A study of 15 sky luminance patterns against Hong Kong data

A good knowledge of the sky luminance distribution is essential for efficient daylighting designs and developments. This paper studies a set of 15 standard skies established by Kittler, Perez and Darula using the measured sky luminance data from subtropical Hong Kong. A statistical analysis of the results has shown that the standard sky set is adequate to cover the various sky conditions. A reduction of the standard set to five skies is sufficient to model the luminance distributions. The ratio of zenith luminance to horizontal diffuse illuminance (L_z/D_v) which can be used to define homogeneous sky standards was analysed based on these five selected skies. It has been shown that the trend of L_z/D_v ratios under different sky types followed the ranges described by Kittler et al.