Computations of diffuse fraction of global irradiance: Part 1 - Analytical modelling

Comparing the three approaches, it was shown that introducing solar altitude into the correlations improved the accuracy of the correlations, while the separation of the dataset into smaller subgroups, according to their solar altitude angle, revealed that higher accuracies can be achieved for higher elevation angles. Overall, correlations higher than 0.85, RMSE lower than 25% and MBE lower than 3% were achieved for all tested scenarios.