USA: GL RC Examines Tropical Cyclones’ Influence on Wind Turbine Design

As wind energy production expands around the world, an increasing number of onshore and offshore wind farms are proposed which would lie in tropical cyclone-affected areas, mainly in the U.S., China, Korea and Japan. A properly designed wind farm should be able to withstand the severe storms that are likely to affect it within its lifetime. 

Mike Woebbeking, Vice President of GL Renewables Certification (GL RC), addressed the question: “How are tropical cyclones influencing wind turbine design?” during GL Renewables Certification’s press conference at AWEA WINDPOWER 2012 in Atlanta. Mr Woebbeking examined how the understanding of tropical cyclone loading-related issues within the wind energy industry can be improved and how wind turbine design methods and standards can evolve to ensure robust operation in these storm conditions.

Recent tropical cyclones such as Hurricane Irene, which left a trail of destruction along the eastern seaboard of the U.S., and Typhoons Megi and Songda, have brought home the potential of extreme weather to impact upon offshore wind farm sites. The lack of clear guidance for categorising the risk a site faces of being hit by a tropical storm and the extreme variability with which such storms effect wind farm structures, means that developers are left with the uncertainties as to the fitness of their developments to deal with extreme weather conditions.

“There are a number of key factors to consider in assessing whether a particular turbine design, or wind farm site, can cope with the stresses of tropical cyclone conditions,” explained Mike Woebbeking, “for example, the category of the hurricane faced, assessment of the site and climatic forecasts, predicting wind speeds at their extremes, the ultimate load on the turbine, and turbulent wind conditions in these storms.”

Wind turbine design for tropical cyclones is one of several issues GL RC is focussing on in its research and development activities. The expansion of wind energy generation into storm-prone areas and the increase in the frequency of extreme weather events means that both developers and designers are relying on the development of guidelines for the construction of storm-safe turbines.

GL RC will develop a Technical Note for wind turbines in tropical cyclones. This will be a supplement to GL RC’s Guidelines for the Certification of Wind Turbines. The Technical Note will be prepared in cooperation with academia and industry and will include knowledge from research and experience from already existing wind farms.

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Offshore WIND staff, June 7, 2012; Image: GL