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1
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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Shaheen, Mohammed Mahmoud Zaki Mohammed. "Design and Assessment of Vertical Axis Wind Turbine Farms." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439306478.
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Weiss, Samuel Bruce. "Vertical axis wind turbine with continuous blade angle adjustment." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/65178.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student submitted PDF version of thesis.<br>Includes bibliographical references (p. 26).<br>The author presents a concept for a vertical axis wind turbine that utilizes each blade's entire rotational cycle for power generation. Each blade has its own vertical axis of rotation and is constrained to rotate at the rate of one half of a revolution per full revolution of the rotor. For a rotor of radius r and blades of width b, a technical analysis predicts a theoretical maximum power coefficient of CP = b 2r+b, neglecting wind flow interference by upwind blades. This theoretical power coefficient is generally greater than the efficiency of a typical Savonius wind turbine (CP ~~ 0.15), and it reaches CP = 0.5 at the limiting blade width, b = 2r. The analysis also predicts a static torque and optimal tip-speed ratio that are both greater than those of a Savonius wind turbine with similar blade dimensions. Design considerations for implementing the kinematic constraint and for blade adjustment to account for changes in wind direction are discussed, and the author's prototype is presented. Testing of the prototype demonstrated that implementation of the kinematic constraint is feasible, and that efficiencies greater than those achievable by a Savonius turbine are plausible. In 4 m s wind conditions, the prototype yielded an estimated CP of 0.15, with much room for improvement through design changes and blade optimization in future iterations of this style of turbine.<br>by Samuel Bruce Weiss.<br>S.B.
4
Waltham, M. R. "Sailwing vertical axis wind turbines." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316334.
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Rynkiewicz, Mateusz. "Design of PM generator for avertical axis wind turbine." Thesis, Uppsala universitet, Elektricitetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-177309.
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The task in this project is to design a generator for a vertical axis wind turbine withpower rated to 20kW at a wind speed of 10m/s. The project is conducted at theDivision of Electricity at Uppsala University with collaboration from ElectricGeneration AB. The design has just a few moving parts, which decreases maintenancecosts and increases its toughness. The turbine absorbs wind from every direction butits rotation speed ratio is lower than horizontal axis wind turbines. It means that thegenerator must be bigger and therefore more expensive. Price is an importantcriterion for the generator. Neodymium magnets are expensive so the amount of thismaterial must be limited.Several designs have been simulated but one final design has proven the mostpromising. It fulfills all specifications such as efficiency above 95%, 20kW outputpower and it also has a relatively low amount of hard magnetic material.A design with a single row of cables per slot was decided upon to eliminate heatpockets between cable rows, which can occur in designs with two cable rows perslot. It would be interesting to study designs with two or more cable rows per slot, asit could lead to a smaller and more efficient machine.
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Robotham, Antony John. "The aerodynamic control of the V-type vertical axis wind turbine." n.p, 1989. http://ethos.bl.uk/.
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Norström, Parliden Jonas, and Mateusz Rynkiewicz. "Design of PM generator for a vertical axis wind turbine." Thesis, Uppsala universitet, Elektricitetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-180910.
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The task in this project is to design a generator for a vertical axis wind turbine withpower rated to 20kW at a wind speed of 10m/s. The project is conducted at theDivision of Electricity at Uppsala University with collaboration from ElectricGeneration AB. The design has just a few moving parts, which decreases maintenancecosts and increases its toughness. The turbine absorbs wind from every direction butits rotation speed ratio is lower than horizontal axis wind turbines. It means that thegenerator must be bigger and therefore more expensive. Price is an importantcriterion for the generator. Neodymium magnets are expensive so the amount of thismaterial must be limited.Several designs have been simulated but one final design has proven the mostpromising. It fulfills all specifications such as efficiency above 95%, 20kW outputpower and it also has a relatively low amount of hard magnetic material.A design with a single row of cables per slot was decided upon to eliminate heatpockets between cable rows, which can occur in designs with two cable rows perslot. It would be interesting to study designs with two or more cable rows per slot, asit could lead to a smaller and more efficient machine.
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Colley, Gareth. "Design, operation and diagnostics of a vertical axis wind turbine." Thesis, University of Huddersfield, 2012. http://eprints.hud.ac.uk/id/eprint/17547/.
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The need for sustainable energy sources becomes greater each year due to the continued depletion of fossil fuels and the resulting energy crisis. Solutions to this problem are potentially in the form of wind turbines which have been receiving increased support at a micro level. At present a number of wind turbines are being developed that are of cross-flow vertical axis operation which have shown significant increases in performance compared to existing technologies. From an extensive literature review a number of key issues have been highlighted which are concerned with design, operation and diagnostics of this new wind power technology which have been used to formulate the scope of this research. A design procedure for a cross-flow machine that features both a multi-blade rotor and fixed outer stator guide vanes has been derived in which both rotor and stator blade profiles have been generated for a low wind speed urban application. Using these blade profiles a prototype wind turbine has been fabricated and used for full scale development testing. In the presented work both experimental and numerical investigations have been carried out to determine the operational characteristics of this new technology. The experimental data obtained under controlled laboratory conditions has been used to validate a Computational Fluid Dynamic (CFD) model which has been used throughout. A flow field analysis of the machine has highlighted large asymmetries in both pressure and velocity about the central axis of the machine in both stationary and rotating frames of reference. This has identified primary inefficiencies within the design which limit the torque generating capability of the rotor due to blockage effects and downstream blade interactions. This asymmetry has been quantified in the form asymmetry ratio and used to determine downstream rotor effects and the optimum location of multiple wind turbines which is seen to be x/D >10 in order to minimize performance reductions. The torque and power generation capabilities of the machine have been characterised at both 'design' and ‘offdesign' conditions in which individual blade torque contributions have been quantified. This has highlighted specific energy transfer zones within the turbine namely at a few key blades on the windward side of the rotor. It has also shown counter-rotating torques generated on the leeward side of the machine at specific blade positions during the cycle. Overall performance has been quantified in which a maximum CT = 1.7 and CP = 0.24 has been observed which has some similarities to the Savonius rotor. Geometric effects on torque and power response have been quantified in which a strong dependence on stator blade number is noticed. Further, maximum performance output of the machine is generated at the baseline design condition. Using torque response data a multiple regression model has been developed in which a design equation for crossflow rotor torque has been derived which can be used during the conceptual design phase. Finally, the effectiveness of a two-dimensional transient CFD model to predict cross-flow wind turbine rotor blade loss has been evaluated against full scale experimental data. It has shown that from analysis in the frequency domain specific blade faults can be recognised which agrees well with experimental data obtained. The use of this model for wind turbine performance emulation has been described.
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D'Ambrosio, Marco, and Marco Medaglia. "Vertical Axis Wind Turbines: History, Technology and Applications." Thesis, Halmstad University, Halmstad University, School of Business and Engineering (SET), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-4986.
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<p>In this Master Thesis a review of different type of vertical axis wind turbines (VAWT) and a preliminary investigation of a new kind of VAWT are presented.</p><p>After an introduction about the historical background of wind power, the report deals with a more accurate analysis of the main type of VAWT, showing their characteristics and their operations. The aerodynamics of the wind turbines and a review of different type on generators that can be used to connect the wind mill to the electricity grid are reported as well.</p><p>Several statistics are also presented, in order to explain how the importance of the wind energy has grown up during the last decades and also to show that this development of the market of wind power creates new opportunity also for VAWT, that are less used than the horizontal axis wind turbine (HAWT).</p><p>In the end of 2009 a new kind of vertical axis wind turbine, a giromill 3 blades type, has been built in Falkenberg, by the Swedish company VerticalWind. The tower of this wind turbine is made by wood, in order to get a cheaper and more environment friendly structure, and a direct driven synchronous multipole with permanent magnents generator is located at its bottom. This 200 kW VAWT represents the intermediate step between the 12 kW prototype, built in collaboration with the Uppsala University, and the common Swedish commercial size of 2 MW, which is the goal of the company.</p><p>A preliminary investigation of the characteristics of this VAWT has been done, focusing in particular on the value of the frequency of resonance of the tower, an important value that must be never reached during the operative phase in order to avoid serious damage to all the structure, and on the power curve, used to evaluate the coefficient of power (Cp) of the turbine. The results of this investigation and the steps followed to get them are reported. Moreover a energy production analysis of the turbine has been done using WindPro, as well as a comparison with and older type on commercial VAWT.</p>
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Eriksson, Sandra. "Direct Driven Generators for Vertical Axis Wind Turbines." Doctoral thesis, Uppsala : Acta Universitatis Uppsaliensis, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9210.
