Gusts and Shear Within Hurricane Eyewalls Can Exceed Offshore Wind-Turbine Design Standards

TL;DR

This study uses large-eddy simulations to show that hurricane eyewalls produce wind gusts and shear exceeding current offshore wind turbine standards, indicating a need to revise design criteria for hurricane-prone regions.

Contribution

It provides new insights into hurricane eyewall wind speeds and shear, highlighting the inadequacy of current standards and suggesting the inclusion of wind veer considerations.

Findings

Gusts and mean winds exceed current design thresholds near eyewalls.

Gust factors are highest at the eye-eyewall interface.

Significant wind direction shifts suggest turbines need faster yaw response.

Abstract

Offshore wind energy development is underway in the U.S., with proposed sites located in hurricane-prone regions. Turbine design criteria outlined by the International Electrotechnical Commission do not encompass the extreme wind speeds and directional shifts of hurricanes stronger than a Category 2. We examine the most turbulent portion of a hurricane (the eyewall) using large-eddy simulations with Cloud Model 1 (CM1). Gusts and mean wind speeds near the eyewall exceed the current design threshold of 50 m s-1 mean wind and 70 m s-1 gusts for Class I turbines. Gust factors are greatest at the eye-eyewall interface. Further, shifts in wind direction at wind turbine hub height suggest turbines must rotate into the wind faster than current practice. Although current design standards omit mention of wind direction change across the rotor layer, large values (15-50 deg) suggest that veer should be considered in design standards.