Performance Assessment Of Hargreaves Model In Estimating Global Solar Radiation In Sokoto, Nigeria.

Abstract

BACKGROUND OF THE STUDYIn many applications of solar energy, the most important parameters that are often needed are the average global solar irradiation and its components. Unfortunately, the measurements of these parameters are done only at a few places. For this reason there have been attempts at estimating them from theoretical models. Latha et al., mentioned that these equations range from the most complex energy balance equations requiring detailed climatological data to simpler equations requiring limited data such as Hargreaves-Samani model [1][2]. Hargreaves-Samani's is widely used because it requires only input variable of minimum and maximum air temperatures and many researchers accepted that its GSR estimates correlate well with observed values in many locations [3].The extraterrestrial solar radiation is the rate at which solar energy arrives on a horizontal surface at the top of the atmosphere. It varies according to the latitude of the location, the distance of the Earth from the Sun, and the time of the year. On any particular day, it varies from zero at sunrise to a maximum at noon and back zero at sunset [4].Despite the large range of applications demanding solar radiation data, direct measurements of solar energy are not available. Thus use of numerical techniques becomes essential. With such indirect techniques, other meteorological parameters are mathematically exploited in order to estimate the amount of solar radiation reaching the earth surface.The estimation of daily global solar radiation has been reviewed in most of the researches based on the duration of sunshine, identifying the best model and determining different coefficients for several locations. There are several types of models (linear,

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