A study of illuminance data generation using the luminous efficacy approach: A case study of Hong Kong

In Hong Kong, the building sector accounts for 90% of the total electrical energy consumption and 13% of this is used on achieving visual comfort through artificial lighting. An alternative approach to this can be the use of daylighting, which brings about significant savings in lighting costs. In view of this, illuminance data is required for obtaining efficient design solutions. However, the generation of illuminance data poses a problem because of the limited number of measuring stations. Thus, an alternative approach, such as deriving illuminance data through luminous efficacy models, is highly desired. Furthermore, the whole spectrum of skies in the world was classified into a range of 15 standard skies by the International Commission on Illumination (CIE) in 2003. This study, therefore, presents the work of modelled global, diffuse and direct luminous efficacy under the 15 CIE skies. Sky luminance distribution of June 2019 to February 2020 was used for CIE Sky classification. It went further to propose a vertical luminous efficacy model needed for the prediction of vertical illuminance data. Results from prediction and other statistical analysis are presented in this study.