WIND ENERGY CLUSTER - RICE RIDGE RENEWABLE ENERGY PARK
by David M. Westine, Ph.D.

The Montana Organization for Research in Energy (MORE) is funded by a grant from the U.S. Department of Energy (DOE) through the Experimental Program to Stimulate Competitive Research (EPSCoR). The Wind Energy Custer is one component of MORE's $2,000,000 annual budget and is managed by a collaboration of Montana Tech of the University of Montana (Montana Tech), Montana State University (MSU), and the University of Montana (UM). Wind energy is a pollution-free and renewable energy source. The single most important problem facing the wind energy market today is the cost of the energy produced. If rotor blades can be constructed economically to last for ten to thirty years without replacement, a large portion of the installation and maintenance costs would be eliminated. The principle focus of this research is the study of fiberglass composite wind turbine rotor blades operating in the field under accelerated fatigue conditions. The high altitude location in Montana enhances

The first wind machine installed and ready for testing and data acquisition.

this effort due to its extremes in temperature and increased ultra violet radiation. The principal investigator of this grant is MSU Chemical Engineering professor Dr. John Mandell who has had years of

fiberglass rotor consulting experience with the American wind energy community. The wind turbine test bed is designed and constructed by Dr. David Westine, Assistant Professor, Montana Tech Engineering Science Department. Dr. Westine was the principal investigator on two previous DOE grants where he was responsible for the design and construction of two different wind turbines. The wind cluster grant also involves an avian study by the Montana Department of Natural Resources and MSU Biology Department, an energy integration component by the MSU Electrical Engineering Department, fiberglass material synthesis and testing by MSU Chemical Engineering and Physics Departments, and a design/analysis component involving the MSU Mechanical and Civil Engineering Departments and the UM Mathematics Department.

The Rice Ridge Renewable Energy Park was formed through the combined efforts of Montana Power Company, Windmaster, Inc. (a wind energy company), and the land owner, Bob Rice. The Park is located on Norris Hill near Norris, Montana, and is one of three premier wind energy sites in the State. Its location between Bozeman and Butte made it an obvious choice for the location of the DOE/EPSCoR Wind Cluster test site. After the legal aspects of the land agreement for the Park were finalized in September of 94, the work on the first of two wind machines began.

The main purpose of the wind turbine test bed is to subject fiberglass rotors to accelerated fatigue conditions. To do this, the wind machine's rotor speed must be controlled so different types of rotors can be optimally tested. The rotor speed is determined from three main factors; wind velocity, angle of the wind with respect to the axis of rotor rotation (yaw angle), and the torque load on the rotor. Controlling the rotor speed then reduces to controlling the amount of torque load on the electrical generator driven by the rotor, and controlling the yaw angle. This would be an easy control problem if the wind velocity was a slowly changing, well behaved function. But anyone who has ever been in a windy area knows that the wind is constantly gusting in both velocity magnitude and direction.

The two different control systems were then designed by Dr. Westine and students in the Engineering Science Department's Control Systems emphasis program. The system that controls the torque applied to the generator is an analog PID controller that monitors the rotor's speed and either connects or disconnects a resistive heater bank depending on whether the rotor speed is greater than or less than the specified set point respectively. The system used to control the yaw angle of the wind machine is a microprocessor-based controller that turns the wind machine out of the wind in over-speed conditions through a worm gear induction motor. The complete yaw control system, including the microprocessor, was designed by Engineering Science (E.S.) students and faculty.

Greg Hilker, an E.S. Control Systems graduate student, is performing his thesis research on the modeling and control of the yaw/rotor-speed system. His research involves the design of an accurate computer model, the subsequent testing of different control strategies on the model and finally, the implementation and testing of these control strategies in the field. Fred Jenkins, an E.S. Control Systems senior has also been extensively involved in the design and construction of the complete wind machine. Frank Raab, also a senior in E.S. and an experienced machinist, has recently joined the Montana Tech effort. Mr. Jenkins and Mr. Raab have designed and constructed the second wind machine to be installed in the summer of 1996. Frank is also responsible for the mold construction of the rotor through a computer interface that he is retrofitting on the numerically controlled Bridgeport mill located at the College of Technology of Montana Tech. A total of seven students have been actively involved with the design and construction of the two wind machines with most of the welding and machine work being performed by E.S. students studying in the Welding emphasis program.

Two other Montana Tech employees, Joe Kujawa and Dirk Danninger have designed telemetry systems for data acquisition of rotor blade strain, the remote transfer of data, and the control of the wind machines. All functions can be performed from Montana Tech to Norris Ridge through a radio frequency communication link. Engineering Science Associate Professor Neil Wahl has been instrumental in providing computer programming, design, and consulting for the blade-strain data acquisition problem. To bring nine channels of strain gauge data from the spinning rotor to the ground with little or no corruption was a challenging problem. Commercial data telemetry packages manufactured for this type of a system can cost anywhere from $20,000 to $30,000. The system designed on campus for this task cost around $2,000 installed with custom computer software.

With the blade strain data and the continuous control and monitoring of the wind machines, the chemical engineers at MSU now study the types of blade failures and premature blade wear associated with fiberglass rotors. With this information, they can start to design new methods for rotor construction to increase the rotor life. This will help make wind energy more cost effective in the energy production market and could lead to wider spread use of this renewable energy resource.