ESTIMATING GLOBAL SOLAR RADIATION IN BALE ROBE TOWN USING ANGSTROM-PRESCOTT AND HARGAREAVES-SAMANI MODELS.

Abstract

In this project, the daily sunshine duration and daily maximum and minimum temperature were used to estimate seasonal mean values of global solar radiation and their percentage difference between the two models in Bale Robe town. The study covered a period of 2010 to 2014. The data analyzed and interpreted using Microsoft Excel. AP and HS models were used to estimate global solar radiation of seasons as well as the percentage between the two models at a location. Estimation of global solar radiation from sunshine duration and air temperature were an important alternative in the absence of direct measurement. However, due to the dynamic nature of atmosphere, accurate estimation of daily solar radiation has been a challenging task. The study conveyed that the value of global solar radiation in summer, autumn, winter and spring seasons were 18.80MJm-2 day-1 , 22.76MJm-2 day-1 , 26.64MJm-2 day-1 and 23.94MJm-2 day-1 using Angstrom-Prescott model respectively. On the other hand, the value of global solar radiation found to be in summer, autumn, winter and spring seasons were 20.60MJm-2 day-1 , 24.42MJm-2 day-1 , 28.60MJm-1 day-1 and 26.12MJm-2 day-1 using Hargreaves-Samani model respectively. The results of the study showed that, there were peak values of global solar radiation estimated in winter and spring and low value of global solar radiation has been observed in summer and autumn in both models. The percentage difference between the two models showed that AP and HS models were favorable models that predict seasonal value of global solar radiation in Bale Robe town with the absence of instrumental installations which are important to measure GSR directly.