A discussion on sensor-based lighting and building management systems and their contribution to energy efficiency.
Building management systems (BMSs) consist of a number of items working in synchronisation for a number of reasons, including energy efficiency.
The control system can be seen as the heart of the BMS. It normally comprises two items. The hardware, often a programmable logistic controller (PLC), a programmable unit which “tells” the electrical control gear (ECG) how to respond to signals, as well as the software, normally an operating system which is easy to access and program, and which allows you to set the demands physically, on a multitude of items.
The system can be based on more than one platform, but the platform used most commonly in South Africa is the Digitally Addressable Lighting Interface (DALI).
By allowing the installer to give each ECG a unique digital address, DALI can then be set up to fulfill a certain function following a string of commands. For example, you can have four light fittings in a room, two next to the window and two further away, with one corner quite dark. You can set the lights next to the window to switch on only when the light level there drops below 180 lx, whereas the other two fittings can switch on at 250 and 200 lx respectively.
These input devices are the star of the show, as you get sensors in all forms and performing all functions. They are also pivotal in any dimming or on-off system. Ranging from a standard movement sensor used only to switch lights on or off and only when somebody is physically moving, to more advanced sensors such as infrared or microwave sensors which can pick up the breathing of a person in a room.
Double-output sensors control both lighting and air-conditioning, as well as other items in office buildings.
The next most common sensor has a built-in lux/light meter. These are also sometimes built directly into the fittings, as their physical size is constantly reduced with new designs.
In some unique projects, even more items could be added to the system in some projects. These include digital multiplex (DMX) controllers or similar.
But why install what seems to be an unnecessarily large number of items just to manage lighting? To make the installations energy efficient, of course.
We can save a lot of energy by ensuring that lights are dimmed down or switched off when a room is empty, and by removing the human element from the switching scenario. LED lighting makes this worth the effort as, unlike with any other lighting technology, you do see a load reduction when an LED lamp is dimmed to reduce energy usage and to assist the drive to achieve even greater energy efficiency.
You would be correct to say that other factors also come into play. These include control gear losses; in-rush current; system control and management self-consumption, and even voltage drop and cable length. These, however, are very close to negligible when the true impact of the infrastructure is seen in the savings.
One can also argue that it is not worth the extra expense to have all these items installed. However, should you have discussed it with and requested a full system design from a reputable lighting company, you would almost always see a great reduction in your energy consumption and an increase in efficiency, at a small premium. This gives you more control over your whole building’s lights while reducing the return on investment period.
Note that this is not exclusive to the DALI environment – it could be the scenario on a standard on-off dimming solution for a parking lot; 1 – 10 V dimming where the maintenance or operation manager will dim the lights physically, and in 3-step dimming. The latter is more common in street or warehousing/factory lighting as more than one function can be completed at the same station and as different lighting levels may be required for them.
Almost all these items have one thing in common: they require sensors to ensure that the system performs optimally.
Suffice it to say that there is a multitude of options and each option comes with its own functions and costs, should you wish to revise or perhaps design a lighting control or dimming system for your building.
One thing, however, remains certain – there is a solution out there for each company. You need only to find it or to partner with the right company to help you to do so.
We could all live in houses and work in offices controlled by touchpads and interfaced through a network of sensors. This would do away with the need for switches completely, if only building owners would embrace the practicality, benefits and beauty offered by lighting and lighting control.
Contact Nick Bekker, LRG International, Tel 012 653-0332, firstname.lastname@example.org