on comparing the power and thrust coefficients and the wake development based on the time-averaged streamwise velocity and turbulent stresses. Further the influence of the tower model is investigated both upstream and downstream of the turbine. The results show that the wake is captured accurately in most cases. The loading exhibits a significant dependence on the Reynolds number at which the airfoil data is extracted. When the helical tip vortices are stable the turbulent stresses at the tip vortices are underestimated in the numerical simulations. This is due to the finite resolution and the projection of the actuator line forces in the numerical domain using a prescribed Gaussian width, which leads to lower induced velocities in the helical vortices.

QC 20170523

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30

Ivanell, Stefan S. A. "Numerical computations of wind turbine wakes." Doctoral thesis, Stockholm : Royal Institute of Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9916.

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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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Walgern, Julia. "Impact of Wind Farm Control Technologies on Wind Turbine Reliability." Thesis, Uppsala universitet, Elektricitetslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388333.

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Cost efficient operation and maintenance strategies are crucial for reducing cost of wind energy. Since the regime change from feed-in tariffs to an auction-based bidding system for capacity in most European wind projects, levelized cost of energy is challenged constantly. Therefore, new technologies such as new controllers are developed to improve operation and to increase profit. Previous research studies demonstrated the advantage of increased power output of wake redirection control. However, understanding and quantifying the impact of wind farm control technologies on operation and maintenance strategies is inevitable to evaluate the economic feasibility of such new technologies. Thus, an event-based O&M simulation tool has been developed. Besides general modules, such as the wind turbine model, the weather forecasting model and a model for simulating corrective and planned maintenance, the developed tool also takes wake effects into account. This allows considering different power productions for each individual turbine and a failure rate distribution within the wind farm which is based on altering loads on the different components. Both aspects are driven by changes in operation when applying a new controller technology. Exemplarily, the economic feasibility of a closed-loop active wake steering control has been analysed. Main achievements of this study are the possibility to quantify the impact of the active wake steering control on O&M related KPIs. Results show that additional loads caused by applying yaw-misalignment and redirecting wake, lead to an increase in OPEX. However, the achieved energy production gain and thus related additional revenue exceeds additional cost in the case study. Nonetheless, the study reveals that the profitability of the controller is highly dependent on the electricity price which can be acquired during the wind farm’s lifetime.

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33

Zhang, Zijun Kusiak Andrew. "Wind turbine vibration study a data driven methodology /." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/454.

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34

Ali, Muhammad Anttho. "In-cloud ice accretion modeling on wind turbine blades using an extended Messinger model." Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53870.

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Wind turbines often operate under cold weather conditions where icing may occur. Icing causes the blade sections to stall prematurely reducing the power production at a given wind speed. The unsteady aerodynamic loads associated with icing can accelerate blade structural fatigue and creates safety concerns. In this work, the combined blade element-momentum theory is used to compute the air loads on the baseline rotor blades, prior to icing. At each blade section, a Lagrangian particle trajectory model is used to model the water droplet trajectories and their impact on the blade surface. An extended Messinger model is next used to solve the conservation of mass, momentum, and energy equations in the boundary layer over the surface, and to determine ice accretion rate. Finally, the aerodynamic characteristics of the iced blade sections are estimated using XFOIL, which initiate the next iteration step for the computation of air loads via combined blade element theory. The procedure repeats until a desired exposure time is achieved. The performance degradation is then predicted, based on the aerodynamic characteristics of the final iced blades. The 2-D ice shapes obtained are compared against experimental data at several representative atmospheric conditions with acceptable agreement. The performance of a generic experimental wind turbine rotor exposed to icing climate is simulated to obtain the power loss and identify the critical locations on the blade. The results suggest the outboard of the blade is more prone to ice accumulation causing considerable loss of lift at these sections. Also, the blades operating at a higher pitch are expected to accumulate more ice. The loss in power ranges from 10% to 50% of the rated power for different pitch settings under the same operating conditions.