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Rossander, Morgan. "Electromechanics of Vertical Axis Wind Turbines." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331844.
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Wind power is an established mean of clean energy production and the modern horizontal axis wind turbine has become a common sight. The need for maintenance is high and future wind turbines may need to be improved to enable more remote and offshore locations. Vertical axis wind turbines have possible benefits, such as higher reliability, less noise and lower centre of gravity. This thesis focuses on electromechanical interaction in the straight bladed Darrieus rotor (H-rotor) concept studied at Uppsala University. One of the challenges with vertical axis technology is the oscillating aerodynamic forces. A force measurement setup has been implemented to capture the forces on a three-bladed 12 kW open site prototype. The normal force showed good agreement with simulations. An aerodynamic torque could be estimated from the system. The total electrical torque in the generator was determined from electrical measurements. Both torque estimations lacked the expected aerodynamic ripple at three times per revolution. The even torque detected is an important result and more studies are required to confirm and understand it. The force measurement was also used to study the loads on the turbine in parked conditions. It was discovered that there is a strong dependence on wind direction and that there is a positive torque on the turbine at stand still. The results can assist to determine the best parking strategies for an H-rotor turbine. The studied concept also features diode rectification of the voltage from the permanent magnet synchronous generator. Diodes are considered a cheap and robust solution for rectification at the drawback of inducing ripple in the torque and output voltage. The propagation of the torque ripple was measured on the prototype and studied with simulations and analytical expressions. One key conclusion was that the mechanical driveline of the turbine is an effective filter of the diode induced torque ripple. A critical speed controller was implemented on the prototype. The controller was based on optimal torque control and according to the experiments and the simulations it was able to avoid a rotational speed span. Finally, the optimal torque control was evaluated for multiple turbines with diode rectification to a common DC-link. The setup can potentially reduce the overall complexity of wind farms. The simulations suggest that stability of the system can be obtained by controlling the DC-link load as a semi constant voltage. The thesis is based on nine papers of which six are treated in the thesis summary.
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Roynarin, Wirachai. "Optimisation of vertical axis wind turbines." Thesis, Northumbria University, 2004. http://nrl.northumbria.ac.uk/1655/.
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A practical Vertical Axis Wind Turbine (VAWTs) based on a Darrieus rotor has been designed and tested and found to be capable of self-starting at wind speeds above 4m/s. The self-start feature has been achieved by replacing the usual symmetrical aerofoil blade in the VAWT rotor and by using a concentric Savonius rotor or semi-cylinder turbine. A computer program was produced to compute the power coefficient versus tip speed ratio characteristics of a selected aerofoil profile employed in a VAWT. The program accounts for chord length, pitch angle, number of blades, and rotor radius at any wind speed. The published data from 40 aerofoil sections were assessed, taking into account the two main criteria — self-starting and efficiency. Computational fluid dynamics software (ANSYS, Flotran) has been used to investigate the lift and drag performance of a NACA 66-212 and NACA 4421 aerofoils in order to check the computer program predictions. Excellent agreement was obtained for the static aerofoil assessment, but only after special ICEM Computational Fluid Dynamics (CFD) meshing interface routines were utilised. However, agreement between the theoretical and published results was not good for the rotating aerofoils in a VAWT. Thus, further CFD work was not pursued and in preference, an experimental route was initiated. In the first series of wind tunnel tests involving three candidate profiles, good agreement was found between the experimental results and the mathematical models. The aerofoils chosen were the NACA 661-212, the 51223 and the Clark-Y standard aerofoils. A number of prototype VAWTs were fabricated and tested for the influence of the blade pitch angle, the chord length ratio, with 2 or 3 blades. The aerofoil surfaces were made from aluminium sheet with a standard surface finish. The prototype designs were tested in the Northumbria University low speed wind tunnel facility - the models were 0.4 m. high with a 0.4 m diameter. The torque versus wind speed characteristics were recorded and analysed. The S 1223 profile was found to be self-starting with high efficiency. This model generated a high power coefficient of about 0.3 at a tip speed ratio of 1.2. The second series of tests were carried out in field sites in the UK with a 2 m diameter straight—bladed Darrieus rotor prototype with 3 blades using the S1223 blade section. Three field trials were undertaken in the UK to produce realistic performance characteristics for wind conditions of 4-10 m/s. The maximum power coefficient of this machine was found to be 0.18 at a tip speed ratio of 1.2. In addition, an alternative semi-cylinder turbine combined with a Darrieus rotor was fabricated and tested in the UK. It demonstrated the advantage that it could self-start at lower wind speeds, that is 3m/s but delivers approximately 50% less power than that obtained from the first proposed design. A final phase of testing was carried out with an enlarged and modified 3 m diameter prototype installed at a shrimp farm in Thailand to demonstrate how the unit could be used to replace an equivalent 2 HP 2-stroke diesel engine and hence eliminate its inherent emission pollution problems. A Savonius rotor was fitted to the prototype to improve self-start capabilities at a wind speed of 4 m/s for a practical application which by its nature required a high starting torque. The designs are easy to fabricate, low cost, pollution free and have been demonstrated to be ideal for applications in developing countries where there are sufficient wind resources.
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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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Mewburn-Crook, Anthony. "The design and development of an augmented vertical axis wind turbine." Thesis, Kingston University, 1990. http://eprints.kingston.ac.uk/20541/.
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The augmented vertical axis wind turbine resulted from a survey of the problems of existing wind turbines, and the identification of the design criteria that it should be inherently safe and reliable. It should be self-starting in low winds and continue to run in high Winds, and it should be environmentally acceptable. The design consisted of a vertical axis rotor, with five vertical and five horizontal blades, surrounded by an augmentor which contained eight converging stators and a dome desigried to increase the flow rate through the rotor, and to decrease the pressure at exit from the rotor. Extensive model tests showed that the wind turbine had attractive operating characteristics, which were confirmed by a prototype machine with a 6m diameter rotor rated at 10kW. However, a detailed analysis of the design and costs showed that it was too expensive. An analysis of an idealised augmented vertical axis wind turbine showed that there was potential for increasing the performance and decreasing costs. Measurements of the detailed flow field through the rotor and around the augmentor demonstrated that augmentation was by means of an increased pressure drop across the rotor, combined with an increased mass flow rate through it. The efficiency of the upstream part of the rotor was also increased by the augmentor. The benefits of turbulent mixing in the wake of the turbine between the external flowfield and the flow through the turbine were also recognised. Major modifications to the design of the augmentor and rotor resulted in two types of wind turbine which maintained the attractive operating characteristics and appeared to be commercially viable. The designs offer particular benefits in terms of inherent safety and reliability. The potential of cost effective, large multi¬megawatt machines is also recognised. The work has also provided further insight into wind turbine augmentation, and in the design and development of vertical axis rotors.
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Robotham, A. J. "The aerodynamic control of the V-type vertical axis wind turbine." Thesis, Open University, 1989. http://oro.open.ac.uk/57284/.
