Evaluation of the electricity savings resulting from a control system for artificial lights based on the available daylight

Abstract

Natural lighting in building environments is an important aspect for the occupants' mental and physical health. Furthermore, the proper exploitation of this resource can bring energy benefits related to the reduced use of artificial lighting. This work provides some estimates of the energy that can be saved by using a lighting system that recognises indoor illuminance. In particular, it is able to manage the switching on of lights according to the daylight detected in the room. The savings from this solution depend on the size and orientation of the window. The analysis is conducted on an office by means of simulations using the INLUX-DBR code. The locations have an influence on the luminance characteristics of the sky. The analysis is conducted with reference to one city in the south and one in the north of Italy (Cosenza and Milan). The energy saving is almost independent of latitude and therefore representative of the Italian territory. it is highly variable according to exposure, being the highest for southern exposure (97% with the window size equal to 36% of the floor area) and between 26% and 48% (as a function of window size) for northern exposure.