Measurement and modelling of global erythemal irradiance on inclined planes

The aim of this paper is the characterization of global erythemal irradiance (UVER) on inclined planes. Different geometric models have been studied, both isotropic and anisotropic, which have been used to estimate the global UVER on inclined planes at 40o in North, South, East and West orientations. This has led to the hypothesis that these models, all of them originally developed to obtain diffuse irradiance in solar spectrum, can be applied in a much more limited range of UVER. The results have been compared with experimental data using the following statistical parameters: mean bias deviation, mean absolute deviation and root mean square deviation. The global UVER was analyzed for all sky conditions and for cloudless sky conditions, and no significant differences were found between the different models in both cases. Overall, the best performing model is Gueymard’s anisotropic model, even though it improves the Isotropic model in less than 2%.