The incidence of widespread low-wind conditions is important to the reliability and economics of electric grids with large amounts of wind power. In order to investigate a future in which wind plants are geographically widespread but interconnected, we examine how frequently low generation levels occur for wind power aggregated from distant, weakly-correlated wind generators. We simulate the wind power using anemometer data from nine tall-tower sites spanning the contiguous United States. The number of low-power hours per year declines exponentially with the number of sites being aggregated. Hours with power levels below 5% of total capacity, for example, drop by a factor of about 60, from 2140 h/y for the median single site to 36 h/y for the generation aggregated from all nine sites; the standard deviation drops by a factor of 3. The systematic dependence of generation-level probability distribution “tails” on both number and power threshold is well described by the theory of Large Deviations. Combining this theory for tail behavior with the normal distribution for behavior near the mean allows us to estimate, without the use of any adjustable parameters, the entire generation duration curve as a function of the number of essentially independent sites in the array.
Bibliographical noteFunding Information:
This material is based upon work supported by the National Science Foundation under Grant No. 1332147 and by the Doris Duke Charitable Foundation , the Richard King Mellon Foundation , the Electric Power Research Institute , and the Heinz Endowments through the RenewElec project. This research was also supported in part by the Climate and Energy Decision Making (CEDM) center , created through a cooperative agreement between the National Science Foundation (SES-0949710) and Carnegie Mellon University. The authors thank Prof. Julie Lundquist for directing them to many of the public sources of historical wind speed records used here. The authors also thank Argonne National Laboratory, Brookhaven National Laboratory, Lawrence Livermore National Laboratory, Los Alamos National Laboratory, National Renewable Energy Laboratory, the U.S. Department of Energy's Hanford Site, and its Atmospheric Research Measurement facility, NASA Kennedy Space Center, and the NOAA Earth System Research Laboratory WLEF site for providing wind speed data. They are acknowledged in more detail in the supplementary data.
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- Effective load carrying capacity (ELCC)
- Geographic diversity
- Large deviation theory
- Wind power
- Wind variability