DefinePK

Abstract

Wind speeds recorded at regular intervals of time for a particular wind site correspond to intermittent source of energy. Reliable estimate of wind potential for the site requires fitting of the recorded data to a continuous distribution function. Weibull function with two parameters is widely used mathematical function for fitting wind speed data for the estimation of wind energy. In the present study, analysis on the data registered in steps of 1 minute interval for the years of 2003 and 2004 for Nooriabad, Sindh were carried out. Recorded data set contains wind speeds and wind directions at 30 m and 100 m mast heights, respectively. Weibull function is applied to the measured monthly and yearly data sets and Weibull shape scale parameters are computed with the help of six numerical methods. Accuracy of these numerical methods and their suitability are assessed by employing two test statistics, namely, R2 and RMSE. The R2 test statistics estimated for all methods gives a value of 0.99 and RMSE gave a lowest value (0.07) for the Method of Least Squares Error (MLE), suggesting MLE to be the most suitable method for obtaining Weibull parameters. Monthly and yearly probability density function (pdf), cumulative distribution function (cdf) and power densities are determined using Weibull distribution. Comparison between Weibull power density values and estimated power densities of raw data show close agreement. As an example, power density of raw data for the month of June is 1935.16 W/m2and is in close agreement with Weibull power density for the same month, which is 1972.92 W/m2.