Rozprawy doktorskie: „Wind speed”

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Ndzukuma, Sibusiso. "Statistical tools for wind energy generation". Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1020627.

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In this study we conduct wind resource assessment to evaluate the annual energy production of a wind turbine. To estimate energy production of a wind turbine over a period of time, the power characteristics of the wind turbine are integrated with the probabilities of the wind speed expected at a chosen site. The first data set was obtained from a wind farm in Denmark. We propose several probability density functions to model the distribution of the wind speed. We use techniques from nonlinear regression analysis to model the power curve of a wind turbine. The best fit distribution model is assessed by performing numeric goodness–of–fit measures and graphical analyses. Johnson’s bounded (SB) distribution provides the best fit model with the smallest Kolmogorov–Smirnov (K-S) test statistic . 15. The four parameter logistic nonlinear regression (4PL) model is determined to provide the best fit to the power curve data, according to the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC). The estimated annual energy yield is compared to the actual production of the wind turbine. Our models underestimate the actual energy production by a 1 difference. In Chapter Six we conduct data processing, analyses and comparison of wind speed distributions using a data set obtained from a measuring wind mast mounted in Humansdorp, Eastern Cape. The expected annual energy production is estimated by using the certified power curve as provided by the manufacturer of the wind turbine under study. The commonly used Weibull distribution is determined to provide the best fit distribution model to our selected models. The annual energy yield is estimated at 7.33 GWh, with a capacity factor of 41.8 percent.

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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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Goodfellow, David. "Variable speed operation of wind turbines". Thesis, University of Leicester, 1986. http://hdl.handle.net/2381/7822.

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This work describes a control system in which a cycloconverter is connected between the secondary windings of a three phase induction machine and the a. c. mains supply to give variable speed sub- and super –synchronously. In order to control the system smoothly in an asynchronous mode a secondary emf signal generator has been designed, which enables the cycloconverter to operate in synchronism with the emf induced in the secondary windings of the machine. A computer programme has been written which calculates the required firing angles for the cycloconverter to produce secondary current in phase with the secondary emf in the machine. An electronic system has been built which ensures that these firing angles are used by the cycloconverter during actual operation. A cycloconverter has been built, using an effective six phases of mains supply, and has been successfully operated over a range of 20% about synchronous speed in both generating and motoring modes. Results show the ability of the cycloconverter to drive the machine up from standstill as a motor to just below 20% subsynchronous speed. An on-line computer simulation of a wind turbine has been developed which enables an assessment of variable speed generation applied to wind turbines to be achieved. This simulation, in connection with a d. c. machine and thyristor controller, can be used to drive the shaft of the induction machine and assess operation of the cycloconverter control scheme under actual wind turbine operating conditions.

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Al-Qahtani, Turki Haif. "An improved design of wind towers for wind induced natural ventilation". Thesis, University of Bath, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323566.

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Orimoto, Mika. "Regional analysis of extreme gust wind speed". Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/7043.

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There are two objectives of this study. The first objective is to determine the domain of attraction of an extreme value distribution of gust wind speeds, at a selected station, when only limited samples from the site are available. The second objective is to perform a series of homogeneity tests for the selected stations, such that homogenous regions for these extreme gust winds may be identified. After carefully examining the wind data available, it was decided that 133 out of more than 750 stations in the contiguous United States were selected for the study. These selected stations all have confirmed Exposure C environments, with at least 15 years of records. All wind speeds used in this study were adjusted to 10 meters above ground level. On the basis of a S-statistic method, the proper representations of extreme gust winds at the 133 selected weather stations in the contiguous United States are examined. The results indicate that the annual extreme gust wind speeds at 65 out of the 133 stations are Gumbel extreme value distributions (Type I), whereas the other 68 stations' extreme gust wind speeds are reverse Weibull (Type III), distributed. Nine homogeneous regions, for the annual extreme gust winds, were identified by applying a Type I based regional analysis. This analysis was applied to the 65 stations in the contiguous United States whose annual extreme gust winds are Type I distributed.
x, 92 leaves

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Harvey, Scott A. "Low-speed wind tunnel flow quality determination". Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5584.

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Approved for public release; distribution is unlimited.
lected points. Incorporated instrumentation includes pressure transducers attached to a pitot-static tube, wall static pressure taps, and a pressure rake; a hotwire anemometry system, and a linear traverse system. These were integrated with a data acquisition (DAQ) processor with analog to digital conversion and digital I/O boards, and controlled using in-house developed LabVIEW software. Testing showed a maximum axial velocity of 38 m/s, which is 84% of the tunnel?s rated speed. The 2-D flow uniformity was within Â±7% by pressure rake, and Â±3% with a turbulence intensity ?0.11% at full speed using a CTA, affirming the tunnel?s viability as a demonstration platform. Spectral density plots in the boundary layer exhibit typical behavior of fully developed equilibrium turbulent flow with an intertial sub-range present. Future testing of a flat-plate wake for drag modification is planned.

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Wilson, Joshua David. "Quantifying hurricane wind speed with undersea sound". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39204.

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Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2006.
Includes bibliographical references (p. 155-169).
Hurricanes, powerful storms with wind speeds that can exceed 80 m/s, are one of the most destructive natural disasters known to man. While current satellite technology has made it possible to effectively detect and track hurricanes, expensive 'hurricane-hunting' aircraft are required to accurately classify their destructive power. Here we show that passive undersea acoustic techniques may provide a promising tool for accurately quantifying the destructive power of a hurricane and so may provide a safe and inexpensive alternative to aircraft-based techniques. It is well known that the crashing of wind-driven waves generates underwater noise in the 10 Hz to 10 kHz range. Theoretical and empirical evidence are combined to show that underwater acoustic sensing techniques may be valuable for measuring the wind speed and determining the destructive power of a hurricane. This is done by first developing a model for the acoustic intensity and mutual intensity in an ocean waveguide due to a hurricane and then determining the relationship between local wind speed and underwater acoustic intensity.
(cont.) Acoustic measurements of the underwater noise generated by hurricane Gert are correlated with meteorological data from reconnaissance aircraft and satellites to show that underwater noise intensity between 10 and 50 Hz is approximately proportional to the cube of the local wind speed. From this it is shown that it should be feasible to accurately measure the local wind speed and quantify the destructive power of a hurricane if its eye wall passes directly over a single underwater acoustic sensor. The potential advantages and disadvantages of the proposed acoustic method are weighed against those of currently employed techniques. It has also long been known that hurricanes generate microseisms in the 0.1 to 0.6 Hz frequency range through the non-linear interaction of ocean surface waves. Here we model microseisms generated by the spatially inhomogeneous waves of a hurricane with the non-linear wave equation where a second-order acoustic field is created by first-order ocean surface wave motion. We account for the propagation of microseismic noise through range-dependent waveguide environments from the deep ocean to a receiver on land. We compare estimates based on the ocean surface wave field measured in hurricane Bonnie with seismic measurements from Florida.
by Joshua David Wilson.
Ph.D.

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Licari, John. "Control of a variable speed wind turbine". Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/46516/.

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Stop signal task of response inhibition, I find that response inhibition (stopping) is slowed in the presence of angry facial expressions, and such slowing is greater in individuals high in trait neuroticism. Further, as predicted, the influence of neuroticism is moderated by individual differences in emotion regulation, such that good emotion regulation ‘buffers’ the impact of neuroticism. The implications of these findings for current cognitive models of threat-processing are discussed.

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Letellier, Baptiste. "Forecasting Maximum Wind Speed at Offshore Sites". Thesis, KTH, Kraft- och värmeteknologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-191790.

