Building Automation Systems (BAS) are inherently technical systems. As such, the BAS industry always seems to serve as a battleground for technological standards. Historical examples of these technology battles include pneumatic vs. electronic control, proprietary vs. open systems, and the BACnet vs. LonTalk protocol wars.
Like in these earlier examples, the BAS technological landscape is no less hostile today. Recent advancements in wireless technology have set the stage for the next big clash: BAS Wireless Standards. In this article we’ll try to provide you with ringside commentary, highlighting three of the biggest contenders for BAS wireless connectivity:
- Bluetooth Low Energy (BLE)
Wireless systems in large buildings have become a rapidly moving target. Dramatic improvements in wireless technologies have made the choices for implementation even more confusing, and the engineers tasked with making BAS decisions have been put in a tough spot. Engineers feel increasing pressure to run buildings more efficiently and with less downtime, and wireless systems are seen as a risk to those comfortable with the reliability of wired products. Before writing off wireless products entirely, engineers should seriously consider the benefits of implementing new wireless solutions.
To start, consider that the amount of wire required in any given BAS is directly proportional to the number of points installed. So the amount of conduit, wire and labor that can be saved from implementing wireless solutions follows the same logic: the larger the system, the bigger the savings. With management teams moving toward more green solutions and cost savings, it’s hard to ignore wireless systems. Less copper, conduit and labor means big savings and smaller environmental impact.
Another less talked-about benefit to wireless systems is sustainability. In wired systems, the communication protocol dictates the type of wire installed. RS-485 communications prefer running over 22 gauge stranded pairs of wires. These 22 AWG wires are twisted, shielded and arranged in a bus topology. In contrast, Ethernet runs over CAT5/CAT6 cable arranged in a star topology. Upgrading to a newer wired protocol may very well mean installing all new wire and throwing out the old wire, creating a negative financial and environmental impact.
Wireless communication protocols are inherently different considering they all use air waves to communicate. Going wireless doesn’t just mean eliminating one set of wires; it means eliminating ALL FUTURE WIRE through all future upgrades. New devices and protocols translate to easy upgrades, forward compatibility, lower cost and higher sustainability.
The Power Problem
Before digging into the main contenders for wireless BAS, it would be remiss not to touch on the most significant deterrent to full implementation of wireless systems in buildings: The Power Problem.
As consumers, most of the devices that we think of when we think of wireless fall into one of two categories:
Mobile Devices – Mobile Devices contain a battery and move with us. They are conveniently charged at night using an available plug for power, then taken with us using battery throughout the day.
Wireless Hubs – Hubs (like your WiFi router) are few in number and usually located with other electronics near convenient wall power.
However, the wireless BAS sensors that we are talking about fall into neither of these two categories. Unlike mobile devices, wireless BAS sensors are stationary and cannot be regularly recharged, and unlike hubs, they are not few in number and usually not located near convenient wall power. In large buildings, wireless sensors will number in the thousands and be located on equipment, in mechanical rooms and in ceilings, nowhere near a wall outlet. Even if they are located near an outlet, this will be useless. Power connections to BAS sensors must be permanent and safe, and air handlers cannot cease to function because a passerby unplugs a critical sensor.
So, what if you run dedicated power wires to the sensor/radio? Well, that defeats the whole point of not running communication wire. This is the essence of the Power Problem: eliminating long communication wire but not long power wire is far from ideal.
There are solutions to the Power Problem, including::
Long-Life Batteries – When combined with low power consumption of new wireless standards, long-life batteries are capable of lasting decades, approaching the reasonable lifetime of modern BAS sensors.
Energy Harvesting – Solutions exist for harvesting light energy, thermal energy, vibration as well as radio energy. However, harvesting light using solar cells is the only mature harvesting technology to date.
So, before considering which wireless standard is best to an application, one must consider the Power Problem. Is local power available? Is bright light regularly available? Can you accept changing batteries every few years? Each use case for wireless should be considered separately.
The Zigbee standard was specifically developed for building automation with low energy in mind. It was developed before the Bluetooth standard committee developed BLE, and it utilizes the IEEE 802.15.4 band. If the use case in mind is meant to provide communication for many nodes, with a minimal amount of communication, Zigbee is something to consider. In theory, Zigbee networks become stronger as more components are connected. This helps with scalability and distance concerns by utilizing mesh technology.
Zigbee is very good at managing many components that need to be connected to a network while communicating messages to each other. Typically, the setup for a Zigbee network consists of a controller that acts as an entry point into the mesh. When the controller passes a message, the mesh delivers that message to the proper recipient. Be sure to consider how much data needs to be passed before making a decision to use Zigbee. If the mesh network is going to be filled with many nodes, throughput will suffer. Streaming data is not recommended.
In building automation, if the implementation needs high throughput with a few components, this is a viable solution. WiFi has the capability of providing very high throughput, with future improvements bumping it up to 5GHz. With so many standards available to building automation, it’s best to consider this a last resort. If you’ve attended a crowded conference and had trouble connecting to the network, this could be because there are so many networks broadcasting in the same range. As an automation engineer, introducing more congestion is something to take into account when introducing another WiFi network into the mix.
Bluetooth Low Energy (BLE)
The standard is fast moving, with the 5.0 specification and BT Mesh both slated to be released within the year. As of the 4.2 specification, Bluetooth makes for good Point-to-Point (P2P) communication as well as beaconing sensors. If the solution requires an exponential amount of components, with consistent back and forth communication, this may not be the right solution right now.
In the commercial building automation environment, BLE is becoming the standard for sensors. With a beacon packet, sensors may emit one-way communication data to a controller. If there are HVAC sensors that need to be read, but never talked to, this is the perfect use case. The sensors can be added cheaply without much thought to the cost or power consumption. In most cases, these sensors are capable of running entirely off of battery power. This is normally implemented with a controller that scans for all beacons in the wild and reads their payload without initiating a full connection. This is a handy way of reducing congestion on the airwaves when initiating a back and forth connection isn’t required.
There are a number different scenarios that one may be faced with when engineering a building automation system, and wireless components can be seen as one of the many solutions available. Implementing a wireless network correctly can provide quite a few benefits, which range from ease of installation to extreme cost savings. If wireless piques your interest, be sure to take into consideration the advice listed above when making engineering decisions. Implementing a wireless system is all about picking the right system for the right scenario.