Energy-efficient lighting: harnessing daylight
The greatest saving effects are achieved by lighting management systems that harness incident daylight. With them, artificial lighting is activated or slowly and steplessly raised only when the daylight available is not sufficient – and it can be deactivated completely when there is enough natural brightness around.
Ideal conditions for harnessing daylight are offered by skylights. They direct a great deal more light into a room than windows in walls. This is why domelights and rooflights are often incorporated into new buildings, sometimes even in combination. Professional lighting design takes account of thermal insulation and glare suppression.
Keeping the lighting level constant
Daylight-dependent regulation systems are designed to maintain a constant level of lighting throughout the room by ensuring that the sum of daylight and regulated artificial lighting components remains the same. The illuminance required at a work surface, for example, is kept more or less steady by raising or lowering the artificial lighting in response to changes in incident daylight. So when conditions outside are bright, the artificial lighting is lowered, and when it is dark outside the artificial lighting is raised.
Luminaires mounted well away from the window wall need to provide more artificial lighting than those installed in the immediate vicinity of a window. For visual tasks that require more light, the system should also be designed to allow the specified lighting level to be varied from a manual control unit.
Automated regulation
To ensure good quality lighting tailored to applications, it makes sense to automate the interplay of daylight and artificial lighting. The lighting level
- light sensors on individual workplace luminaires
- light sensors in the room
- light sensors outdoors.
Where motion detectors are integrated in the lighting management system, presence control is possible. Here, lighting is instantly activated when a person enters the room and deactivated a few moments after the room is vacated.
Different configurations
Daylight-dependent regulation systems are realised in various configurations: options include
- simple regulation of individual luminaires
- regulation of groups of luminaires in a system
- integration of all lighting in the building management system.
Components of these lighting regulation systems include dimmable electronic ballasts (EBs) and signal amplifiers with light sensors. Each luminaire or group of luminaires is assigned a sensor, which registers the amount of light present in the room or outdoor area and regulates the artificial lighting accordingly to raise it to the pre-defined level.
