Author : GarimaTiwari, V.K. Katiyar, C. K. Panday and A.K. Katiyar

The day length So is the essential parameter for calculating the solar radiation data. In order to determine the day length, two correlations have been developed by Cooper and Hay, and both correlations have been frequently used by different researchers. The main objective of this study is to test the applicability of these two correlations available for computing the day length value on horizontal surface in India. For this purpose, the developed correlations are employed to estimate the day length values on horizontal surface for nine locations with latitude between 8.50 N to 28.630 N. The performances of these correlations have been checked by it with the measured value. From this study, a close agreement has been observed between the Cooper correlations and the measured data on the duration between sunrise and sunset. Furthermore, in order to evaluate the accuracy of Cooper’s method reported in this paper for computing the day length S0 for India, the developed correlations were then compared on the basis of statistical error indices such as root mean square error (RMSE), mean bias error (MBE), relative percentage error, and t-statistics test. According to the results the Cooper method showed the best estimation of day length values for nine Indian stations.

Keywords: Cooper, Hay, Day length

Article published in International Journal of Current  Engineering  and Technology, Vol.3,No.5(Dec- 2013)