Adding wired lighting controls and environmental sensors in commercial buildings is expensive. But it's often necessary, to achieve improvements in energy efficiency or indoor air quality. That's one reason wireless devices are becoming popular for building automation.

Last year about a dozen prototype wireless devices were released by the ZigBee Alliance, a group whose open protocol was first aimed at home automation. According to an article in MIT's Technology Review, the alliance now plans to target larger buildings.

ZigBee chips can be embedded in devices such as controllers, switches, and sensors for light, heat, or moisture. The devices can be cheap, but the savings for commercial facilities are in the avoided cabling cost. With no wiring required, peel-and-stick devices like these can be added anywhere, and moved easily.

Even greater is the cost savings associated with more efficient control of a building's HVAC and lighting systems, an improvement that often requires the addition of many controllers and sensors.

Mark Pacelle, VP of marketing for Millennial Net, says wireless networking is fundamentally changing the economics of deploying monitoring and control networks.

"Today, industrial plant managers are coming under increasing competitive pressure to improve plant efficiency by even two to three percent," Pacelle said in an interview with Automated Buildings. "Wireless sensor networking is a technology that will play a pivotal role in this effort."

Zig meets Big
Entering the building automation market with a new network protocol is not child's play. Established manufacturers have a tight grip on the rapidly growing market.

Technologically, a new entrant must deal with existing equipment -- both wired, like RS-485, and wireless, like Millenial Net -- and connect to the major energy-management systems. Protocols such as ASHRAE's BACnet are ahead of the game.

ZigBee has some serious backing of its own. Honeywell, Motorola, and some 160 other companies are behind the protocol.

Milennial's Pacelle isn't worried about a protocol war in the building systems space. Facility managers will rely on gateways to enable their various systems to communicate.

"The wireless community understands the need to communicate effectively with other protocols," said Pacelle. "The majority of wireless networks being deployed are to augment an existing wired network, which could be using one of a number of protocols."

Mark Walters, Director of Residential Systems for Leviton, said mesh networking protocols promise new levels of system performance. He thinks ZigBee and competing technology Z-Wave are protocols to watch.

"True two-way reliability combined with interoperability between multi-vendor platforms provides integrators and end-users with control options that previously were only available to the very high-end market," Walters told the Lighting Controls Association for a white paper on wireless controls published this month.

From latte to lighting
ZigBee is built on IEEE 802.15.4, an open standard similar to the Bluetooth that connects your wireless headset to your cell phone, and the Wi-Fi that connects your laptop to the web at Starbucks.

Whereas Bluetooth is limited to networking a handful of devices, ZigBee can create a network of 64,000 devices building-wide. Wi-Fi could handle that, too, but it consumes a lot of power and its high speed (and cost) would be overkill for the application. In addition, it would need central hubs to connect the devices.

Reliability, security, interference and device selection
ZigBee creates a mesh network, which is more resilient than a network that relies on centralized control. A message sent by one node is passed along by any other node within range. When the intended recipient node receives the message, it acts on it. A mesh network effectively routes around a failure, immediately.

That added reliability is especially important in medical buildings and secure facilities.

Speaking of security, all of these protocols rely on radio frequencies, which are inherently exposed. Each protocol has security features available within their definitions, and those features must be implemented by the device manufacturer and installer.

RF is also prone to interference, as we learned with broadband over powerlines, but this usually can be overcome with careful planning.

Open standards generally encourage innovation and competition, which work in the building owner's favor. In the case of ZigBee, that innovation is happening now. Widespread device availability is still around the corner.

Events
ZigBee Open House and Exposition, Chicago, September 14, 2005

ZigBee Developers Conference, Las Vegas, October 3-5, 2005