Predicting lighting energy use under daylight linked lighting controls

For daylight to make a real contribution to energy efficiency, appropriate control of electric lighting is essential. This paper outlines methods to predict electric lighting use for various different types of control, given internal daylight illuminances. Two different kinds of calculation are considered. Annual lighting use can be determined from yearly daylight data, usually in the form of a cumulative distribution. More sophisticated computer programs use hourly daylight data to give a continuous profile of lighting use and the consequent energy flows and environmental conditions within a building. For both types of application, appropriate algorithms are given to quantify the savings from various types of photoelectric and manual controls.