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Wireless Building Controls: Less is More

May 1, 2012
Trying to pin down the state-of-the-art of an emerging and rapidly developing technology always is difficult, and wireless building-automation system (BAS) controls are no exception.

Trying to pin down the state-of-the-art of an emerging and rapidly developing technology always is difficult, and wireless building-automation system (BAS) controls are no exception.

Retrofits are the key market for wireless control systems. Wireless systems are especially effective in buildings where space uses and configurations change often as tenants exercise their need for an easily varied floor plan.

Although the “pros” of a flexible, easy-to-install wireless controls system would seem apparent to anyone who has ever dealt with the miles of cable and conduit in a building, there are some “cons” in the technology that still are being worked out.

“Wireless technologies for building automation are still in the more costly stages of product evolution,” Ben H. Dorsey III, LEED Green Associate, vice president, marketing and communications, KMC Controls, said. “That is, in a function-by-function comparison of wired and wireless devices, there is still a cost premium for wireless.”

According to Dorsey, some of the higher per-device costs of a wireless controls system can be mitigated through labor savings at installation, and the remaining cost differential will diminish as production volumes increase for wireless devices.

“That is simply a matter of time,” Dorsey said.

Certain facility environments are not conducive to the current capabilities of wireless technology, and reliable communications can be adversely influenced by such environments. A site survey by a building-automation contractor is an essential step in the process to determine if wireless control is an option and what issues might be encountered, Dorsey said.

Dorsey added that education will be a key component of a successful future for wireless controls.

“We on the manufacturing, engineering, and contracting side of the equation need to be prepared to educate building owners and managers regarding our wireless capabilities,” Dorsey said. “There are misconceptions to overcome. There are security-related fears to address. There may be maintenance-related concerns to discuss. It is important that we set the proper expectations to avoid heartache down the road.”

According to Dorsey, it is only through project usage that all parties involved—manufacturers, engineers, and contractors—gain the experience and learn the lessons that will make this evolution possible.

“I can draw an analogy to green buildings,” Dorsey said. “We’ve been pursuing sustainable designs in buildings for years, and even today there remain some cost differentials in green practices vs. more conventional practices. But it is our pursuit of sustainability that will lead to true and complete cost parity—or better. By the same token, we must pursue the use of wireless automation technologies to continue to advance the science and drive down the costs.”

Hub and Mesh Networks
In the broadest sense, there are two types of wireless control networks: hub networks, in which all signals from “spoke” wireless controllers transmit data to a central point, and mesh networks, in which all sensors communicate directly with each other.

J. Christopher Larry, PE, CEM, CEP, CIPE, LEED AP, director of energy engineering for Teng Solutions, said there is no state-of-the-art choice per se, as both types of networks have their advantages. However, he prefers to create mesh networks because of their “self-healing” powers. In a mesh network, nodes are interconnected so that multiple pathways connect each node. Mesh networks are decentralized in nature; each node is capable of self-discovery on the network. Such networks are self-healing, in that any communication loss will be redirected to another node.

“A self-learning, self-healing, self-addressing mesh network seems to be the most advanced option,” Larry said. “Of course, if a building’s floor plan is compact and open, a hub network will work and may be less expensive and simpler.”

Not only is a mesh network easier to install than a hub network, it addresses the sometimes vexing issue of device interoperability.

“Many of these systems do not work together, so a designer may like a certain carbon dioxide sensor and a different type of temperature sensor, but they cannot be connected wirelessly since the wireless signals vary,” Larry said. “Often, system designers must find the best wireless network and then find out what sensors it supports. It is the cart driving the horse, so to speak.”

Larry agrees with Dorsey that education will play a key role in the future of wireless building control networks.

“Most owners are not experienced with this technology and see a rapid growth in their business with wireless, such as Internet, phones, and so on, but don’t really understand it,” Larry said. “We need to help educate them.”

A New Protocols Alphabet
For years, building control protocols were well-known by such anagrams as BACnet, LonWorks, and CABA. Today a new alphabet soup, including ZigBee, Z-Wave, and EnOcean, has arisen in the wireless controls market.

Jay Hendrix, business line manager, wireless, Siemens Building Technologies Division, said many of the differences between the protocols stem from their uses and origins. He provided brief overviews of three leading wireless protocols:

• ZigBee, a low-power wireless mesh networking and sensing technology created and controlled by an open alliance of companies. ZigBee defines interoperability and ensures it through product testing and certification. ZigBee builds upon the physical layer and medium-access control defined in IEEE Standard 802.15.4-2003 for low-rate wireless personal area networks.

