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Publication Date
1 December 2020

Variability in Wind Energy Generation Across the Contiguous United States



ERA5 provides high-resolution, high-quality hourly wind speeds at 100 m and is a unique resource for quantifying temporal variability in likely wind-derived power production across the USA. Gross capacity factors (CF) in seven independent system operators (ISOs) are estimated using the location and rated power of each wind turbine, a simplified power curve, and ERA5 output from 1979-2018. Excluding the California ISO, the marginal probability of a calm (zero power production) is less than 0.1 in any ERA5 grid cell. When a calm occurs, the mean co-occurrence across wind turbine containing grid cells ranges from 0.38-0.39 for ISOs in the Midwest and Central Plains (MISO, SPP and ERCOT), increasing to 0.54-0.58 for ISOs in the eastern USA (PJM, NYISO, and NEISO). Periods with low gross CF have a median duration of  6 hours except in California and are most likely during summer. Gross CF exhibits the highest variance at periods of one day in ERCOT and SPP, on synoptic scales in MISO, NEISO, and NYISO, and on inter-annual timescales in PJM. This implies differences in optimal strategies for ensuring the resilience of supply. Theoretical scenarios show adding wind energy capacity near existing wind farms is advantageous even in areas with high existing installed capacity (IC) while expanding into areas with lower IC is more beneficial to reducing ramps and the probability of gross CF falling below 20%. These results emphasize the benefits of large balancing areas and aggregation in reducing wind power variability and the likelihood of wind droughts. ‘Wind drought’, ERA5 reanalysis, gross power production, net capacity factors, spatial correlation, ramps
“Variability In Wind Energy Generation Across The Contiguous United States”. 2020. Journal Of Applied Meteorology And Climatology 59: 2021-2039. doi:10.1175/jamc-d-20-0162.1.
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