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Hack, Brian E. "Analysis of MIT campus wind resources for future wind turbine installation." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45837.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
Includes bibliographical references (p. 23).
As our nation's continuing dependence on fossil energy and the problems that result from that dependence grow more apparent, we must look to alternative sources of energy to power the country. As a global scientific and technological leader, MIT is expected to take a part in the search for and support of alternative energy sources. One such source that has tremendous potential, yet tends to be underrepresented, is wind energy. Following the previous wind resource analysis done by Richard Bates, Samantha Fox, Katherine McCusker, and Kathryn Pesce, I have expanded upon the suggestions made at the conclusion of their analysis. The Eastgate building on MIT's campus was identified as one possible location for small scale wind turbines. I completed a computational fluid dynamics (CFD) analysis on that building as well as the Johnson Athletic Center to determine if there were adequate wind resources to make the installation of a wind turbine on one of these buildings economical. The results of the CFD analysis show that the west edge of the roof on the Johnson Athletic Center is a promising location for the installation of a roof-top wind turbine. Further investigation of the wind resources at that location should be conducted.
by Brian E. Hack.
S.B.

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36

Fossum, Peter Kalsaas. "Aeroelastic analysis of an offshore wind turbine : Design and Fatigue Performance of Large Utility-Scale Wind Turbine Blades." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18547.

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Aeroelastic design and fatigue analysis of large utility-scale wind turbine blades are performed. The applied fatigue model is based on established methods and is incorporated in an iterative numerical design tool for realistic wind turbine blades. All aerodynamic and structural design properties are available in literature. The software tool FAST is used for advanced aero-servo-elastic load calculations and stress-histories are calculated with elementary beam theory.According to wind energy design standards, a turbulent wind load case is implemented. Fatigue loads are estimated based on 100% availability and a site-specific annual wind distribution. Rainflow cycle counting and Miner’s sum for cumulative damage prediction is used together with constant life diagrams tailored to actual material S-N data. Material properties are based on 95% survival probability, 95% confidence level, and additional material safety factors to maintain conservative results. Fatigue performance is first evaluated for the baseline blade design of the 10MW NOWITECH reference wind turbine. Results show that blade damage is dominated by tensile stresses due to poorer tensile fatigue characteristics of the shell glass fiber material. The interaction between turbulent wind and gravitational fluctuations is demonstrated to greatly influence the damage. The need for relevant S-N data to closely predict such blade stress cycle events is investigated to avoid non-conservative conclusions. State-of-art wind turbine blade trends are discussed and different designs of the NOWITECH baseline blade are analyzed in a parametric study focusing on fatigue performance and material costs.

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37

Zhang, Xu. "Analysis and optimisation of a novel wind turbine." Thesis, University of Hertfordshire, 2014. http://hdl.handle.net/2299/13897.

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The technologies of urban wind turbines have been rapidly developed in recent years, but urban wind turbines have not found a wide application due to the limitations of their designs. The power output of urban wind turbine is significantly affected by urban terrain, which can cause low speed flow with frequent change of its direction. Thus, there is a need for a new wind turbine to meet the requirements of an urban wind turbine. In this study, a novel wind turbine for urban areas was designed and developed. The investigations of the novel urban wind turbine were carried out by using computational fluid dynamic (CFD) simulations and wind tunnel tests. The results from the investigation have shown that the novel wind turbine has a great potential to harvest wind energy in urban areas. A detailed study of effects of each parameter on wind energy concentration of the novel wind turbine was carried out with CFD simulations. According to the simulation results, the shroud structure of the novel wind turbine was modified and the dimensions of the final structure were identified. It was determined that the capability of wind energy concentration of the novel wind turbine shroud has been significantly improved through the structure optimisations. Furthermore, guide vane and impulse turbine were implemented in the novel wind turbine. The flow characteristics through the guide vane was studied and discussed. It was found that the wind flow characteristics can be properly modified by implementing guide vane and the structure of impulse turbine was suitable to be implemented in the novel wind turbine due to the flow characteristic through the guide vane.

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38

Kishore, Ravi Anant. "Small-scale Wind Energy Portable Turbine (SWEPT)." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23099.

