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CEIC-13-04

What Day-Ahead Reserves are Needed in Electric Grids with High Levels of Wind Power?
Brandon Mauch, Jay Apt, Pedro M.S. Carvalho, and Paulina Jaramillo

Abstract:
Day-ahead load and wind power forecasts provide useful information for operational decision making, but they are imperfect and forecast errors must be offset with operational reserves and balancing (real-time) energy. Procurement of these reserves is of great operational and financial importance in integrating large-scale wind power. We present a probabilistic method to determine net load forecast uncertainty for day-ahead wind and load forecasts. Our analysis uses data from two different electric grids in the U.S. with similar levels of installed wind capacity and large differences in wind and load forecast accuracy due to geographic characteristics. We demonstrate that the day-ahead capacity requirements can be computed based on forecasts of wind and load. For 95% day-ahead reliability, this required capacity ranges from 2,100 MW to 5,700 MW for ERCOT and 1,900 MW to 4,500 MW for MISO (with 10 GW of installed wind capacity), depending on the wind and load forecast values. We also show that each MW of additional wind power capacity in ERCOT must be matched with up to 0.30 MW day-ahead dispatchable generation capacity. For MISO (with its more accurate forecasts), the requirement is 0.13 MW of dispatchable capacity for each MW of additional wind capacity.

 

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