An atmospheric scientist probes the dynamics of wind power.
By Sarah Khan
Wind is the nation’s fastest-growing renewable energy source. By 2030, if the U.S. Department of Energy gets its way, wind will generate 20 percent of America’s electric power, up from 4 percent today. To make that happen, DOE’s Office of Energy Efficiency and Renewable Energy will spend more than $88 million for wind research and development this year and has asked Congress for $115 million for 2015, seeking novel ideas that will drive down costs and stimulate innovation.
Julie Lundquist and her interdisciplinary research team at the University of Colorado, Boulder are at the forefront of that quest. Lundquist, an atmospheric scientist, sees herself as an intermediary between wind turbine engineers and pure wind scientists. Her research on the wind flow resulting from turbines strives for insights that will enable engineers to design taller, stronger, more efficient, and smarter turbines.
Colorado is an ideal location for this work. Not only is it home to the National Renewable Energy Laboratory (NREL) and the National Wind Technology Center, but of the 50 states, it’s the 13th largest in available windblown land. An NREL survey found that Colorado could generate 380,000 megawatts of wind energy. The Colorado energy company Xcel, which has been taking advantage of wind since the late 1990s, has shown that it can rely on wind to supply as much as 60 percent of its total electricity output.
To date, research has shown that when it comes to turbines, taller is better. Once around 65 feet, turbines now soar to more than 260 feet, with larger rotor disks and blades that can take advantage of greater wind speeds at higher altitudes. “Places that used to be unattractive for wind development are now very attractive,” Lundquist says.
But it gets tricky up there: “The higher you go, the more you get into areas of very complicated dynamics.”
Employing light detection and ranging (lidar) technology, which measures wind speed by capturing the Doppler effect on dust in the air, Lundquist’s group discovered how a turbine alters nearby wind patterns. As a turbine’s blades rotate, they swirl and muddle the wind, creating wake streams that often blow more slowly than the surrounding wind. Downwind turbines catch the slower wake streams, resulting in reduced turbine speed and less energy output. Understanding these effects will help engineers figure out where to place turbines so as to optimize power production.
Use of lidar holds the promise of “smart” turbines able to take a variety of measurements. A Danish research group from the Risø National Laboratory for Sustainable Energy demonstrated that lidar technology affixed to a turbine’s hub could detect incoming wind speed, direction, and turbulence, and adjust the blades’ positions accordingly.
Besides lidar, Lundquist’s group is starting to use unmanned aerial vehicles, built by the university’s College of Engineering, to measure the temperature and other differences upwind and downwind of turbines.
“We have much more information about what’s going on in the atmosphere than we did 10 or 15 years ago,” she says.
Lundquist, who holds a joint appointment at NREL, also collaborates with Lawrence Livermore National Laboratory, Pacific Northwest National Laboratory, and Los Alamos National Laboratory. But some of her most important collaborators are private wind-energy companies, which consider her work important enough to share highly guarded, competitive data on their turbines’ efficiency.
Lundquist took up the study of the atmosphere after earning a B.A. in English and physics at Trinity University. While pursuing a Ph.D. in astrophysical, planetary, and atmospheric science at Boulder, she initially studied the lower atmosphere to understand air quality and pollution. She switched to wind energy when she realized how rapidly the field was growing. “It’s the perfect time to be doing this type of work,” she says.
And it doesn’t look like this renewable energy source will be blown off the grid anytime soon.
Sarah Khan is assistant editor of Prism.
Image by Francis Igot/Thinkstock