Lighting Energy Reduction by Optimizing Daylight while Maintaining Cooling Load in Tropical Educational Building, Depok, Indonesia

This study aims to reduce the lighting energy consumption in educational buildings while avoiding an increase in cooling load. The Faculty of Engineering building in Universitas Indonesia, Depok, West Java, Indonesia is used as a case study. Daylight optimization can have an impact on lighting energy, which is the largest energy consumer in educational buildings. However, given Indonesia’s tropical climate, daylight leading to heat gain is a concern. Current passive design interventions for controlling daylight and heat gain include light shelves, clerestories, and glazing materials. Daylighting performance is simulated using DIALux software. Results of each intervention are analyzed quantitatively and qualitatively by theories and parameters, namely illuminance level, light uniformity, and overall thermal transfer value (OTTV). Light shelves result in increased uniformity and lower OTTV. Clerestories result in increased average illuminance but higher OTTV.  Active intervention with a dimming and grouping system is applied after daylight increases. The combination of passive design interventions and active dimming of electric lights reduces lighting energy with the same OTTV as existing. This study recommends the use of passive and active daylighting strategies considering their effect on the cooling load of buildings.