Research Abstracts 1992-1993: Report No. 93-02

Barbour, P.L. and S. N. Walker, "Year-to-Year Variations of Wind Speed and Wind Turbine Output for Sites in the Pacific Northwest," OSU Wind Research Cooperative, WRC Report No. 93-02, June 30,1993, 31 pp., $7.75

Wind speed records from 10 potential wind sites in the Pacific Northwest (PNW) are examined using the methods of Justus et al. (1978) to characterize the typical magnitude of variability in both wind speed and energy production. This variability is used to determine the typical sampling time required to define the mean characteristics to within various tolerances. The results are compared to those found by Justus et al. (1978). Results indicate that the sites used are generally more variable from year-to-year and thus require slightly longer sampling periods to define the means to within tolerances similar to those identified by Justus et al. (1987) after examining wind data from several National Weather Service (NWS) sites. A majority of the PNW sites examined fall into the moderate to high variability categories. Estimation of the annual mean to within +/-10% of the long term mean at a 90% confidence level requires between one and two years of data for the moderately variable case and up to three years for the high variability case. Year-to-year variations of monthly means indicate that sites in the PNW have much higher variability than those examined by Justus et al. (1978) and may require between three to six years of sampling for the moderate variability cases and up to eight years for the high variability cases to define a monthly mean to within +/-15% of the true mean at the 90% confidence level. Values for the year-to-year variation of energy capacity factor are also presented.