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The air temperature and sunshine duration data were obtained from Kombolcha Meteorological Agency to predict daily global solar radiation at Lalibela, Ethiopia. The mean daily clearness index and mean daily global solar radiation was calculated based on sunshine and air temperature model for the study sites. The validation of the models for predicting mean daily global solar radiation was done using statistical tests such as: MBE, RMSE, MPE and R. The result of these statistical tests for temperature based model: (MBEtem=. -0.50, RMSEtem=0.67, MPEtem=-2.9 and Rtem=0.06) and for sunshine based model: (MBEsun=. 0.08, RMSEsun= 0.49, MPEsun= 1.50 and Rsun= 0.05). From overall, it was concluded that the better value of the mean daily global solar radiation was observed with sunshine based model (Angstrom-Prescott) than the temperature based model (Hargreaves and Semani) in almost all of the days of the study and be applied to locations with comparable weather condition with Lalibela sites. The maximum average daily global solar radiation that predicted from sunshine hours was 5.86 KWh/m2 and the maximum average daily global solar radiation that predicted from air temperature was 5.28 KWh/m2 over a period of 3 years (2014-2016). The result of this study was between the minimum and maximum value of [14] and therefore, the region has high potential for solar energy application., Applied Journal of Environmental Engineering Science, Vol 6, No 3 (2020): Vol6(3)2020

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/m2 ) and lowest in the month of August (3.77 W/m2 ) 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/m2) and in the month of August (39.33 W/m2) 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(R2) and root mean square error(RMSE) (for Rayleigh: PDE10 = 0.68, R210 = -1.1 and RMSE10 =11.08, for Weibull: PDE10 = 0.17 , R210 = 0.86 and RMSE10 = 2.82) as well as at height of 50.0 m: (for Rayleigh: PDE50 = 0.38, R250 = -0.7 and RMSE50 = 30.8, for Weibull: PDE50 = -0.06 , R250 = 0.96 and RMSE50 = 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., Applied Journal of Environmental Engineering Science, Vol 6, No 3 (2020): Vol6(3)2020