Iowa student makes case for larger wind turbines

Posted: Monday, May 27, 2013

article photo

Grant Schmitz, an Audubon, Iowa, native, is a graduate student at Iowa State University, whose master’s degree project helped show that concrete wind turbine towers are possible.

Grant Schmitz can’t remember exactly what triggered his interest in engineering. But it might have been family vacations to Colorado as a child.

Schmitz, now 24, can remember traveling there from his home in Audubon, Iowa, in the late 1990s and walking over the Royal Gorge Bridge. He was fascinated with how one of the world’s highest suspension bridges, at more than 950 feet above ground, could safely span the gorge.

“I’m not sure exactly what it was, but I was always interested in bridges and a lot of other large, civil structures,” Schmitz said.

A different kind of large structure has been the focus of Schmitz’s graduate studies in civil engineering, which wrapped up this month at Iowa State University.

As part of his graduate thesis, Schmitz and adviser Sri Sritharan, an engineering professor, showed that larger and more productive wind turbines were possible, in Iowa and elsewhere

“He never fell short of my expectations. He always exceeded what I expected out of him,” Sritharan said

Schmitz’s studies were centered on a simple notion: Wind turbines, such as the ones that line the sky in western Iowa where he grew up, could generate more energy — if the towers were a few feet taller.

Now the towers are built from prefabricated steel and limited to about 260 feet. That’s primarily because the bottom of the tower can’t be wider than 14 feet or it won’t fit under bridges while being trucked from the factory to the wind farm.

Since about 2008, Sritharan has been trying to find a way to build taller wind towers out of concrete, which would allow them to be built more cheaply and shipped in smaller components.

After the first graduate student Sritharan worked with graduated in 2011, Sritharan went looking for a replacement. At the same time, Schmitz was looking for a research topic for his graduate thesis in civil engineering.

At 325 feet, winds are steadier. Taller towers also allow for longer blades, which can increase energy production by 15 percent, according to the university.

“It is easier to go bigger,” Sritharan said.

The towers would be made of six concrete columns linked by concrete panels 3 to 6 inches thick

Schmitz and Sritharan began investigating precast fasteners and different kinds of high-performance concrete. Schmitz’s studies showed that, by using the right kind of fasteners, such a tower could withstand an average wind speed of 100 mph over a 10-minute period.

“Based on the results of this test, we could start to see some commercial applicability in the next couple of years,” Schmitz said. “Our goal is to potentially partner with one of the larger energy producers.”

It’s too early to tell if one of those partners could be Iowa’s largest utility, MidAmerican Energy. The company, which has proposed building up to 656 new wind towers in Iowa, said Friday that it’s supportive of and interested in the research.

The project was supported in part by a $109,000 grant from the Grow Iowa Values Fund, a state economic development program.

A few concrete wind towers can be found in Europe and the United States, said Harold Prior, executive director of the Iowa Wind Energy Association.

“The concrete is more readily available. It’s cheaper to transport to the site,” Prior said.

Concrete towers are the future of wind energy, Prior said. “I don’t think there is any question about it.”

It’s a future Schmitz may not be a part of. This summer, Schmitz will move to Omaha, where he has an engineering job waiting for him with HDR Inc. He will work as a bridge engineer.

He does not plan to go into wind turbine work, but he hasn’t ruled it out. And he’s happy he got involved in developing technology that’s a huge part of the region where he grew up.

“Now when I go home, I can say I work on these designs,” he said. “I can talk to people about … what we are looking at in terms of future technologies.”