Hurricane impacts in the United States East Coast offshore wind energy lease areas

Abstract. Wind turbines deployed in offshore wind energy lease areas along the U.S. East Coast could significantly contribute to the national electricity supply. This region is also impacted by powerful tropical and extra-tropical cyclones that may lead to high structural loading on wind turbines and support structures and, in the event of above cut-out wind speeds, low power production (capacity factors < 0.2). Four sets of high-resolution simulations are performed for two category 3 tropical cyclones that tracked close to current offshore wind energy lease areas to assess the possible impacts on, and from, wind turbines. Simulations of Hurricanes Irene and Sandy are performed at convective permitting resolution with both the Weather Research and Forecasting Model (WRF) and the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Model to characterize geophysical conditions of relevance to offshore wind turbines. These simulations are performed without and with a wind farm parameterization (WFP) active with the latter using the assumption that existing lease areas are fully populated with 15 MW wind turbines at a 1.85 km spacing. Many aspects (e.g., track, near-surface wind speed, sea level pressure, precipitation volumes) are well reproduced in control simulations (no WFP) with both WRF and COAWST particularly for Hurricane Sandy. COAWST simulations lead to more intense cyclones with a slightly larger area of storm-force wind speeds, a higher likelihood of hub-height wind speeds > 25 m s^-1, plus higher precipitation volumes, possibly indicating under-estimation of hurricane risk in uncoupled simulations. All eight simulations indicate maximum hub-height wind speeds (HH WS) within the existing lease areas below 50 m s^-1. However, COAWST simulations indicate frequent wind-wave misalignment of > 30° and the joint occurrence of significant wave height, hub-height wind speed, and wave period in some lease areas reach levels that are likely to be associated with large structural loads. This work re-emphasizes the utility of coupled simulations in describing geophysical conditions of relevance to offshore wind turbine operating conditions.