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For energy companies involved in the construction and operation of offshore wind power plants, such as Vattenfall, the knowledge of maximum wind speed is critical for logistics, safety and economic reasons. This thesis investigates the possibility to forecast maximum wind speeds at offshore sites, studies the accuracy of these forecasts, and details the employed methodology, so that it can be adapted to other cases in the future. In order to produce maximum wind speed forecasts, different statistical models were selected, some of them appropriate for short-term predictions (from 1h to 6h ahead), the others aiming at longer-term predictions (days ahead, up to 72h). The methodology consisted in selecting the right parameters for each model, depending on wind measurements and weather forecasts at the tested sites. Then forecasts were issued using the models’ equations, forecasted maximum wind speeds were compared with the real values, and the model delivering the best forecasts selected. The study demonstrated that, if appropriate statistical models were chosen – such as Vector Auto-Regression for short-term, and Generalized Additive Model for long-term – the average errors of precision for maximum wind speeds prediction were lower than 2 m/s, making the forecasts accurate enough to be used. Some work on the models still has to be done before they can be fully integrated into Vattenfall’s in-house weather forecasting system, but the first results are promising.
Energiföretag som Vattenfall, som deltar i byggandet och driften av vindkraftverk, behöver löpande ha korrekt kunskap om vindhastighetsvärden, som är avgörande för logistiken, säkerheten och ekonomin. Detta examensarbete undersöker möjligheten att förutsäga maximala vindhastigheter på offshore platser, studerar riktigheten i dessa prognoser, och specificerar tillgängliga och beprövade metoder för väderprognoser så att de kan anpassas till Vattenfalls behov. För att komma fram med prognoser om maximalt vindhastighet, olika statistiska modeller har valts. Några av dem är lämpliga för kortsiktiga prognoser (från 1 timme och upp till 6 timmar i förväg), andra syftar till att leverera förutsägelser på längre sikt (dagar framåt, upp till 72h). Metodiken bestod i att välja rätt parametrar för varje modell, beroende på vindmätningar och väderprognoser på de testade platserna. Prognoserna utfärdades med hjälp av modellernas ekvationer och de prognostiserade maximala vindhastigheterna jämfördes med de uppmätta värden i verkligheten, därmed kunde den mest lämpade modellen identifieras. Studien visar att i förekommande fall då statistiska modeller valdes - såsom Vector Auto-Regression för kortsiktiga, och respektive Generaliserad Additiv Modell för långsiktiga prognoser - det genomsnittliga precisionsfelet för förutsägelsen av maximal vindhastighet var lägre än 2 m/s, således var prognoserna tillräckligt noggranna för att appliceras i riktiga tillämpningar. En del arbete på modellernas inlärning återstår att göras innan de kan integreras fullt ut i Vattenfalls interna väderprognossystemet, men de första resultaten härmed är mycket lovande.

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Ramtharan, Gnanasambandapillai. "Control of variable speed wind turbine generators". Thesis, University of Manchester, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556174.

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Weiss, Austin M. "REMOVING VEHICLE SPEED FROM APPARENT WIND VELOCITY". UKnowledge, 2019. https://uknowledge.uky.edu/bae_etds/67.

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Variable-rate technologies for sprayer applications stand to increase efficacy by ensuring the right amount of chemical is applied at the right location. However, external environmental factors such as droplet drift caused by variable ambient condition, are not yet integrated into modern sprayer systems. Real-time wind velocity measurements can be used to control droplet spectra for reducing spray drift by actuating a variable-orifice nozzle. This work aimed to develop data processing methods needed to filter noise and remove vehicle speed from wind velocity measurements collected with an ultrasonic anemometer aboard a moving platform. Using a global navigation satellite system (GNSS), vehicle speed was calculated in the field and subtracted from apparent wind velocity for comparison to static measurements. Experiments under stationary and dynamic sensor deployments were used to develop an algorithm to provide instantaneous local wind velocity and to better understand the local spatiotemporal variability of wind under field conditions.

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Gustafsson, Eric, i Kalle Svensson. "Wind Energy Analyzing System : An audio doppler interferometer for wind speed determination". Thesis, Halmstad University, School of Business and Engineering (SET), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-4692.

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I dagens samhälle diskuteras miljö- och energifrågorna i allt större utsträckning. Projektgruppen valde att bidra till utvecklingen genom att underlätta för vindkraftbolagen att nå ut med grön energi på marknaden.

Projektgruppen har tillsammans med samarbetspartnern Lars Bååth professor i fotonik på Högskolan i Halmstad tagit fram en produkt som mäter vind inför byggandet av vindkraftverk. Wind Energy Analyzing System mäter vindförhållandena kontinuerligt från marknivå med hjälp av ljud och förvandlar informationen till vindriktning och vindhastighet på specifika höjder. Wind Energy Analyzing System är enkelt för kunden att använda och ger överlägsen information över vindförhållandena jämfört med de produkter som finns på marknaden idag. Priset för Wind Energy Analyzing System kommer att ligga en bra bit under konkurrenternas och tillverkas endast av standard komponenter vilket gör att produkten kan säljas med stor vinst.

Tidigare har man behövt investera stora summor för att säkerställa vindförhållandena innan man bygger ett vindkraftverk. Samtidig har informationen från dessa mätningar varit delvis uppskattade vilket har bidragit till en viss osäkerhet vid etablerandet av vindkraftverk. Wind Energy Analyzing System medför bättre vindmätningar till ett lägre pris.

Wind Energy Analyzing System är ett steg i rätt riktning, ett steg mot en framtid med förnyelsebar energi.

In the society today there are a lot of discussion about the environment and energy. The project group chose to contribute to the development by making it easier for wind energy companies to reach out with the green energy.

The project group has with cooperation of Lars Bååth, professor of photonics at Halmstad University, been developing a product for measuring wind before establishing of wind power plants. Wind Energy Analyzing System continuously measures the wind conditions from ground level by means of audio and converts the information to wind directions and wind speed at specific heights. Wind Energy Analyzing System is easy for customers to use and provide superior information on wind conditions compared to the products on the market today. The Price for Wind Energy Analyzing System will be well below its competitors and manufactured only of standard components so that the product can be sold with great profit.

Previously the wind power companies had to invest large sums to ensure the wind conditions before building a wind turbine. Meanwhile, information from these measurements was partly estimated which has contributing to some uncertainty of the establishment of wind power plant. Wind Energy Analyzing System will contribute with better wind measurements at a lower price.

Wind Energy Analyzing System is a step in the right direction, a step toward a future of renewable energy.

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

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Wind turbines typically rely on feedback controllers to maximize power capture in below-rated conditions and regulate rotor speed during above-rated operation. However, measurements of the approaching wind provided by Light Detection and Ranging (lidar) can be used as part of a preview-based, or feedforward, control system in order to improve rotor speed regulation and reduce structural loads. But the effectiveness of preview-based control depends on how accurately lidar can measure the wind that will interact with the turbine.

In this thesis, lidar measurement error is determined using a statistical frequency-domain wind field model including wind evolution, or the change in turbulent wind speeds between the time they are measured and when they reach the turbine. Parameters of the National Renewable Energy Laboratory (NREL) 5-MW reference turbine model are used to determine measurement error for a hub-mounted circularly-scanning lidar scenario, based on commercially-available technology, designed to estimate rotor effective uniform and shear wind speed components. By combining the wind field model, lidar model, and turbine parameters, the optimal lidar scan radius and preview distance that yield the minimum mean square measurement error, as well as the resulting minimum achievable error, are found for a variety of wind conditions. With optimized scan scenarios, it is found that relatively low measurement error can be achieved, but the attainable measurement error largely depends on the wind conditions. In addition, the impact of the induction zone, the region upstream of the turbine where the approaching wind speeds are reduced, as well as turbine yaw error on measurement quality is analyzed.

