The principal benefits of lighting controls are:
Movement sensors are used to turn off lighting automatically in an area when nobody is there. In some areas, including those with no natural light at all, movement sensors are also used to turn lights on automatically when somebody enters the area.
Some people believe that to be truly energy conscious a lighting control system must operate automatically and it is the users that waste electricity. This is not always the case; fully automatic regimes may use more energy than those relying on the staff to use local switches.
Light level sensors reduce energy consumption by reducing artificial light when there is adequate and suitable natural light. For street lighting and other external lighting, simple ON/OFF operation at dusk and dawn is widely used. In contrast, successful daylight harvesting schemes for buildings are more complex and must operate in a way that is unobtrusive to building occupants. They typically reduce artificial light levels slowly in response to increasing natural light levels. For best results, dimmable light fittings should be fitted. Both fluorescent and LED lighting can be dimmed; dimming is also available for other light sources, such as High Intensity Discharge lamps.
Most artificial lighting sources lose some of their brightness over time. Also, when designing a regular grid of luminaires to light a space, an aesthetically pleasing arrangement may not be able to produce exactly the required light level with each luminaire full on. Design specifications therefore refer to the required lighting levels as a ‘maintained level’. The ‘as new’ capability of the installed lighting will be substantially above the maintained level, so that the scheme will be over-lit on day one if it is not controlled. A control system that uses dimming control to keep illuminance down to the maintained level can save between 10% and 20% of the lighting electricity over the maintenance cycle of cleaning and re-lamping, with larger peak savings being achieved on day one.
In some schemes, such as shopping malls, time control is an effective way to reduce energy consumption. Time control may use fixed times, such as the opening hours of a mall, or astronomical times, such as sunrise and sunset.
Time controls may also be used to vary the light level to suit different daily tasks. A factory area may require bright lighting when machinery is being operated but only much lower levels when the area is occupied by cleaners or security staff.
Time control may also be used to affect the control regime. For example a control system may be set up so that users must switch lights on manually during daylight hours but they come on automatically in response to movement during hours of darkness, or vice versa.