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The V-type vertical axis wind turbine (V-VAWT) is of simple design and construction, has a low aerodynamic efficiency, yet its originators consider that it will be a cost effective configuration in electricity generation applications. However, the quality and reliability of its power output must be ensured; this necessarily requires continual control of rotor speed and power. The initial V-VAWT investigations of Sharpe and Taylor, and methods of wind turbine control are reviewed. Partial-span pitch angle variation is considered the most promising option, and the systematic investigation of this control method in V-VAWT applications is reported. This work includes the design, construction and performance testing of a small V-VAWT with pitching blade tips. The tests showed that rotor power can be regulated with small blade tip areas, however, correlation between the measured and theoretical results was not good. Wind tunnel test were undertaken to determine the characteristics of the NACA0025 aerofoil used for the model blades. Performance predictions using this data showed better correlation between experimental and- theoretical results. This has allowed the theoretical model to be used with confidence for predicting the performance of larger V-VAWTs with partial-span pitch control. A theoretical model of the dynamic behaviour of a V-VAWT generator integrated with an electricity supply network has been developed and embodied in the computer program DYNVAWT. This program has allowed the dynamic behaviour of a 5kW sized V-VAWT to be simulated, and an active control strategy developed. The simulation studies show that active partial-span pitch control ensures the quality and reliability of the electricity supply can be maintained even when the V-VAWT is operating in turbulent wind conditions.
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Courtney, M. S. "An investigation of H configuration vertical axis wind turbine dynamic instability." Thesis, City University London, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370930.
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Marnett, Markus [Verfasser]. "Multiobjective Numerical Design of Vertical Axis Wind Turbine Components / Markus Marnett." Aachen : Shaker, 2012. http://d-nb.info/1067735100/34.
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Ross, Ian Jonathan. "Wind Tunnel Blockage Corrections: An Application to Vertical-Axis Wind Turbines." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271306622.
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Deglaire, Paul. "Analytical Aerodynamic Simulation Tools for Vertical Axis Wind Turbines." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132073.
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Wind power is a renewable energy source that is today the fastest growing solution to reduce CO2 emissions in the electric energy mix. Upwind horizontal axis wind turbine with three blades has been the preferred technical choice for more than two decades. This horizontal axis concept is today widely leading the market. The current PhD thesis will cover an alternative type of wind turbine with straight blades and rotating along the vertical axis. A brief overview of the main differences between the horizontal and vertical axis concept has been made. However the main focus of this thesis is the aerodynamics of the wind turbine blades. Making aerodynamically efficient turbines starts with efficient blades. Making efficient blades requires a good understanding of the physical phenomena and effective simulations tools to model them. The specific aerodynamics for straight bladed vertical axis turbine flow are reviewed together with the standard aerodynamic simulations tools that have been used in the past by blade and rotor designer. A reasonably fast (regarding computer power) and accurate (regarding comparison with experimental results) simulation method was still lacking in the field prior to the current work. This thesis aims at designing such a method. Analytical methods can be used to model complex flow if the geometry is simple. Therefore, a conformal mapping method is derived to transform any set of section into a set of standard circles. Then analytical procedures are generalized to simulate moving multibody sections in the complex vertical flows and forces experienced by the blades. Finally the fast semi analytical aerodynamic algorithm boosted by fast multipole methods to handle high number of vortices is coupled with a simple structural model of the rotor to investigate potential aeroelastic instabilities. Together with these advanced simulation tools, a standard double multiple streamtube model has been developed and used to design several straight bladed rotor ranging from 2 kW to 20 kW.<br>Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 704
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Elmabrok, Ali Mohammed. "The aerodynamics of vertical axis wind turbines." Thesis, University of Manchester, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629477.
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One of the operational problems encountered with vertical axis wind turbines is their low starting torque. A number of analytical methods were investigated to see whether they could predict the starting performance of vertical axis turbines. The chosen methods used " actuator disc theory" for both single and multiple streamtubes. Two different forms of the multiple streamtube model are applied, one using a single actuator disc and the other using two discs in tandem. The computational analysis of all models simulates the blade aerodynamics throughout the full range of incidence from -180° to 180°. The effects of varying various geometric parameters of the windmill upon the performance of the rotor are investigated to find a design with improved self starting characteristics. The best agreement between theory and experiment was obtained using the multiple streamtube (double disc) method. Savonius rotors have been commonly employed as " starters "for Darrieus turbines. A new analytical method has been developed to model the performance characteristics of the Savonius rotor. In this method the blade is divided up into small elements, and each element is treated as a thin airfoil. The rotor torque and power are computed taking into account the blades' motion, the blade shape and momentum consideration. This method shows good agreement with experimental results for a variety of Savonius rotors.A new experimental technique has been developed to provide information about the variation of torque within a cycle. These results have been used as a check on all the theoretical methods. The agreement between these experimental results and the theoretical methods show that they predict both the time averaged and the instantaneous performance.
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Högberg, Lars. "Automated electric control of a vertical axis wind turbine in island operation." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-162559.
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At the Division of Electricity at Uppsala University, a wind power concept has been developed. The concept uses a vertical axis wind turbine with a direct driven generator. The turbine has fixed blades, making speed control the only way to regulate power absorption. The speed is controlled with the electric load. The turbine is not self-starting, but can be started using the generator as a motor. In this project, an unsupervised electric system with automatic control is designed and constructed. The starting point is a detailed study of the earlier developed control system. To be able to select the rating of the components, theoretical calculations are done. Simulations in MATLAB are performed to predict the behavior of the system. The resulting system is a working prototype in operation outside of Uppsala. The system starts the turbine using a new start-up strategy. Loading of the generator is controlled by primarily supplying a regular consumer with direct current and secondly dissipating additional power as heat. A circuit stopping the turbine, in case of different failures, is included in the system.
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Wang, Yuchen. "Blade Design of Vertical Axis Wind Turbine at Low Tip-speed-ratios." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524224348317784.
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Hammar, Henning, and Daniel Constanda. "Kraftanalys och framtagning av mätanordning för vertikala vindkraftverket Lucias bärarmar." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-159839.
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The project contains a force analysis of the vertical axis wind turbine Lucia's supporting arms and a measuring device to experimentally measure the forces is made. The forces between the supporting arms and the tower are calculated theoretically and then simulated by a computere. A measuring devise is then designed to measure the forces experimentally. The forces acting on the attachment between the supporting arms and the tower is primarily the centripetal force, gravitational force and the aerodynamic forces on the rotor wings. The maximum forces were theoretically calculated and is 13.38 kN along the x-axis, -0.25 kN along the y-axis and then 0.5 kN along the z-axis. The axis are acording to a rotational reference system where the x-axis runs along the supporting arm and the y-axis runs along the axis of rotation. The maximum torque that occurs is 0.53 kNm along the y-axis and 1.29 kNm along the z-axis. The size of the forces have been confirmed with a deviation of up to 1.8 % in the simulation using SolidWorks 2010. For the experimental measurements a measuring device has been developed which consists of S-load cells with wave indicator and transmitter, an attachment for the measuring equipment and distanceplates to stabilize the rotor. S-load cells, wave indicator and transmitter were ordered and drawings for the attachment of the measuring equipment and spacer plates was done. The eigenfrequencies and the stress have been investigated for the parts. The eigenfrequencies for the wind turbine was estimated to decline up to 13 % when the measuring device was mounted and the lowest Factor of Safety was 1.67. Before the attachment of the measuring device and the spacer plates can be ordered the attachment of the supporting arms, how the loadcells should be attached to the device and the safety margins need to be examined.
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Bülow, Fredrik. "A Generator Perspective on Vertical Axis Wind Turbines." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-197855.
