Annual Variability of Wake Impacts on Mid-Atlantic Offshore Wind Plant Deployments

Abstract

Abstract. The mid-Atlantic will experience rapid wind plant development due to its promising wind resource located near large population centers. Wind turbines and wind plants create wakes, or regions of reduced wind speed, that may negatively affect downwind turbines and plants. Long mid-Atlantic wakes are causing growing concern. We evaluate wake variability and annual energy production with the first year-long modeling assessment using the Weather Research and Forecasting Model, deploying 12-MW turbines across the domain at a density of 3.14 MW km−2, matching the planned density of 3 MW km−2. Using a series of simulations with no wind plants, one wind plant, and complete build-out of lease areas, we calculate wake effects and distinguish the effect of wakes generated internally within one plant from those generated externally between plants. The strongest wakes, propagating 58 km, occur in summertime stable stratification, just when New England’s grid demand peaks in summer. The seasonal variability of wakes in this offshore region is much stronger than diurnal variability of wakes. Overall, the mean year-long wake impacts reduce power output by 35.9 %. Internal wakes cause greater year-long power losses (27.4 %) compared to external wakes (14.1 %). Additional simulations quantify wake uncertainty by modifying the added amount of turbulent kinetic energy (TKE) from turbines, introducing power output variability of 3.8 %. Finally, we compare annual energy production (AEP) to New England grid demand and find that the lease areas can supply roughly 60 % of annual load.

The Effects of Wind Farm Wakes on Freezing Sea Spray in the Mid-Atlantic Offshore Wind Energy Areas

“…The WFP incorporates the effects of turbines by implementing a drag-induced deceleration of wind flow and an addition of turbulence at model levels intersecting the rotor area. We execute WFP simulations adding both 0 % and 100 % turbulent kinetic energy (TKE) (Rosencrans et al, 2023), although a smaller value of 25 % agrees better with neutrally stratified large-eddy simulations (Archer et al, 2020). The differences in icing results between 0 % and 100 % added TKE are slight, so we report those from 100 % added TKE only.…”

“…We explore the seasonal variability and impacts of wind plants on icing conditions using high-fidelity numerical weather prediction simulations over the period 01 September 2019 to 31 August 2020. These validated WRF version 4.2.1 simulations are described in detail in Rosencrans et al (2023) but are summarized here for the reader's convenience. This period is chosen for the availability of lidar measurements for validation of the wind speed profile.…”

“…We define input freezing conditions following the most liberal thresholds defined by the latter studies (Guest and Luke, 2005;Dehghani-Sanij et al, 2017;Line et al, 2022), which produce more freezing events, to compensate for a negative wind speed bias in unstable stratification (Rosencrans et al, 2023), which mitigates freezing occurrence. These criteria require 1) wind speeds in excess of 9 m s −1 , 2) air temperatures below −1.7° C, and 3) SST less than 7° C. The skin temperature (WRF output variable "TSK") is used because the SST field inherits coarse blocks of missing data around coastlines from the ERA5 dataset.…”

Offshore wind farms modify low-level jets

“…To make maximum use of the wind lease areas, wind turbines are arranged in large clusters that often interact with each other. Large arrays of turbines produce wakesregions of slower wind and more turbulent flow downwind of the turbines -that can propagate for tens of kilometers (Hasager et al, 2006;Platis et al, 2018;Rosencrans et al, 2023). The wake wind speed reduction downwind of the wind farm can reduce power output (Nygaard, 2014;Lundquist et al, 2019).…”

“…To understand how wind turbines may modify LLJs, we compare the Weather Research and Forecasting (WRF) model (Skamarock et al, 2021) simulations of Rosencrans et al (2023) that represent conditions in the region from September 2019 to September 2020. Three of these simulations include different wind farm layouts, and one simulation does not include any wind farms in the model.…”