According to the U.S. Environmental Protection Agency (EPA), commercial buildings in the United States consume energy with costs of upwards of $100 billion each year. This accounts for approximately 17% of greenhouse gas emissions in the nation, while the EPA estimates that nearly a third of this energy produced for building operations is wasted and/or unnecessary. Facility managers (fms) striving to reduce the economic and environmental impacts of their organizations’ energy use have numerous options to consider in moving toward this goal, and technology continues to play a part in this evolution.
During the 1970s, installation of building automation systems (BAS) began to appear in facilities, a shift that enabled fms to monitor and control the lighting, mechanical, and even security systems in their buildings in a less labor-intensive manner. A BAS is a control system comprised of a computerized, intelligent network of electronic devices. The emergence of BAS technology meant that altering building system operations could be executed through the electronic devices, versus the traditional way of physically walking to the equipment in question to make a change. This reduced the labor expended by facility management (FM) departments, while improving the efficiency of a building’s operation.
Another benefit for organizations that invested in a BAS was an increase in energy efficiency; for instance, cooling systems could be programmed to set back or shut off at predetermined times, so its operation was not dependent on a person flipping a switch.
Some years later, wireless technology began to appear in facilities, and this elevated building automation to a new level of efficiency. But this efficiency was not only tied to energy consumption; wireless also heralded the ability to reduce the need for wiring during new construction and renovation projects.
While wires are necessary for central functions, the devices (e.g. light switches, temperature sensors) connected to the BAS do not require wires. The number of these devices vary by a facility’s size and function; however, no matter the number (which could run into the tens of thousands in some larger structures), removing the need for wiring for these devices can be a huge boon for both the construction and operation aspects of a building.
The U.S. Department of Energy (DOE) asserts that wireless controls have the potential to reduce the cost of advanced sensing and control systems significantly, particularly in existing buildings “where the installation of wiring can represent 20% to 80% of a controls project cost.” In addition, wireless sensors and controls offer greater flexibility since they can be installed, moved, and moved again without the need to change related wiring.
EnOcean Technology: No Batteries Required
Flexibility and energy efficiency goals are at the forefront of a specific wireless technology gaining ground in the building automation realm. This technology is EnOcean, an approach that uses energy harvesting techniques to power the sensors, switches, and other devices that comprise a facility’s BAS.
Devices manufactured with EnOcean technology are self powered; through an electrodynamic process these items draw power from changes in motion in their vicinity. This power is then used by the device to carry out its function. The energy harvested from a person pressing a switch for instance is converted into electrical energy, which in turn is used to power the function of the device.
Jim O’Callaghan, president of EnOcean, Inc., explains the process, “There will be a light switch that looks exactly like a line power light switch, but the press of a finger on that switch generates sufficient energy to power a radio that ‘wakes up’ and sends a series of radio transmissions to deliver the message.”
As a result, unlike other wireless devices, EnOcean products do not require batteries. This eliminates the maintenance required to track battery life and to replace them. Small devices such as those in a wireless control system might need to have their batteries replaced every year or so. And while that frequency may not seem high, fms need to have someone track where the devices are, what their expected battery life is, and schedule a maintenance. Depending on their frequency of use and specific energy consumption, device battery life can vary.
“Some buildings contain thousands of devices,” says O’Callaghan, “and many are attached in hard to reach places—on ceilings, on water pipes, or in ductwork, for example. As one looks at the issue of powering devices by batteries, you can see some challenges associated with the maintenance.”
Development of EnOcean’s energy harvesting devices began in 1995 at the Siemens central research labs in Munich, Germany, and the first patent for energy harvesting sensors was secured in 1997.
Says O’Callaghan, “Historically, the big challenge [with wireless] has been that sensors require power, as do the radios to wirelessly communicate the information. The sensors have required either line power or a battery to provide power. So conventionally there’s been two solutions—wired wireless (using a power wire) or a battery. The impetus to EnOcean’s energy harvesting research was that in order to make wireless sensors really viable, a way to self power those devices was needed.”
