Correlation procedure in the computation of solar irradiation

摘要

Analysis and modelling are carried out on the reported experimental data of global radiation and sunshine duration for 11 widely spread locations in India. The correlations thus developed are used to find the effect of multiple reflection of the radiation between the ground and the atmosphere and also the performance characteristics of the sunshine recorder on the accuracy of the estimated global insolation. Multiple linear regression analyses are also carried out on these data, after including the latitude and the elevation parameters, and more correlations are reported. A study of all these correlations shows that an equation of the form G-bar/G-bar_0 = a + b(S-bar/S-bar_0) + c cosφ + dh + eh~2 is most accurate for computing the monthly mean daily global radiation on a horizontal surface, suggesting that a multiple linear correlation with sunshine fraction, elevation and the latitude parameters as independent variables is most suitable for estimation purposes. More complicated correlations obtained by including the effects of multiple reflection of the radiation and the performance characteristics of the sunshine recorder do not provide any additional advantage in improving the accuracy of estimation.