Presence detection

Other installation-related measures significantly influence the energy requirements:

• reducing or switching off the artificial lighting in the entire room or in parts of it when daylight is sufficient, and

• reducing or switching off the artificial lighting in the room or parts of it when no one is present by using presence or movement detectors.

Hence, a great potential for saving using electronic light management systems unfolds by detecting absence periods, during which artificial light is not required or only needed as background lighting. Correspondingly, during these periods, the light can either be switched off, or the lighting level can be reduced.

Detectable absence periods, however, strongly depend on the utilisation of the room to be illuminated. It is therefore a case-by-case decision whether or not the installation of a presence detection function makes sense and what potential savings can be expected. References for application-specific relative absence periods can be found e.g. in the standard DIN V 18599-10 (see table "Utilisation and types and periods according to DIN V 18599-10").

In switching systems, a further distinction is possible according to reactivation function, specifically between

• fully automatic switching, which switches the lighting off during absence and switches it back on when presence is detected again, and

• semi-automatic switching, which switches the lighting off during absence, but requires manual switching when someone is present again.

The  potential energy savings with semi-automatic switching is ca. 10% higher.

Presence-dependent reactivation functions generally also relates to the preceding daylight-dependent switching-off of lighting, even when persons were present permanently. Daylight-dependent reactivation without presence detection would equate to a twilight switch, which is not as suitable for energy saving in comparison.