Lighting control systems
Lighting controls can help us avoid wasteful lighting, while at the same time ensuring that the right amount of light is delivered to each area in a site at each point in time. The amount of light needed in various areas may vary with the amount of daylight entering the space, and at times, occupancy patterns may mean that no lighting is needed. Using automated controls in the right situations can help save energy by overcoming the “human behaviour factor”.
A number of different control systems may be considered - the economic viability of each will depend on the particular application, and should be discussed with an experienced lighting designer.
Leaving lights on in vacant buildings results in significant energy wastage. Timers can be used to automatically turn all lighting off during periods when the area is normally vacant, such as at night or weekends. A timed manual override allows for lighting the building outside normal hours if necessary. There is potential for substantial savings at relatively low cost by installing timers in buildings that have this occupancy pattern.
Lights left on in unoccupied areas like toilets, storage rooms and meeting rooms are a common occurrence. Automating the process by installing occupancy sensors to automatically turn lights off when rooms are unoccupied (while retaining standard switching) can achieve save up to 70% of the electricity normally used.
Occupancy sensors are not only applicable to specific rooms, but can also be used (through software control systems) in open plan environments by defining occupancy ‘zones’.
- For open plan spaces, install wall or ceiling-mounted occupancy sensors set to maximum sensitivity, on 15-minute delay. (Note: multiple sensors may be needed in larger open plan spaces as well as those with partitions that obstruct sensor coverage).
- For corridors and circulation areas, install ceiling-mounted sensors with increased sensitivity, on a 15-minute delay. Choose models specifically designed for corridor use – these activate lights long before a person reaches an unlit area.
Where skylights or large windows are present, indoor lighting is often still left on when natural light is sufficient. If you want to save even more energy than with occupancy sensors alone you can combine occupancy sensors with daylight-reactive dimming control. Automatic daylight reactive dimming control is a step up from the manual version and precisely controls how much light hits the work surface. The average electricity savings achieved through the use of reactive dimming controls (or daylight harvesting) near windows is 30%. Savings of 80% can be achieved by daylight harvesting in a warehouse environment where there are both skylights and perimeter windows.
- Install switching or automatic dimming for light fixtures within 3-6metres of windows or glazed facades
- Use separate switches for light fixtures in zones less than 100m2 – and connect them to a separate occupancy sensor
- Use daylight sensors and dimmers on lights in daylight zones more than 100m2 (check these are appropriate for dimming first)
- Specify smooth, continuous dimming (daylight harvesting) to avoid sudden light changes that can distract workers and require them to adjust to different lighting levels.
- For workstations near windows, the placement of the desk and seating is critical to utilizing daylight while at the same time avoiding glare on computer screens.
- In new buildings, use of exterior louvres, micro perforated blinds etc can be used to aid in controlling daylight penetration.
Automated dimming or switching systems are also recommended for outdoor lighting circuits.
Dimmers and separate switching
Dimmable lighting manually gives you the most flexibility. But fitting a secondary light switch, so you can easily switch off some lamps and not others, is good too. Whatever control you choose, it must be suitable for the lighting technology used in your business. Discuss your needs with an experienced lighting designer.