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The wind energy conversion system considered in this thesis is based on a vertical axis wind turbine with a cable wound direct drive PM generator. Diode rectifiers are used to connect several such units to a single DC-bus and a single inverter controls the power flow from the DC-bus to a utility grid. This work considers the described system from a generator perspective i.e. the turbine is primarily seen as a torque and the inverter is seen as a controlled load. A 12 kW VAWT prototype with a single turbine has been constructed within the project. The power coefficient of this turbine has been measured when the turbine is operated at various tip speed ratios. This measurement determines both how much energy the turbine can convert in a given wind and at what speed the turbine should be operated in order to maximise the energy capture. The turbine torque variation during the revolution of the turbine has also been studied. A PM generator prototype has been constructed in order to study power loss in the stator core at low electrical frequencies. Heat exchange between the stator and the air-gap between the stator and the rotor has been studied. Heat exchange between the stator and the air-gap is increased by turbulence caused by the rotor. The generator was also used in a demonstration of a DC-grid where two diode rectified PM generators supplied power to a single DC load. An initial study of an inverter suitable for grid connection of the 12 kW PM generator has been performed. Several turbine control strategies are evaluated in simulations. The control strategies only require the parameter "turbine speed" to determine the optimal system load.
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Scheurich, Frank. "Modelling the aerodynamics of vertical-axis wind turbines." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2897/.
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The current generation of wind turbines that are being deployed around the world features, almost exclusively, a three-bladed rotor with a horizontal-axis configuration. In recent years, however, a resurgence of interest in the vertical-axis wind turbine configuration has been prompted by some of its inherent advantages over horizontal-axis rotors, particularly in flow conditions that are typical of the urban environment. The accurate modelling of the aerodynamics of vertical-axis wind turbines poses a significant challenge. The cyclic motion of the turbine induces large variations in the angle of attack on the blades during each rotor revolution that result in significant unsteadiness in their aerodynamic loading. In addition, aerodynamic interactions occur between the blades of the turbine and the wake that is generated by the rotor. Interactions between the blades of the turbine and, in particular, tip vortices that were trailed in previous revolutions produce impulsive variations in the blade aerodynamic loading, but these interactions are notoriously difficult to simulate accurately. This dissertation describes the application of a simulation tool, the Vorticity Transport Model (VTM), to the prediction of the aerodynamic performance of three different vertical-axis wind turbines - one with straight blades, another with curved blades and a third with a helically twisted blade configuration - when their rotors are operated in three different conditions. These operating conditions were chosen to be representative of the flow conditions that a vertical-axis wind turbine is likely to encounter in the urban environment. Results of simulations are shown for each of the three different turbine configurations when the rotor is operated in oblique flow, in other words when the wind vector is non-perpendicular to the axis of rotation of the rotor, and also when subjected to unsteady wind. The performance of the straight-bladed turbine when it is influenced by the wake of another rotor is also discussed. The capability of the VTM to simulate the flow surrounding vertical-axis wind turbines has been enhanced by a dynamic stall model that was implemented in the course of this research in order to account for the effects of large, transient variations of the angle of attack on the aerodynamic loading on the turbine blades. It is demonstrated that helical blade twist reduces the oscillation of the power coefficient that is an inherent feature of turbines with non-twisted blades. It is also found that the variation in the blade aerodynamic loading that is caused by the continuous variation of the angle of attack on the blades during each revolution is much larger, and thus far more significant, than that which is induced by an unsteady wind or by an interaction with the wake that is produced by another rotor. Furthermore, it is shown that a vertical-axis turbine that is operated in oblique flow can, potentially, produce a higher power coefficient compared to the operation in conditions in which the wind vector is perpendicular to the axis of rotation, when the ratio between the height of the turbine and the radius of the rotor is sufficiently low.
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Möllerström, Erik. "Vertical Axis Wind Turbines : Tower Dynamics and Noise." Licentiate thesis, Högskolan i Halmstad, Energiteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-242267.
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Vertical axis wind turbines (VAWTs) have with time been outrivaled by the today common and economically feasible horizontal axis wind turbines (HAWTs). However, VAWTs have several advantages such as the possibility to put the drive train at ground level, lower noise emissions and better scaling behavior which still make them interesting for research. The work within this thesis is made in collaboration between the Department of Construction and Energy Engineering at Halmstad University and the Division for Electricity at Uppsala University. A 200 kW VAWT owned by the latter and situated close to Falkenberg in the southwest of Sweden has been the main subject of the research even if most learnings has been generalized to fit a typical vertical turbine. This particular turbine has a wooden tower which is semi-guy-wired, i.e. the tower is both firmly attached to the ground and supported by guy-wires. This thesis has two main topics both regarding VAWTs: eigenfrequency of the tower and the noise generated from the turbine. The eigenfrequency of a semi-guy-wired tower is studied and an analytical expression describing this is produced and verified by experiments and simulations. The eigenfrequency of the wire itself and how it is affected by wind load are also studied. The noise characteristics of VAWTs have been investigated, both theoretically and by noise measurement campaigns. Both noise emission and frequency distribution of VAWTs has been studied. The work has resulted in analytical expressions for tower and wire eigenfrequency of a semi-guy-wired tower as well as recommendations for designing future towers for VAWTs. The noise emission of VAWTs has been studied and proven low compared to HAWTs. The noise frequency distribution of the 200 kW VAWT differs significantly from that of a similar size HAWTs with for example lower levels for frequencies below 3000 Hz.
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Bedon, Gabriele. "Aero-Structural Optimization of Vertical Axis Wind Turbines." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424493.
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This Thesis focuses on the aero-structural simulation and optimization of Darrieus Vertical Axis Wind Turbines.
Aerodynamic simulation tools based on different techniques are developed, improved with respect to state-of-art tools, and validated against experimental data. The main considered approaches are based on the Blade Element Momentum, Vortex, two- and three-dimensional Unsteady Reynolds-Averaged Navier-Stokes (URANS) Computational Fluid Dynamics (CFD) models. The models are developed keeping in mind the final coupling with an optimization algorithm, therefore with particular emphasis on the computational effort and simulation robustness. A structural simulation tool based on the Euler-Bernoulli beam theory is also developed and validated against experimental data to perform an efficient aero-structural simulation.
The validated models are coupled with an optimization algorithm under certain constraints to create an iterative loop able to produce improved designs. Different applications are considered based on the most relevant research topics and real case scenarios. The particular case of a floating Troposkien Vertical Axis Wind Turbine is analysed by improving the baseline aerodynamic design for the 5 MW rotor developed in the FP7 DeepWind project and evaluating the aerodynamic performance under rotor tilted conditions for the 1 kW demonstrator. The airfoil shape for the blade of a 500 kW H-rotor is also subjected to an optimization analysis with the aim to increase the aerodynamic production, obtaining a new geometry different from literature design. Finally, the aerodynamic and structural simulation tools are coupled to perform a complete aero-structural optimization of blade shape and chord distribution for a 500 kW Troposkien rotor. Both aerodynamic production and rotor stress are targeted in the routine and new blade shapes are found and discussed.
The Thesis results, beside the increased performance with respect to the baseline case, prove that iterative loops, obtained by coupling a fast simulation tool and an optimization algorithm, can be adopted in the design and test phase of Darrieus Vertical Axis Wind Turbines, by providing the designer an advanced insight on the aerodynamic and structural phenomena experienced by these complex machines.<br>Questa Tesi ha come oggetto la simulazione e l'ottimizzazione aero-strutturale di Turbine Eoliche ad Asse Verticale Darrieus.
Strumenti per la simulazione aerodinamica basati su differenti tecniche sono sviluppati, migliorati rispetto allo stato dell'arte, e validati rispetto a dati sperimentali. I principali approcci considerati sono basati sui modelli Blade-Element Momentum, Vortex e Unsteady Reynolds-Averaged Navier-Stokes (URANS) Computational Fluid Dynamics (CFD) bi- e tri-dimensionali. I modelli sono sviluppati tenendo a mente l'accoppiamento con un algoritmo di ottimizzazione, quindi con particolare enfasi sullo sforzo computazionale e sulla robustezza della simulazione. Uno strumento di simulazione strutturale basato sulla teoria della trave di Eulero-Bernoulli è, in aggiunta, sviluppato e validato rispetto a dati sperimentali per effettuare una efficiente simulazione aero-strutturale.
