Integration with Daylighting Controls

Electric lighting systems can be switched or dimmed in proportion to available daylight to reduce annual energy use and peak electric demand in sidelit perimeter zones or skylit core zones. Historically, these daylighting control systems have had a poor reputation for responsiveness and reliability, and to this day, this reputation continues. One critical challenge is how to obtain proper proportional dimming using a ceiling-mounted photosensor when the relationship between the photosensor and the desired work plane illuminance is non-linear. LBNL researchers have characterized this behavior using field tests and developed modeling tools that enable more comprehensive detailed studies to be conducted.

Maintaining proper light dimming levels (yellow shaded area) as the distribution of daylight (blue) varies over the course of the day requires proper positioning of the photosensor, the correct algorithms, and careful commissioning and tuning.  This LED-dimmable system, installed in LBNL's FLEXLAB^®, maintains a minimum total light level of 300 lux across the 30 foot deep space in combination with an automated shade.  Image: Andrew McNeil