Lighting- control systems - Intelligent Buildings and Building Automation - page 221

of the spaces is predictable according to a space-booking system, a time-based
strategy can be considered and the lighting of the spaces can be scheduled
automatically. Monitoring the occupancy of the spaces is another typical
means for lighting control nowadays. Typical occupancy-monitoring tech-
niques are the use of occupancy detectors. If access control of the spaces is
available and integrated with the lighting-control system, the lighting-control
system can obtain the information on occupation of the spaces from the
access-control system.
Providing the right amount of lighting may be achieved simply by proper
switching of lights in the zones. But dimming control is a much more precise
means of controlling a lighting system to provide the right amount of lighting
for the functional need of the space. The maximum use of daylight reduces
the need for artificial lighting and therefore energy consumption. Shading
control as a special function of the lighting-control system enables the effec-
tive use of daylight and provides visual comfort. A few basic technologies
and options for energy-effective lighting control are discussed in the follow-
ing sections.
10.5.1 Switching and dimming controls
Switching and dimming controls are the two basic means of controlling light
outputs for the purposes of energy management and visual needs. The main
benefits of dimming control are better occupant satisfaction and comfort
and flexibility. The main advantage of switching control is that it is relatively
inexpensive and simpler for commissioning. The main advantages of dim-
ming control is that the light output can be set at any level and greater user
acceptance can be achieved due to smooth transitions between light levels.
The main disadvantage of switching control is lower user acceptance in
occupied spaces with stationary tasks due to abrupt and noticeable changes
in light level. The main disadvantages of dimming control are higher instal-
lation costs and more complications in commissioning.
10.5.2 Scheduled and sensor-based controls
If the occupation of spaces is fixed or predictable, the lighting-control system
can be programmed to switch the lighting on or off in spaces, including the
lighting levels, according to a schedule. These schedules can be fixed, which
may be different for different days in the week or on working days and
holidays. The operators may update or set these schedules according to the
actual booking of the spaces. In the case where the lighting-control system
is integrated with the space-booking system or access-control system, these
schedules can be set and updated automatically according to the actual book-
ing or use of the spaces.
Nowadays, sensor-based control is very widely used to control lighting
systems automatically, which is based on monitoring the occupancy in the