In order to minimize the mean square measurement error, an optimal measurement prefilter is employed, which depends on statistics of the correlation between the preview measurements and the wind that interacts with the turbine. However, because the wind speeds encountered by the turbine are unknown, a Kalman filter-based wind speed estimator is developed that relies on turbine sensor outputs. Using simulated lidar measurements in conjunction with wind speed estimator outputs based on aeroelastic simulations of the NREL 5-MW turbine model, it is shown how the optimal prefilter can adapt to varying degrees of measurement quality.

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Wilson, Graeme. "Quantifying the relationship between wind turbine component failure rates and wind speed". Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25467.

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Onshore wind turbine technology has matured to the point when assets are now expected to produce availabilities greater than 97%. The wind speed a wind turbine operates in has an impact on its reliability. Hitherto this relationship has not been defined, quantified or used to undertake analysis to assess how wind turbine performance would be affected by conditions at a prospective site. Wind turbine reliability data comes from two modern onshore wind farms, located in Scotland, using multi-megawatt wind turbines. This information is used alongside data from meteorological masts, located on each site, to determine the mean wind speed on the day of each recorded failure that resulted in corrective maintenance. A methodology is proposed in this thesis to define the relationship between wind turbine component failure rates and wind speed using Bayes Theorem. With these relationships known and wind speed dependent failure rates calculated, component reliability is modelled using discrete Markov Chains and Monte Carlo Simulation. The model is used to extrapolate the failure rate and wind speed relationships found within the onshore dataset to a proposed onshore and offshore site. From the generated data, wind turbine annual component failure rates are calculated for each site and analysis is performed to determine how component failure rates are likely to change throughout a year due to seasonal wind speeds at each site. The calculated seasonal failure rates allow wind turbine performance to be analysed more closely than if using traditional annual failure rates. A spares optimisation model is finally proposed using the wind speed dependent failure rate model. The output of this thesis is of particular relevance to operators of offshore wind farms.

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Lloyd, Simon H. "Variable speed control of a small wind turbine". Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/14376.

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An electronic controller has been developed for a wind turbine which uses a passive pitching mechanism and a permanent magnet generator. The turbine rotor is a 3 bladed, down wind horizontal axis design with a diameter of 3.4m. The machine, manufactured by Proven Engineering Ltd., produces 2.2kW at a wind speed of 12m/ s and a rotor speed of 30Orpm. Passive regulation is achieved through a variation of blade pitch controlled by balancing the aerodynamic, centrifugal and spring forces acting on each blade. A production machine has been instrumented and laboratory and field test data collected; from this data a mathematical model has been derived. A power electronic interface (DC-DC booster) was designed and built to transform the generator voltage to a fixed DC voltage. A controlled load is used together with feedback to the booster to set an appropriate load resistance according to operating conditions. Current demand from the generator (used in the control) is derived either from the difference between the rotor speed and a reference speed, or directly as a function of the rotor speed (feed-forward control). This thesis deals with the design and testing of the 3 compensators which govern the wind turbine control using both simulated and measured results. The overall objective of the controller is to maximise the energy yield from the wind turbine, subject to realistic constraints imposed by the power electronic design in the context of this particular design.

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Heyward, Moses A. "High speed air pneumatic wind shield wiping design". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/59703.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 28).
In this creative design process a number of designs were constructed, implemented and tested in order to assess the feasibility of using high speed to create a curtain to repel the rain from the automobile windshield instead of using the traditional wiper blades. The primary two methods tested used a compression system and a blower system that allowed the air to flow upward and parallel to the windshield. Both of the applications showed potential especially when coupled with a hydrophobic coating covering the windshield. The design using the high-speed squirrel cage blowers was implemented on an actual car in which it revealed positive results, which will be further assessed for patenting potential.
by Moses A. Heyward.
S.B.

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Piper, Benjamin. "SODAR comparison methods for compatible wind speed estimation". Thesis, University of Salford, 2011. http://usir.salford.ac.uk/16501/.

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This thesis includes the results of a PhD study about methods to compare Sonic Detection And Ranging (SODAR) measurements to measurements from other instruments. The study focuses on theoretical analysis, the design of a transponder system for simulating winds and the measurement of the acoustic radiation patterns of SODARs. These methods are integrated to reduce uncertainty in SODAR measurements. Through theoretical analysis it is shown that the effective measurement volume of a range gate is 15% of a cone section based on the SODAR's Full Width Half Maximum (FWHM). Models of the beam pattern are used to calculate the ratio of air passing a turbine to that measured by a SODAR over 10 minutes with values of 3-5% found at 10ms-1. The model is used to find angles where significant Sound Pressure Levels (SPLs) occur close to a SODARs baffle giving the highest chance of fixed echoes. This is converted into an orientation guide for SODAR set-up. The design of a transponder system is detailed that aims to provide a calibration test of the processing applied by a SODAR. Testing has shown that the transponder can determine the Doppler shift equation used by a SODAR although further work is needed to make the system applicable to all SODARs. It is shown that anechoic measurements of single elements are useful for improving array models. Measurements of the FWHM and acoustic tilt angle can be achieved in the field using a tilt mechanism and a Sound Level Meter (SLM) on a 10m mast. The same mechanism can be used to calculate an effective tilt angle using the Bradley technique. It is proposed that these methods are integrated to calculate error slopes for the SODAR measurement with regards to a secondary location. It is shown that the slopes could be between 0 and 5% if the methods are fully realised and a Computational Fluid Dynamics (CFD) model is incorporated.

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Mitchell, Erin. "Statistical methods for short term wind speed prediction". Thesis, Lancaster University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.747984.

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One of Earth’s most powerful natural resources is wind; harnessing its power in order to generate electricity is an ever expanding market throughout the world. In order to best utilise this resource it is important to be able to make accurate predictions of future wind speeds. This thesis focuses on accurately forecasting future wind speeds using statistical methods, in particular utilising past wind speed data and numerical weather prediction (NWP) data. Wind speed data are non-stationary time series, and the relationship between future wind speeds and NWP data may change over time. With this in mind, we look at models that can capture smooth variation in the series, specifically looking at dynamic linear models. In practice, many different forms of model can be used for predicting future wind speeds. We also look at methods for choosing between models, or for combining the predictions that different models make. We offer novel approaches that allow for abrupt changes in the choice of model based on the accuracy of recent predictions, with these approaches offering improvements in forecast accuracies. The final focus of this thesis is on developing novel methods for predicting ramp events: sudden, sharp changes in wind speeds. Predicting these events accurately is important, as ramp events can lead to substantial changes in the amount of wind energy produced. However, such events are currently not predicted well by standard forecasting models.

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Feldman, Michael A. "Efficient Low-Speed Flight in a Wind Field". Thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/36527.

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A new software tool was needed for flight planning of a high altitude, low speed unmanned aerial vehicle which would be flying in winds close to the actual airspeed of the vehicle. An energy modeled NLP formulation was used to obtain results for a variety of missions and wind profiles. The energy constraint derived included terms due to the wind field and the performance index was a weighted combination of the amount of fuel used and the final time. With no emphasis on time and with no winds the vehicle was found to fly at maximum lift to drag velocity, V_md. When flying in tail winds the velocity was less than V_md, while flying in head winds the velocity was higher than Vmd. A family of solutions was found with varying times of flight and varying fuel amounts consumed which will aid the operator in choosing a flight plan depending on a desired landing time. At certain parts of the flight, the turning terms in the energy constraint equation were found to be significant. An analysis of a simpler vertical plane cruise optimal control problem was used to explain some of the characteristics of the vertical plane NLP results.
Master of Science

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

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Dler, Dler Kamiran. "STUDYING THE STABILITY OF FIXED SPEED WIND TURBINES BY DETERMINING THE CRITICAL ROTOR SPEED". OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/569.

