Wind Fields in Category 1–3 Tropical Cyclones Are Not Fully Represented in Wind Turbine Design Standards

Abstract

Offshore wind energy deployment in the U.S. is expected to increase in the years to come, with proposed wind farm sites located in regions with high risk for tropical cyclones. Yet, the wind turbine design criteria outlined by the International Electrotechnical Commission for extreme events may not account for wind field characteristics unique to tropical cyclones. To evaluate if current design standards capture the extreme conditions of these storms, we perform idealized large‐eddy simulations of five tropical cyclones (two Category 1, two Category 2, and one Category 3 storms) using the Weather Research and Forecasting model. Wind conditions near the eyewall of Category 1, Category 2, and Category 3 storms can exceed current design standards for offshore wind turbines. Winds at 90 m can be faster than outlined in the design criteria for Class I and Class T turbines for 50‐year recurrence periods. Wind speed shear across the turbine rotor layer is also larger than assumed in design specifications. Moreover, vertical variations in wind direction across the turbine rotor layer are large for tropical cyclones of all intensity levels, suggesting design standards should include veer, which can amplify loads in wind turbines. The existence of hurricane wind field characteristics that are not represented in design standards does not imply that damage or failure will certainly occur. Engineering safety factors incorporated in the design of the turbine’s blades and structural components may prevent damage from occurring.

Enhanced shear and veer in the Taiwan Strait during typhoon passage

“…With that, this study is important to understand and complement wind measurements at fixed locations during typhoon events. Studies based on LES [4] find larger wind shear than in mesoscale simulations for tropical cyclone simulations as discussed in more depth in [5]. Therefore, the analyzed mesoscale simulation may underestimate wind shear.…”

“…The wind field in tropical cyclones over the open ocean has been invested in several numerical studies with a focus on its implication for wind energy [2,3,4,5]. Large eddy simulations (LES) suggest a substantial change in wind direction with height, wind veer [2,3,4]. Such enhanced wind veer can lead to increased loads acting on wind turbines [3,6].…”

“…Such enhanced wind veer can lead to increased loads acting on wind turbines [3,6]. LES further produced larger wind shear than specified in the international design standards (IEC) in the eyewall [4]. Using mesoscale simulations, [5] analyzed shear and veer in the eyewall region, and an outer cyclone region.…”

Assessment of Offshore Wind Energy Opportunities and Challenges in the U.S. Gulf of Mexico

“…Reducing design uncertainty through advanced hurricane design methods will reduce the probability of catastrophic failures, allow designers and developers to manage financial and project risk at acceptable levels, and ultimately reduce turbine and project costs in hurricane-prone regions. Some of this research has already begun (Sanchez Gomez et al 2023;NOWRDC n.d.).…”