Thesis - Open Access
Master of Science (MS)
Agricultural and Biosystems Engineering
Leslie L. Christianson
Developing wind energy suitable for agriculture applications is a critical step towards providing a reliable, affordable energy supply for United States agriculture. United States agriculture, due to its energy intensive nature-, is dependent on petroleum fuels. Because agriculture is extremely sensitive, to supply interruptions, steps must be taken to reduce this dependence on oil, including developing wind energy systems. It appears that the potential is there since winds over the United States contain more than 30 times the total energy consumed in this nation (Soderholm, 1979).
Agricultural applications (e.g. irrigation pumping, product processing and building heating) are uniquely suited to the variable power produced by the winds because many agricultural tasks can effectively use variable rates of energy supply. Many agricultural tasks can tolerate short energy interruptions and are easily adapted to inexpensive storage (Hunt, 1981).
The economical viability of wind energy for agricultural applications' is highly dependent on initial costs and total energy produced. Darrieus wind turbines are one of the most promising models, because of relatively low capital costs inherent in the simple design (Sullivan, 1979). The Darrieus is a vertical-axis machine that resembles an egg beater. It needs no yaw control mechanism, since it accepts wind frOm any direction, and power conversion equipment can be located on the ground, due to its vertical shaft. Two methods of supporting the Darrieus are the . cable tie-down system and cantilevered system. The cable tie-down support method uses several guy cables which are connected from the ground to the top of the turbine rotor. The cantilevered system, which supports the rotor only at the base, is simpler since there is no need for guy cables, cable anchors and tensioning mechanisms. Vibration problems with the guy cables, are also eliminated (Karnitis, 1980). Most Darrieus turbines operate at a constant rotational speed to better adapt the systems for electric power generation, however, variable-speed Darrieus turbines have higher efficiencies and a higher potential power output (Kamitis, 1980). Many agricultural applications can use the direct mechanical energy generated by the wind turbine. Losses caused by the intermediate generation of electricity as well as the capital costs of the additional equipment are thus avoided (Black, 1981). However, operating the Darrieus in a variable-speed mode poses problems in limiting vibrations and rotational speeds. Load matching to maintain optimal performance may also be difficult.
Therefore, research was initiated to design, construct and test a variable-speed cantilevered Darrieus for agricultural applications. The principal objectives were:
(1) Design a Darrieus system suitable for variable-speed operation.
(2) Construct a Darrieus according to the proposed design.
(3) Develop a suitable testing procedure for a variable-speed Darrieus system.
(4) Test and evaluate the performance of the variable-speed Darrieus system.
(5) Compare the efficiency measured during variable-speed operation with the theoretical efficiencies of constant-speed operation.
Library of Congress Subject Headings
Includes bibliographical references (93-97)
Number of Pages
South Dakota State University
Copyright © 1982 Kasey W. Abbott. All rights reserved
Abbott, Kasey W., "Performance and Evaluation of a Variable-Speed Darrieus Wind Turbine" (1982). Theses and Dissertations. 615.