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

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.