Publication Number: CEC-500-2007-014
Publication Date: March 2007
PIER Program Area: Renewable Energy Research

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Abstract

The State of California intends to expand the use of renewable energy sources for generating electricity. Intermittent resources such as wind energy, when deployed in large quantities, can create significant challenges for utility system operations. The California Energy Commission (Energy Commission) initiated the Intermittency Analysis Project (IAP) to address this issue by studying the impacts of large amounts of new wind generation on the reliability, operation, and economic performance of the California Bulk Power System (CABPS). AWS Truewind, LLC, was engaged by the Energy Commission to simulate the output of existing and future wind projects as an input to grid impact analyses to be performed by GE Consulting. This report describes the methods employed by AWS Truewind for this purpose, presents sample results, and compares the results to data obtained for existing wind projects.

Keywords: forecasts, power curves, wind capacity, wind generation profiles, wind resource areas

Executive Summary

AWS Truewind was engaged by the California Energy Commission (through a subcontract with the University of California, Davis) to provide simulated wind plant output data to support the Intermittency Analysis Project (IAP). AWS TruewindÕs role was to identify and characterize a large number of potential sites for new wind projects, simulate three years of hourly wind generation from both existing and proposed new projects, simulate next-day and four-hour-ahead hourly wind generation forecasts, and produce samples of one-minute output data for representative or significant time periods.

First, AWS Truewind selected 233 sites representing existing and potential new wind projects in 14 wind resource areas. The sites were chosen to maximize mean plant output (derived from the California wind map), after considering various factors such as distance to the existing transmission grid, protected areas, and slope. The sites were allocated to three scenarios: the existing scenario, 2010 scenario, and 2020 scenario.

For each site, AWS Truewind simulated the plant output on an hourly basis for three years from 2002 to 2004. The calculations take into account the evolution of wind turbine technology, including the existing mix of old and new turbines, state-of-the-art turbines under the 2010 scenario, and hypothetical turbines to be developed in the future under the 2020 scenario. AWS Truewind also simulated four-hour-ahead and next-day wind plant forecasts for each site for the same time period, based on experience with wind forecasts in California. Finally, AWS Truewind produced samples of one-minute plant output data for a number of representative and significant periods within the three years.

By comparing the simulated data with actual data from operating wind projects in the state, AWS Truewind confirmed that the simulated data provide a realistic picture of the dynamic and stochastic behavior of wind projects and wind forecasts.