Research Abstracts 1991-1992: Report No. 92-03

Walker, S.N. and P. L. Barbour, "Pacific Northwest Wind/Energy Variability," OSU Wind Research Cooperative, WRC Report No. 92-03, June 30, 1992, 61 pp., $15.25

In this project, wind records from three long term wind monitoring sites established by Bonneville Power Administration (BPA) and seven National Weather Service (NWS) upper air sites were examined to gain an understanding of wind and energy variability over the Pacific Northwest.  Variation over several time scales were examined to interpret the effects of long term, inter annual, month-to-month and diurnal changes in the wind speed and energy characteristics.  Estimates of energy production were computed and examined to bother characterize energy variability and to estimate the firm or minimum reliable energy available from each of the sites.

Results confirmed earlier findings that indicate that the mean annual wind speeds recorded after 1976 were on average below the wind speeds observed before 1976. This behavior was observed at three levels of all seven NWS sites examined. This implies that the region's wind resource potential may be underestimated since most of the long term wind monitoring sites in the Northwest were activated after 1976. An examination of the monthly mean wind speeds from the three BPA sites along with the wind speed ranges, the departures from the means and the diurnal characteristics illustrate the differences that exist in a region as diverse as the Northwest. An analysis of wind persistence was also performed that shows that the length of time that the wind speed is observed in a particular wind speed class is important to the energy potential of a site.

An analysis of energy capacity factors was performed and included a comparison of capacity factors calculated using both data and Weibul fits. The two methods showed remarkable similarity. The Weibul fits are used to construct capacity factor probability curves that can be used to predict the probability of various capacity factors. In addition, an analysis has been performed to estimate the firm energy available from each of the three BPA sites. The results show that the largest firm energy factor would be at Browning during the months of January and December reaching a value of slightly over 0.4. This analysis showed that the firm energy available at both Goodnoe Hills and Cape Blanco was less than this and varied more from year to year.