measurement and comparison of solar radiation estimation models ...

CHAPTER 7
CONCLUSION
In this thesis, firstly solar radiation models for predicting the average daily and
hourly global and diffuse radiations on horizontal surface are reviewed. Then data of
global and diffuse solar radiations are analyzed from February, 2005 to May, 2007 and
from February, 2004 to December, 2005 on the campus area of IZTECH,
respectively. Empirical correlations are developed to estimate the monthly-average
daily global and diffuse radiations on a horizontal surface for Izmir, Turkey. 3 new
models are developed for estimating the monthly-average daily global solar radiation,
whereas 4 new models are developed for estimating the monthly-average daily diffuse
solar radiation. The developed models are compared with the models form the literature
on the basis of statistical methods namely, RMSE, MBE, T-stat and “e”.
It is concluded that, the third-order polynomial equation gave the closest results
to the measured data for global solar radiation. The developed model given by Eq.
(4.14) is found to be the most accurate model for all test methods. For diffuse part, it is
concluded that the new models developed during this study are found to be reasonably
good for Izmir, Turkey comparing to the previous studies. The eq. (5.4.3) is found to
have the best results for MBE, t-stat and “e” methods. In RMSE the eq. (5.2.2) gave the
closest result according to the measured data.
It can be deduced from the results that the new developed correlations are found
to be reasonably reliable for estimating or predicting the daily global and diffuse
radiations for Izmir, Turkey and, possibly, elsewhere with similar climatic condition.
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