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Large Scale Wind Turbines (LSWTs) have been extensively examined for decades but very few studies have been conducted on the small scale wind turbines (SSWTs) especially for the applications near ground level where wind speed is of order of few meters per second. This study provides the first systematic effort towards design and development of SSWTs (rotor diameter<50 cm) targeted to operate at low wind speeds (<5 m/s). An inverse design and optimization tool based on Blade Element Momentum theory is proposed. The utility and efficacy of the tool was validated by demonstrating a 40 cm diameter small-scale wind energy portable turbine (SWEPT) operating in very low wind speed range of 1 m/s-5 m/s with extremely high power coefficient. In comparison to the published literature, SWEPT is one of the most efficient wind turbines at the small scale and very low wind speeds with the power coefficient of 32% and overall efficiency of 21% at its rated wind speed of 4.0 m/s. It has very low cut-in speed of 1.7 m/s. Wind tunnel experiments revealed that SWEPT has rated power output of 1 W at 4.0 m/s, and it is capable of producing power output up to 9.3 W at wind speed of 10 m/s. The study was further extended to develop a piezoelectric wind turbine which operates below 2.0 m/s wind speed. The piezoelectric wind turbine of overall dimension of 100mm x 78mm x 65mm is capable of producing peak electric power of about 450 microwatt at the rated wind speed of 1.9 m/s.
Master of Science

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39

Lee, Donghoon. "Multi-flexible-body analysis for applications to wind turbine control design." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04052004-180040/unrestricted/lee%5Fdonghoon%5F200312%5Fphd.pdf.

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Zamacona, M. Carlos, and A. Fernando Vanegas. "Robust Control Solution of a Wind Turbine." Thesis, Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-1449.

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Power generation using wind turbines is a highly researched control field.

Many control designs have been proposed based on continuous-time models

like PI-control, or state observers with state feedback but without special

regard to robustness to model uncertainties. The aim of this thesis was to

design a robust digital controller for a wind turbine.

The design was based on a discrete-time model in the polynomial framework

that was derived from a continuous-time state-space model based on

data from a real plant. A digital controller was then designed by interactive

pole placement to satisfy bounds on sensitivity functions.

As a result the controller eliminates steady state errors after a step

response, gives sufficient damping by using dynamical feedback, tolerates

changes in the dynamics to account for non linear effects, and avoids feedback

of high frequency un modeled dynamics.

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41

Nygard, Øyvind Vik. "Wake behind a horizontal-axis wind turbine." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13691.

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In this paper theory on cylinder and wind turbine wakes have been studied, and experimental work on the wake behind a wind turbine have been carried out in the Fluids engineering laboratory at NTNU.The objective of this paper is to show and explain how the wake from the tower of a wind turbine develops and interacts with the rotor wake. It is desirable to study the wake for different operating conditions of the wind turbine to see how the wake development is affected. A summary of classical wake theory, aerodynamics and wind turbine wakes will be given. Measurements in the wake of a cylinder fitted with pressure taps for drag calculation will be compared to theory and used as a reference. Also, the wake behind the wind turbine tower with the blades taken off will be studied and compared to the tower wake found behind the operating wind turbine.For comparison, reference measurements were done in the wake behind a cylinder and behind the free standing wind turbine tower without blades. The drag coefficient obtained from pressure measurements on the cylinder surface were 1.077 and match the expected value of 1.2 fairly well. However, neither the shape nor the maximum velocity deficit measured in the wake fit the theoretical profile. Drag coefficients calculated from the momentum deficit across the wake were only in the range of 0.65, which is almost half of the expected, and the huge deviation from theory could not be explained. With values between 1.07 and 1.50 the measured drag coefficients in the wake of the tower alone were also not consistent with theory. The shape of the tower wake profile coincides better with theory than the cylinder wake, but the maximum velocity deficit is generally lower than predicted by theory. Difference in drag can be explained with blockage effect and the smaller velocity deficit may be attributed to the free stream flow over the top of the tower interfering with the wake downstream of the tower.Wake surveys behind the wind turbine were done at three operating conditions: Optimum tip speed ratio; low tip speed ratio, with power output half of output at best point operation; and high tip speed ratio, with power output half of output at best point operation. The increased turbulence level behind the rotor the flow seen by the tower is believed to creates a turbulent boundary layer which stays attached to the surface to a point further back on the tower, creating a narrower and weaker wake compared the free standing tower wake. Optimum turbine operation gives a stronger rotation of the wake doe to the higher torque on the blades compared to the two other cases. At high TSR the wake is more uniform, and the tower wake disappears faster than in the wake of the turbine operating at lower TSR. The Strouhal number found in all the wakes match well with theory and does not seem to be affected by the rotor wake except that the tower vortices dies out quicker.

