Will Hurricanes Topple U.S. Wind Turbines?

[wtmusic]

"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."

http://green.blogs.nytimes.com/2012/02/13/will-hurricanes-topple-u-s-wind-turbines/

[izquierdista]

1. That's what insurance is for

And not siting them right where all the hurricanes come ashore (Cape Cod, OK; Wilmington, NC, no way).

If you want to catch the wind, you have to realize that sometimes you may be catching too much of it.

[OKIsItJustMe]

2. In short, not terribly likely, but addressable, by planning ahead

...

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.

...

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.

...

http://dx.doi.org/10.1073/pnas.1111769109

...

There is a very substantial risk that Category 3 and higher hurricanes can destroy half or more of the turbines at some locations. By knowing the risks before building multiple GW of offshore wind plants, we can avoid precipitous policy decisions after the first big storm buckles a few turbine towers. Reasonable mitigation measures—increasing the design reference wind load, ensuring that the nacelle can be turned into the wind, and building most wind plants in the areas with lower risk—can greatly enhance the probability that offshore wind can help to meet the United States’ electricity needs.

...

[wtmusic]

3. Seems like the blades should separate from the tower at a pre-determined stress

but I'm sure that's already been thought of.

[txlibdem]

4. The blades are fiberglass

They'll shred long before the tower/nacelle is in any danger.

[wtmusic]

5. According to the article the wind has caused towers to "crumple" nt

[txlibdem]

6. Wow

Technically, there is nothing that we've built in the past 200 years that Mother Nature cannot destroy. I guess we'll have to add wind turbines to that list.

[OKIsItJustMe]

7. Wind Farm Risk from a Single Hurricane

http://dx.doi.org/10.1073/pnas.1111769109

…

Wind Farm Risk from a Single Hurricane. Wind turbines are vulnerable to hurricanes because the maximum wind speeds in those storms can exceed the design limits of wind turbines. Failure modes can include loss of blades and buckling of the supporting tower. In 2003, a wind farm of seven turbines in Okinawa, Japan was destroyed by typhoon Maemi (13) and several turbines in China were damaged by typhoon Dujuan (14). Here we consider only tower buckling, because blades are relatively easy to replace (although their loss can cause other structural damage). To illustrate the risk to a wind farm from hurricane force wind speeds, we calculate the expected number of turbine towers that buckle in a 50-turbine wind farm as a function of maximum sustained (10-min mean) wind speed, assuming that turbines cannot yaw during the hurricane to track the wind direction (we later consider the case in which the nacelle can be yawed rapidly enough to track the wind direction of the hurricane). Fig. 1 plots the median, fifth percentile, and 95th percentile of the number of turbine towers that buckle as a function of wind speed. The vertical dotted line shows the design reference wind speed for wind turbines in IEC (International Electrotechnical Commission) Class 1 wind regimes, which includes the NREL 5-MW turbine we simulate, and nearly all offshore wind turbines currently in production. The IEC 61400-3 design standard for Class 1 wind regimes requires that a turbine survive a maximum 10-min average wind speed with a 50-y return period of 50 m∕s (97 knots) at hub height (15); we scale this wind speed from 90-m height to 10-m height assuming power-law wind shear with an exponent of 0.077 (16) because hurricane wind speeds are given for 10-m height.

A Category 2 hurricane (wind speeds of 45 m∕s or higher) will buckle up to 6% of the turbine towers in a wind farm. Hurricane Ike in 2008, for example, had a maximum sustained wind speed of 95 knots (49 m∕s) at 10-m height (Category 2) when it passed over the meteorological tower erected by the developers of the Galveston Offshore Wind project. If a 50-turbine wind farm had been located off the coast of Galveston when Hurricane Ike struck, our model predicts that Hurricane Ike would have had a 50% probability of buckling two or more towers and a 10% probability of buckling four or more turbine towers.

Higher-category hurricanes will destroy a significant number of turbines; a Category 3 (wind speeds of 50 m∕s or higher) will buckle up to 46% of the towers. The damage caused by Category 3, 4, and 5 hurricanes is important for offshore wind development in the United States because every state on the Gulf of Mexico coast and 9 of the 14 states on the Atlantic Coast have been struck by a Category 3 or higher hurricane between 1856 and 2008 (17).

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