Giant wind farms could steer storms

In the United States, wind power still only accounts for a little over 1 percent of electricity generation. But the industry is growing fast, from 17 gigawatts of installed capacity at the end of 2007 to 21 through the end of September.

And the U.S. Department of Energy is upping the ante even further, with plans for the country to generate 20 percent of its electricity through wind by 2030. Wind turbines could soon be carpeting the countryside wherever there is a steady breeze.

To find out what effects, if any, large scale wind farms might have on wind patterns, Daniel Barrie and Daniel Kirk-Davidoff of the University of Maryland concocted an experiment. They took the pattern of expanding turbine fields to an extreme, and used a computer model to calculate what might happen if all the land from Texas to central Canada, and from the Great Lakes to the Rocky Mountains were covered in one massive wind farm.

On average, the mammoth installation lowered wind speeds by 5.5-6.7 miles per hour immediately downwind. But the turbines also disrupted air currents on a large scale that rippled out like waves across the northern hemisphere.

As they spread out, the waves sometimes ran into storms systems a few days later, knocking them several hundred miles off course.

"This is the butterfly effect, right?" Kirk-Davidoff said. "It's just that we have a really big butterfly."

Kirk-Davidoff acknowledged the hypothetical wind farm was far larger than anything humans are likely to build. But meeting the Department of Energy's goal of wind power generation by 2030 would require that scores of huge wind farms be built throughout the Midwestern United States. The total disturbance caused by turbines could be enough to steer storms.

"If all of the farms were concentrated in the same place, they'd occupy a substantial portion of Texas, and it could probably have an effect," James McCaa of 3Tier, Inc., a renewable energy forecasting company based in Seattle, said. "But they'll be distributed around the country."

However Kirk-Davidoff said that if large farms are ever built that affect storm tracks, it could be a good thing.

"Let's say a big snow storm is headed for New York City and if you leave the wind farms on, it has an 80 percent chance of hitting, but if you turn them off, there's only a 40 percent chance," Kirk-Davidoff said. "That's about the best we could probably ever do, because weather forecasting is full of uncertainty.

"But then you'd want to weigh the cost of turning off the electricity generation against the cost of cleaning up all that snow."