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Thesis (M.Eng.). / Written for the Dept. of Electrical & Computer Engineering. Title from title page of PDF (viewed 2008/07/ 29). Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 163-169) Also available in print.

Thesis (Ph.D.) -- University of Glasgow, 2002. / Ph.D. thesis submitted to the Faculty of Engineering, Department of Aerospace Engineering, University of Glasgow, 2002. Includes bibliographical references. Print version also available.

Thesis (Ph.D.)--University of California, Berkeley, 2005. / Adviser: Daniel M. Kammen. Includes bibliographical references.

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.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 163-169) Also available online.

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.

Wind turbines are the largest contributor to renewable energy both in Britain and the rest of Europe. With a rise in the installed capacity and an increase in offshore wind energy due to governments green targets by 2020, there has been a large development in new wind turbines for optimized performance. The present thesis deals with the uncertainties in regards to the lightning phenomenon on wind turbines with emphasis on the rotor blades. Rotor blades are the most expensive part to replace in the event of lightning related damage. The research presents results based on lightning data analysis on wind turbines, backed up by finite element analysis testing of wind turbine systems. The final chapters include the testing and improving of lightning protection systems installed on modern day rotor blades. The first part of the thesis deals with the theoretical understanding of the lightning phenomenon and its effect on wind turbine systems. The core work of the research begins with the analysis of lightning data collected over Nysted wind farm and different wind turbines installed over the world. The data analysis helps in identifying the parts of the wind turbine that are at high risk to lightning attachment and related damage. The peak current levels of the lightning strikes seen on the wind turbine are compared with those in modern day lightning standards, and show that historic data in the standards are not an exact match to the real case scenarios. The lightning data analysis also sheds light into the importance of upward initiated lightning, which will become important for large wind turbines, especially in their new offshore environment. A full scale 3D FEA model of a wind turbine, with lightning protection systems installed in its rotor blades, is subjected to electrical stresses to find likely attachment points in regards to upward initiated lightning, and these results are later compared to those found in the data analysis. The second half of the thesis deals with the testing of new materials and prototype blades, to be introduced to reduce their radar cross section. The new materials include a large amount of carbon content which affects the efficiency of the lightning protection system. High voltage and high current tests backed up with finite element analysis have been performed to find how these new materials affect the performance of the lightning protection system. The results indicate that further work needs to be done before these new materials can be integrated into the blade, as they increase the risk of lightning related damage to the blade.

Thesis (M.Eng.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 112-116.