December 2010
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Benefits of Lighting Control Integrating DALI and BACnet.
From theory to real application.

Josep Ceron

Business Development Manager

Intesis Software

 

Benefits of lighting control. The theory.

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According to different studies and experts, around 40% of the energy consumed globally is buildings’ related. Artificial lighting consumes a significant part of all electrical energy consumed. In offices from 20 to 50 percent of total energy consumed is due to lighting. And most importantly, for some buildings over 90 percent of lighting energy consumed can be an unnecessary expense through over-illumination.

Looking at the figures above it seems clear that in today’s world there are plenty of commercial buildings (the majority of them by far) in which lighting is not automatically controlled at all, in other words, someone switches on and off lights at the start and at the end of the day. Other more sophisticated buildings (few of them) implement some sort of automatic control of lighting making this switching on and off by automatic control based on presence detection, or calendar/hourly basis. And other even more sophisticated ones (very few of them all) implement really effective lighting control providing just the appropriate light level in any part of the building at anytime, having in consideration many variables like daylight coming from outside, presence of people in each area, the required light level according to workplaces, etc.

It is obvious that the more effective control we apply to lights in a building the more comfortable we’ll make it for people who spend a good part of their lives tere, and of course the more energy efficient we’ll make the building itself, with all the benefits related to it: reduction in electricity bill, reduction of maintenance budget, reduction of carbon footprint, etc. Fortunately it seems that nowadays (and luckily for all) all related to green buildings, energy efficiency, and rational use of energy sells, and sells well. According to recently published McGraw-Hill Construction's Green Outlook 2011: Green Trends Driving Growth report, the Green Building Market has grown 50% in the 2008-2010 period despite recession.

But how to choose the appropriate lighting control system, what basic and advanced features must it provide, which of them do we need or want for our building, based on what technology, with open communication protocol or proprietary, what’s the cost and what will be the ROI, what  level of integration do we want with the rest of the building’s installations, which are the real benefits it will give to buildings’ owner, users, installer, maintainer, system integrator, etc., … Lots of questions with difficult answers, answers that greatly depend on several different variables in each case and thus with a complicated uniform response, so I defer to the answers of expert consultants and advisors in this field.

Until here in the article it has been about the theory, now let’s get down to earth and try to explain how flexible and effective lighting control can be done with real technology used for building automation, such as BACnet-based building management systems and DALI lighting, and how both can be fully integrated in real applications in commercial buildings.

Throughout the next part of the article, while explaining features of the lighting control system proposed, I will be showing some clear benefits that both systems, DALI and BACnet, can bring together to different actors in a building (owner, installers, users, system integrators…) but for sure the reader will identify many more depending on their profile and experience. 

Why DALI

Lighting control systems existing in the market provide a set of features by themselves to do effective control of lighting (switching, dimming, grouping of luminaries, scenes, etc.). Some of them are proprietary, I mean those in which different elements of the system communicate with each other using proprietary (not open) protocol. Others are open, providing just a common hardware interface and interconnection specification, an open communication protocol (available to anybody), and a set of control features available using this protocol.  This enables manufacturers of any kind to put in the market interoperable devices with this system, such as ballasts, lighting sensors, controllers, gateways, etc., making this way a truly open lighting control system, as is the case of DALI. The advantages of adopting an open system compared to a proprietary one are numerous, to name a few: a wide variety of products and manufacturers to choose from, interoperability, reduction in costs of maintenance and upgrades, security of future availability, etc.

DALI is an acronym and stands for “Digital Addressable Lighting Interface“. It is an international standard that guarantees the exchangeability of dimmable ballasts from different manufacturers. The DALI-interface has been described in the fluorescent lamp ballast standard IEC 60929 under Annex E.

Features available when installing DALI ballasts are:

DALI has been defined for:

Each ballast stores its own set of parameters:

Information on DALI technology and a list of existing ballast manufacturers can be found at AG DALI association’s website (http://www.dali-ag.org).

Why  BACnet

These features related to lighting control provided by the lighting systems can be fully optimized when integrated with the building management system who is in charge of controlling the rest of the building’s installations. Some examples of this: use the information of presence detectors of the security system to switch on the light in each zone only when needed, and at the same time actuate on HVAC setting the heating/aircon in stand-by mode when there is no one and back to comfort mode when there is someone; Dimming appropriately the luminaries and actuate on window blinds to reach the optimum light level in each zone at any time according to information provided by light level sensors; Control of lighting from the BMS’ scada; Logging of data for energy consumption calculations; Automated notifications to maintenance workforce when lights are failing or are about to reach end-of-life. The advantages of this integration seem to be endless.

There are plenty of different building management systems, intended for different types and sizes of buildings, with more or less capabilities, using proprietary or open protocols… I will not explain here building management systems and their goods and bads, probably the reader knows all this very well. BACnet-based building management systems are probably the most popular ones nowadays, and probably the ones with more future ahead, but I am aware that this could lead to exciting discussions depending on who you talk to. Anyway, BACnet has been chosen as the BMS for this integration of DALI lighting, but it could have been any BMS. 

A huge amount of information on BACnet can be found at BACnet website (http://www.bacnet.org).

Integration of DALI and BACnet. Key points to have in mind.

Integration of DALI and BACnet is made by means of gateways, one example is the IntesisBox BACnet - DALI gateway from Intesis Software, more technical details can be found at http://www.intesis.com/eng/intesisbox_bacnet_ip_server_dali_frame_eng.htm
 

Integration f DALI and BACnet.  


These kind of devices should not only serve as purely gateways allowing bidirectional communication between BACnet and DALI but also providing as many configuration, commissioning, maintenance and troubleshooting tools as possible. The more useful tools they provide the more we can reduce engineering time needed for configuration and commissioning,  and later for maintenance work. It is very important to have in mind when choosing a gateway that the price of the device itself is just a small part of the whole integration cost.

Roughly, an integration process of DALI ballasts with a BACnet BMS would follow these steps:

CatNet Systems In design phase (in the office), according to drawings of the building and desired functionality:

In commissioning phase (on site):
It is very important at this stage that the gateways allow Ethernet connection, this gives you non-priced flexibility to walk along the building with your laptop using for example a wifi connection to the building’s LAN.

In general, a good integration solution for DALI and BACnet should provide the following key points:

Application example. A simple and cost-effective automatic regulation of light level in individual spaces

Let’s propose an easy, cost-effective, yet good enough continuous regulation of light level, individually per workplace, using the integration described above and without going to closed regulation loops needing complicated engineering and control resources. Let’s explain it with a room but it can be extrapolated to any building’s space.

DALI allows grouping ballasts. DALI allows scenes (up to 16), a scene is a given light level that can be applied to individual ballasts, and to groups. Then using a light sensor in the room to give you a reference of the light level, you can group the ballasts appropriately an set levels for scenes, individually per ballast or per group, to obtain the desired light level in each workplace of the room according to the light level measured by the sensor. Having 16 available scenes in the ballasts means you can apply 16 different regulation steps, good enough for many applications.

Bibliography

Wikipedia
McGraw-Hill Construction's Green Outlook 2011: Green Trends Driving Growth report
www.bacnet.org
www.dali-ag.org

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