  This paper presents initial values of global and diffuse luminous efficacy at
Saint-Pierre (Reunion Island). Firstly, data used were measured for a period of
6 months, from February to June 2008. During this period, all defined day-types
have been studied (clear, cloudy and intermediate). Generally, the
meteorological database of Reunion does not contain information for illuminance
values. On the other hand, the local meteorological center has a 60-years-old
database for solar irradiance (W.m-2). So it is important to determine Luminous
Efficacy in order to find illuminance from solar irradiance (or luminance from
solar radiance). The measured data were analyzed, and empirical constant models
were developed and presented in this paper in order to determine luminous
efficacy under different sky conditions. A comparison between these empirical
constants (models) and existing models has been made. The method used to define
sky conditions (overcast, intermediate and clear) and day-types
characterization as well as classification will be presented in this work.