In 2001, the technology that harvested energy from changes in motion was spun off from Siemens through the founding of EnOcean GmbH, and the first products were shipped to customers in 2003.
EnOcean did not invent energy harvesting; rather the company’s aim was to optimize an energy harvester that would put out maximum energy, while simultaneously reducing the energy required to perform its function. O’Callaghan explains, “In reducing the consumption, one of the tradeoffs could not be poor performance; it had to meet the needs of the application. The devices needed to consume less energy than traditional wireless devices, but they could not be short range. We needed low energy consumption, but not lower power.”
O’Callaghan continues, “Power is energy over time. And even though the energy consumption was reduced, it still needed to remain at a level that would enable it to send a sufficient radio signal. That meant we had to reduce the time. So when our devices ‘wake up’ they send a very fast, very short radio transmission. The consumption is for a short duration, and the accumulated energy requirement is less.”
In order to ensure a message reaches its intended destination, the device sends the data multiple times. This not unique to EnOcean technology; other wireless architectures send multiple messages. But in other technologies, those multiple transmissions use battery life, whereas EnOcean devices use the energy harvesting ability to power those transmissions.
In addition to motion powered devices, EnOcean also developed devices that operate on solar energy. “A switch is usually employed in a situation where there is a mechanical intervention (such as turning a light on or off),” explains O’Callaghan. “But there are other devices that operate 24/7, and a different type of energy harvester was needed. So we designed a solar powered device. The challenge was that solar cells are usually located outdoors, but our device needed to operate off low levels of indoor light, and it needed to be small. Some of these devices operate on a ceiling where they only receive light reflected from the floor, for instance.”
Further, these devices needed to be able to store energy for those instances when the device needs to function even when light is not available. “A temperature sensor still needs to work overnight or during the weekend,” says O’Callaghan, “so we had to design small solar cells to operate off low light that would also generate enough energy to bridge the time between availability of new energy (light). One of the keys is to reduce energy consumption, and we developed new technology that would sleep most of the time and (in the case of a temperature sensor) wake up periodically to take the temperature.”
In terms of range, transmissions sent by EnOcean devices travel up to 100′ inside and up to 1,000′ outside. In the U.S., the EnOcean wireless signal uses the 315 MHz frequency band (868 MHz elsewhere in the world).
Standard Offerings To The Market
In 2008, the EnOcean Alliance was formed to develop and promote self powered wireless monitoring and control systems for buildings by formalizing its interoperable wireless standard. With founding members from across North America and Europe, the San Ramon, CA-based group currently has 150 member organizations. These include manufacturers, building professionals, academics, and smaller distribution partners, as well as those involved in training and other advancements.
Creating the EnOcean interoperability standard, which was approved in 2009, involved a collaborative process during which members defined its specifications. Says O’Callaghan, “It is essential that if a building manager, or perhaps an electrical contractor, installs a wireless control system, they have flexibility to procure devices from a variety of sources knowing these will interoperate. The standard was agreed upon by the Alliance members to define a structure for the data contained in the wireless communication. Facility managers will know these products are interoperable because they adhere to the same standard.”
With the standard now defined, fms should expect to see an increasing number of EnOcean enabled products. Leviton is a member of the Alliance, and the company offers more than 30 devices using the technology. Bob Freshman, marketing manager at Leviton, explains why the company decided to be part of this development. “The decision was based on what this technology offers in terms of solutions. The devices do not require batteries, and we felt this was a huge benefit to the end user, since there is no maintenance needed and no disposal of batteries.
Freshman states the interoperability standard was also a factor, along with the fact that EnOcean devices use the 315MHz frequency. “This [frequency] has the advantage of having the best range of similar wireless devices with the least chance of interference from other RF [radio frequency] devices,” he says.
WAGO, a provider of automation solutions to facilitate BAS systems, has also developed EnOcean compatible products, and Charlie Norz, product manager for I/O systems there, says these products provide a gateway from devices to an automation fieldbus. “This enables users to develop and manage a comprehensive BAS, or to integrate existing systems with the organization’s other process and infrastructure,” he explains.
