Control System

Proper control using appropriate equipment can significantly reduce the energy consumption of lighting systems. For example, we can control the on/off or/and light level of the lamps at specific time period and different situations. This section describes the energy efficient installations related to lighting control system.

Digital and addressable lighting interface (DALI)
Digital and addressable lighting interface (DALI) is a digital communication standard that guarantees the exchangeability of dimmable electronic ballasts from different manufacturers. It provides a simple and digital way of communication among intelligent components in a local system in a way that is free of interference. DALI provides simple wiring of control lines, no separate conduit/trunking is needed. It allows control of individual units (individual addressing) or groups (group addressing). Also, simultaneous control of all units is possible at any time. The figure below shows a typical configuration of a DALI control system.

Typical configuration of DALI control system. The text above describes the image.
Typical configuration of DALI control system

How it can save energy:
With traditional analogue 1 - 10V interface, it involves a significant change to provide flexible grouping and control. Therefore, a new communication standard, DALI, with low-cost components, minimal wiring and user-friendly operation has been developed for the lighting system. It can also be used as a subsystem integrated in a building management system.
With the DALI, the lighting system in buildings can be designed to suit various dimming and functional requirements via Central Control and Monitoring Systems. Optimisation of energy consumption could also be achieved by automatic dimming and switching by local daylight or photocell and occupancy sensors.

Further sources of information:

  1. EMSD website, Digital and Addressable Lighting Control at Kowloon Bay Indoor Games Hall: This web page has hyperlinks which may transfer you to third-party website.http://www.emsd.gov.hk/emsd/e_download/pee/ digital_lighting_control_at_kbigh.pdf
     
  2. EMSD Energyland, Innovative Energy-Efficient Equipment - Energy efficient lighting control: This web page has hyperlinks which may transfer you to third-party website.http://www.energyland.emsd.gov.hk/en/ appAndEquip/equipment/lighting/ lighting_control.html

Occupancy sensors
A typical occupancy sensor is comprised of a motion detector, electronic control component, relay and power supply. Motion detectors are typically infrared type or ultrasonic sensors. Infrared sensors detect motion when the heat source moves form one zone to another. The sensors must have direct line of sight to the occupants to detect motion. Ultrasonic sensors emit high-frequency waves in the range of 25-40kHz. These waves bounce off objects in the room and return to the sensors. Objects moving in the space shift the frequency of the returning signal and this shift is detected by the sensors. The electronic control sends signal to the relay, which opens or closes the power circuit, after receiving signals from the detectors.

A typical occupancy sensor for lighting control. The text above describes the image.
A typical occupancy sensor for lighting control
(ceiling mounted)

How it can save energy & how much energy can be saved:
Occupancy sensors can reduce a building's lighting energy by turning lights off in unoccupied spaces. A number of local and overseas case studies of occupancy sensor installations show savings of 15-25% in different space and occupancy type. The amount of saving is highly dependent on the occupancy pattern.
Sensitivity of the sensors is also a critical factor affecting its energy performance. In general, infrared type sensors are not sensitive to relatively small movement, such as typing on a keyboard. However, ultrasonic sensors can detect small movements and do not require a direct line of sight to occupants, but wind-blown curtains or papers can trigger the sensor incorrectly. New generation of occupancy sensor utilize both infrared and ultrasonic technology for maximum reliability and coverage with a minimum of false triggers. Another new technology incorporates a microphonic sensor, which "listen" for minute sounds, such as turning of pages, even though an occupant would not show any appreciable movement in the room.

Further sources of information:

EMSD Energyland, Innovative Energy-Efficient Equipment - Energy efficient lighting control:
This web page has hyperlinks which may transfer you to third-party website.http://www.energyland.emsd.gov.hk/en/appAndEquip/ equipment/lighting/lighting_control.html

Photocell sensors
Photocells can be used for automatic control of indoor lighting. A photocell is a type of resistor. When light strikes the cell, its resistance decreases and allows current to flow more freely. In contrast, its resistance increases when dark. Therefore, when applying in lighting control, a photocell can read the level of lighting, incorporating daylight influence, and automatically adjust the artificial lighting level of a single or a group of luminaries. Lighting system must be installed with dimmers in order not to induce abrupt change of lighting level.

How it can save energy & how much energy can be saved:
The use of photocell sensors in lighting systems can save energy by the parallel use of dimmers. Photocell sensors are usually mounted to detect the lighting level near the working area beside the windows of a building. A properly designed and commissioned daylight system can cut lighting operating hours up to 50% and reduce electricity use. The effectiveness of daylight dimming relies on photocells placement and the amount of window area and ambient light available.

Further sources of information:
EMSD Energyland, Innovative Energy-Efficient Equipment - Energy efficient lighting control: This web page has hyperlinks which may transfer you to third-party website.http://www.energyland.emsd.gov.hk/en/appAndEquip/ equipment/lighting/lighting_control.html

   
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