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The stability of fixed-speed wind turbines in case of fault happening in the grid is studied in this thesis by determining the critical rotor speed. Fixed-speed wind turbines are subjected to various types of fault when they are connected directly to grid [3]. In this study, the critical rotor speed is the maximum speed that the rotor of the wind turbine can reach before the wind turbine loses its stability. The factors that can affect the critical rotor speed are investigated such as the generator parameters, the duration of the fault, the parameters of the grid, and the type of the fault. Simulation studies are carried out in this thesis. The results of the simulation studies show the effect of the factors mentioned above on the stability of fixed-speed wind turbines. The results also show that the time of the fault duration varies with the type of the fault; therefore, designing a protection unit by observing the rotor speed of the rotor during the fault is more suitable that designing a control unit depending on the fault duration.

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Schmidlin, Thomas W. Hammer Barbara King Paul Ono Yuichi Miller L. Scott Thumann Gregory. "Unsafe at any (wind). speed? Testing the stability of motor vehicles in severe winds". [Emmitsburg, MD : National Emergency Training Center], 2002. http://ams.allenpress.com/archive/1520-0477/83/12/pdf/i1520-0477-83-12-1821.pdf.

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Tang, Yunmo. "The current situation of high-altitude wind power". Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-14734.

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The importance of the use of renewable energy sources is obviously. But what the problem confused us, is that renewable energy unlike the fossil fuel have such high energy density which means the renewable generally was dispersed form. In other words, in order to obtain amount of the energy we need, require to exploitation a wider cover area. Therefore, scientists and companies are struggling to find high densely renewable energy as possible, which is high altitude wind energy, have very promising but not developed so much by humans. High altitude wind power is indicating the altitude between 3000 meters and 10000 meters. So far, high altitude wind power is a new renewable energy that basically not development or utilization yet, but which is an abundant reserves. High altitude wind power is a widely distributed renewable clean energy. The characterized of high-altitude wind energy is fast speed, wide distribution, high stability and perennial. Utilize high-altitude wind power can get high stability with low cost of wind power generation, which is one of the notable features for high-altitude wind power, but also is one of the most significant advantages for high-altitude wind energy compared to conventional wind energy. High altitude wind power generation equipment is more compact and flexible, far superior then the traditional fan, which equip with thick blades and the tower must be fixed in the depths of the ocean or in the ground.To development renewable power in a large scale, to face the global climate change, achieve the sustainable development become the inevitable for human development. How to solve the energy shortage problem has become an important question, harness high altitude wind power was becomes the focus of multinational technology.

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DANTAS, TIAGO MENDES. "TIME‐FREQUENCY MODEL FOR SHORT TERM WIND SPEED FORECASTING". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19157@1.

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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
A quantidade de energia gerada através de energia eólica está aumentando no mundo todo. O Brasil tem um enorme potencial devido a sua localização geográfica e governo brasileiro dá claros sinais de que está propenso a investir neste tipo de energia. Previsões precisas de velocidade vento são essenciais para a operação planejamento do sistema elétrico de energia. Este trabalho tem como objetivo fazer previsões mais precisas na Nordeste do Brasil. Para isso, usamos um modelo que leva em conta as características diárias e o comportamento da memória longa. O modelo aplicado nesta região particular mostrou-se mais preciso que o modelo de persistência e outros modelos (por exemplo, modelo híbrido neuro-fuzzy)
The amount of energy generated by wind sources is increasing all over the world. Brazil has a huge potential due to its geographic localization and the Brazilian Government has given a clear signal that is prone to invest in this kind of energy. Accurate wind speed forecasts are essential in the operation planning for the electrical wind power system. This work aims to make more accurate forecasts in the northeast of Brazil. To do so, we use a model that takes into account the daily characteristics and the long memory behavior. The model applied in this particular region proved to be more accurate than the persistence model and other models.

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Mesrobian, Chris Eden. "Concept Study of a High-Speed, Vertical Take-Off and Landing Aircraft". Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/35574.

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The purpose of the study was to evaluate the merits of the DiscRotor concept that combine the features of a retractable rotor system for vertical take-off and landing (VTOL) with an integral, circular wing for high-speed flight. Tests were conducted to generate basic aerodynamic characteristics of the DiscRotor in hover and in fixed-wing flight.

To assess the DiscRotor during hover, small scale tests were conducted on a 3ft diameter rotor without the presence of a fuselage. A â hover rigâ was constructed capable of rotating the model rotor at speeds up to 3,500 RPM to reach tip speeds of 500fps. Thrust and torque generated by the rotating model were measured via a two-component load cell, and time averaged values were obtained for various speeds and pitch angles. It has been shown that the DiscRotor will perform well in hover. Ground Effects in hover were examined by simulating the ground with a movable, solid wall. The thrust was found to increase by 50% compared to the ground-independent case. Pressure distributions were measured on the ground and disc surfaces. Velocity measurements examined the flow field downstream of the rotor by traversing a seven hole velocity probe. A wake behind the rotor was shown to contract due to a low pressure region that develops downstream of the disc.

Wind tunnel experimentation was also performed to examine the fixed wing flight of the DiscRotor. These experiments were performed in the VA Tech 6â X6â Stability Tunnel. A model of the fuselage and a circular wing was fabricated based upon an initial sizing study completed by our partners at Boeing. Forces were directly measured via a six degree of freedom load cell, or balance, for free stream velocities up to 200fps. Reynolds numbers of 2 and 0.5 million have been investigated for multiple angles of attack. Low lift-to-drag ratios were found placing high power requirements for the DiscRotor during fixed-wing flight. By traversing a seven-hole velocity probe, velocities in a 2-D grid perpendicular to the flow were measured on the model. The strengths of shed vortices from the model were calculated. A method to improve fixed-wing performance was considered where two blades were extended from the disc. An increase of 0.17 in the CL was measured due to the interaction between the disc and blades.

This research utilized a wide range of experiments, with the aim of generating basic aerodynamic characteristics of the DiscRotor. A substantial amount of quantitative data was collected that could not be included in this document. Results aided in the initial designs of this aircraft for the purpose of evaluating the merit of the DiscRotor concept.
Master of Science

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Sangpanich, Umarin. "Optimization of wind-solar energy systems using low wind speed turbines to improve rural electrification". Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18944.

