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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Grid integration study of brushless doubly-fed induction generators for wind turbines

Long, Teng January 2014 (has links)
No description available.
72

Maximizing Real-Time Distribution of Wind-Electricity to Electrical Thermal Storage Units for Residential Space Heating

Barnes, Andrew 23 August 2011 (has links)
Wind-electricity is unpredictable in both intensity and duration. This thesis presents the design and implementation of Client-pull and Server-push architectures for the distribution of wind-electricity to Electrical Thermal Storage (ETS) units to match the electrical load of the ETS units with the electricity generation levels. Wind as an energy source is reviewed and the smart grid concept of a communication layer for the transmission, production and usage of electricity is explored. ETS operation is explained and a survey of the Client-pull and Server-push concepts. These implementations are evaluated on their ability to dispatch wind-electricity over a full heating season, short term latency, single day performance and complexity. Client-pull and Server-push architectures have nearly identical performance over a full heating season and identical performance over the 24 hour period evaluated. The Server-push architecture has lower short-term latency but is more complex than the Client-pull.
73

Part I, The effect of screens in a wide angle diffuser of square cross-section; part II, The influence of the proximity of a wall to the test section exit of a wind tunnel

Wharton, Charles Lancaster 08 1900 (has links)
No description available.
74

From technology transfer to local manufacturing China's emergence in the global wind power industry /

Lewis, Joanna Ingram. January 1900 (has links) (PDF)
Thesis (Ph.D.)--University of California, Berkeley, 2005. / Adviser: Daniel M. Kammen. Includes bibliographical references.
75

The use of wind instruments in seventeenth-century instrumental music

Lewis, Edgar J. January 1964 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 512-526).
76

Variable-speed wind turbine controller systematic design methodology : a comparison of non-linear and linear model-based designs /

Hand, M. Maureen. 1999 July 1900 (has links) (PDF)
Thesis (M.S.)--University of Colorado, 1998. / Includes bibliographical references (leaves 45-46). Also available full text via Internet in .pdf format. Adobe Acrobat Reader required.
77

Development of a reciprocating aerofoil wind energy harvester

Phillips, Russell Leslie January 2008 (has links)
Cross flow wind turbines are not unique. The performance of Savonius and Darrieus turbines is well documented. Both share the advantage of being able to accept fluid flow from any direction. The Savonius is drag based and hence has poor power output while the Darrieus is lift based. Due to the fact that the Darrieus has fixed blades the fluid flow through the rotor does not result in optimal lift being generated at all points in the rotation circle. A drawback of the Darrieus system is that it has to operate at a high tip-to wind-speed ratio to obtain reasonable performance with the fixed blades. Deviation from a small optimal range of tip speed ratios results in poor performance. The Darrieus also has poor starting torque. The research conducted in this project focused on overcoming the shortcomings of other turbines and developing an effective cross flow turbine capable of good performance. A number of different concepts were experimented with, however all were based on a symmetrical aerofoil presented to the actual relative airflow at an angle that would produce the highest lift force at all times. The lift force was then utilized to generate movement and to do work on an electrical generator. All concepts contemplated were researched to ascertain their appropriateness for the intended application. During development of the final experimental platform and after lodging of a provisional patent (RSA 2007/00927) it was ascertained that the design shared some similarities with an American patent 5503525 dated 28/4/1994. This patent employed complex electronic sensing and control equipment for control of blade angle. This was thought to be overly complex and costly, particularly for small scale wind energy generation applications and a simpler mechanical solution was sought in the design of the final experimental platform used in this project. The design of the mechanical control system was refined in an attempt to make it simpler, more durable and employ the least number of moving parts. Literature studies and patent searches conducted, suggested that the mechanical control system as developed for the final experimental platform was unique. The enormous variation in the power available from the wind at the different wind speeds likely to be encountered by the device necessitated some means of control. In high wind conditions control of the amount of wind power into the device was deemed to be the preferable means of control. A number of different concepts to achieve this were devised and tested. The final concept employed limited the tail angle deflection and hence the lift produced by the aerofoils. This resulted in a seamless “throttle” control allowing the device to be used in any wind strength by adjusting the control to a position that resulted in the device receiving a suitable amount of power from the wind. The outcome of performance tests conducted indicated that the device has the potential to be developed into a viable wind turbine for both small and large scale applications. The ability to control the power input from the wind to the machine from zero to a maximum is considered to be one of the most beneficial outcomes of this project and together with the quiet operation and low speed, are considered the main advantages of the device over existing wind turbine designs. The possibilities of using the device to compress air for energy storage are exciting avenues that warrant further research.
78

