Extreme Wind and Waves in U.S. East Coast Offshore Wind Energy Lease Areas

Rebecca J Barthelmie,Sara C Pryor,Kaitlyn E Dantuono,Emma J Renner,Frederick L Letson

doi:10.3390/en14041053

Abstract

The Outer Continental Shelf along the U.S. east coast exhibits abundant wind resources and is now a geographic focus for offshore wind deployments. This analysis derives and presents expected extreme wind and wave conditions for the sixteen lease areas that are currently being developed. Using the homogeneous ERA5 reanalysis dataset it is shown that the fifty-year return period wind speed (U50) at 100 m a.s.l. in the lease areas ranges from 29.2 to 39.7 ms−1. After applying corrections to account for spectral smoothing and averaging period, the associated pseudo-point U50 estimates are 34 to 46 ms−1. The derived uncertainty in U50 estimates due to different distributional fitting is smaller than the uncertainty associated with under-sampling of the interannual variability in annual maximum wind speeds. It is shown that, in the northern lease areas, annual maximum wind speeds are generally associated with intense extratropical cyclones rather than cyclones of tropical origin. Extreme wave statistics are also presented and indicate that the 50-year return period maximum wave height may substantially exceed 15 m. From this analysis, there is evidence that annual maximum wind speeds and waves frequently derive from the same cyclone source and often occur within a 6 h time interval.

Highlights

Uref is not a prediction of U50 per se but a conservative value to be used within the wind turbine standards
U50 values derived from ERA5 output at heights characteristics of wind turbine hubheights range from 30 to 40 ms−1
LA that are impacted by tropical cyclones are more difficult to characterize and Uref is much less likely to be conservative [22]

Summary

Introduction

As of the end of 2019, over 5000 wind turbines with a total rated capacity of 22 GW are installed in the offshore areas of 12 European countries. Over 10% of European installed wind capacity is located offshore [1]. Trends in the industry incorporate upscaling of turbines and wind farms and decreases in the levelized cost of energy such that offshore wind is cost competitive in mature markets without subsidies [2,3]. The mean rated power of wind turbines installed offshore in Europe during 2019 is 7.8 MW and the average size of offshore wind farms in construction is 621 MW [4]. There is a transition to deployment at increasing water depth (average 33 m) and distance to shore which increased from a mean of about 35 km in 2018 to nearly 60 km for installations in

Objectives

Methods

Results

Discussion

Conclusion