Will Hurricanes Topple U.S. Wind Turbines?

Source: DIANE CARDWELL • New York Times • Posted: Tuesday, February 14, 2012

Bloomberg News

As plans for wind farms rising out of the ocean along the Atlantic and Gulf coasts inch closer to fruition, a new study from Carnegie Mellon University suggests that hurricanes could destroy a significant number of turbines in some of these areas, even coming close to wiping them out.

Although turbines are designed to both harness and withstand the forces of wind, they can be severely damaged by too much of it. In the United States, Europe and Asia, turbines have caught fire, blades have shredded and towers have crumpled when hit by stormy gales.

The authors of the study, published on Monday in the National Academy of Sciences magazine  PNAS, set out to quantify the likelihood that a hurricane could topple towers in American waters where projects are under consideration or development.

They looked what might happen to 50-turbine farms off the coasts of four states: North Carolina, New Jersey, Massachusetts and Texas. Feeding historical data about hurricane occurrence and intensity into a probabilistic model, they simulated potential damage to the turbine towers over several 20-year periods and then took an average.

Of the locations studied, Galveston County in Texas was the riskiest, followed by Dare County in North Carolina; the risk to farms in Atlantic County, N.J., and Dukes County, Mass., were found to be much lower. In Galveston, the researchers found, there is a 60 percent chance that at least one tower would buckle in a 20-year period and a 30 percent probability that more than half would be destroyed.

In North Carolina, there is a 60 percent probability that at least one tower would suffer damage but only a 9 percent chance that more than half would be destroyed.

The researchers found that the damage could be reduced by using turbines that can yaw, or rotate, quickly enough in the chaotic winds of a hurricane to relieve stress on the tower. In the case of Galveston, the use of rotating equipment would drop the risk of at least one tower buckling to 25 percent and the risk of more than half coming down to 10 percent.

With yawing turbines in North Carolina, the study found a 15 percent likelihood that a hurricane would take out at least one tower but a less than 1 percent likelihood that winds would take out more than half. The challenge, though, is providing a backup power source, given that the turbines cannot function in hurricane-speed winds.

Paulina Jaramillo, an assistant research professor in the Department of Engineering and Public Policy who is one of the study’s authors, said she hoped the study would help guide decisions about siting and design of wind farms.

“There is a trade-off because some of the states with the largest offshore wind resources are in the hurricane-prone areas,” she said. Building stronger turbines with more steel in the towers and fiberglass in the blades would be more expensive, she noted, as would furnishing batteries to fuel rotation when the turbine is not producing power.

“These are things that we can do, it’s just a matter of cost,” said Ms. Jaramillo, who manages the RenewElec project, which focuses on ways to help integrate renewable energy into the system.