I modelli validati sono accoppiati con un algoritmo di ottimizzazione per la creazione di un ciclo per l'ottenimento di configurazioni migliorate. Differenti applicazioni sono considerate, basate sui temi di ricerca più rilevati e scenari reali. Il caso particolare di una Turbina Eolica ad Asse Verticale Troposkiana è stato considerato al fine di migliorare la configurazione aerodinamica di base di un rotore da 5 MW sviluppato nell'ambito del progetto FP7 DeepWind e di valutare le prestazioni aerodinamiche del dimostratore da 1 kW con rotore inclinato. La forma del profilo per la pala di un rotore ad H da 500 kW è oggetto anch'essa di un'attività di ottimizzazione finalizzata all'aumento della produzione aerodinamica, ottenendo una nuova geometria completamente differente da quelle disponibili in letterature. Infine, gli strumenti di simulazione aerodinamica e strutturale sono accoppiati per condurre una completa ottimizzazione aero-strutturale della forma della pala e della distribuzione di corda per un rotore Troposkiano da 500 kW. Sia la produzione aerodinamica che lo stato tensionale sono considerati come obiettivi e nuove forme palari sono individuate e discusse.
I risultati della Tesi, oltre all'incremento di prestazioni rispetto alle geometrie di base, provano che i cicli iterativi, ottenuti tramite l'accoppiamento di un veloce strumento di simulazione e un algoritmo di ottimizzazione, possono essere adottati nella progettazione e test di Turbine Eoliche ad Asse Verticale Darrieus, fornendo al progettista un avanzato strumento di analisi dei fenomeni aerodinamici e strutturali agenti in queste complesse macchine.
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Alverbäck, Adam. "LQG-control of a Vertical Axis Wind Turbine with Focus on Torsional Vibrations." Thesis, Uppsala universitet, Avdelningen för systemteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-169330.
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In this thesis it has been investigated if LQG control could be used to mitigate torsional oscillations in a variable speed, fixed pitch wind turbine. The wind turbine is a vertical axis wind turbine with a 40 m tall axis that is connected to a generator. The power extracted by the turbine is delivered to the grid via a passive rectifier and an inverter. By controlling the grid side inverter the current is controlled and hence the rotational speed can be controlled. A state space model was developed for the LQG controller. The model includes both the dynamics of the electrical system as swell as the two mass system, consisting of the turbine and the generator connected with a flexible shaft. The controller was designed to minimize a quadratic criterion that punishes both torsional oscillations, command following and input signal magnitude. Integral action was added to the controller to handle the nonlinear aerodynamic torque. The controller was compared to the existing control system that uses a PI controller to control the speed, and tested usingMATLAB Simulink. Simulations show that the LQG controller is just as good as the PI controller in controlling the speed of the turbine, and has the advantage that it can be tuned such that the occurrence of torsional oscillations is mitigated. The study also concluded that some external method of dampening torsional oscillations should be implemented to mitigate torsional oscillations in case of a grid fault or loss of PWM signal.
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Ross, Ian J. "Wind tunnel blockage corrections : an application to vertical-axis wind turbines /." Dayton, Ohio : University of Dayton, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1271306622.
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Thesis (M.S. in Aerospace Engineering) -- University of Dayton.<br>Title from PDF t.p. (viewed 06/22/10). Advisor: Aaron Altman. Includes bibliographical references (p. 101-104). Available online via the OhioLINK ETD Center.
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Österberg, David. "Multi-Body Unsteady Aerodynamics in 2D Applied to aVertical-Axis Wind Turbine Using a Vortex Method." Thesis, Uppsala universitet, Elektricitetslära, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-131932.
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Vertical axis wind turbines (VAWT) have many advantages over traditional Horizontalaxis wind turbines (HAWT).One of the more severe problem of VAWTs are the complicated aerodynamicbehavior inherent in the concept. Incontrast to HAWTs the blades experience varying angle of attack during its orbitalmotion. The unsteady flowleads to unsteady loads, and hence, to increased risk for problems with fatigue.A tool for aerodynamic analysis of vertical axis wind turbines has been developed.The model, a Discrete vortex method, relies on conformal maps to simplify the taskto finding the flowaround cylinders. After the simplified problem has been solved with Kutta condition,using the Fast Fouriertransform, the solution is transformed back to the original geometry yielding the flowabout the turbine.The program can be used for quick predictions of the aerodynamic blade loads fordifferent turbines allowing the method to be validated by comparing the predictionsto experimental data from realvertical axis wind turbines. The agreement with experiment is good.
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Madani, Nima. "Design of a Permanent Magnet Synchronous Generator for a Vertical Axis Wind Turbine." Thesis, KTH, Elektrisk energiomvandling, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-53688.
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Different types of permanent magnet generators for wind power application have been subject of research during last two decades. In this thesis different topologies of electrical generators have been investigated for small scale vertical axis wind turbine application. A two stage induction generator is proposed as a alternative solution with respect to the cost of such a system. However, a biggest emphasis in the report has been put on the design of Permanent Magnet Synchronous Generator (PMSG) suitable for a small scale Vertical Axis Wind Turbine (VAWT)T˙ he characteristics of PMSG makes it highly compatible for variable speed Wind Energy Conversion System (WECS) without any pitch mechanism. Chapters 2 and 3 summarize a thorough literature survey on wind energy systems and corresponding electrical machines. The principles of wind aerodynamics is preceded by a review on wind turbine characteristics and challenges with emphasis on VAWT s. Further different topologies of electrical machines with focus on PMSG s including Permanent Magnet (PM) configurations, different windings and thermal behavior is presented. In chapter 4 a brief review on an alternative solution which includes an Induction Generator (IG) for fixed speed WECS is given. Next, In chapters 5, 6 and 7, a PMSG is designed and the design is verified by means of Finite Element Method (FEM) analysis and thermal modeling. Chapter 5 describes an analytical optimisation of a longitudinal, inner rotor, radial flux, surface mounted PMSG with concentrated winding and natural air cooling system. Cost of active material is chosen as the optimisation criterion. Concepts like "constraints", "requirements", "parameters" (including material, geometry and winding) and procedure of the design are described here. In chapter 6, a FEM model of the optimised machine is developed and the results are illustrated. The iron losses, calculated in this chapter are utilised in thermal analysis in chapter 7 . Thermal model developed is based on a lumped parameter circuit . It ensures the safe thermal behavior of the machine in nominal operation mode.
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Park, Kyooseon. "Optimal design of a micro vertical axis wind turbine for sustainable urban environment." Thesis, University of Huddersfield, 2013. http://eprints.hud.ac.uk/id/eprint/19032/.
