By Craig DiLouie
Lighting automation’s benefits of energy savings, worker satisfaction, and flexibility may soon be achievable in commercial buildings at a lower cost and with a high assurance of interoperability between devices.
In recent years, radio-frequency (RF) wireless control has begun to penetrate the residential market with a number of protocols available. One popular protocol, Z-Wave, developed by Zensys, is backed by the Z-Wave Alliance, which includes more than 125 partners, such as Leviton and Motorola. According to Mark Walters, director of residential systems for Leviton Manufacturing Inc., Z-Wave offers the advantages of low power consumption (enabling battery-operated control devices); good node (device) count; range and bandwidth highly suitable for command and control for residential applications; reliability; an attractive price point; and a strong vendor alliance to help guide the technology. However, Z-Wave characteristics appear to limit its utility to residential and light commercial applications.
Meanwhile, Bluetooth and Wi-Fi, two of the first open-source wireless protocols using a star topology, are ideally suited for computers and personal devices but have disadvantages for control of lighting and other building automation systems, say lighting control manufacturers.
Enter ZigBee, a recently introduced open-source, mesh-network protocol (IEEE 802.15.4) that promises the characteristics needed to achieve RF wireless control strategies for large commercial buildings. While no ZigBee-based commercial products had yet been introduced at the time of writing, this protocol is supported by the ZigBee Alliance of more than 100 manufacturers, including Philips, Motorola, Honeywell, Samsung, Invensys, and Mitsubishi. One manufacturer, Philips Lighting Electronics, says it is planning to introduce a ZigBee-based wireless integrated lighting control system (including ballasts, sensors, controllers, and software) within the next year. The system, controlled by a central computer, will enable dimming and on/off switching, daylight and occupancy sensing, scheduling, and the ability to group and reconfigure fixtures.
ZigBee is an open-source protocol that provides a common performance standard and the capability for designing multivendor control systems. ZigBee has a mesh topology, meaning each device in the network’s layout is connected independently to all the others, providing reliability and flexibility. ZigBee also offers a high node count, moderate bandwidth (192 Kbps), moderate range (100 to 1,000 feet), low power consumption (devices can be battery-operated, enabling “peel and stick” occupancy sensors), AES hardware encryption, and a high level of scalability.
“It appears that protocols that are public and open will, in the future, be ideal for commercial applications,” says William Sandoval, business development manager, digital systems, for Philips Lighting Electronics and the Advance division. “Today, there are very few open protocols, such as ZigBee and BACnet, in the marketplace, but they are starting to take command. Customers like options, and open protocols allow for those options. In addition, customers do not want to be tied down to a single vendor,” he says, adding that in the wireless arena, ZigBee as an open standard will allow other devices to integrate and interoperate so specifiers can choose how, why, and when to use a specific vendor.
Advantages of RF wireless control start with reduced capital and operating expenses. According to Sandoval, wireless control can save as much as 30 to 40 percent on installation and material costs compared to a wired control system, making this option potentially attractive for retrofit as well as new construction. Maintenance expenses can be reduced because devices can be replaced one to one without control wiring being involved.
As another potential benefit for future products based on ZigBee, RF wireless control offers flexibility centered on the mobility of devices, which can be moved and grouped based on evolving application needs without changing wiring. Wireless control systems are scalable, as devices can be added and removed easily. Based on adoption of open protocols, lighting control systems can be more easily integrated with other building systems such as HVAC and security. Intelligence can be both centralized and decentralized, with devices receiving commands from a central computer (and sending information back in a two-way stream), while also interacting with each other independently and allowing occupant control of local systems without location restraints.
“Complete SCADA systems can be configured using wireless technology,” says Walters. Supervisory control and data acquisition (SCADA) systems gather and analyze real-time data, enabling the system to respond to a variety of inputs as they occur. “The main benefit will be a lower cost of implementation. A secondary benefit will be increased flexibility in deployment. With wireless components, the system can grow over time and be reconfigured if needed at a much lower cost for a hard-wired system.”
Sandoval says the possibilities in commercial control are endless, but it will take time for new technologies to penetrate the market. He believes wide adoption will occur in 2 to 3 years. The first customers, he adds, will likely be applications such as commercial A-grade buildings, hospitals, and big box retail stores.
When evaluating RF wireless control protocols for a particular application, architects should ask:
- What will be the topology, or layout, for the network of devices?
- What is the communication range needed for each node, or device, in the network?
- How much power does the system require?
- What is the bandwidth and speed that are possible for transmission of data?
- What is the cost of the system?
“Z-Wave systems place the emphasis on low power consumption to allow for battery-powered devices while maintaining excellent range, node count, and sufficient bandwidth for residential control,” says Walters. “ZigBee provides greater bandwidth and node count at the cost of range and power consumption, and is more suitable for commercial applications. Both of these technologies promise reliability and attractive price points. Both emphasize low power consumption so that battery-powered devices can be used, providing application solutions such as ‘peel and stick’ occupancy sensors. Finally, there are powerful, flexible, affordable technologies that can be used to bring high-performance automation to the mass market.”
Craig DiLouie, principal of ZING Communications Inc. (www.zinginc.com), is a consultant, analyst, and reporter specializing in the lighting and electrical industries.
