A fast daylight model suitable for embedded controllers

This paper describes a fast daylight model suitable for embedded daylight controllers. For a given room geometry (including position and tilt of venetian blinds, and the sun’s position), the indoor illuminances are modeled as a linear combination of outdoor global and diffuse irradiances. A controller can implement this model by continuously recording simultaneous measurements of illuminance, blinds’ settings and sun positions. Illuminances resulting from arbitrary blinds’ settings are then predicted from a linear fit on that data. This model has been validated against a Radiance model of an office room, and a “toy” controller that uses this model has been shown capable of keeping the horizontal workplane illuminance close to a given setpoint.