Computerised control of artificial light for maximum use of daylight

Controlling artificial lights to act solely as a supplement to available daylighting requires continuous knowledge of natural lighting levels within a space. Although this information is readily obtained by measurement while lights are extinguished, once illuminated the determination of the underlying natural light level is not so straightforward. This paper describes a self-commissioning, adaptive algorithm capable of the real-time prediction of natural light levels at chosen points within a room using external measurements of vertical-plane illuminance. The algorithm is compact and efficient and readily implemented on a microprocessor. As such, it is suggested that it could form the basis of a robust and practical lighting controller. Results obtained with a prototype are presented.