A tolerant axisymmetric wind tunnel

Premnath, S. M. Jason January 1988 (has links)
A solution to the current problem of wind tunnel wall interference could be achieved by ventilating the test section and thereby controlling the flow pattern around the model. The motivation for the slotted wall test section arises from the fact that a fully open jet and a fully closed jet introduce corrections of opposite sign to the wind tunnel data. This current work is limited to axisymmetric wind tunnels and solid blockage corrections. Such a tolerant axisymmetric wind tunnel (TAWT), which does not need any correction to the measured flow quantities and which is also independent of the test model shape and size would find wide application in the field of industrial aerodynamics. A numerical model based on a surface singularity potential flow method showed that at 70% OAR (open area ratio) for models of size up to 25% blockage and for three different shapes the tunnel design would yield results (coefficient of pressure) with less than 2% error while such models might need up to 75% data correction if tested in a solid wall wind tunnel. Experiments indicated good agreement with the numerical investigation and at 60% OAR the TAWT gave results close to free air results for all the models tested (up to 25% blockage). / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate
79

Offshore-Windenergie zur Stromerzeugung

Viertel, René, Tetzlaff, Gerd, Kaltschmitt, Martin 31 January 2017 (has links) (PDF)
Der mittlere Wind in der atmospärischen Grenzschicht über den deutschen Nord- und Ostseegebieten unterscheidet sich gegenüber Landflächen durch höhere Windgeschwindigkeiten, eine stärkere Zunahme mit der Höhe und schwache Tages- sowie ausgeprägte Jahresgänge der Windgeschwindigkeit in Bodennähe. Neben diesen Vorteilen ergeben sich auch Nachteile im Hinblick auf die Windenergienutzung offshore. Das betrifft die Anforderungen an die Technik der Windstromerzeugung sowie wie die Messung und Prognose der relevanten meteorologischen Parameter. Nach Abschätzungen möglicher Flächen für die Windnutzung offshore und anlagentechnischer Möglichkeiten ist von einem enormen technischen Angebotspotenzial an Elektroenergie auszugehen, dem jedoch auch Beschränkungen seitens der Netzstruktur und Nachfrage entgegenstehen. Um das große Potenzial zur Stromerzeugung und Umweltentlastung nutzen zu können, sollte die Entwicklung in den kommenden Jahren im Bereich Windprognose, Anlagenbau, Regelungstechnik und Energiespeicherung zu weiteren Verbesserungen führen. / The averaged wind in the Planetary Boundary Layer over the german North Sea and Baltic Sea areas shows some differences to the wind over land areas. There are higher wind speeds, a stronger increasing with height and slight daily and more distinctive annual variations of the near surface winds. Thats why the utilization of wind energy offshore has advantages. But also exists certain drawbacks in reference to technical requirements and the measurement and prediction of meteorological parameters. Estimations of suitable areas and technical prospects indicate a large technical offer potential of electric energy offshore, though additional restrictions must be considered. To make this potential of electric energy and environmental protection usable todays knowledge of systems and control engineering, energy storage and wind prediction should be improved in the coming years.
80

Kürzestfristvorhersage der Windgeschwindigkeit in einem Wirbelschleppenwarnsystem für Flughäfen

Schlink, Uwe, Tetzlaff, Gerd 08 November 2016 (has links) (PDF)
Die lange Lebensdauer und die hohe Intensität der Wirbelschleppen landender Großraumflugzeuge kann zu einer Gefährdung des nachfolgenden Verkehrs führen. Zur Vorhersage einer gefährdungsfreien Nutzungszeit der Landebahn, nach der die Staffelungsabstände der landenden Flugzeuge bestimmt werden, dient ein Wirbelschleppenwarnsystem. Ein wesentlicher Teil dieses Warnsystems ist die Vorhersage des quer zur Landebahn wehenden Windes. Dafür wird bisher ein auf Persistenz beruhendes Verfahren eingesetzt. Die vorliegende Arbeit zeigt, daß durch Verwendung eines autoregressiven Modells die Querwindprognose verbessert werden kann. Dazu werden die Meßdaten analysiert und die Modellparameter geschätzt. Der Einsatz der AR Prognose im Wirbelschleppenwarnsystem führt im Vergleich zur bisherigen Methode zu längeren Nutzungszeiten und vermeidet das Auftreten von Diskontinuitäten (Sprüngen) in der Vorhersage. Besonders durch letzteres wird die Akzeptanz des Warnsystems bei den Fluglotsen verbessert.

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