SOLAR-RADIATION ON INCLINED SURFACES

Measured solar radiation data for one location in Lesotho is used to test the applicability of two theoretical models for computing total solar radiation on inclined surfaces. The models selected for discussion are the isotropic model suggested by Liu and Jordan and the anisotropic model by Hay. The models are compared and tested for their applicability to locations in Lesotho and Southern Africa in general, on the basis of statistical error tests. A comparative study of the models shows that both the models are equally accurate for stations in Lesotho. The isotropic model is then used to estimate total radiation for five other locations on north-facing surfaces of various tilt angles, and the results are presented. © 1990.