WAGO’s I/O products were put into use earlier this year as part of the 2010 Olympic Village in Vancouver, British Columbia. (Another EnOcean application employed at this Olympic site is outlined in the sidebar at the end of this article.)
In facility settings, wireless controls systems are often applied to lighting, HVAC, and, security systems. This trifecta of applications presents both challenges and opportunities for fms who operate and oversee these aspects. Building automation technology increasingly enables industry professionals to improve efficiencies in operations.
In this regard, fms can develop their wireless systems as far as their various resources allow. Cross application use across one, two, or more building systems creates dynamic functioning between BAS components and eases the time and effort an fm’s staff must spend monitoring and controlling building conditions.
In a hotel room, for instance, an occupancy sensor that turn lights on or off by “knowing” if the room is occupied can communicate with a thermostat sensor that acts to operate the heating/cooling system. Additionally, a magnetic contact sensor on the room’s sliding door can act as a signal to set back the air conditioning if it senses the door is opened; this sensor can also be linked with a security system to know if the door is opened when no guests are checked into that room.
EnOcean products are deployed in more than 100,000 buildings throughout the world. Freshman notes that Leviton products are installed in a wide variety of facility types, including schools, hotels, government offices and military bases, medical facilities, offices and manufacturing plants. “Recently, our wireless controls were used in an office space of a large military base,” he says. “The results were so successful that the project was expanded from one office building to the entire base. In addition to the energy savings from the wireless controls, they gained the ability to reconfigure the offices without rewiring.”
In new construction, typical advantages are lower cost and easier installation. O’Callaghan notes that a wireless system typically costs about 15% less than a wired system. “First cost is less,” he says, “The real advantage comes if [fms] decide to refurbish or change the function of a room. You don’t need to break into the wall and pull new wire [to accommodate the space changes]. You simply move the switch.”
This type of flexibility also applies to existing facilities transitioning from a wired to a wireless control system. In an office with movable walls or workstations that are reconfigured often, this approach provides fms options over the long-term.
Tracy Lenz, senior application engineer at WAGO, says, “An ideal application is for banks of office cubicles. An EnOcean switch is placed in a cubicle to operate corresponding lighting, and this provides greater control over specific areas and ultimately saves energy.” WAGO makes a transceiver that can accommodate up to 32 EnOcean switches.
Historic and other structurally sensitive facilities are also candidates for wireless controls. Says WAGO’s Norz, “EnOcean products can simplify restorations and electrical upgrades if drilling for wiring is not permitted or would greatly diminish historic significance.”
And while Lenz notes that another common application for EnOcean wireless technology is in conference rooms (for control of lighting, video screens, and window blinds), all sorts of facilities are candidates. “One of our current projects is a riverboat,” he explains. “The builder is switching to EnOcean so the crew can board the darkened boat, walk to one cabinet, and turn on every light wirelessly.”
Moving Forward With New Energy
As EnOcean technology increases its presence in the wireless controls market, research into another source of energy harvesting is being conducted. The focus is the use of thermodifferential energy, which is produced when ambient temperatures change.
O’Callaghan explains, “With several degrees of difference in temperature, the devices can start to generate electricity. In facilities that use hot water radiators for instance, which is common in New York City or Europe, our devices use the differential between water temperature and air to generate electricity. And this is proving sufficient not only to make the device wake up and send messages, but also to power a valve in order to adjust the amount of water and hence the amount of heat generated by the radiator. This is beginning to show that if you can start [self] powering not just sensors and switches but also the actuators—which are more power hungry—there are increased opportunities.”
Fms seeking long-term benefits from changes to their building system controls can look to wireless technologies to ease operations and construction tasks going forward. Self powered devices that use EnOcean technology take this one step further by eliminating the need to maintain them once installed.
This article was based on interviews with Freshman (www.leviton.com), Lenz (www.wago.com), Norz, and O’Callaghan (www.enocean.com). To learn more about the companies that offer EnOcean enabled products, visit www.enocean-alliance.org.
Do you have a comment? Share your thoughts by sending an e-mail to firstname.lastname@example.org.