measurement and comparison of solar radiation estimation models ...

According to Table 9 the maximum value of the monthly-average daily global
radiation for the average of 2005, 2006 and 2007 was recorded to be 7,702.66W/m² in
June. The minimum value of H was 1,822.15W/m² observed during December. The
highest value was recorded between 13 -14 pm. The graph for the average of the 3 years
was shown in Figure 9. As for each month, the monthly-average hourly global solar
radiation tables were attached in Appendix A.
The models used to estimate the monthly-average daily global radiation on a
horizontal surface (H) were categorized in 4 groups, as seen from Eq. (4.1) to Eq.
(4.14). These groups consisted of the relations gained from Angstrom-type equations.
The types of the models and the calculated results were illustrated below in Table 10.
The regression coefficients “a and b” of the Angstrom-type correlation for the monthly
average daily global solar radiation of Eq. (4.2) and Eq. (4.3) were determined as given
in Table 11.
The comparison of solar radiation models can be seen in Figure 10. The results
are close to each other. To analyze the comparison in detail, statistical equations have
been referred. Values of MBE, RMSE and t-stat of selected models were shown in
Table 12. The error percentages of the models were also added in the table.
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