Wind Energy potential Estimation Using Weibull and Rayleigh Distribution Models and surface measured data at Debre Birehan, Ethiopia.

Abstract

There is a vital need for clean and accessible energy in the Ethiopia, particularly, Debre Berhan sites. Ethiopia possesses a potential of renewable energy, such as wind energy, solar energy and, geothermal energies. Wind energy is one of the fastest growing renewable energy technologies of electricity generation in the world. In this study, the wind speed that measured at a height of 2.5 m was used to calculate the monthly mean wind speed and monthly mean wind power density of the sites at heights of 10.0 m and 50.0 m numerically. The energy pattern method was used to obtain wind Weibull distribution parameters. The monthly average values of the Weibull shape parameter and Weibull scale parameters are varies from 3.52 to 4.07 and 1.97 m/s to 3.79 m/s respectively at height of 10.0 m. On the other hand, the monthly average values of Weibull shape parameter and Weibull scale parameter are varies from 4.29 to 4.49 and 4.05 m/s to 5.72 m/s respectively for a height of 50.0 m. Weibull distribution and Rayleigh distribution models were used for assessment of wind power density of the study sites. The monthly mean wind power density was observed to be highest in the month of February (26.68 W/m 2 ) and lowest in the month of August (3.77 W/m 2 ) and with the corresponding mean wind speeds were 3.44 m/s and 1.79 m/s respectively at a height of 10.0 m. In addition, at height of 50.0 m the highest and lowest the monthly mean wind power densities was also occurred in the month of February (111.60 W/m 2 ) and in the month of August (39.33 W/m 2 ) with corresponding mean wind speeds were 5.59 m/s and 3.95 m/s. The results reveal that the Weibull distribution model is more accurate and efficient model for determining wind power density of Debre Berhan, Ethiopia, than Rayleigh distribution model according to statistical performance error at heights of 10.0 m and 50.0 m: power density error(PDE), correlation coefficient(R 2 ) and root mean square error(RMSE) (for Rayleigh: PDE 10 = 0.68, R 2 10 = -1.1 and RMSE 10 =11.08, for Weibull: PDE 10 = 0.17 , R 2 10 = 0.86 and RMSE 10 = 2.82) as well as at height of 50.0 m: (for Rayleigh: PDE 50 = 0.38, R 2 50 = -0.7 and RMSE 50 = 30.8, for Weibull: PDE 50 = -0.06 , R 2 50 = 0.96 and RMSE 50 = 4.63 ). Therefore, the wind power density of Debre Berhan, Ethiopia was classified under class 1 according to the results of the study. This paper provides information of wind characteristics and wind power potential of the sites, which helps in selecting suitable wind turbines to fulfill the energy needs especially in remote and rural areas.