Offshore wind turbines vulnerable to Category 5 hurricane gusts

Offshore wind turbines
Credit: CC0 Public Domain

Offshore wind turbines built according to current standards may not be able to withstand the powerful gusts of a Category 5 hurricane, creating potential risk for any such turbines built in hurricane-prone areas, new University of Colorado Boulder-led research shows.

The study, which was conducted in collaboration with the National Center for Atmospheric Research in Boulder, Colorado and the U.S. Department of Energy's National Renewable Energy Laboratory in Golden, Colorado, highlights the limitations of current design and could provide guidance for manufacturers and engineers looking to build more hurricane-resilient turbines in the future.

Offshore -energy development in the U.S. has ramped up in recent years, with projects either under consideration or already underway in most Atlantic coastal states from Maine to the Carolinas, as well as the West Coast and Great Lakes. The country's first utility-scale offshore wind farm, consisting of five turbines, began commercial operation in December 2016 off the coast of Rhode Island.

Turbine design standards are governed by the International Electrotechnical Commission (IEC). For offshore turbines, no specific guidelines for hurricane-force winds exist. Offshore turbines can be built larger than land-based turbines, however, owing to a manufacturer's ability to transport larger molded components such as blades via freighter rather than over land by rail or truck.

For the study, CU Boulder researchers set out to test the limits of the existing design standard. Due to a lack of observational data across the height of a wind turbine, they instead used large-eddy simulations to create a powerful hurricane with a computer.

"We wanted to understand the worst-case scenario for , and for hurricanes, that's a Category 5," said Rochelle Worsnop, a graduate researcher in CU Boulder's Department of Atmospheric and Oceanic Sciences (ATOC) and lead author of the study.

These uniquely high-resolution simulations showed that under Category 5 conditions, mean wind speeds near the storm's eyewall reached 90 meters-per-second, well in excess of the 50 meters-per-second threshold set by current standards.

"Wind speeds of this magnitude have been observed in hurricanes before, but in only a few cases, and these observations are often questioned because of the hazardous conditions and limitations of instruments," said George Bryan of NCAR and a co-author of the study. "By using large-eddy simulations, we are able to show how such winds can develop and where they occur within hurricanes."

Furthermore, current standards do not account for veer, a measure of the change in wind direction across a vertical span. In the simulation, wind direction changed by as much as 55 degrees between the tip of the rotor and its hub, creating a potentially dangerous strain on the blade.

The findings could be used to help wind farm developers improve design standards as well as to help stakeholders make informed decisions about the costs, benefits and risks of placing turbines in hurricane-prone areas.

"The study will help inform design choices before offshore wind energy development ramps up in hurricane-prone regions," said Worsnop, who received funding from the National Science Foundation Graduate Research Fellowship Program to conduct this research. "We hope that this research will aid wind turbine manufacturers and developers in successfully tapping into the incredibly powerful wind resource just beyond our coastlines."

"Success could mean either building turbines that can survive these extreme conditions, or by understanding the overall risk so that risks can be mitigated, perhaps with financial instruments like insurance," said Professor Julie Lundquist of ATOC and CU Boulder's Renewable and Sustainable Energy Institute (RASEI), a co-author of the study. "The next stage of this work would be to assess how often these extreme winds would impact an on the Atlantic coast over the 20-to-30-year lifetime of a typical wind farm."

The findings were recently published online in the journal Geophysical Research Letters, a publication of the American Geophysical Union.

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More information: Rochelle P. Worsnop et al, Gusts and Shear Within Hurricane Eyewalls Can Exceed Offshore Wind-Turbine Design Standards, Geophysical Research Letters (2017). DOI: 10.1002/2017GL073537
Journal information: Geophysical Research Letters

Citation: Offshore wind turbines vulnerable to Category 5 hurricane gusts (2017, June 7) retrieved 17 August 2019 from
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User comments

Jun 07, 2017
I think Al Gore said storms will get bigger in the future so what do we do, build the most vulnerable power system to storms, brilliant !!

Jun 07, 2017
Is there any type of power plant that isn't vulnerable to category 5 eye wall winds?

Jun 07, 2017
I can't help but think of the evolution of cathedral architecture. Eventually flying butresses were devised to handle the stresses imposed by building larger and larger cathedrals. It is no stretch to imagine someone will come up with some similarly innovative idea that solves the problem.

I am not generally a proponent of building "better technology" on a never ending scale to deal with problems the existing technology has caused since the newer technology tends to create problems of it's own. In this case I fervently hope to be proven incorrect. Since we are not wise enough of a species to greatly reduce the number of our species we will simply have to make do with structures that can handle the situational stresses we have created or excacerbated.

Jun 07, 2017
50 k wind and the wind turbines shutdown.

Jun 08, 2017
@fraudulent bubba the pseudoscience cult "oxymoronic" quack
The technique was demonstrated by Jesus Christ on the Sea of Galilee
1- no, it wasn't
2- there is absolutely no empirical evidence that your sky faerie jc even existed
10-100 gallons of soybean oil
big problem here: historically this was traded not only using roads, but ships

you can't tell me that no ship has ever went down with it's soybean oil intact, especially since it's a common cooking oil in asia

so how in the hell did all those storms continue to worsen ???

this is the reason idiot religious people like you should never consider attempting to do science

it's not about your faith in the idiocy you spout
it's about evidence, validation and replication

it's why you're considered a fraud
but at least now we know you're a religious fanatical nut

Jun 08, 2017
"In a 2003 publication, the National Research Council of the National Academy of Sciences reported that roughly 343,200,000 gallons of oil were released into the sea annually, worldwide.

Of this amount, the report estimates the origin of that oil as follows:

Use or consumption of oil (which includes operational discharges from ships and discharges from land-based sources): 37%
Transportation (accidental spills from ships): 12%
Extraction: 3%
Natural seeps: 46%"
That's almost a million gallons/day, and our resident crank Bubba is trying to suggest 10-100 gallons will have some affect.

Jun 14, 2017
It is great to see new types of wind turbines being developed. One important consideration is the risk, specifically risk of failure and accidents, associated with new designs. We have completed the most extensive research study on wind turbine accidents, and we share it on our dedicated web page: http://ertekproje...cidents/ Please pass to us any news regarding accidents of new designs.

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