“From a standards perspective, our industry now has an official standard available for BACnet with the release of the ZigBee Building Automation Standard in September 2011,” Hendrix said. “This started as a partnership between BACnet and the ZigBee Alliance. ANSI/ASHRAE Standard 135-2010, BACnet—A Data Communication Protocol for Building Automation and Control Networks, made ZigBee an approved datalink option in BACnet. The release of the ZigBee Building Automation Standard by the ZigBee Alliance completed the picture.”

• Z-Wave, part of the Z-Wave Alliance, a group that was established around a proprietary wireless networking protocol. A low-power wireless mesh technology, Z-Wave operates in the sub-gigahertz bands.

Z-Wave’s open standard means every product that bears the Z-Wave mark will work with all other Z-Wave products, with no special programming, regardless of who originally manufactured the item.

• EnOcean, a point-to-point wireless technology with the ability to be batteryless (or use energy harvesting), primarily used for sensors or switches.

“Uses of these wireless technologies vary based on the requirements of the customer,” Hendrix said. “Does proprietary technology or open availability matter? Do they want a solution capable of supporting controller networks, or just simple sensing devices? How important is adherence to open standards? Are they interested in product certification?”

According to Dorsey, both ZigBee and EnOcean products are finding application in the commercial and institutional buildings spaces.

“Both are evolving, and both are perfectly suited for sensor-related applications, but it may be challenging for both to handle more complex control responsibilities,” Dorsey said. “That is not to dismiss the product advancements that are being made. But a hybrid wired/wireless approach that combines wireless sensing with wired control represents a foot in the door and ensures proper management of various facility systems.”

Growing Pains, but a Bright Future
What is the future of wireless building controls?

“Wireless BAS technology growth has remained in an incubation period for the past couple years, awaiting new advancements in batteryless sensor technology, Internet protocols, and low-cost, low-power WiFi,” Patrick Harder, product manager, building efficiency, Johnson Controls, said. “Within these three areas, most of the technology growth has taken the form of integrating technology that has been available for the past few years into a broader range of sensor and control products.

“Also during this time, wireless BAS implementations have continued to gain market acceptance as building owners and general contractors become more comfortable cutting loose from the wired chains that hold them captive to the technology of yesterday,” Harder continued. “Standards are continuing to evolve that will ensure an interoperable ecosystem of secure, green, reliable wireless control products suitable for the commercial BAS marketplace.”

Harder added that as standards mature and BAS vendors implement these standards, design engineers should expect to see more interoperable wireless devices, especially at the sensor level. This will provide a larger selection of wireless-sensor types which will make it easier to add monitoring and control capabilities.

“Also within the sensor arena, expect to see an increased focus on batteryless sensor technology,” Harder said. “EnOcean specializes in energy-harvesting techniques that store energy from ambient light (photocells) or kinetic energy (piezoelectric) to power the batteryless devices. EnOcean also has batteryless valve actuators that operate on thermal differences between ambient air and hot-water pipes. ZigBee is entering the batteryless-sensor market and has a green power standard that uses smaller data packets to enable wireless communications at 2.4 GHz using energy-harvesting techniques.”

As with any rapidly growing technology, there will be growing pains associated with wireless building-controls technology. However, Hendrix is confident that it will become the preferred method for buildings in the future.

“The use of wireless for building-automation communication within facilities will continue to increase over time,” Hendrix said. “Considering how pervasive, in general, wireless technology is becoming in contemporary society, one can be reasonably assured that it will. Today, wireless permeates our lives in so many ways. From smartphones to wireless Internet access in your office, home, or local coffeehouse, we depend on it. The technology will only get better and less expensive going forward. Less wiring also means less strain on our environment and natural resources. The electronics will become more power-efficient, and installation methods and tools will improve, taking the mystery out of commissioning and troubleshooting.”

Dorsey, too, is upbeat about the future of wireless building controls.

“You will continue to see an increase in the diversity of control products capable of functioning wirelessly,” Dorsey said. “The low-hanging wireless fruit, such as wireless sensors, is already fully evolved. And we are seeing more sophisticated control devices in the home-automation arena. In order to meet the needs for our commercial and institutional projects, such devices need to evolve further.”

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