Performance modeling of daylight integrated photosensor-controlled lighting systems

Some building energy codes now require the incorporation of daylight into buildings and automatic photosensor-controlled switching or dimming of the electric lighting system in areas that receive daylight. This paper describes enhancements to the open-source Daysim daylight analysis software that permit users to model a photosensor control system as it will perform in a real space, considering the directional sensitivity of the photosensor , its mounting position, the space and daylight aperture geometry, window shading configuration; the electric lighting equipment and control zones; exterior obstructions; and site weather conditions. System output includes assessment of the daylight distribution in a space throughout the year, the photosensor's ability to properly track the daylight and modify electric lighting system output, and the energy savings provided by the modeled control system. The application of daylight coefficients permits annual simulations to be conducted efficiently using hourly or finer weather data time increments.