Designing For Smarter Lighting Control - Understanding The Options
- Published: Wednesday, 18 October 2017 06:56
When it comes to making buildings smarter, the lighting control choices have a key role to play. Stewart Langdown of CPN Lighting Control considers the options
As in so many other areas of building technology, the field of lighting management has seen some significant advances and choosing the best control strategy for a particular building, or different spaces within a building, depends on understanding all of the options. These options relate to both control strategy and protocol of choice. DALI addressable systems are the protocol of first choice, but are they necessarily compliant.
Getting to grips with the latest lighting control technologies is clearly worthwhile because the energy savings can be considerable – not to mention the ability to enhance the visual comfort of occupants. For example, using effective lighting control can deliver energy savings exceeding 25% in a commercial office to 80% in warehousing and storage.
The lighting infrastructure is increasingly seen as providing part of the backbone for building-wide connectivity to enable lighting and other services to become part of the Internet of Things and facilitate improved sharing and integration of operational and performance data.
On and off or up and down?
A key decision to make early on in the project is how the lighting is to be regulated besides provide a ‘smarter’ solution that is responsive to change. It may also be that the smart solution for one space is different to that for another. For example, in an office building there will usually be a few cellular offices and small meeting rooms, where the space is either occupied or unoccupied. Here, a simple on/off response to occupancy or lack of it may be all that’s needed.
In the same building, there will typically be larger areas of open plan office space where at any one time some workstations will be in use while others aren’t. Such areas will also receive variable amounts of daylight depending on time of day and proximity to windows. In these situations, a smarter regulated solution will be to configure the system to respond to daylight levels across the space and include some zoning to detect occupancy of individual or small groups of workstations. In such cases, absence detection is usually the most efficient form of occupancy control.
A typical UK office building has around 60% of its space as corridor, yet these areas are lit to the same levels as workstations. Simply commissioning the lighting to reflect the office layout would have a huge impact on energy efficiency.
Similarly, in a warehouse where certain racking aisles are only visited very occasionally, on/off switching may be acceptable. However, there may also be aisles in the same warehouse that are accessed frequently during the day. Here, it makes more sense to dim the lighting when the aisle is unoccupied and then ramp up the light levels when someone approaches.
Tailoring each system to the precise needs of the building, and re-commissioning the lighting as those needs change through the life of the building, is essential for achieving maximum benefits. BSRIA talk about Post occupancy Evaluation which is lighting control maintenance and in reality simply installing a flexible platform that allows you to better manage and adapt your lighting can have significant benefits.
Choosing the protocol
Providing a regulated lighting control system necessitates the use of regulated control gear, of which there are three main types. These are 1-10V analogue, DSI (Digital Serial Interface) and DALI (Digital Addressable Lighting Interface). Each has advantages and disadvantages.
1-10V analogue dimming systems are very familiar as they’ve been around for years and the ballasts were in their heyday cheaper than digital equivalents. On the downside, analogue dimming lacks the functionality of digital dimming and is not as flexible for multi-circuit dimming. It also suffers from signal noise and losses on longer cable runs so that screened cable is required for runs longer than 5m. Also, the control pair is polarity conscious.
DSI ballasts are relatively affordable when compared to other protocols, will provide dimming to 10%, 3% and 1%, have the best dimming curve and protocol structure and are suitable for dimming across multiple circuits. Certain DSI models can also provide a ‘switch dim’ feature, optimised energy efficiency and lamp error feedback. The control cable is not polarity conscious and does not need to be screened.
However, DSI ballasts are only available from one supplier, the ballast constantly draws current (parasitic) and specialist tools are required to test the dimming signal.
DALI systems address many of the disadvantages described above. They are less prone to noise than 1-10V systems and supported by multiple lighting manufacturers so it’s possible to ‘shop around’. They will dim down to 10%, 3%, 1% and, theoretically, 0.1%.
Another major benefit of DALI is that it also supports emergency lighting testing and reporting and dimming across multiple circuits. The introduction of DALI as an international lighting control interface has led to the creation of the DALI emergency control definition. This standard allows the use of emergency lighting devices on the same DALI line as other DALI devices such as ballasts, transformers, led lighting and other lighting types. The DALI emergency standard allows for emergency devices to run two key emergency tests as well as feeding back many other pieces of important information.
The requirements for DALI emergency control is almost the same as those of normal DALI devices, and the minimum requirements can be summarised to DALI power supply, DALI emergency device and control system that can communicate with DALI emergency devices.
When used in conjunction with standard DALI devices DALI emergency reduces wiring. Moreover, the amalgamation of two independent control systems (emergency and normal) into a single control system decreases installation and maintenance costs, and the ability to monitor emergency lighting and normal lighting in one step can lead to a safer lighting solution.
Not only do such smart systems offer the functionality and other benefits described above, they can also be easily reconfigured. This is a major advantage for building operators, who may need to change the lighting control system when building usage changes. Individual addressability, combined with the ability to easily add general and emergency light fittings makes it much easier to ensure the lighting system evolves with the building. A building without smart lighting is not a smart building.