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Electricity is significant in improving the quality of life for people in rural and remote areas in developing countries. There are two main options for Rural Electrification (RE), namely grid extension and stand-alone systems. The governments and developers face the challenges of their limitations, namely technical, economic and environmental effects of each RE choice. This thesis intends to improve RE by focusing on renewable energy technologies, namely Wind Turbine (WT) and Photovoltaic (PV) systems. They have been developed and applied to RE because they are simple and environmentally friendly. They can be installed as separate units and they are sustainable alternative energy solutions. Installation, cost and performance are crucial issues of WT and PV applications, and are based on the terrain and climate where the renewable are installed. The efficiency of WTs and PV modules has increased, while their cost has declined continuously. However, a PV system still has installatio n costs around two times more expensive per watt than WTs. Most WTs using current technology can be financially worthwhile for high wind speed areas, having wind speeds greater than 6.4 m/s at 10 m hub height, but most rural areas have wind speeds of less than 6 m/s at the same height. Therefore, Low Wind Speed Turbines (LWSTs) have evolved, by increasing rotor diameter and while maintaining similar generator capacity. This is to reduce Levelized Cost of Energy (LCOE) for WTs in low wind speed areas. This thesis proposes simple cost models, namely the Sum-component cost model and the Total-cost model in order to calculate the LCOE of LWSTs. In addition, novel aspects of this thesis are that the optimization processes of stand-alone hybrid WT-PV systems and hybrid WT-PV systems using batteries at peak demand in remote area power systems provide simple, fast and flexible methods, by applying Multi-objective Evolutionary Algorithm (MOEA). The MOEA can analyze complex objective problems a nd provide an accurate multi-objective method. Results from relevant case studies show that the cost models and the optimization processes proposed are novel and are valuable tools for analysis and design, including the approaches for improving the system reliability and for estimating the Initial Capital Cost (ICC) of WTs having different rated wind speeds. The proposed algorithms are generic and can be utilized for other energy planning problems.

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Clemow, Philip R. "Smoothing wind farm output power through co-ordinated control and short term wind speed prediction". Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9504.

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In recent years the energy sector has looked to renewables as a means to reduce emissions. Wind power is able to provide large amounts of energy at a reasonable cost from presently available products. Thus the amount of wind generation has risen steeply in recent years, notably in the countries of northern Europe. However, this rise in wind power has lead to issues regarding the variability of the wind power output. Wind power is related to the wind speed, which varies greatly. This variability can cause issues with wind operators' ability to participate in electricity markets and can also lead to a rise in balancing costs. The system proposed in this thesis aims to reduce the variation of wind farm output seen in the minute to minute time-scale and provide controllability in longer time-scales. To do this the system uses short-term wind speed predictions and the inertial energy storage of the wind turbines themselves and does so in a co-ordinated fashion across the whole farm. Using short term wind speed predictions, the amount of energy in the wind is calculated for the next short period. This energy can be exported in a controlled manner using the inertial energy to cover short-term wind energy shortfall or excess. The rotor speed must vary for the storage effect to be achieved and this requires extra control systems to prevent over-speed or turbine stalling. The system was tested and found to be effective at smoothing the output power in a range of different wind scenarios. Tests were performed to assess the effects of using co-ordinated control on the frequency of an example grid and on the use patterns of portfolio generators. Both tests show that the use of a co-ordination controller at wind farm level reduces the balancing burden on the remainder of the system in comparison with the common maximum power form of control.

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Jones, Scott Alan. "Effect of pruning type, pruning dose, and wind speed on tree response to wind load". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013321.

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Iqbal, Muhammad Tariq. "Dynamic control strategies for fixed and variable speed wind turbines". Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/7737.

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Baseer, Mohammed Abdul. "Wind resource assessment and GIS-based site selection methodology for efficient wind power deployment". Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/61314.

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An enormous and urgent energy demand is predicted due to the growing global population, increase in power intensive industries, higher living standards, electrification of remote areas, and globalisation (transportation). Moreover, the global consciousness about the harmful effects of traditional methods of power generation on the environment. That, in turn, has created a need to strategically plan and develop renewable and sustainable energy generation systems. This study presents a wind resource assessment of seven locations proximate to the largest industrial hub in the Middle East, Jubail Industrial City, Kingdom of Saudi Arabia, and a Geographic Information System, GIS based model considering a multi-criteria wind farm site suitability approach for the entire Kingdom of Saudi Arabia and elsewhere. The hourly mean wind speed data at 10, 50 and 90 m above the ground level (AGL) over a period of five years was used for a meteorological station at the Industrial Area (Central) of Jubail. At the remaining six sites, the meteorological data were recorded at 10 m AGL only. Five years of wind data were used for five sites and three years of data were available for the remaining one site. At the Industrial Area (East), the mean wind speeds were found to be 3.34, 4.79 and 5.35 m/s at 10, 50 and 90 m AGL, respectively. At 50 and 90 m AGL, the availability of wind speed above 3.5 m/s was more than 75%. The local wind shear exponent, calculated using measured wind speed values at three heights, was found to be 0.217. The mean wind power density values at measurement heights were 50.92, 116.03 and 168.46 W/m2, respectively. After the assessment and comparison of wind characteristics of all seven sites, the highest annual mean wind speed of 4.52 m/s was observed at Industrial Area (East) and the lowest of 2.52 m/s at the Pearl Beach with standard deviations of 2.52 and 1.1 m/s, respectively. In general, at all sites, the highest monthly mean wind speed was observed in February/June and the lowest in September/October. The period of higher wind availability coincides with a high power demand period in the region attributable to the air conditioning load. The wind rose plots show that the prevailing wind direction for all sites was from the north-west. Weibull parameters for all sites were estimated using maximum likelihood, least-squares regression method (LSRM), and WAsP algorithm. In general, at all sites, the Weibull parameter, c, was the highest in the months of February/June and the lowest in the month of October. The most probable and maximum energy carrying wind speed was determined by all three methods. The highest value of most probable wind speed was found to be in the range of 3.2 m/s to 3.6 m/s at Industrial Area (East) and the highest value of maximum energy carrying wind speed was found to be in the range 8.6 m/s to 9.0 m/s at Industrial Area 2 (South) by three estimation methods. The correlation coefficient (R2), root mean square error (RMSE), mean bias error (MBE), and mean bias absolute error (MAE) showed that all three methods represent wind data at all sites accurately. However, the maximum likelihood method is slightly better than LSRM, followed by WAsP algorithm. The wind power output at all seven sites, from five commercially available wind turbines of rated power ranging from 1.8 to 3.3 MW, showed that Industrial Area (East) is most promising for wind farm development. At all sites, based on percentage plant capacity factor, PCF, the 1.8 MW wind turbine was found to be the most efficient. At Industrial Area (East), this wind turbine was found to have a maximum PCF of 41.8%, producing 6,589 MWh/year energy output. The second best wind turbine was 3 MW at all locations except the Al-Bahar Desalination Plant and Pearl Beach. At both of these locations, 3.3 MW was the next best option. The energy output from the 3 MW wind turbine at Industrial Area (East) was found to be 11,136 MWh/year with a PCF of 41.3%. The maximum duration of rated power output from all selected wind turbines was observed to be between 8 to 16.6% at Industrial Area 2 (South). The minimum duration of rated power output, less than 0.3% for all wind turbines, was observed at Pearl Beach. The maximum duration of zero power output of between 35 to 60% was also observed at Pearl Beach.
Thesis (PhD)--University of Pretoria, 2017.
Mechanical and Aeronautical Engineering
PhD
Unrestricted

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Golya, David Andrew. "Statistical methods for maxima and means". Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389758.

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彭運佳 i Wan-kai Pang. "Time series analysis of meteorological data: wind speed and direction". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1993. http://hub.hku.hk/bib/B30425979.

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Singh, Jaskirat. "Wind Speed Profiles and Pressure Coefficients Obtained in the Wind Induced Damage Simulator for Silsoe Cube Model". Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41094.

