Projecting Future Energy Production from Operating Wind Farms in North America. Part III: Variability

Daily expected wind power production from operating wind farms across North America are used to evalu-ate capacity factors (CF) computed using simulation output from the Weather Research and Forecasting (WRF) Model and to condition statistical models linking atmospheric conditions to electricity production. In Parts I and II of this work, we focus on making projections of annual energy production and the occurrence of electrical production drought. Here, we extend evaluation of the CF projections for sites in the Northeast, Midwest, southern Great Plains (SGP), and southwest U.S. coast (SWC) using statewide wind-generated electricity supply to the grid. We then quantify changes in the time scales of CF variability and the seasonality. Currently, wind-generated electricity is lowest in summer in each region except SWC, which causes a substantial mismatch with electricity demand. While electricity of residential heating may shift demand, research presented here suggests that summertime CF are likely to decline, potentially exacerbating the offset between seasonal peak power production and current load. The reduction in summertime CF is manifest for all regions except the SGP and appears to be linked to a reduction in synoptic-scale variability. Using fulfillment of 50% and 90% of annual energy production to quantify interannual variability, it is shown that wind power production exhibits higher (earlier fulfillment) or lower (later fulfillment) production for periods of over 10-30 years as a result of the action of internal climate modes.SIGNIFICANCE STATEMENT: Electrical power system reassessment and redesign may be needed to aid efficient increased use of variable renewables in the generation of electricity. Currently wind-generated electricity in many re-gions of North America exhibits a minimum in summertime and hence is not well synchronized with electricity demand, which tends to be maximized in summer. Future projections indicate evidence of reductions in wind power during sum-mer that would amplify this offset. However, electrification of heating may lead to increased wintertime demand, which would lead to greater synchronization.

Automated summary

This study evaluates the capacity factors of wind farms in different regions using daily expected wind power production, and quantifies the time scales and seasonality of capacity factor variability. The research suggests that the current summertime wind power production is not well synchronized with electricity demand, and there is a potential decline in summertime capacity factors, exacerbating the offset between peak power production and load. These findings are significant for the efficient use of renewable energy and the redesign of power systems.