Emerging wireless technologies in building automation
Engineers need to consider wireless technologies for building automation systems and realize the benefits of wireless systems for each scenario.
A building automation system (BAS) is an inherently technical system. As such, the BAS industry always seems to serve as a battleground for technological standards. Historical examples of these technology battles include pneumatic versus electronic control, proprietary versus open systems, and the BACnet versus LonTalk protocol wars.
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. There are three big contenders for BAS wireless connectivity including:
- Bluetooth low energy (BLE).
Benefits to wireless systems
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, however, engineers should consider the benefits of implementing wireless solutions.
- Big savings and smaller environmental impact: 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.
- Sustainability: For 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 Category 5 and/or 6 cable arranged in a star topology. Upgrading to a new, wired protocol may result in installing new wire to replace the old wire, creating a negative financial and environmental impact.
- Easy upgrades: 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 wire going forward and for upgrades. New devices and protocols translate to easy upgrades, forward compatibility, lowered cost, and higher sustainability.
Deterrents for using wireless systems
The most significant deterrent to full implementation of wireless systems in buildings is the power problem.
As consumers, most of the devices we think of when it comes to wireless falls into two categories: mobile devices and wireless hubs.
However, the wireless BAS sensors that we are talking about don’t fall into these 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 that are nowhere near a wall outlet. Even if they are located near an outlet, they 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: a truly wireless device has neither communication wire nor power wire running to it. If you were going to run a power wire to the device(s), you may as well run the communication wire.
- 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, and radio energy. However, harvesting light using solar cells is the only mature harvesting technology to date.
Before considering which wireless standard is best for an application, it’s necessary to consider the power connections. Are both local power and bright light available? Can you accept changing batteries every few years? Each use case for wireless systems should be considered separately.
The Zigbee standard
The Zigbee standard was specifically developed for building automation with low energy in mind. Developed before the Bluetooth standard committee developed BLE, Zigbee uses the IEEE 802.15.4- IEEE Standard for Low-Rate Wireless Networks. If the use case in mind is meant to provide communication for many nodes, with a minimal amount of communication, Zigbee should be considered. In theory, Zigbee networks become stronger as more components are connected. This helps with scalability and distance concerns by using mesh technology.
Zigbee is 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 also is not recommended.
For building automation, if the implementation needs high throughput with a few components, this is a viable solution. Wi-Fi has the capability of providing very high throughput, with future improvements bumping it up to 5 GHz. With so many standards available to building automation, it’s best to consider this as a last resort. For example, 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. Introducing more congestion is something to take into account when introducing another Wi-Fi network into the mix.
Bluetooth low energy (BLE)
The standard is fast moving, with the 5.0 specification and Bluetooth mesh both slated to be released within the year. As for the 4.2 specification, Bluetooth makes for good point-to-point (P2P) communication as well as beaconing sensors. If the solution requires an exponential number of components, with consistent back-and-forth communication, this may not be the right solution.
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 ideal use case. The sensors can be added at a low cost without much thought to the 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 way to reduce congestion on the airwaves when initiating a back-and-forth connection isn’t required.
There are various different scenarios that one may face when engineering a BAS, and wireless components can be seen as one of the many solutions available with several associated benefits. However, implementing a wireless system is all about picking the right system for the right use case.
Bryce Jacobs is a software engineer for Computrols Inc. In this role, he is tasked with new product development and the ongoing maintenance and improvement of Computrols’ BAS.