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Hazardous winds, such as tornadoes and hurricanes, have a great impact on civil engineering structures and cause significant social and economic disturbances. The wind speed and pressure tested in the conventional wind tunnel experiments are much smaller than the actual wind speed and pressure measured in the field. Therefore, the Wind-induced Damage Simulator (WDS) was constructed at the University of Ottawa to overcome the wind speed limitations of wind tunnels and to simulate different types of wind speed profiles. WDS is an isolated cubic box with dimensions 3.65m x3.65 m and 3.0 m height, with multiple inlets on the side faces of the testing chamber and an outlet on the top side. This unique equipment creates a controlled environment for studying wind speed profiles in a confined space, by regulating the air flow with the aid of an attached industrial blower. To measure the simulated wind velocities inside the WDS and to obtain the wind speed profile in the testing chamber, Aeroprobe (12- Hole Probe) sensor was used for different combinations of opened inlets and at four different locations. The data collected from the Aeroprobe was processed by the use of the Aeroflow 2.7.5.7346 software, to get the velocity of wind in three different directions (u, v and w) and the mean velocity at a single point. After determining the mean velocity at different heights and RPM values at all four positions, Matlab software was used to determine the wind profile and the spectra of the turbulence intensities and these were compared for different heights at the four investigated locations and for various rotations per minute (RPM) values (400 to 800 RPM) for controlling the blower. Once the flow characterization was completed, the wind-induced pressure for three models of the Silsoe Cube were measured as a part of the second phase of the test. The current experiment employed 3 different scales of Silsoe cube: 1:40, 1:30 and 1:20, while the pressure coefficients were determined at 16 different points along a vertical line crossing the faces of the cube. A pressure taps system with 16 channels and a Scanivale pressure scanner were used to measure the pressure at 16 different positions on the cube. Matlab software was used to determine the pressure coefficients from the data measured by pressure taps. The pressure coefficienst for the Silsoe Cube were plotted and compared for the three different scales. Also, for determining the best scale to be used in future experiments. The pressure coefficients of the 3 different scaled model of Silsoe Cubes was compared with full-scale data reported in the literature for the same structure. Based on the results obtained from the experiments, recommendations for the best location in the testing chamber for the future experiments employing the WDS were formulated.

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Nchaba, Teboho. "Verification of gridded seasonal wind speed forecasts over South Africa". Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/4970.

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Includes abstract.
Includes bibliographical references.
The Climate System Analysis Group (CSAG) at the University of Cape Town produces provisional global and Southern African seasonal wind forecasts generated using the United Kingdom Meteorological Office Atmospheric General Circulation Model (AGCM) HadAM3P (non-standard version of HadAM3). This study examines the quality of the seasonal wind speed forecasts through a forecast verification process for continuous variables using reanalysis products of the National Centers for Environmental Prediction and the Department of Energy (NCEP-DOE) as observations data. The verification analyses are performed using summary measures Mean Error (ME), Mean Absolute Error (MAE), Mean Squared Error (MSE), correlation coefficients, Linear Error in Probability Space (LEPS) and exploratory methods, scatter and conditional quantile plots. These methods are used to determine the aspects of forecast quality namely, bias, accuracy, reliability, resolution, and skill over a 20 year period (1991 to 2010). The results of the study have determined that the use of both accuracy and skill measures for the verification analyses provide more information about the quality of the forecasts, as opposed only one of these. In all provinces, the highest quality seasonal wind speed forecasts are made at 500 hPa and the lowest quality forecasts at 1000 hPa. Furthermore regions, pressure levels, and seasons with the highest forecast quality share the common characteristic that their wind speeds are relatively high. The forecasts add value to the climatology and thus are a useful tool for wind assessment at a seasonal scale. It is suggested that adding spatial resolution to the forecasts through downscaling may prepare them for use in applications such as wind power output forecasting.

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Pang, Wan-kai. "Time series analysis of meteorological data : wind speed and direction /". [Hong Kong] : University of Hong Kong, 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13456933.

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Chew, Lup Wai. "Outdoor wind speed enhancement in residential precincts in tropical cities". Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122217.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 129-139).
Wind speeds in urban areas are significantly reduced due to the blockage effects of urban structures. Lower wind speeds inhibit passive ventilation and reduce thermal comfort in tropical cities. This thesis uses both experimental and computational fluid dynamics (CFD) modeling to explore the potential of building porosity to increase wind speeds at the pedestrian level. The computational models are first validated with experiments to justify the exclusion of thermal effects, as the models over-predict the thermal effects on heated surfaces. Validated computational simulations show that void decks can increase pedestrian-level wind speeds by more than twofold in two-dimensional urban street canyons. In three-dimensional urban street canyons, void decks not only increase the wind speeds in the street canyons, but also along the streets. The effectiveness of void decks to increase wind speed is significantly influenced by the height of void decks but not the building height. Next, the heat wave in April 2016 in Singapore is simulated with the Weather Research and Forecasting model to identify two residential precincts with high temperatures for detailed case studies. Both selected precincts are simulated with CFD models to obtain the pedestrian-level wind fields. The effects of void decks in these two real urban areas are evaluated by comparing the wind field with void decks to that in the control case without void decks. The first precinct with smooth upwind areas shows significant wind speed enhancement up to 80% of the freestream wind speed (the wind speed above the roof level) with void decks. The second precinct with rough upwind areas shows wind speed enhancement up to 50% of the freestream wind. In conclusion, void decks are an effective architectural intervention to enhance pedestrian-level wind speeds, but the effectiveness is influenced by the upwind conditions.
by Lup Wai Chew.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering

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Joseph, Liselle AnnMarie. "Transition Detection for Low Speed Wind Tunnel Testing Using Infrared Thermography". Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/78145.

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Transition is an important phenomenon in large scale, commercial, wind tunnel testing at low speeds because it is an excellent indicator of an airfoil performance. It is difficult to estimate transition through numerical techniques because of the complex nature of viscous flow. Therefore experimental techniques can be essential. Over the transition region the rate of heat transfer shows significant increases which can be detected using infrared thermography. This technique has been used predominantly at high speeds, on small models made of insulated materials, and for short test runs. Large scale testing has not been widely undertaken because the high sensitivity of transition to external factors makes it difficult to detect. The present study records the process undertaken to develop, implement and validate a transition detection system for continual use in the Virginia Tech Stability Wind Tunnel: a low speed, commercial wind tunnel where large, aluminium models are tested. The final system developed comprises of two high resolution FLIR A655sc infrared cameras; four 63.5-mm diameter circular windows; aluminium models covered in 0.8-mm silicone rubber insulation and a top layer of ConTact© paper; and a series of 25.4-mm wide rubber silicone fiberglass insulated heaters mounted inside the model and controlled externally by experimenters. This system produces images or videos of the model and the associated transition location, which is later extracted through image processing methods to give a final transition location in percentage chord. The system was validated using two DU96-W-180 airfoils of different chord lengths in the Virginia Tech Stability Wind Tunnel, each tested two months apart. The system proved to be robust and efficient, while not affecting the airfoil performance or any other system in use in the wind tunnel. Transition results produced by the system were compared to measurements obtained from pressure data and stethoscope tests as well as the numerical predictions of XFOIL. The transition results from all four methods showed excellent agreement with each other for the two models, for at least two Reynolds numbers and for several angles of attack on both suction and pressure side of the model. The agreement of data obtained under such different conditions and at different times suggests that the infrared thermography system efficiently and accurately detects transition for large aluminium models at low speeds.
Master of Science

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38

Gogas, Kyriakos. "Design of a robust speed and position sensorless decoupled P-Q controlled doubly-fed induction generator for variable-speed wind energy applications". Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99762.

