Wind-Energy Research at Montana Tech
Daniel J. Trudnowski, Ph.D.
and David M. Westine, Ph.D.
Department of Engineering Science
Since 1993, Montana Tech of The University of Montana (Montana Tech) has been conducting wind-energy research in collaboration with Montana State University–Bozeman (MSU) and The University of Montana–Missoula (UM). This major research effort is funded as a cluster of the U.S. Department of Energy (DOE)/EPSCoR–MORE program. The original focus of the grant was to develop new fiberglass composite wind turbine blades that perform under accelerated fatigue conditions. Since then, the scope of the grant has expanded to include studying the impact of wind-generation systems on radial electrical distribution systems. Montana Tech researchers have led in the development and implementation of two wind-energy research parks as well as operation and control of the sites. The lead investigator for the grant is Professor John Mandell of the MSU Chemical Engineering Department. Montana Tech investigators include Engineering Science Department Associate Professors David Westine, Neil Wahl, and Dan Trudnowski. In addition, many Montana Tech graduate and undergraduate students have contributed to the program; graduate students include Greg Hilker, Frank Raab, Jim Freebourn, Kim McClafferty, Kris Johnson, and David LeMieux.
The lifetime cost of the turbine blades is a fundamental limitation of the cost-effective implementation of wind-energy systems. Typical wind gusts induce forces and vibrations on the blades that result in significant fatigue and reduced life. Thus, a goal of the research program is to provide new technologies for cost-effective blade development. One aspect for increasing the life of a wind system involves new control techniques for operating the system. Montana Tech researchers studied whether the turbine can be controlled under high, gusty wind conditions in such a way as to reduce fatigue.
The first wind park, Rice Ridge Renewable Energy Park, was formed through the combined support of the DOE, Montana Power Company (MPC), Windmaster Inc. (a wind-energy company), and the landowner, Bob Rice. The primary purpose of the energy park is to provide a test site to study the fatigue of various blade designs; a secondary goal is to study new control strategies for reducing fatigue. The Rice Ridge site is located on Norris Hill near Norris, Montana, and is one of three premier wind-energy parks in the state. Because it is located between Bozeman and Butte, it was an obvious choice for the location of the DOE/EPSCoR wind-cluster test site. After the legal aspects of the land agreement for the Rice Ridge site were finalized in September 1994, construction of two wind machines began. Currently, the Rice Ridge site has facilities for complete stand-alone testing and control of two wind turbines.
Blade strain and fatigue data provide essential information for MSU researchers in the design of new blade materials and construction methods. To conduct the testing, a novel data acquisition system was developed and implemented by Montana Tech researchers. The system allows the telemetric data acquisition of rotor blade strain and for the remote data transfer and control of the wind machines from Montana Tech through radio-frequency communications. A challenging problem was to bring nine channels of high-frequency strain-gauge data from the spinning rotor to the ground with little or no corruption. Data telemetry packages manufactured for this type of a system can cost between $20,000 and $30,000. The system designed on campus for this task costs approximately $2,000 installed with custom computer software. Presently, the system is performing well.
Montana Tech researchers are also studying several methods to vary the yaw angle of the rotor to control the rotor speed. Basically, as the wind increases, the rotor is turned away from the wind, which reduces the spinning torque. Because of the gusty random nature of the wind, this is a challenging control problem. Montana Tech has developed two successful control methods, and current research involves analyzing the effect of these methods on reducing blade fatigue.
The second test site is the Luzenac Renewable Energy Park. This site is being developed through the combined efforts of the DOE and MPC. Luzenac mine, located adjacently, has also provided significant in-kind support. This site is located approximately 20 miles south of Ennis, Montana, near the Madison River. Currently, a 50-kilowatt wind generator, constructed by the Atlantic Orient Corporation, is being installed at the site and will be connected to a 12-kilovolt MPC distribution line nearby. The unit is a down wind, horizontal-axis, three-blade system and powers a three-phase induction generator. Each blade of this three-blade system is 25 feet long, and the entire system rests on an 80-foot tower.
The fundamental purpose of the Luzenac site is to study the interaction of a wind-turbine system with a long radial electrical distribution system. Radial distribution lines extend to a specific destination and end without returning to the main power grid system. Montana has many remote sites that require electrical power, resulting in numerous long radial electrical lines. The capacity of these radial lines is limited; therefore, it is necessary to consider how future load additions will be served. Two possible alternatives are as follows:
When the cost of building or upgrading transmission lines is weighed against the cost of distributed generation, the latter may be more cost effective. In addition to economic concerns, questions regarding power quality, reliability, and stability must be addressed in the distributed generation case. Because winds are gusty, distributed wind generators can cause detrimental voltage fluctuations and power quality problems in radial systems. Because of the radial nature and loading of the electrical grid at the Luzenac Renewable Energy Park, it provides a good test site.
Montana Tech researchers are collaborating with Professor Don Pierre and his Ph.D. graduate students in the Electrical Engineering Department at MSU, to study electrical system interaction. A developed in-depth computer simulation model of the system and the test site will be ready for operation in the spring of 1999. The site will include detailed electrical instrumentation as well as the same strain-gauge blade instrumentation used at the Rice Ridge Renewable Energy Park.