Incorporating Daylight in buildings: a prediction approach using low- cost sky-luminance measurement device

Building design optimization needs information of dynamic angular sky-luminance distribution, through measurement or models, for simulating indoor illuminance. Most simulation packages use standard sky-types of the established Commission International de l'Eclairage (CIE) sky-models for calculating sky-luminance data. However, owing to dynamic conditions of sky, there is a need for more realistic sky-data incorporating solar contribution, as compared to standard overcast skies. This paper presents a low-cost device for measuring angular sky-luminance distribution, and compares the measured datasets with established CIE standard skies. Proposed calibrated Light Dependent Resistor based device is used to measure the sky-luminance at various angles over time, and statistical analysis is performed on the measured datasets to determine the frequency of occurrence of various sky-types. Indoor predictions based on various datasets are calculated to assess accuracy of closest determined sky-type, and the applicability of the device for predicting indoor illuminance is demonstrated