Lighting- control systems - Intelligent Buildings and Building Automation - page 220

may be connected to the automation LAN directly. A dimmer may handle
a number of light loads. A sensor or other control device may be a smart
device which can be connected to the automation LAN directly. It may be
linked to a controller. Many different devices can be selected and many dif-
ferent system configurations can be designed depending on the availability
of devices from manufacturers. If a large system needs to be formed, more
subsystems should be integrated via the same automation LAN or other
(higher speed) automation LAN. The integration of the lighting-control sys-
tem could be carried out with other BA systems at the subnet level directly
or at the higher level depending on the compatibility of the networks and
the need for interoperation.
10.5 Strategies for energy management and lighting control
The control objective of lighting systems in spaces for living, working or
other generic purposes is to provide the optimal visual environment for the
visual comfort and productivity of occupants with a minimum of energy
consumption. The typical approaches to achieve such an objective may be
summarized as follows:
￿ providing lighting where lighting is needed;
￿ providing lighting when lighting is needed;
￿ providing the right amount of lighting;
￿ making use of daylight as much as possible.
The most effective means of saving energy in buildings is to turn off the
systems where and when they are not needed. The run-up time for many
general-purpose lamps is either negligible (such as incandescent lamp) or
very short (such as fluorescent lamps). That makes it practical to turn off
the lighting systems in a space when it is not occupied as it can provide the
lighting services almost immediately after it is switched on when the space
is occupied.
To control the lighting system providing the service only where lighting is
needed, proper zoning or grouping of lighting fixtures is essential. The zon-
ing of lighting fixtures is typically established according to the functions of
the spaces, lighting schedules, architectural layout, availability of daylight,
and so on. There is a need to compromise on sizing the control zones of the
lighting systems correctly due to the fact that smaller control zones generally
result in greater control resolution, greater energy-saving potential as well as
greater opportunity to enable the lighting system to meet the lighting needs.
But smaller control zones generally will make the lighting-control system
more complicated in terms of operation and control, and more expensive in
terms of initial installation and maintenance.
Providing light only when it is needed can be achieved typically by includ-
ing scheduled control and occupancy-based control. For instance, if the use