A. S. Nafeya,*, M. A. Mohamadb, M. A. Sharafa
a Dept. of Engineering Science, Faculty of Petroleum and Mining Engineering, Suez Canal Univ,
b Energy Department, National Research Center, Cairo-Egypt.
It is important for many solar energy systems to estimate and predict the instant or daily
mean direct and diffuse irradiation on horizontal or tilted surfaces at any known location.
One of the targets of the present article is to perform a simple statistical evaluation of 7
model results. These models are employed to estimate and predict the solar radiation on
different surfaces and locations. They are fed with local measured data. The results of the
evaluation would help to recommend one or more models for the considered region
(latitude: 29o N; longitude: 33o E). Statistical indicators, such as Mean Bias Error (MBE),Root Mean Square Error (RMSE) and Mean Relative Percentage Error (MPE) are used in
this comparison. The considered models are ASHREA, ATWATER&BALL, BIRD,
DAVIES&HAY, HOYT, LACIS&HANSEN and SPECTRAL2. The obtained results
have shown that, BIRD and DAVIES&HAY models could be recommended for
estimating both the instantaneous hourly direct and diffuse radiation on horizontal
surfaces for the considered region. And, ASHREA, SPECTRAL2 and
ATWATER&BALL are occupied the second rank. Models such as HOYT and
LACIS&HANSEN would not recommend for the considered region. Also, a new
correlation is developed by which the total insolation could be predicted.