Characterization of offshore vertical wind shear conditions in Southern New England

Abstract

Vertical wind shears could have a significant effect on the energy produced by a wind turbine and on its loads. Although the development of several wind farms has been planned on the East Coast of the United States, there are no studies that characterize the vertical wind shear over this area. This study focuses on characterizing wind shears in the marine boundary layer in Southern New England and along the East Coast of the United States. The analysis looks at the statistical distribution of vertical wind shear values and at their associated meteorological conditions. The analysis relies on remote‐sensing wind measurements and other meteorological data recorded at the Woods Hole Oceanographic Institution Air–Sea Interaction Tower located 3 km to the South of Martha's Vineyard, together with buoy measurements and ERA5 reanalysis data. This work shows that large vertical wind shear values (>0.05 m/s/m) calculated using wind measurements at 60 and 53 m were often observed (≈25.3% of all the valid wind profiles analyzed) for South‐Westerly winds within a range of positive bulk Richardson numbers 0–0.1. These large‐shear values are the result of the presence of a strong high‐pressure system (Bermuda‐Azores High) over the North Atlantic basin and low pressures over land, which result in warm Southerly winds flowing over the cold waters of the Labrador current. The power density computed considering the vertical wind shear by means of the rotor equivalent wind speed is 5.5% smaller than that considering wind speed measurements at 110 m only.

Scientific challenges to characterizing the wind resource in the marine atmospheric boundary layer

“…Evidence of an offshore wind farm influencing the mixed layer can be seen from photos and has been additionally confirmed in numerical modeling (Hasager et al, 2017;Siedersleben et al, 2018Siedersleben et al, , 2020. Current abilities to simulate IBL characteristics and impacts on operating wind plants need to be further investigated to assess the adequacy of resource characterization and wind plant operation guidelines in areas influenced by IBLs (Borvarán et al, 2021). Observations are needed to characterize how often IBLs form, the significance of their effect on wind and turbulence in the rotor plane, and what model improvements are needed to confidently account for their impact on wind power production.…”

Assessing Obukhov Length and Friction Velocity from Floating Lidar Observations: A Data Screening and Sensitivity Computation Approach

“…They found empirical dependency between the bulk-Richardson number, Ri, and the dimensionless stability parameter. Their method has been used in recent studies [33,56].…”

Observation and Large Eddy Simulation of Coastal Winds at Anholt Offshore Wind Farm

“…The performance and structural loads of turbines in wind farms are dependent on the thermal stratification of the Atmospheric Boundary Layer (ABL), which affects the wake flows via atmospheric turbulence [1,2] and directional wind shear [3,4]. A Low-Level Jet (LLJ) is a distinctive characteristic of a stable ABL, identified by a wind speed maximum located between 100 and 500 m height [5], and is also known to affect wind farm performance [4]. To predict wind farm power output and turbine structural dynamics more accurately, it is important to understand the variability of an offshore ABL that is observed in a seasonal cycle, and LLJ occurrence when the ABL becomes stable.…”