UNC Charlotte scientist’s research helps debunk wind energy forecasts

03/15/2013 12:00 AM

03/13/2013 10:48 AM

Since the 1980s, when large-scale wind farms began to dot the land with more frequency, wind has been touted as a nearly perfect source of energy, mainly for its clean and renewable nature.

But while some forecasted its popularity would grow with hurricane-strength force, wind power’s development has developed gradually, more like a steady but gusty breeze, for the past three decades.

Energy harvested from wind, it turns out, is difficult to store on a large scale. And because it’s not always consistently blowing, it needs to be partnered with another energy source, usually a fossil fuel, for continuity.

Now a new study is delivering one more blow to the wind. According to research conducted by UNC Charlotte’s Amanda Adams and Harvard University’s David Keith, scientists may have originally miscalculated the power-generation capacity of large-scale wind farms.

Adams and Keith’s research was funded by the Natural Sciences and Engineering Research Council of Canada. Their findings were published last month in the journal “Environmental Research Letters.” The error, they wrote, stemmed from a failure to consider the influence a turbine can have on the wind.

“As soon as you start to harvest the resource, you’re changing the resource,” said Adams, the paper’s lead writer. She’s a geoscientist who studies mesoscale atmospheric modeling – computerized versions of motions in the atmosphere that are larger than five miles across but less than 620 miles – such as a sea breeze or a line of severe thunderstorms.

“You can estimate how a single turbine will behave,” said Adams. “But if you build a second turbine downwind, the second one is not going to have the same wind the first one had, because the first one has slowed down the wind.”

Previous calculations didn’t take into account the drag, or wind shadow, caused by other turbines.

The findings, although unfavorable, shouldn’t diminish the public’s perception of wind energy’s potential, said Adams. “Even though our paper says that previous estimates were way too large, there’s still an awful lot of energy that we could get from the wind.”

In the United States, wind energy now makes up 6 percent of the nation’s electricity generating capacity.

Large-scale wind farms – those with 100 or more turbines – have popped up all over the country in recent years; Texas, California, Iowa, Illinois and Oregon have the most wind turbines. According to the American Wind Energy Association, as of December 2012, a combined 45,100 turbines were operating in 39 states and Puerto Rico.

Some states use wind energy more than others. Iowa draws 20 percent of its electricity from wind power. North Carolina’s on-shore turbines have enough power to supply 1.8 percent of the state’s electricity, according to the National Renewable Energy Lab.

“It’s still a small percentage of energy,” said Adams, “but there’s long-term potential with wind.”

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