Using Large Eddy Simulations to Estimate the Vulnerability of Offshore Wind Farms to Tropical Cyclones

Offshore wind turbines have been proposed for much of the Gulf and Atlantic coasts of the United States.  As these regions are vulnerable to tropical cyclones, it is imperative that the risk of future wind farms encountering damaging winds is understood, both for economic viability of the farms and for determining appropriate design standards.  Several recent studies have attempted to estimate the risk that wind turbines will be destroyed by TCs during their expected lifetime.  These studies have relied on statistical modeling of the hurricane wind field, which may or may not reflect the actual distribution of damaging wind gusts associated with intense TCs.  The hurricane eyewall is inherently turbulent, and extreme near-surface winds are often highly localized.  Therefore, the expected maximum winds encountered by a given wind turbine in a 30-year period is still quite uncertain.

Here, we use a combination of large eddy simulations of idealized TCs and statistical-dynamical modeling of the climatological distribution of intense tropical cyclones, in order to estimate the probability that a hypothetical wind turbine will encounter 3-s gusts exceeding 70 m/s and/or 1-min mean winds exceeding 50 m/s.  Using the CM1 model, we simulate TCs of varying intensities and sizes, examine time-series of simulated anemometers in the path of the eyewall, and calculate the probability that a given location will encounter extreme winds.  We then combine these probabilities with the climatological probability of a TC passing over a given location, and obtain an estimate of the total risk of extreme winds at a given point within a given time period.  Finally, we use a comprehensive dataset of all observed dropsondes within tropical cyclones for a complementary analysis of the risk of TCs to offshore wind farms.