Creating Virtual Wind for Physical Turbines

February 3, 2015

It’s hard to figure out which way the wind blows. It’s full of random fluctuations, changes of direction, currents and eddies, and it can have a completely different profile a short distance away. And it doesn’t help that it’s invisible.

But accurately creating computer models of the wind is important if you’re trying to engineer a good wind turbine. With the goal of generating energy multiple hours per day over several decades of use, a few extra percentage points of efficiency can add up fast.

Jenni Rinker on top of the National Wind Technology Center’s 135-meter tower that holds the sensors that records the wind data that Rinker analyzes.Armed with a grant from the Department of Energy’s Office of Science Graduate Student Research (SCGSR) Program, Pratt graduate student Jenni Rinker will try to put a more accurate wind in the sails of turbine simulators. She’ll spend an entire year working on her dissertation at the National Wind Technology Center (NWTC) in Boulder, Colorado, which is part of the National Renewable Energy Laboratory.

“If the wind you’re using in computer simulations of wind turbines doesn’t look like real wind, then your results are going to be terrible,” said Rinker, a PhD student in the mechanical engineering and materials science department, who completed her MS in the civil and environmental engineering department and came to Duke from Harvey Mudd College in Claremont, California. “So I am trying to develop new statistics and data validation to improve our simulation methods.”

The SCGSR Program provides graduate students research opportunities at DOE laboratories while working on projects deemed critically important to the DOE Office of Science mission. The research advances the graduate students’ overall doctoral theses while providing them access to the expertise, resources and capabilities available at DOE laboratories.A wind turbine at the National Wind Technology Center.

Rinker caught wind of the program while working on her research last summer at NWTC. As part of Duke’s PhD Plus program, which helps graduate students prepare for the career world, she was strongly encouraged to seek an internship. With this encouragement, Rinker contacted the laboratory’s chief engineer, Paul Veers, to ask for one.

“It was an unusual situation because I didn’t actually have a position at NWTC, but my advisor was supportive of me continuing my research there, and Dr. Veers let me have some desk space for a couple of months,” said Rinker, whose advisor is Henri Gavin, the Yoh Family Associate Professor of Civil and Environmental Engineering and an associate professor of mechanical engineering and materials science. “The quality of my research improved a lot just from the conversations I was able to have with people there. I would encourage anyone to try to get a similar opportunity if possible—it goes a lot further than you would think.”

While getting to know the people in Boulder, Rinker found her work fit into the laboratory’s puzzle quite well; many of the researchers were interested in looking into computer wind simulations but hadn’t had the time. One engineer in particular, Andy Clifton, suggested that Rinker apply for the SCGSR grant so that she could continue her work at the center officially.

A computer-generated turbulent wind field generated by the code Rinker is working on for her PhD thesis.Now, with the help of Clifton, Rinker will be delving into a gigantic wind dataset that is constantly being updated by the meteorological tower at the lab. She’ll spend the first half of her visit devising new ways of measuring wind flows important to turbines and creating a better computer algorithm for generating virtual wind. The second half of her stay will focus on showing that her new method provides better results than current methods when plugged into wind turbine simulations.

“It’s an incredibly complex problem just in the math and science alone,” said Rinker. “And of course it’s always nice to be working on research that you really appreciate the end goal of. I think wind energy is extremely important to the world’s future.”