Hurricane Risk to Offshore Wind (Proceedings of the National Academy of Sciences study still relevant)

By Robert Bradley Jr.

“Modern wind farms are reliable, safe, state-of-the-art power plants with well-tested technologies that meet approved standards and hundreds of thousands of hours of operating experience,” the U.S. Department of Energy states. Except when they fail under normal conditions–or abnormal ones.

“Wind Turbines Destroyed by Typhoon Yagi,” read one recent headline. This (during peak hurricane season 2024) has wind power in the (not-so-good) news. Not only were older turbines destroyed by the 150 mile-per-hour typhoon (Category 4 in hurricane terms); new “more efficient typhoon-resistant versions” were leveled too. For multi-million dollar structures, the risk and the cost of insurance are major issues.

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The U.S. offshore wind industry will be spared–but only because of projects that have been abandoned or delayed. But what would happen if such naked structures are built, particularly in the Gulf of Mexico or off the Atlantic Coast?

The Proceedings of the National Academy of Sciences research article, “Quantifying the Hurricane Risk to Offshore Wind Turbines” (February 13, 2012), remains relevant today to the energy policy debate. DOE’s recent confident statement, in fact, was pre-refuted by the five scholar authors.

The article’s conclusions follow:

“The U.S. Department of Energy has estimated that if the United States is to generate 20% of its electricity from wind, over 50 GW will be required from shallow offshore turbines. Hurricanes are a potential risk to these turbines. Turbine tower buckling has been observed in typhoons, but no offshore wind turbines have yet been built in the United States.”

“We present a probabilistic model to estimate the number of turbines that would be destroyed by hurricanes in an offshore wind farm. We apply this model to estimate the risk to offshore wind farms in four representative locations in the Atlantic and Gulf Coastal waters of the United States. In the most vulnerable areas now being actively considered by developers, nearly half the turbines in a farm are likely to be destroyed in a 20-y period.”

“Typically, wind turbines are designed based on engineering design codes for northern Europe and the North Sea, where nearly all the offshore and coastal wind turbines have been built. These codes specify maximum sustained wind speeds with a 50-y return period of 42.5–51.4 m/s (83–100 knots), lower than high intensity hurricanes.”

“Offshore wind turbines … will be at risk from Atlantic hurricanes…. 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, and several turbines in China were damaged by typhoon Dujuan. Here we consider only tower buckling, because blades are relatively easy to replace (although their loss can cause other structural damage).”

“There is a very substantial risk that Category 3 and higher hurricanes can destroy half or more of the turbines at some locations.”

Final Comment

Hurricane Category 4 and 5 winds are a threat to existing and even state-of-the-art industrial wind turbines. Category 3 (the baseline of the above article) is a real threat as far as is known. Category 6 (which climate alarmists predict is the future) will make all existing structures in hurricane prone waters susceptible.

The authors stay politically correct by looking to a new future:

Reasonable mitigation measures—increasing the design reference wind load, ensuring that the nacelle can be turned into rapidly changing winds, 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.

But such would increase cost, reduce output, and/or limit offshore wind below politically desired levels. All aggravate the already bad economics and poor prospects of offshore wind in the U.S.