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The need for sustainable energy sources becomes greater each year due to the continued depletion of fossil fuels and the resulting energy crisis. Solutions to this problem are potentially in the form of wind turbines, for sustainable urban environment, that have been receiving increased support. At present, a number of wind turbines have been developed that show significant increase in performance compared to existing technologies. From an extensive literature review, a number of key issues have been highlighted which are concerned with the design, optimisation and diagnostics of Vertical Axis Wind Turbines (VAWTs) that have been used to formulate the scope of this research. A design procedure for a vertical axis wind turbine, that features both multi-blade rotor and fixed outer stator guide vanes, has been derived, in which both rotor and stator blade profiles have been generated for a low wind speed application. In the presented work, numerical investigations have been carried out extensively to determine the optimised design of the VAWT. Sliding mesh technique has been used for the rotation of rotor blades. This new technique captures the transient flow phenomena that occur when the rotor and the stator blades interact with each other. Hence, the results predicted by CFD using this technique are much superior in accuracy. Furthermore, a detailed flow field analysis of the VAWT has highlighted large asymmetries in both pressure and flow velocity about the central axis of the VAWT in both the stationary and the rotating frames of references. Various geometric parameters associated with the design of the VAWT have been investigated over a wide range in order to analyse the effect of these parameters on the performance output of the VAWT. These geometric parameters are the blade angles, the number of blades in the VAWT and the size of the rotor/stator sections of the VAWT. It has been shown that all these parameters considerably affect the performance output of the VAWT and hence have been optimised in the present study for maximum performance output of the VAWT. One of the key elements of this study is the development of a performance prediction model of the VAWT that takes into account the effects of the aforementioned geometric parameters of the VAWT. This novel prediction model is both robust, user-friendly and has shown to predict the performance output of the VAWT with reasonable accuracy. Hence, the prediction model can be used by the designers of the VAWT. Nowadays, condition based health monitoring of mechanical systems is topic of vast research. Most of the studies in this field use experimental facilities and conventional toolboxes to handle the output data from the sensors. With the advent of advanced CFD tools, it has now become possible to use CFD as an effective tool for fault detection in VAWTs. An attempt has been presented in this study regarding condition monitoring of VAWTs for sustainable urban environment. Various faults like missing blade and slits in blade have been investigated and analysed. It has been shown that CFD can detect these faults and show the effects of these faults on local flow parameters such as pressure and velocity.
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Perera, Guruge Elmo Lakshman. "A vertical axis wind turbine generator based on the tangential wall-jet action." Thesis, University of Huddersfield, 1988. http://eprints.hud.ac.uk/id/eprint/7480/.
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Lan, Wei-Chen, and 藍威政. "Characteristics Of Vertical Axis Wind Turbine." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/69901264973666309305.
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碩士<br>中華科技大學<br>機電光工程研究所碩士班<br>100<br>Due to their location and climate, Taiwan has a rich energy of the wind farm, if with sharp optimized power generation system is a very suitable environment for the development of wind power generation. The vertical axis wind turbine characteristics, with low start up wind speed from the direction of the impact of simple structure. Therefore, this study will be Elizabeth Vilnius wind turbine vertical axis wind turbine for the design basis.
This study was to investigate the impact of different horizontal torque generating capacity and efficiency. Second set of different wind speed and the size of the different cross-sectional area of the fairing to the measurement of the parameters (voltage, current, CP and wind power) into the wind characteristics of formulas and effectiveness of the formula to calculate the wind turbine power generation system attribute parameter and comparative analysis of their advantages and disadvantages.
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Tien-HsinChao and 趙天昕. "Performance analysis and comparison between cross-axis wind turbine and vertical axis wind turbine." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/846ue5.
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碩士<br>國立成功大學<br>航空太空工程學系<br>105<br>Wind energy has been considered as one of the primary renewable energy sources globally. In urban areas, due to the irregular arrangement of buildings, small scale wind turbine plays an important roles for household energy grid. In this study, a newly designed small scale wind turbine namely cross-axis wind turbine (CAWT) was examined experimentally on the power performance in a low speed, open-loop circuit wind tunnel at Reynolds numbers of Re=42900, 57100 and 71400. The results were compared to a traditional straight-bladed vertical axis wind turbine (VAWT). The performance analyses are evaluated in terms of static performance, dynamic performance, and blade force measurement. The results of static and dynamic performances indicate that CAWT has not only better starting characteristics but also higher power coefficients over VAWT. The tangential forces measurement on the horizontal blade of CAWT proves its superior power performance compared to VAWT.
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Chen, Si-Han, and 陳思翰. "Optimization of Novel Vertical-Axis Wind Turbine." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/3kpkzv.
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碩士<br>國立臺灣科技大學<br>機械工程系<br>102<br>This research uses ANSYS FLUENT software to analyze the new vertical-axis wind turbine in order to investigate the relationship between the flow field, force and torque. When conventional vertical-axis wind turbine blades translate wind power into thrust on the windward side, the blade of upwind side also generate resistance against the effective moment; The new vertical-axis wind turbine has fixed outer guide blades in order to make wind be imported effectively to the rotor blades on the windward to improve the positive torque. In addition, block the wind the guide blades which hits on the rotor blades, on the upwind side. Thus, the reverse torque will be declined.
Finally, using Taguchi method to find the optimal experimental parameters by 9-level orthogonal arrays. Four factors, the angle of rotor blades, the number of rotor blades, the angle of fixed outer guide blades and the number of fixed outer guide blades. The optimal parameters are rotor blade angle of 90 degree, 15 rotor blades, the fixed outer guide blades angle of 48 degree and 12 fixed outer guide blades.
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Lee, Jun-Ting, and 李俊廷. "Magnetism Floats Applied on Vertical Axis Wind Turbine." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/42651913122977070537.
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碩士<br>國立高雄海洋科技大學<br>輪機工程研究所<br>97<br>This research focuses on the functional combinations between vertical axis wind turbine and magnet disk for reducing weigh systems. Such a construction is mainly composed by the two pieces of circular magnetic discs. Through the insertion of the upper disc with a circular permanent magnetism NdFeB, the fixation of both compartments could be achieved. The ironic lower disc would then be connected with the generator, blades, and framework of the vertical axis wind turbine. According to the law of magnetic suction, a force of attraction would be generated by both upper and lower discs. It is predicted that such an application can effectively reduce required spare parts, thus decreases the ponderousness of the turbine itself.
The main concerns of the article are as follows:
1. The comparison of the magnets and their force of the attraction of different models (operated under static simulation).
2. The graphic comparison of magnetic force curve under different rotational speed.
3. The comparison of the magnetic field intensity (H) and the magnetic flux density (B).
The experiments will be able to get the required data of the system, under which condition it reaches the maximum stability. The data not only help minimizing the vibration, but also reduce generated friction during high speed rotation of the vertical axis wind turbine.
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Yu, Luo Sheng, and 羅勝禹. "Development of Small Vertical Axis Wind Turbine Blade." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/44296369380828706717.
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碩士<br>建國科技大學<br>機械工程系暨製造科技研究所<br>101<br>A small vertical axis wind turbine (SVAWT) with lift-type and drag-type blades were designed and tested in this paper. In order to improve the performance of the SVAWT with low start up wind speed, the struts connecting lift-type blades and rotating axis were designed as drag-type blades. The cross section of lift-type blades using in the SVAWT was NACA0018 for maintaining the rotating speed under higher wind speed. The parts of the SVAWT including blades and struts were designed by computer-aided design software and manufactured with the aid of computer-aided manufacturing, rapid prototyping and rapid tooling. The SVAWT was tested in a wind tunnel with the wind speed ranging from 2 to 7 m/sec. The test results containing rotating speed and torque were recorded to evaluate the performance of the SVAWT. The results showed that the drag-type blade could start up the SVAWT wind low speed, but would reduce the rotating speed under higher wind speed.
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Chen, Hung-Ju, and 陳虹汝. "3D Simulation of a Vertical-Axis Wind Turbine." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/82161970916439943950.
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碩士<br>國立交通大學<br>機械工程學系<br>100<br>A vertical-axis wind turbine which combines the merits of the lift type and drag type wind turbines is studied in this project. It consist of three S-type and two airfoil-type turbine blades. Several stages of these turbine blades can be stacked together to achieve better performance. The aerodynamic characteristics and performance are investigated by using computational fluid dynamic. The numerical scheme is based on the finite volume method. The moving mesh technique is adopted to tackle the rotation of the turbine wheel.With use of the RNG model to characterize turbulence, unsteady calculations are undertaken. Experiments are also conducted to assess the accuracy of the numerical simulation.
