Research rock star: Wind star

Kathryn Johnson says one of the biggest challenges she faces in her wind energy research is the lack of test sites. “Most modern utilities won’t let you run tests on their million-dollar turbines,” she says. “It’s difficult to get test time on turbines.”

The Clare Boothe Luce Assistant Professor at Colorado School of Mines Division of Engineering says she makes up for it by doing simulation work, and by working on one of the large turbines at the nearby National Renewable Energy Laboratory in Golden. She worked at NREL as a summer intern, then worked there four years, and still does research in collaboration with the lab.

Johnson researches control systems on wind turbines. The analogy, she says, is cruise control or traction control in a car. On a wind turbine, the control system makes the turbine operate as efficiently as possible, and also works to reduce the dynamic loads on the turbine structure. “When a wind gust comes in and hits the turbine, that puts force that bends the tower or bends the blade, so the idea with control systems is, can we do anything to reduce the bending?”

The system can pitch the blades, which means to adjust the angle to change their rotation speed. Another process relies on sophisticated generator and power electronics. “We can ask the generator to draw a certain load torque or load power from the turbine,” she says. “It gets very complex.”

She says everything she does has the ultimate goal of reducing the cost of wind energy. That includes increasing efficiency of the turbine, figuring out how to get more energy from a turbine, and reducing loads, which will increase the turbine lifetime.

Johnson earned her bachelor of science degree in electrical engineering from Clarkson University in Potsdam, N.Y., in 2000. Two years later she earned a master of science in electrical engineering from the University of Colorado Boulder. In 2004 she earned her Ph.D. at CU Boulder. The title of her 107-page dissertation was, “Adaptive Torque Control of Variable Speed Wind Turbines.”

Control systems is not one of the divisive topics in wind, so Johnson doesn’t often deal with controversies such as where to build wind farms. The question she does often field is, why does it seem like the turbines at NREL, off the very windy Highway 93, are almost never turning?

“They are intended as research turbines, not power production turbines,” she says. “Many times they are setting up experiments, so if you’re going up and down the tower with equipment, you want the turbines shut off.”
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