Variance Analysis of Wind Characteristics for Energy Conversion

Abstract

Variance analysis of hourly wind data is utilized to assist in wind characteristic assessment for direct energy conversion systems. Feasibility of large-scale wind energy utilization, as well as sitting, sizing and operating policy, depend on the variability of the wind. Several Midwestern sites are used to illustrate a temporal study of variance sources that leads to the evaluation of equivalent independent hours. For the sites considered these vary from two to three per day. This information is utilized to determine duration of survey requirements for stated confidence levels and desired accuracy. Reasonably reliable and accurate estimates of the mean seasonal wind can be obtained in one or two years for the sites analyzed. Autocorrelation and cross-correlation analysis confirms the existence of significant correlation in the wind at a single site for a period of 8–12 h and between sites for similar time lags and separations up to 100 km or more. Meaningful prediction of variation from the mean appears possible in these cases. The diurnal cycle effect is seen to depend significantly on season and elevation.