Evaluation of slope irradiance and illuminance models against measured Hong Kong data

This paper presents the evaluation of three inclined irradiance and illuminance anisotropic models (Klucher, Hay and Perez) for Hong Kong using two-year (1996–1997) measured data. A statistical analysis of the three models has shown that predictions for solar irradiance tend to be more accurate than daylight illuminance. All three models produce large errors for north-facing surfaces. Predictions for south-facing surfaces show reasonably good agreement with measured data, indicating good estimations of anisotropic diffuse component at sunlit surfaces. In general, Perez’s model shows the best predictions for vertical solar irradiance and daylight illuminance followed by, Hay’s, then Klucher’s models.