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42

Blomhoff, Hedda Paulsen. "An experimental investigation of wind turbine wakes." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18412.

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In the present study the wake behind a scaled; Horizontal Axis Wind Turbine (HAWT) has been investigated. The experiments were performed at the Department of Energy and Process Engineering, at the Norwegian University of Science and Technology, NTNU. The turbine was installed in the wind tunnel at the department and measurements were performed at several distances behind the turbine to examine the development of the flow. A five-hole pitot probe was applied as measurement instrument. The instrument made it possible to calculate both size and direction of the velocity components.Through the experiments, characteristic curves of the turbine and grid measurements over the cross-section of the wind tunnel, were obtained. The power and thrust coefficients were measured against the local velocity ratio at the tip of the blade, the 'Tip Speed Ratio' (TSR). The power coefficient had a peak at TSR=5,5. The maximum value at this point was 0,45. The highest measured thrust coefficient was 1,15, achieved at TSR=10,3. During the experiments the turbine operated at optimal conditions, at the highest obtained power coefficient.Measurements behind the turbine found that the axial velocity distribution developed as expected. A significant velocity deficit was measured in the wake behind the turbine, which gradually decreased with increased distance to the turbine. Due to the presence of the hub and tower, the middle of the wake was characterized by disturbances. Moving down the wake the profile got more symmetric. The tangential profile was almost symmetric about the origin, right behind the turbine, but drifted to the left at increased distance downstream. Contribution from the tangential components were gradually reduced further down the wake.The tower shadow moved with the rotation of the wake, in clockwise direction, as a region of lower velocities than the prevailing wake. Further downstream the tower shadow merged with the surrounding wake.The rotational axis relocated in the wake behind the turbine. Downstream, measurements showed that the center of rotation moved to the left of the origin. To investigate if the tower was responsible for the experienced downshift, an additional tower was mounted to the tunnel roof, above the turbine. The additional tower created symmetry about the hub and gave a symmetric development of the flow field. Thus, it was concluded that the tower was responsible for the relocation of the rotational axis.

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43

Charreron, Damien, and David Moreno. "Case study wind turbine at Läkerol Arena." Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-7296.

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44

Simmons, Anton Dominic. "A comparison of wind turbine control policies." Thesis, Imperial College London, 1993. http://hdl.handle.net/10044/1/7447.

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45

Ma, Xin. "Adaptive extremum control and wind turbine control /." Online version, 1997. http://bibpurl.oclc.org/web/24097.

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46

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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47

Buckney, Neil. "Optimisation of wind turbine blade structural topology." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633206.

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Wind turbines become more cost effective as they grow larger; however the blade mass increases at a greater rate than the power. For a continued size increase, reducing the mass of the blades is necessary. Additionally, lighter blades lower overall turbine costs because the loads on the rest of the structure are decreased. Therefore, the use of lightweight blades can have a significant impact on the cost of wind energy. To achieve blade mass reductions, an alternative structural layout is generated using topology optimisation. The result is a topology which varies along the blade length, transitioning from a structure with trailing edge reinforcement to one with offset spar caps. An alternative beam topology optimisation method is developed that enabled a buckling constraint to be applied. The structural efficiency of the topologically optimised blade is then assessed using shape factors and performance indices, measures which have been expanded to account for asymmetric bending of beams with multiple materials. The utility of shape factors is first demonstrated on six example beam sections before being applied to the blade. To demonstrate application to a more refined design, the performance of a 100m wind turbine blade is assessed , using maps to visualise the structural efficiency. The effect of using carbon fibre and offsetting the spar caps is evaluated, providing a greater understanding of the improved designs. Overall , the results show that wind turbine blades can be improved with structural layouts that take advantage of favourable bend-bend coupling between the out-of-plane and in-plane directions. Because traditional design concepts do not account for bending coupling, a missed opportunity for further mass reduction exists. To this day, the structural topology of the blades has remained fixed despite increasing length and changing loads. Topology optimisation and structural efficiency analysis are shown as methods used to challenge this design convention and reduce blade mass, thereby lowering the cost of wind energy.

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48

Al, Kaysee Ahmed, and Marek Wronski. "Dynamic Substructuring of an A600 Wind Turbine." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-36194.

