Avangrid Renewables and the wind power industry say Hurricane Florence and the threat of global warming-fueled future hurricanes won’t stand in the way of offshore wind farm development along the East Coast.
Avangrid holds the nation’s southernmost offshore wind lease near Kitty Hawk, N.C.—a hurricane-prone region of North Carolina’s Outer Banks that missed Hurricane Florence, which churned ashore Sept. 14 near Wilmington, N.C.
Coastal waters from Massachusetts to South Carolina are targeted for offshore wind power development, including regions of the Carolina coast that are prone to major hurricanes.
Climate change could send more major hurricanes—Category 3 or greater with winds faster than 110 mph—into waters off the Carolinas and Mid-Atlantic states in the coming decades, threatening to damage or topple planned offshore wind farms there, scientists predict.
Industry officials, however, say hurricanes pose little threat to offshore wind turbines.
Only one offshore wind farm has been built in North America so far—the Block Island Wind Farm in Rhode Island, completed in 2016.
Storm-Proofing a Wind Farm
Avangrid says it’s aware of the hurricane threat and is looking for solutions.
“We will work with our global engineering teams to harness their expertise and experience gleaned from other offshore projects across the globe, also built to withstand extreme weather and challenging conditions,” Avangrid Renewables spokesman Paul Copleman told Bloomberg Environment.
“Years of scientific evaluations, on a number of environmental variables, go into site selection and design, and that as an owner-operator of renewable energy projects, we are making a long-term investment anticipating that these projects will run for decades,” Copleman said.
But offshore wind farms using today’s international standards are not designed to withstand the most extreme winds in major hurricanes, according to a 2017 study estimating U.S. offshore wind farm hurricane risk.
Today’s standards require offshore wind turbines to withstand a 155 mph wind gust for three seconds. Turbine foundations adhere to similar standards as offshore oil rigs in the hurricane-prone Gulf of Mexico, study co-author Walter Musial, an engineer and offshore wind manager at the Energy Department’s National Renewable Energy Laboratory, told Bloomberg Environment.
“Offshore wind farms would not likely survive a [Category] 5 hurricane if the eyewall were to pass near the turbines,” Musial said. “Not much survives these storms.”
A Changing Climate for Wind
The risk climate change-fueled major hurricanes pose to offshore wind farms along the East Coast is uncertain.
But recent research suggests that global warming may intensify hurricanes and typhoons worldwide so they’ll reach “unobserved strength” and possibly track into waters where offshore wind farms are planned.
“Climate change, while leading to stronger, bigger Atlantic hurricanes producing large storm surges, is projected to cause a northward drift in storm trajectories,” Michael Mann, a climatologist at Penn State University, told Bloomberg Environment.
Mann co-authored a 2017 study estimating the future hurricane risk to New York City as the climate warms.
Only a few major hurricanes have struck land along the East Coast north of Georgia in the last century, and Atlantic hurricanes are defying the global trend of hurricanes and typhoons churning northward.
In the North Atlantic, hurricane tracks have been trending southward for decades and scientists don’t know exactly why, said Jim Kossin, a National Oceanic and Atmospheric Administration atmospheric scientist based in Madison, Wis.
Atlantic hurricanes may begin migrating north as ocean temperatures warm, but it’s unclear when or if that might happen, Kossin said.
Not A Threat
The industry says hurricanes pose little threat to offshore wind turbines, which could be exposed to the full brunt of a catastrophic hurricane’s winds.
“I don’t think they’re going to pose much threat at all,” Liz Burdock, executive director of the Business Network for Offshore Wind, told Bloomberg Environment. “We’ll lose a couple turbine blades. They might break off if winds are at such high speeds.”
Engineers test offshore wind farms sufficiently to ensure they are resilient enough to operate for decades in harsh conditions. But any man-made structure is vulnerable to the most extreme weather, according to Michele Myers-Mihelic, standards director at the American Wind Energy Association.
“Companies carefully weigh the risk of extreme weather when they decide where to invest hundreds of millions of dollars into a project like a wind farm,” Myers-Mihelic said.
Storms Too Rare
Even if more major hurricanes affect areas with offshore wind farms, designing turbines for the most intense storms makes little sense because they’re rare, engineers say.
“Engineering designs to withstand these superstorms may be possible but these storms are so rare at any given site in the U.S. that it is not likely that [Category] 5-resistant designs will be needed, even in hurricane-prone regions,” Musial said.
Design standards for offshore wind farms are based on lessons learned from turbines that have survived typhoons in Asia and on standards for offshore oil platforms in the Gulf of Mexico, many of which have survived major hurricanes, said Sandy Butterfield, renewable energy certification chair for the International Electrotechnical Commission. The commission sets international design standards for wind turbines.
“The overwhelming majority of oil and gas rigs survived Hurricane Katrina,” Butterfield said. “But those that didn’t enabled industry to reevaluate their standards and adjust them to meet more severe 100-year events for future installations.”
Prep for Category 2
Offshore wind turbines are designed to withstand weather conditions predicted to occur every 50 years at a particular site, usually the equivalent of a Category 2 hurricane, Rudolph Hall, a principal at Mandeville, La.-based Keystone Engineering, Inc., told Bloomberg Environment.
Keystone’s clients include NREL, Deepwater Wind Inc., and other East Coast offshore wind developers.
Most catastrophic winds in a hurricane—which blow in a narrow field closest to the storm’s core—are extremely unlikely to hit any given wind turbine, Hall said.
For example, a hurricane of the magnitude of Hurricane Camille, which barreled through offshore oil fields and struck the Gulf Coast in 1969 packing 175 mph winds, may occur once every 20 years. But the highest winds near Camille’s core are projected to strike any given oil platform every 400 years, Hall said.
“Design conditions are based on probability of occurrence at a specific site—a very small area” compared to thousands of miles of coastline that may be exposed to the relatively small area of a hurricane wind field, Hall said.