measurement and comparison of solar radiation estimation models ...

CHAPTER 4
ANALYSIS OF GLOBAL RADIATION MODELS
In the literature, many models were developed to estimate the global solar
radiation. In this study 9 models and 3 new developed equations were used to estimate
monthly-average global solar radiation. They were grouped and examined according to
type of the equation that were namely, angular equations (Group 1), linear equations
(Group 2), quadratic equations of second (Group 3) and third order (Group 4).
4.1. Kılıc and Ozturk’s Model
The coefficients a and b were determined as a function of solar declination (δ) ,
latitude of sight (ϕ) and altitude (Z).
where,
H
Hₒ
S
= a + b (4.1)
Sₒ
a = 0.103 + 0.000017푍 + 0.198 cos(휙 − 훿) (4.2)
b = 0.533 + 0.165 cos(휙 − 훿) (4.3)
The model was in the angular type group (Group1) of which were derived by
modifying the original Angstrom-type equation.
4.2. Akinoglu and Ecevit’s Model
of Turkey.
The following equation placed in Group 3 was obtained for the various regions
H = Hₒ [0.145 + 0.845 S
S
− 0.280
Sₒ Sₒ
] (4.4)
20