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A limited and extendable master thesis is representing the first step in the experimental substructuring of an A600 wind turbine. Additional masses have been designed, manufactured and added to the sub components for the laboratory experimental tests. Further preparations for dynamic experimental tests have been described and implemented. Vibrational tests of a modified wind turbine blade have been made using the Leuven Measurements System (LMS) for excitations and data acquisition purposes. The theory of frequency response function based substructuring applied on the wind turbine blade model is demonstrated. The theory and an example of a Matlab coded spring-mass system, an experimental model of a wind turbine blade and FRFs stemming from measurements are reported.

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49

El-Bardisi, Mansour Mohamed Mansour. "Reduction of wind turbine noise through design." Thesis, City University London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332781.

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50

Tautz-Weinert, Jannis. "Improved wind turbine monitoring using operational data." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/36199.

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With wind energy becoming a major source of energy, there is a pressing need to reduce all associated costs to be competitive in a market that might be fully subsidy-free in the near future. Before thousands of wind turbines were installed all over the world, research in e.g. understanding aerodynamics, developing new materials, designing better gearboxes, improving power electronics etc., helped to cut down wind turbine manufacturing costs. It might be assumed, that this would be sufficient to reduce the costs of wind energy as the resource, the wind itself, is free of costs. However, it has become clear that the operation and maintenance of wind turbines contributes significantly to the overall cost of energy. Harsh environmental conditions and the frequently remote locations of the turbines makes maintenance of wind turbines challenging. Just recently, the industry realised that a move from reactive and scheduled maintenance towards preventative or condition-based maintenance will be crucial to further reduce costs. Knowing the condition of the wind turbine is key for any optimisation of operation and maintenance. There are various possibilities to install advanced sensors and monitoring systems developed in recent years. However, these will inevitably incur new costs that need to be worthwhile and retro-fits to existing turbines might not always be feasible. In contrast, this work focuses on ways to use operational data as recorded by the turbine's Supervisory Control And Data Acquisition (SCADA) system, which is installed in all modern wind turbines for operating purposes -- without additional costs. SCADA data usually contain information about the environmental conditions (e.g. wind speed, ambient temperature), the operation of the turbine (power production, rotational speed, pitch angle) and potentially the system's health status (temperatures, vibration). These measurements are commonly recorded in ten-minutely averages and might be seen as indirect and top-level information about the turbine's condition. Firstly, this thesis discusses the use of operational data to monitor the power performance to assess the overall efficiency of wind turbines and to analyse and optimise maintenance. In a sensitivity study, the financial consequences of imperfect maintenance are evaluated based on case study data and compared with environmental effects such as blade icing. It is shown how decision-making of wind farm operators could be supported with detailed `what-if' scenario analyses. Secondly, model-based monitoring of SCADA temperatures is investigated. This approach tries to identify hidden changes in the load-dependent fluctuations of drivetrain temperatures that can potentially reveal increased degradation and possible imminent failure. A detailed comparison of machine learning regression techniques and model configurations is conducted based on data from four wind farms with varying properties. The results indicate that the detailed setup of the model is very important while the selection of the modelling technique might be less relevant than expected. Ways to establish reliable failure detection are discussed and a condition index is developed based on an ensemble of different models and anomaly measures. However, the findings also highlight that better documentation of maintenance is required to further improve data-driven condition monitoring approaches. In the next part, the capabilities of operational data are explored in a study with data from both the SCADA system and a Condition Monitoring System (CMS) based on drivetrain vibrations. Analyses of signal similarity and data clusters reveal signal relationships and potential for synergistic effects of the different data sources. An application of machine learning techniques demonstrates that the alarms of the commercial CMS can be predicted in certain cases with SCADA data alone. Finally, the benefits of having wind turbines in farms are investigated in the context of condition monitoring. Several approaches are developed to improve failure detection based on operational statistics, CMS vibrations or SCADA temperatures. It is demonstrated that utilising comparisons with neighbouring turbines might be beneficial to get earlier and more reliable warnings of imminent failures. This work has been part of the Advanced Wind Energy Systems Operation and Maintenance Expertise (AWESOME) project, a European consortium with companies, universities and research centres in the wind energy sector from Spain, Italy, Germany, Denmark, Norway and UK. Parts of this work were developed in collaboration with other fellows in the project (as marked and explained in footnotes).

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Dissertations / Theses on the topic 'Wind turbine'

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