measurement and comparison of solar radiation estimation models ...

5.3. 퐇 퐝 as a Function of 퐇ₒ and the Clearness Index (Group 3)
5.3.1. Ulgen and Hepbasli’s Model
Monthly-average diffuse solar radiation was calculated as a function of clearness
index for Ankara, Istanbul and Izmir, Turkey was given as:
5.3.2. Aras et al. Models
H = Hₒ [0.1155 + 0.1958 H
] (5.3.1)
Hₒ
The new model developed was based on the average values predicted by the
twenty models in the literature, as given in the following:
H = Hₒ 0.3276 − 0.7515 H
H
+ 1.9883
Hₒ Hₒ
− 1.8497 H
Hₒ
5.3.3. New Developed Equation C
Using regional data, an equation has been developed that was given by;
(5.3.2)
H = Hₒ [0.514 − 0.619 H
] (5.3.3)
Hₒ
5.4. 퐇 퐝 as a Function of 퐇ₒ and Sunshine Fraction (Group 4)
5.4.1. Ulgen and Hepbasli’s Model
Using regional data for 3 big Cities of Turkey, an equation has been developed
that was given by;
H = Hₒ [0.1677 − 0.0926 S
] (5.4.1)
Sₒ
26