Two-dimensional and three-dimensional, unsteady simulations are conducted. It is shown that the resulting moment coefficient becomes a linearly decreasing function of the tip speed ratio and the power coefficient is a quadratic function of the tip speed ratio. Comparison with experimental measurements for a one-stage wind turbine indicates that good agreement is obtained by the 3-D unsteady simulation. However, the torques and powers are over-predicted by the 2-D unsteady calculations. It can be detected from the results that after the flow passing the wind turbine, a periodic shedding vortex is formed in 2-D calculations while a relativity steady flow is observed in 3-D calculations. This implies that the flows beyond the upper and lower sides of the wind turbine have an effect of stabilizing the flow in the near wake of the turbine. This 3-D effect cannot be accounted for in 2-D calculations.
Comparing with the single-stage wind turbine, only slightly higher power performance can be obtained by stacking several stages of turbines together. However, the variation of the torque with respect to time becomes smoother as the number of stage increase. This character helps stabilize operation of the wind turbine.
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Lin, Chien-Yao, and 林健耀. "Numerical studies of the vertical axis wind turbine." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/61616991835331149572.
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碩士<br>國立屏東科技大學<br>車輛工程系所<br>96<br>The development and application of wind power for renewable energy has been grown vigorously in recent years. With the characteristics of operating in all directions, simple structure and low rotating noise, the vertical axis wind turbine is also used in the production of electrical power. In this study, the different conditions included five kinds of rotating speeds and three kinds of wind speeds are used to simulate and analyze the flow field which caused by the vertical axis wind turbine. The SIMPLE finite volume method, the k-ε model and sliding mesh model are employed to solve and compare the complex flow field and the torque in each case. The purpose is to provide the fundamental flow phenomena caused by the rotating vertical fan and the design concept of vertical axial wind turbine in the future. In the results, we can observe that while the rotor rotates to the region of upper flow, the separation bubble on the surface of rotor disappears and causes the difference of pressure increased between top and bottom surfaces of rotor. Meanwhile, the torque will be heightened while the difference of pressure increased. The rotor’s rotating speed and torque also increased while the inlet velocity of flow speeded. However, the increased proportion of speed between rotating rotor and inlet flow is not entirely linear.
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CHANG, CHIA-HUI, and 張珈誨. "Performance Optimization of the Vertical-Axis Wind Turbine." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/f3u9mq.
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碩士<br>逢甲大學<br>航太與系統工程學系<br>107<br>Environmental problems such as global warming and extreme weather have become more and more serious. Reducing carbon emissions is the most problem that needs to be addressed at present. It is also a top priority to develop renewable energy, not only to solve the energy crisis but also to reduce the load on the earth.
In recent years, green energy wind energy is the most growing energy source, so wind power generation is also receiving more and more attention. The purpose of this study is to use the CFX module of ANSYS software to develop the wind turbine’s flow-field simulation, and then correctly predict the power generation efficiency of the wind turbine.
In this study, two different configurations of the Lift type of the vertical axis wind turbine (VAWT) is used as a model for simulation analysis. The chord length, the blade’s scale and the number of blade torsion turns are used as parameters to test, and then divided into four different speeds and four different wind speeds. Perform flow-field Simulation to analyze the optimal torque from the speed and wind speed and obtain the best power generation.
This analysis is used to shorten the development time, find the optimal combination of wind turbine, and further build a good performance vertical axis wind turbine (VAWT) to generate electricity.
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KAO, KUO-CHUN, and 高國峻. "Aeroacoustic Analysis of a Vertical Axis Wind Turbine." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/41726379423056837522.
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碩士<br>國立中央大學<br>機械工程學系<br>101<br>In this study, the aeroacoustic characteristics of a small vertical axis wind turbine are analyzed by using ANSYS FLUENT. The FW-H theory with a permeable surface is chosen for formulation. The pressure and the velocity on the rotating blades surface provide the monopoles and dipoles while turbulences surrounding the blades give the quadrupole effect. Then, the aeroacoustic noise due to the rotating wind turbine are investigated for different wind speeds and rotating frequencies.
For a simple model of blades with or without considering the supporting tower, the numerical results show that the maximum sound pressure, due to blade rotating, usually occurs at the blade passing frequency although it is in the subsonic region. There is additional broadband noise, resulted from turbulences, near the frequency region 200Hz to 500 Hz. Actually, the broadband noise dominates the sound from a turbine. The maximum sound pressure level and its corresponding frequency usually increase with rotational frequency.
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Yi-ChenKuo and 郭奕甄. "The Performance Analysis of Rotor Blades for Horizontal-Axis Wind Turbine (HAWT) and Vertical-Axis Wind Turbine (VAWT)." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/50081116018964036703.
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碩士<br>國立成功大學<br>航空太空工程學系碩博士班<br>100<br>This thesis employs the modified blade element momentum theory, computational simulation, and wind tunnel experiment to analyze and compare respectively the performance rotor blades used in Horizontal-Axis wind turbine (HAWT) and Vertical-Axis wind turbine (VAWT).
The Blade element momentum theory is used to predict the rotor performance of HAWT and the adopted double-multiple streamtube model to calculate that of VAWT. For computational simulation, it uses the same turbulent model to simulate the rotors. Furthermore, the performance of the rotor is obtained through the experiments rotor rotation speed, output torque and current and voltage from the generator in terms of the wind speed at various tip speed ratio. It can identify the optimum operation regions of both wind turbines via experiment. Results indicate that the torque output of both wind turbines obtained has almost the same range between 0.3 to 0.4 N-m in experiment under the wind speed of 8 m/s. The maximum torque of VAWT is at TSR of 0.5 while that of HAWT is at TSR of 3.5. The maximum power of HAWT is about 30 watt, which is 6 times larger than VAWT. In addition, the power coefficient of HAWT is about 5 times larger than VAWT, which means that the HAWT has much higher ability to extract the energy in wind than the VAWT. These results are also verified by the modified BEM theory and CFD simulation.
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Kuo, Tai-Hsin, and 郭岱鑫. "Performance Enhancement of an Innovative Vertical-Axis Wind Turbine." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/27244y.
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碩士<br>國立臺灣科技大學<br>機械工程系<br>99<br>This analytic and experimental investigation is aimed to enhance the performance of an innovative small vertical axis wind turbine (VAWT). At first, a flexible experimental platform is designed and installed on a building rooftop for executing the performance evaluation of VAWT. By utilizing the data acquisition system (DAQ), environmental information and power data on the platform are recorded and transferred to the computer automatically. With the aids of a visual software programming within the framework of Labview, the real-time monitoring on the input/output parameters of generator and the wind condition on the rooftop can be carried out simultaneously. Afterwards, the data processing and in-depth analysis on the experimental outcomes are performed via the established computer program together with the statistic concept. Consequently, the actual performance of the wind turbine generator system is attained easily in an automatic and systematic manner.
Furthermore, an innovative multi-blade vertical axis wind turbine is constructed and installed for performance evaluation on this platform. The performance outcomes of original VAWT design indicate a consistent correlation with the physical interpretation and thus verify the reliability of this VAWT test system. Moreover, to enhance its performance, blade radius and number of this VAWT are varied for understanding their influence on turbine performance. Consequently, a bigger radius results in significant enlargements on TSR, torque and power coefficients, and total power output. Besides, an increasing blade number not only improves its aerodynamic characteristics, but also generates more torque for attaining better start-up ability under the low wind speed. In summary, the maximum power coefficient and power output are improved from 3.5% to 5.5% and 90W to 150W at wind speed of 10 m/sec for the case of 1m-radius VAWT, respectively. Also, the maximum power coefficient and power generation can be further upgraded to 7% and 290W at wind speed of 10m/sec for a 1.5m-radisu modified VAWT.
