Hurricanes are destructive, and protecting coastlines with seawalls costs money. What if coastal areas could not only protect themselves from dangerous storms, but also earn back money by generating renewable energy?
This may be possible if those seawalls are offshore wind turbines — as long as there were a lot of them. A new study published Wednesday in Nature Climate Change suggests that a large array of wind turbines installed offshore could have slowed down the wind speeds and reduced the storm surge of some of the most devastating hurricanes in U.S. history.
Mark Jacobson is a civil and environmental engineering professor at Stanford, and for more than two decades he has developed a very complex computer model to better examine air pollution, wind power, weather, climate, and hurricanes. He decided to combine the hurricane modeling with the wind power modeling to see what would happen if a hurricane met a giant wind farm. Working with University of Delaware researchers Cristina Archer and Willett Kempton, Jacobson modeled three big, damaging storms: Katrina, Isaac, and Sandy.
“We found that when wind turbines are present, they slow down the outer rotation winds of a hurricane,” Jacobson said. “This feeds back to decrease wave height, which reduces movement of air toward the center of the hurricane, increasing the central pressure, which in turn slows the winds of the entire hurricane and dissipates it faster.”
The researchers found that 78,286 large wind turbines arrayed off the coast of New Orleans would have dropped Hurricane Katrina’s wind speeds by 81 miles per hour, and reduced storm surge by up to 71 percent. Covering most of the Gulf Coast with wind turbines (meaning over half a million individual turbines) slowed down a modeled Katrina even more (wind speeds by 90 mph and storm surge by 79 percent). The same area covered by half as many turbines would still cut storm surge by 63 percent. Hurricane Isaac would have lost up to 60 percent of its storm surge and 57 mph of wind speed. Their model of Hurricane Sandy found that 112,014 offshore turbines would cut wind speed by 80 mph and drop storm surge by 21 percent.
The purpose of a wind turbine is to transmit kinetic energy from wind into electrical energy used to power homes and businesses. The wind that comes out the backside of a wind farm has less energy than it did when it entered the array. And a recent study found that wind farms, even on a huge scale, do not affect the climate as some have claimed. And Archer and Jacobson said in 2012 that 4 million turbines spread around the world could generate half the world’s energy needs without interfering with atmospheric circulation too much.
Since hurricanes are violent storms, it is reasonable to wonder if that violence would harm or destroy the front-line offshore turbines. But Jacobson says that the presence of the turbines would slow the extremely fast winds down before they hit the array. As the outer bands of the storm hit the turbines, a feedback mechanism would start up that would keep the highest winds from hitting the turbines.
“The little turbines can fight back the beast,” said the University of Delaware’s Archer.
Asked if wave power devices could be added to a wind array to further dampen strong hurricanes, Jacobson told Climate Progress that while he hadn’t done research on it, he thought that if they can survive, a large enough array “would probably be of some help.”
Hurricane Katrina caused $108 billion worth of damage and Superstorm Sandy hit three states for $65 billion, so Jacobson’s theory is that spending billions to construct thousands of offshore wind turbines is worth the investment — especially if coastal areas have to spend money on climate resilient coastal defenses like seawalls anyway. Former New York City Mayor Michael Bloomberg outlined a climate resiliency plan last year that started at $19.5 billion, with large investments in seawalls.
Wind turbines start to pay for themselves when they provide power. The problem with any plan to dramatically expand offshore wind in the United States is that there are currently zero real offshore wind turbines installed in American waters. Plans have been in the works for years, and there has been some progress on auctions and leasing recently, but the fact remains that the rest of the world is leaving the U.S. far behind in offshore wind.
The arrays Jacobson tested were all huge, well over 300 gigawatts in size. An analysis last year by the Center for American Progress and the Brattle Group found that an initial investment of $18.5 billion in offshore wind with no subsidies would yield 54 gigawatts. Once the initial investments to get the industry off the ground are made, those costs should go down.
Building one offshore wind turbine has so far been too much for the U.S. Around 200 are slated to be built in the Texas and Massachusetts wind farms that are closest to reality. Thousands of turbines would be a huge lift, and tens of thousands stretch the bounds of current credulity.
But the stakes are high. It would be expensive, but the damages from climate impacts are expensive, and adapting to those impacts are expensive. So an idea that combines valuable clean power production with climate resiliency and storm protection could gain some interest from coastal residents tired of wondering when the next superstorm will hit, and tired of fueling those storms with heat-trapping carbon pollution.