Offshore wind turbines like those being planned off the East Coast could one day do double duty for residents, according to a new study.
Scientists at the University of Delaware and Stanford University say that in addition to generating several thousand megawatts of electricity, giant wind farms could also help mitigate the destructive forces of hurricanes such as Katrina and Sandy that occasionally smash into the eastern seaboard. That could save a city like New York billions of dollars on the cost of a sea wall.
"If you add a large wind farm, there's a diminishment of the power of the hurricane -- and the destructiveness," said Mark Z. Jacobson, a civil and environmental engineering professor at Stanford University who led the study with Willett Kempton and Cristina Archer from the University of Delaware.
The team had spent years building computer models just to simulate hurricanes. Separately, Jacobson also studied wind extraction: how much wind there is in the world to potentially pull from turbines and what that means for the climate.
When Hurricane Sandy hit, he wondered whether enough wind turbines could extract energy from a hurricane and even lessen the impact. Then, once the computer models had advanced, the theory was put to the test.
Each computer model divides the atmosphere up into horizontal boxes stacked on top of each other like 3-D grids, Jacobson explained. Equations are added that describe the atmospheric motions happening inside and between the boxes. The scientists created models that simulated Hurricanes Isaac, Sandy and Katrina -- with and without wind farms.
According to their simulations, turbines could reduce a hurricane's wind speeds by up to 92 miles per hour. When the scientists modeled Hurricane Katrina, they found that 78,000 wind turbines -- a little more than 300 gigawatts of installed power -- stationed within 60 miles of the Louisiana shore would have significantly slowed the winds and also decreased the storm surge up to 79 percent.
The models also showed substantial wind speed and storm surge reductions for Isaac and Sandy. And using even half as many turbines would still have a benefit, Jacobson said.
The effects depended in part on where the wind turbines were placed. "The more turbines you have, the bigger the benefit," Jacobson said. He and his colleagues published their research in the journal Nature Climate Change.
Julie Lundquist is a professor of atmospheric and oceanic sciences at the University of Colorado Boulder who studies how wind turbines and the atmosphere interact. "These very large wind farms that appear in Mark's model are essentially extending the effect of the land out into the water," she said. "Hurricanes dissipate very quickly once they strike land so we shouldn't be surprised that they will lose strength when interacting with large wind farms."
"If you pack enough of these in, it seems like it's realistic to think you can take some of the punch out of the storm," said Rick Luettich, who directs the University of North Carolina's Institute of Marine Science and its Center for Natural Hazards and Disasters in Chapel Hill. "This kind of out-of-the box thinking is what we need over the next 50 years or so to help us get right with Mother Nature."