Will Hurricanes Wipe Out Offshore Wind Farms?

The future of wind energy is out to sea. For the United States to reach ambitious goals for tapping the energy?the Department of Energy estimates that wind could provide 20 percent of American energy by 2030?wind farms may need to go places where the wind blows steadily?and where there are no people to complain about turbines ruining the view from their veranda.

Offshore wind farms are already popular in Europe, and they?re garnering major interest by U.S. developers. But the U.S. has something Europe doesn?t have to worry much about?hurricanes. A new study released yesterday in the Proceedings of the National Academy of Sciences warns that within two decades, hurricanes could destroy nearly half of turbines built in the most vulnerable areas off the U.S. coastline.

A team from Carnegie Mellon University used historical hurricane data to see if wind farms in different coastal areas could stand up to the storms. They looked at four areas in the Atlantic and Gulf Coast regions currently under consideration as locations for wind farms. They then modeled how much hurricanes in these areas could damage a 5-megawatt wind turbinedesign similar to those being installed in northern Europe.

According to the researchers? model, hurricanes ranked Category 3 (those with wind speeds of 50 miles per second) and higher could buckle up to 46 percent of these traditional turbine towers. Hurricanes that severe aren?t rare either: Records show that every state in the Gulf Coast and nine of the 14 states on the Atlantic Coast were struck by a Category 3 or higher hurricane between 1856 and 2008.

So will hurricanes kill offshore wind power before it can get started? Stephen Rose, an engineer and lead author of the new study, says wind-energy companies could minimize the problem by building smarter.

One thing to do to prevent turbine damage would be to build in less risky areas. The mid-Atlantic and New England states are at fairly low risk, he says, because they experience fewer and less intense hurricanes. "Hurricane Irene passed right over some wind turbines on the beach in Atlantic City, and as far as I?ve been able to find, the turbines were undamaged," he says.

Color-coded map of hurricane risk to wind turbines for every coastal county in the Eastern?U.S. Credit: Rose et. al.

The orientation of the turbine matters, too. Rose and his team found that if a turbine were pointed into hurricane-force winds, it would be much less likely to buckle. If high-speed winds hit the turbine?s broad side, however, they can cause a great deal of damage because they push against the part of the nacelle (the housing that holds the blades) that has the most surface area.

Keeping the turbine pointed into the wind during a hurricane is complicated, however. "The wind speed can pick up and change direction in a matter of a minute or two," Rose says. Turbines also would need strong motors to turn quickly enough to cope with changing winds. They?d also need to be able to sense wind direction. And because many turbines run on grid power?which often goes out during hurricanes?they?d need battery backup. Rose estimates these upgrades might cost $50,000 per turbine. "But these are $5 million to $10 million turbines," he says.

Dominique Roddier is an engineer working on a new design for a floating wind turbine called WindFloat by Principle Power, which is being tested in Portugal. He couldn?t say how accurate the estimates by Rose?s team might be, he tells PM, but he doesn?t think that hurricane risk poses an insurmountable obstacle for the offshore wind industry?it?s something that?s been taken into consideration all along.

"We know very well what a hurricane?s winds are," Roddier says. "We can design turbines that will sustain the highest hurricanes without a problem; they will just be a lot more expensive and maybe not worth it."

Building turbines to withstand big hurricanes would mean bumping up the strength of the structures with thicker, heavier towers and blades that require more steel and fiberglass to build. That means they?d be much pricier. Roddier says wind-power companies will have to weigh that expense against how much energy they expect to get from a particular location, and consider whether it would be cheaper to replace a turbine that breaks rather than build one that can withstand any storm.

"If we?re in an area with good wind resources but where we are going to see hurricanes every year, we?ll build them much stronger," he says. "If we?re in an area that doesn?t have a lot of wind, but where we are going to see hurricanes every year, we?ll probably think twice about building wind farms there."

Source: http://www.popularmechanics.com/science/energy/solar-wind/will-hurricanes-wipe-out-offshore-wind-farms-6655421?src=rss

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