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Wind energy is a relatively young but rapidly expanding industry. In order for wind generation to be cost effective, it must produce energy at a minimum cost per dollar of investment. Performance characteristics such as power output versus wind speed must be optimized in order to compete with other energy sources. Also, if the utility uses wind power for a part of its generation, the output power of these turbines must have the same high quality and reliability when it enters the utility grid. The ability to vary operating speed is important in wind generation because it allows for an optimization of the transfer of power from the wind to the turbine shaft. Doubly-fed induction generators (DFIG) are an interesting solution for variable-speed systems with limited variable speed range, and are typically used in wind energy conversion systems.
The objectives of this thesis are to implement a decoupled P-Q control of a DFIG that does not rely on mechanical sensors and to design a speed and position sensorless algorithm that is robust to variations of the values of the machine parameters. The sensorless DFIG control algorithm presented in this thesis is based on a modified phasedlock loop with an improved positioning algorithm. With the measured stator voltages, stator and rotor currents, the speed and position of the DFIG are estimated. The speed is estimated independent of machine parameters, which results in a significant improvement in speed control robustness to parameter variations. In addition, the algorithm avoids using differentiation, which significantly improves its immunity to noise and does not require the measurement of the rotor voltages. Also, it is shown that the positioning algorithm has an improved operation in generator mode. Although the accuracy of the positioning algorithm is depended on machine parameters; it is shown with the designed controller that the P-Q decoupled control is robust to changes of machine parameters. Theoretical and simulation results are validated on an experimental setup.

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39

Hand, M. Maureen. "Variable-speed wind turbine controller systematic design methodology : a comparison of non-linear and linear model-based designs /". Golden, CO : National Renewable Energy Laboratory, 1999. http://www.nrel.gov/docs/fy99osti/25540.pdf.

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Stott, Paul Anthony. "Renewable variable speed hybrid system". Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4781.

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At present many remote and Island communities rely solely on diesel powered generators to provide electricity. Diesel fuel is both expensive and polluting and the constant speed operation of the diesel engine is inefficient. In this thesis the use of renewable energy sources to help offset diesel fuel usage and an alternative way of running the diesel generator with the aim of reducing electrical energy costs is investigated. Diesel generators have to be sized to meet peak demand, in one or two diesel generator island grids, these generators will be running at a fraction of maximum output for most of the time. A new variable speed diesel generator allows for a reduction in fuel consumption at part load compared to constant speed operation. Combining the variable speed diesel generator with renewable generation should maximise the diesel fuel offsetting of the renewable source due to the increased efficiency at low loads. The stability issues of maintaining transient performance in a renewable variable speed hybrid system have been modelled and simulated. A control strategy has been developed and the use of energy storage as a buffer for any remaining stability problems has been explored. The control strategy has then been experimentally tested along with one of the possible energy storage solutions. An economic feasibility study has been performed on a case study community to validate the main aim of this research of reducing the cost of electrical energy in diesel generator grids.

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41

Benjanirat, Sarun. "Computational studies of the horizontal axis wind turbines in high wind speed condition using advanced turbulence models". Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-08222006-145334/.

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Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2007.
Samual V. Shelton, Committee Member ; P.K. Yeung, Committee Member ; Lakshmi N. Sankar, Committee Chair ; Stephen Ruffin, Committee Member ; Marilyn Smith, Committee Member.

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Bourlis, Dimitrios. "Control algorithms and implementation for variable speed stall regulated wind turbines". Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/28800.

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In this research control algorithms and implementation for variable speed stall regulated wind turbines are presented. This type of wind turbine has a simpler and more robust construction and can have lower requirements for maintenance than the existing pitch regulated wind turbines. Due to these features these wind turbines can have reduced cost, which is a crucial parameter especially for large scale wind turbines. However, this type is not commercially available yet due to existing challenges in its control. In this research a complete control scheme for variable speed stall regulated wind turbines has been developed and implemented in a fully dynamic hardware-in-loop simulator for variable speed wind turbines. The simulator was developed as part of the project in order to validate the designed control algorithms. The developed control system uses novel adaptive methods in order to maximize the energy production of the wind turbines at below rated wind speeds as well as to control the power of the wind turbine at above rated wind speeds. In addition, several types of controllers including robust controllers have been used and tested, which resulted to novel control solutions for stall regulated wind turbines. The main advantage of the proposed control method is that it uses existing hardware without requiring additional sensors, so it more effectively exploits information coming from measurements available in existing wind turbine converters. Through software and hardware simulations the proposed control algorithms seem to be quite promising and give confidence for the future development of variable speed stall regulated wind turbines.

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43

Bu, Yiming. "Switching linear parameter-varying control of a variable-speed wind turbine". Thesis, California State University, Long Beach, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1596455.

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For variable-speed wind energy conversion systems, control objectives may be different in partial and full load regions (or in low and high wind speed regions). Typical control objectives are to maximize the energy capture in low wind speeds, and to maintain the generated power and the rotational turbine speed within safety limits during high wind speeds. In such a case, it is difficult to design a single robust controller covering both partial load and full load conditions. This paper presents a systematic switching control method for a variable-speed variable-pitch wind turbine over a wide wind speed region. The whole framework is based on the linear parameter-varying (LPV) control theory, which is an extension of robust control for linear systems to nonlinear ones.

Two LPV controllers are designed, each suitable in a different wind speed region. A hysteresis switching logic is applied to guarantee the stability when the switching event occurs between the two controllers. Nonlinear simulations are conducted to demonstrate the proposed control scheme.

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Wise, John Nathaniel. "Optimization of a low speed wind turbine using support vector regression". Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2737.

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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009.
NUMERICAL design optimization provides a powerful tool that assists designers in improving their products. Design optimization automatically modifies important design parameters to obtain the best product that satisfies all the design requirements. This thesis explores the use of Support Vector Regression (SVR) and demonstrates its usefulness in the numerical optimization of a low-speed wind turbine for the power coe cient, Cp. The optimization design problem is the three-dimensional optimization of a wind turbine blade by making use of four two-dimensional radial stations. The candidate airfoils at these stations are selected from the 4-digit NACA range. A metamodel of the lift and drag coe cients of the NACA 4-digit series is created with SVR by using training points evaluated with XFOIL software. These SVR approximations are used in conjunction with the Blade Element Momentum theory to calculate and optimize the Cp value for the entire blade. The high accuracy attained with the SVR metamodels makes it a viable alternative to using XFOIL directly, as it has the advantages of being faster and easier to couple with the optimizer. The technique developed allows the optimization procedure the freedom to select profiles, angles of attack and chord length from the 4-digit NACA series to find an optimal Cp value. As a result of every radial blade station consisting of a NACA 4-digit series, the same lift and drag metamodels are used for each station. This technique also makes it simple to evaluate the entire blade as one set of design variables. The thesis contains a detailed description of the design and optimization problem, the implementation of the SVR algorithm, the creation of the lift and drag metamodels with SVR and an alternative methodology, the BEM theory and a summary of the results.

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45

Huenefeld, Joshua. "A report on the effects of wind speed on timber construction". Kansas State University, 2012. http://hdl.handle.net/2097/13606.

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Streszczenie:

Master of Science
Department of Architectural Engineering
Kimberly Waggle Kramer
Main lateral force resisting systems (MLFRS) in timber buildings consist of two components: diaphragms and shear walls. Diaphragms are used to collect the shear induced by the lateral force at each of the levels. The shear is transferred from the diaphragms to the shear walls via plywood sheathing and connections. The shear walls transfer shear to the sill plate via plywood sheathing and then into the foundation via anchors. Two approaches for designing shear wall are: the segmented shear wall approach and the perforated shear wall approach. The segmented shear wall approach uses only full height segments to resist shear; each individual segment must be designed to resist the shear and overturning force induced by the lateral load. The perforated shear wall approach uses both full height segments and segments around openings to resist shear; the wall as a whole is used to resist shear and overturning forces induced by the lateral load. This report examines one-, two-, and three-story timber buildings located in three different wind regions: a) 115 mph, b) 140 mph, and c) 160 mph. This report presents the design process for the MLFRS components and a comparison of the designs for each of the buildings. The purpose of this report is to determine how the design changes depending on the magnitude of the lateral load, the height of the building, and the approach used to design the shear walls.

