Des Moines Register: Researcher Works to Improve Turbines
By Jens Manuel Krogstad
Des Moines Register
A University of Iowa researcher is working to improve the reliability of turbines, a key hurdle to bringing down the cost of wind energy.
Whipping winds and extreme temperatures hundreds of feet above ground mean gearboxes inside wind turbines require replacement about every eight years, according to government estimates.
K.K. Choi, a U of I engineering professor, says computer software he has developed over the past 20 years for vehicles could produce designs that cut turbine repairs down to once every 20 years without added manufacturing costs.
“That is a big improvement,” said Paul Veers, chief engineer at the National Renewable Energy Laboratory’s wind technology center in Colorado. “Reliability is the watchword in the whole industry right now. It’s a central tenet.”
Turbine reliability, in fact, is one major obstacle to wind energy providing 20 percent of the nation’s energy by 2030, according to a 2008 U.S. Department of Energy report.
More durable turbines are as essential to wider adoption of wind energy as building new transmission lines to carry electricity to Chicago and the coasts, industry experts say. That’s because increased reliability will lower costs, experts say.
Greater adoption would also produce a windfall for the economy of Iowa, which has bet big on the industry with tax credits, research and other investments.
Iowa is the nation’s second-leading producer of wind power, with 3,675 megawatts of capacity. The state also has more manufacturing for the industry than any other state. Texas is the country’s top producer of energy.
MidAmerican Energy of Des Moines last week announced a 258-turbine, 597-megawatt expansion. The project would increase the state’s capacity to 4,200 megawatts.
The Iowa Alliance for Wind Innovation and Novel Development — a partnership among government, universities and businesses — last year awarded Choi a three-year, $300,000 grant. The money was matched by Clipper Windpower of California, which submitted its turbine designs for research.
Choi and two U of I researchers, including engineering professor Pablo Carrica, have received nearly $700,000 in grants from the organization IAWIND to improve turbine reliability.
Funding for the projects originated from the Iowa Power Fund, a $100 million, four-year renewable energy project established by the Iowa Legislature in 2007.
Choi’s ambition is rooted in experience. He has refined the software to design lighter and more reliable Ford Tauruses and U.S. Army tanks.
U of I Provost Barry Butler, who heads the wind alliance, first saw the potential to use Choi’s work on turbines.
When Butler cranes his neck up at a turbine, he sees your grandfather’s old Chevy — a quality machine with room for improvement. Since vehicles and wind turbines share similar mechanical components, it struck him as a natural extension of Choi’s work.
“The cost-per-mile today of a car versus what your grandfather paid on his 1957 Chevy is quite different,” he said. “In any product, you’re trying to make it more reliable. The ultimate goal is cheaper electricity.”
Choi’s software runs simulations to determine weak points in a mechanical design.
He said it’s a process he pioneered called reliability-based design optimization method.
The software’s origins trace back to Detroit in the early 1990s. Ford Motor Co. made a seemingly counterintuitive request: Design a Taurus sedan with both a smooth, quiet ride — characteristics of a heavy car — and a lighter body for increased fuel efficiency.
The design never made it to production. The parts had to be manufactured so precisely that the final product would have been a $100,000 Ford Taurus, he said.
Choi started tweaking his software to allow parts of slightly different sizes to keep costs down, he said.
The Army sponsored his research for years after working with Ford. More recently, he produced designs of an Army Stryker tank that was 20 percent lighter and ten times as durable by making small changes in important places.
Choi’s next goal — more than double the reliability of wind turbines to 20 years without repairs — may be his biggest challenge. To prepare the software, U of I researchers are compiling wind measurements from around the globe, from Des Moines to South Africa.