Comparative study of four methods for estimating Weibull parameters for Halabja, Iraq

The Weibull distribution is the standard function used by the wind energy community to model the wind speed frequency distribution. In this study, four methods are presented for estimating Weibull parameters (Shape and Scale), namely, Maximum likelihood method (MLM), Rank regression method (RRM), Mean-standard deviation method (MSD), and Power density method (PDM). To compare the methods, a period of 4 years (2001 - 2004) of monthly time series data of Halabja city was considered. Two distinct analytical methods are studied to determine the parameter estimation accuracy of these methods; coefficient of determination and root mean square error (RMSE) are used as measurement tools. The Rank regression and MSDs are recommended to estimate the shape parameter; also the Rank regression is recommended for use with our time series wind data to estimate the scale parameter.   Key words: Weibull distribution, parameter estimation, energy pattern factor, accuracy.