Hourly solar radiation on inclined surfaces

The present study investigates the variation of hourly global solar radiation for inclined surfaces. We have measured the data for horizontal surface and different south-facing (γ = 0°) inclined surfaces at Lucknow (Latitude 26.75°, Longitude 80.85°), Uttar Pradesh, India. These inclined surfaces data have been compared with the estimated tilted results from measured horizontal data using circumsolar model, the isotropic model suggested by Liu and Jordan [1], and the two anisotropic models by Klucher [3] and Hay [2]. Statistical error tests are also performed for the critical analysis of the models. The comparative study of the model validates the performance of isotropic model for all inclined surfaces.