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peng, yanpang, and 彭彥榜. "Optimization of Vertical-Axis Wind Turbine with Free Blades." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/22428531911316148303.
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碩士<br>聖約翰科技大學<br>自動化及機電整合研究所<br>96<br>In this study, vertical-axis wind turbine blades are analyzed with finite-volume numerical simulation method. A design based on free blades is proposed. The forces and moments of different wind turbines are compared. Because of the complicated geometry of the flow field, unstructured meshes are used to discrete the three-dimensional geometry models. The effects of blade angles, blade numbers and blades expansions are also studied. In order to obtain the best parameters of wind turbine design, the Taguchi method is utilized with the experiments of orthogonal arrays. From the current results, it is shown that the free blade design is better than fixed blades. The tradition vertical-axis wind turbines have the positive and negative torques at the same time. It may decrease the available torque. However, the free blade design can change the windward blades angle, and the acting force on the blade can work more efficiently. On the other hand, blades are set free in the upwind stroke. According to the current results, the wind turbine that has three free blades with L type revolving inward gives the maximum moment.
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Yuan-ZhiTsai and 蔡元智. "Simulation of Vertical Axis Wind Turbine Under Gust Conditions." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/02743662842717892386.
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碩士<br>國立成功大學<br>航空太空工程學系碩博士班<br>101<br>This research uses commercial software,Ansys CFX,to investigate the flow-field for a Straight-Blade VAWT under gust conditions. In the ANSYS CFX,we use a high resolution scheme and shear stress transport turbulence model with translational periodicity and detached eddy simulation to simulate the flow-field of VAWT with gust flow.The grid system is a combinations of quadrilateral / prism meshing.The incompressible Navier - Stokes equations are solved.The gust model is defined by the IEC61400-1.
First,the flow around a circular cylinder is simulated to understand the setting affects of boundary conditions and grid construction in the flow field.The numerical researchs are compared with the experimental data.Then the flow over an NACA0015 aerofoil is simulated under different angles of attack.Finally,the flow field past a VAWT with NACA0022 airfoil is simulated. We Investigate the force behavior of VAWT under a gust in flow. We sutudy the force and momentum in the airfoil under different gust model.
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Chung-Ping, Fu, and 傅忠平. "MPPT for a Small-Scale Vertical Axis Wind Turbine." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/58282514978470016051.
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碩士<br>高苑科技大學<br>電子工程研究所<br>101<br>A wind turbine system, either of horizontal or vertical type, converts wind energy into electricity. Large-scale wind turbines usually have huge caption areas of wind power and therefore, run more economically than small-scale wind turbines. However, due to noise, safety, and space requirements in the residential and urban areas, large-scale wind turbines are not applicable but small-scale wind turbines. For the applications of small-scale wind turbines (< 1 kW) in urban areas, vertical axis wind turbine (VAWT) have some further merits over horizontal axis wind turbine (HAWT) since VAWT is simple in structure, insensitivity to wind direction, lower noise, and etc.
A wind turbine performance can be described by the power coefficient versus tip-speed-ratio (TSR). The optimal power coefficient usually occurs around TSR=2 to 4, which differs from turbine to turbine. However, without any controls, a wind turbine has little chance to run at the optimal point due to the wind speed and loads of the circuit may be varying. Therefore, a maximum peak power tracking (MPPT) strategy is deemed necessary to maximize the power output of a wind turbine at various operating conditions. From literature, different MPPT techniques can be found, including TSR control, optimal torque control, power mapping control, and perturbation and observation searching control.
In this study, the perturbation and observation searching algorithm was applied to a lab-made vertical axis wind turbine to enable the wind turbine performs at around its optimal point. The MPPT control algorithm was fulfilled by an ARM 7 (saying MCU). The wind turbine has been made with three twisted blades of NACA 0015 with a chord length of 15cm. The rotating diameter is 60cm. The maximum power output is about 200W.
A simple testing facility, namely an open-type blowing-down windtunnel, was built for evaluating the effectiveness of the MPPT algorithm. The windtunnel can provide a maximum wind speed of about 7m/s. Experimental results show that with the MPPT control, the wind turbine can maintain at its optimal state at each wind speed examined, no matter what the load (resistor) varies.
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Wang, I.-Chang, and 王怡昌. "Aeroacoustics Analysis of a Small Vertical-Axis Wind Turbine." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/40537357773835762775.
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碩士<br>國立中央大學<br>機械工程研究所<br>99<br>Two small vertical axis wind turbines(VAWT), 10kW and 50kW, are analyzed for understanding their noise due to rotation of the blades. The vertical axis wind turbine compared with horizontal axis wind turbine(HAWT) has a lower efficiency. However, the supporting structure of VAWT structure is relatively simple. It is suitable in poor wind conditions. Besides, VAWT also generate lower noise.
In this study, ANSYS FLUENT is used to calculating fluid dynamic effects. Then, ANSYS FLUENT and LMS Virtual.Lab are chosen to obtain aeroacoustic noise. The aeroacoustic sound pressures due to the operation of the 10kW wind turbine at different wind velocities and rotational speeds are investigated. The noise of a 50kW wind turbine is studied to give the effects due to additional winglets on the blade tips. This thesis can provide information to understand the noise resulted from VAWT.
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Cai, Yao-Ting, and 蔡耀庭. "The Blade Analysis of Small Vertical Axis Wind Turbine." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/80427664688503329326.
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碩士<br>明道大學<br>光電暨能源工程學系碩士班<br>100<br>To address the lack of energy and global warming problem, people should develop clean and renewable energy resources. Renewable energy development is the world trends and is also the energy policy of Taiwan. The record shows that wind power generation worldwide has expanded with an annual growth rate of 25 percent since 1990. In recent years, the worldwide wind turbine installation capacity has dramatically increased. The global wind turbine market is expected to continue growing rapidly and stably, making wind turbines an increasingly important energy source.
Since 2007, MingDao University has set up a 2kW VAWT prototype that is test verified to have excellent performance. In 2010, to reach the goal of reducing carbon emissions and saving energy, the Ministry of Economic Affairs granted us a research project to develop the 4kW VAWT to provide the electrical power for small families or public power use in local communities.
Emerging markets need small sized VAWT (vertical-axis wind turbine) for residential energy supplement. MingDao university wind power R&D team has developed a 4kW VAWT system is response to this need. The development items include innovative blades, generator, power control and mast design. The newly developped 4kW VAWT system demonstrates superior performance. The average VAWT efficiency is 0.24 and the average Cp is 0.30. The preliminary results showed this approach has potential for future applications.
Keywords : VAWT, Renewable Energy, Innovative Blades
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Hong, J. S., and 洪雋翔. "Stress Analysis of Small Vertical Axis Wind Turbine Blades." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/04293726243858341649.
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碩士<br>建國科技大學<br>機械工程系暨製造科技研究所<br>100<br>A compact aerodynamics model combined computer-aided engineering analysis software was used to investigate the stresses of small scale vertical wind turbine blades subjected to the aerodynamics loads in this paper. The airfoil types used in the paper are NACA0012, NACA0015 and NACA0018 with the rotational speed 150 rpm and wind velocity 4 m/s. The model used to decide the aerodynamics loads on the blades was formulated with the blade element momentum method (BEM) and multiple stream-tubes method. The relations between lift-coefficient/drag-coefficient and angle of attack from X-FOIL are compared to experimental data to validate the data. Although the maximal errors are up to 50% in some ranges of Reynolds’ number and angle of attack, the comparison data shows that the two data are agree with well when Reynolds’ number is greater than 1.6 x 105 and the angle of attack less than 10°. The angle of attack, lift coefficient and drag coefficient are varied with the angles of rotation of blades, which change the stresses distribution of the blades. The results show that the stresses of blades varied with the angles of rotation of blades. The maximal von Mises stresses occurs when the blade chord is almost parallel to the direction of wind.