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46

Chou, Chun-Hung, i 周俊宏. "The Wind Speed Characteristics Assessment for Wind Generation". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/66149918650814782582.

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碩士
南台科技大學
電機工程系
95
It is an important issue to master the characteristics of wind speed distribution exactly during estimating the wind energy. There are many factors, e.g., unreliable wind speed data、uncertain terrain and weather conditions near by the wind field, which effect the error of wind energy estimation. The paper utilizes Bins、Weibull and Gamma function to analyze the wind speed distribution of Tainan and Penghu, the shape & scale parameters of Weibull probability density function were evaluated by the method of the maximum likelihood and moments (expected value & standard deviation). The results show that there are significant differences between the characteristics of wind speed distribution in the Tainan and Penghu. The Weibull distribution is feasible for Tainan’s wind speed, and the Gamma distribution is better for Penghu’s wind speed in the summer & some specific months. The modified formula for wind speed is proposed to solve iteratively the difference of two different wind fields. The complete historical wind data from weather station can be used to infer some important information about wind speed/generation surroundings where wind field may be established. Other parameters, like friction coefficients of environment, can also be assessed by the proposed wind speed formula. Some uncertainties obtained from the parameters during evaluation will be managed by a fuzzy number. The derived fuzzy wind speed accounts for the potential wind energy/generation near by the weather station with similar environment.

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Ting, Yi-Ju, i 丁怡汝. "Wind speed forecasting by time series". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/19452499978509014297.

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碩士
國立暨南國際大學
資訊管理學系
103
Due to gradual reduction of oil, insecurity of nuclear power and pollution to the environment, many developed countries have been actively looking for alternative energy sources. Wind power is one of the priority alternatives. However, unstable wind speeds cause the instability of power generation. Therefore, to predict the wind speed accurately and make good use of the generated energy is able to reduce the dependence on oil. For predicting wind speed, most of the previous studies focused on one wind speed attribute without data preprocessing procedures. In this study, seasonal adjustment and the form of logarithm were used to preprocess data. Three time series prediction method, namely AutoRegressivee Integrated Moving Average model (ARIMA), Seasonal ARIMA (SARIMA) and Nonlinear AutoRegressive (NAR) were used to predict the wind speeds. In addition, the Correlation-based Feature Selection method (CFS) and the method based on the formation characteristics were utilized to selected wind speed features. Then, four techniques, namely the multi feature prediction method of Least Squares Support Vector Machines (LSSVM), Nonlinear AutoRegressive eXogenous model (NARX), multiple nonlinear regression and multiple linear regression, were employed to forecast wind speeds. Finally, the performances of different models were compared. Climate data collected from Central Weather Bureau Wuqi Weather Station in 2013 annual observations were employed to examine the performance of the proposed model. The experimental results showed that the NAR with seasonal adjustment has the smallest prediction error rate

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48

Zhou, Ting-Wei, i 周廷威. "Simulation of Wind Speed-Up Effect". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/v5jazc.

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碩士
國立臺灣科技大學
營建工程系
107
Pedestrian wind environment is a very important issue which can not be ignored since an uncomfortable wind environment would affect the usability and planning of the region around the building. The pedestrian wind comfort assessment and improvement become an important issue when building a highrise building. This study simulates wind speed-up effect of the pedestrian wind environment by Computational Fluid Dynamic (CFD). The first part of this study is the comparison between the simulation results of the wind speed-up effect around escarpment, ridge and hill by CFD and those specified in Taiwan Code(2015) and National Building Code of Canada(2005). It shows that the CFD simulation results are closer to those provided in NBCC (2005), and the simulation error (8~10%) in the near-ground region is larger than the average error (3~5%). The second part and the third part of this study are respectively the simulation of the wind speed-up effect around a 1:1:2 independent building and that in an urban area. By comparing with the wind tunnel test results provided by Architectural Institute of Japan (AIJ), the CFD simulation results in the region affected by the corner flow (high wind region) at the pedestrian height are relatively good (about 10% error), and those on the leeward side of the building (low wind region) are relatively inaccurate (about 32% error). In addition, it is found that based on the simulation results, pedestrian discomfort will occur under Kaohsiung prevailing wind. The windbreak vegetation can reduce 14.5% of the highest wind speed while the windbreak canopy can reduce 19.7% of the highest wind speed.

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Human, Jacobus Daniel. "Design of a shrouded wind turbine for low wind speeds / Jacobus Daniel Human". Thesis, 2014. http://hdl.handle.net/10394/15291.

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The use of renewable energy is promoted worldwide to be less dependent on fossil fuels and nuclear energy. Therefore research in the field is driven to increase efficiency of renewable energy systems. This study aimed to develop a wind turbine for low wind speeds in South Africa. Although there is a greater tendency to use solar panels because of the local weather conditions, there are some practical implications that have put the use of solar panels in certain areas to an end. The biggest problem is panel theft. Also, in some parts of the country the weather is more suitable to apply wind turbines. Thus, this study focused on the design of a new concept to improve wind turbines to be appropriate for the low wind speeds in South Africa. The concept involves the implementation of a concentrator and diffuser to a wind turbine, to increase the power coefficient. Although the wind turbine was not tested for starting speeds, the implementation of the shroud should contribute to improved starting of the wind turbine at lower wind speeds. The configuration were not manufactured, but simulated with the use of a program to obtain the power production of the wind turbine over a range of wind speeds. These values were compared to measured results of a open wind turbine developed for South Africa. The most important matter at hand when dealing with a shrouded wind turbine is to determine if the overall diameter or the blade diameter of the turbine should be the point of reference. As the wind turbine is situated in a shroud that has a larger diameter than the turbine blades, some researchers believe that the overall diameter should be used to calculate the efficiency. Theory was revised to determine the available energy in the shroud after initial calculations showed that the power coefficients should have been higher than the open wind turbine with the same total diameter. A new equation was derived to predict the available energy in a shroud. The benefits of shrouded wind turbines are fully discussed in the dissertation content.
MSc (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

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Ko, Chih Shing, i 柯志軒. "Effects of wave height,wind speed on sea-surface wind stress". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/38993908586679021907.

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碩士
國立中山大學
海洋資源學系
82
A stable research platform,located at a coastal site off Taichung Harbor with an average water depth of about 8m,has been instrumented with a sonic anemometer with three-component wind speed, and air temperature sensors,and with three wind monitors at three different heights above the sea surface. A telemetry system has been used to transmit data to an inland receiving station.The wind turbulence data for the period between April 30 and November 19,1993 from this platform have been analyzed by the eddy correlation method to obtain wind stress and heat fluxes at various wind speeds. Data from near south-bound direction with longer fetch were used separately by the present study because it is unobstructed from the land and marine structures.Our results indicate that the wind stress is proportional to the square of wind speed.At lower winds,the drag coefficient,Cd,decteases with increaseing wind speed.At higher winds,it seems that Cd increases or remains unchanged with the wind speed.Cd was found to be generally larger for growing waves(smaller Co/u*)than for steady or decaying waves( larger Co/u*).The value of Cd with longer fetch from near north direction is generally higher than that with shorter fetch from near west direction.On the other hand,heat fluxes increase with the increasing wind speed and wave height.

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