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Study: Wind turbines may cool, but they could inhibit crops' growth

WASHINGTON – Wind farms could make days a little cooler and nights a little warmer, make crops grow better and shift the course of a storm.

All that might sound like science fiction, but researchers are creating such studies of turbines and wind farms much like those in the Big Country.

“It’s best that we try to glean as much information as possible doing this kind of research instead of postponing it for later,” said Somnath Baidya Roy, a researcher in turbines and temperatures.

Wind energy’s contribution to the electricity supply is less than 2 percent. The Department of Energy’s goal for the nation is 20 percent by 2030.

Wind energy growth has been explosive in the United States. The industry added more than 35 percent of new generating capacity just over the last four years, according to the America Wind Energy Association.

Baidya Roy, an atmospheric sciences professor at the University of Illinois at Urbana-Champagne, said the timing is just about perfect for a study he led. The study report, “Impacts of wind farms on surface air temperatures,” written by him and Justin J. Traiteur, was published late last year in the Proceedings of the National Academy of Sciences.

Downwind of a wind farm, turbines create cooler local temperatures during the daytime and warmer temperatures in the early morning and at night, the study indicated.

Researchers used data collected from a wind farm at San Gorgonio, Calif., in 1989, corroborating model simulations Baidya Roy had run before.

The cooling effect could mean a temperature of about 86 degrees Fahrenheit instead of 93.2 during the day near the surface.

The warming effect could mean about 69.8 instead of 68 degrees at night.

Baidya Roy said wind turbines generate wakes in the air, akin to those motorboats make in the water. You just can’t see a turbine’s wake.

“The turbulence in the wake, what it does is it kind of triggers a mixing effect in the atmosphere,” he said.

He theorizes a turbine’s wake mixes cooler air with warmer air, changing the temperature.

To counteract that, the study suggests adjusting turbines’ design to cut down on turbulence in their wakes. It also suggests developing wind farms on sites with already bountiful natural turbulence.

Turbines have less of an effect on temperatures in naturally turbulent areas such as the Great Plains. The region cuts a wide swath down the middle of the country and encompasses much of Texas, including the Big Country.

Wind is a plentiful resource in Texas, which has more wind power capacity than any other state – 10,135 megawatts, according to the America Wind Energy Association’s 2011 first-quarter marketing report.

A wind industry advocate was skeptical of Baidya Roy’s study.

“As a practical matter, it sounds outlandish, and it’s not worth commenting on,” said Greg Wortham, executive director of the Texas Wind Energy Clearinghouse based in Sweetwater.

Baidya Roy sees positives in wind energy development.

“With the dangers that we face like fossil fuels and climate change, I think the positive effects of wind farms are going to probably outweigh the negative impacts,” he said.

Eugene Takle was intrigued by Baidya Roy’s study and what it might mean for agriculture.

Takle is studying how wind farms might affect temperature, evaporation and photosynthesis for corn crops in their vicinity.

Turbines are popping up all over Iowa, almost all in agricultural fields, he said.

“Farmers are beginning to ask questions of whether these turbines might have an influence on, for instance, pollination or other factors,” he said.

Takle is a professor of atmospheric sciences and agricultural meteorology at Iowa State University, as well as director of the climate science program.

“If the wind turbines are allowing the crop to be more efficient at photosynthesis, that would be a good thing,” Takle said. “But on the negative side, it may be that they’re keeping the crop a little bit too warm at night.”

Takle and other scientists took some measurements last summer to look for turbines’ effects on corn crops, but they need more research to determine the net effect of wind farms on growing corn.

“On Monday, we’re going to start setting out more instruments,” he said.

Takle also was one of the authors of an earlier study on wind speeds in the United States declining, possibly because of climate change.

A pair of scientists at the University of Maryland’s Department of Atmospheric and Oceanic Science focused on turbines and the weather in their paper “Weather response to a large wind turbine array,” published in the Atmospheric Chemistry and Physics journal early last year.

Dan Barrie and Daniel Kirk-Davidoff created a computer model of a massive amount of turbines in wind farms stretching from downwind of the Rocky Mountains to the Mississippi River and from Texas into Canada.

The simulated wind farms would cover 23 percent of North America and produce enough electricity to power the United States.

Large-scale wind farms like those in the simulations don’t exist, but there’s no known resource limitations that would prevent them from being built, the paper said.

“I was looking into whether there might be impacts on particular storm systems if we developed wind energy in the United States,” Barrie said.

The model array of turbines could indeed affect a large rainstorm by shifting it. Turning off the turbines would perhaps change the storm’s course by an area the size of a small state.

“But it’s not clear exactly what would happen to precipitation or to temperature or to impacts that humans would be aware of,” Barrie said.

He said he and Kirk-Davidoff are fine-tuning their research to create more realistic scenarios and to, for instance, determine the effects of meeting the DOE’s goal of 20 percent by 2030.