The Growth of 'Energy-Harvesting' Wireless Building Controls
By Graham Martin, Greener Buildings
For the past few years, self-powered wireless technology has been gaining traction in building automation applications, especially in Europe and now in North America.
Besides simplifying the cabling run of a building, self-powered wireless technology allows a faster response to changes in how a building is internally configured -- cutting cost by saving time and expense in needed retrofits.
Also attractive from an operations and maintenance standpoint, self-powered wireless sensors require no regular servicing and, as an added benefit, provide office occupants with maximum freedom of movement and convenience in locating the various control devices that impact their “quality of life” in the work environment.
If there are no batteries to replace, for example, there’s no restriction in where a building control device can be located. Indeed, why install that rocker switch operating the sun blinds on a wall across the room, when it could be placed as easily as a cup of coffee on your desk?
Wireless sensor modules that harvest the power they need for operation from their surroundings are able to do so by means of super-efficient energy converters and ultra-low-power electronic circuitry that transmits in the 868 MHz or 315 MHz frequency band, which makes them suitable for worldwide application.
The wireless control signals themselves, called “telegrams,” are just one millisecond long, or about one hundred times shorter than the signal of a conventional wireless switch.
To prevent transmission errors, these telegrams are randomly repeated twice in the space of about 30 milliseconds. Transmitting data packets in random intervals makes the probability of a data collision extremely rare and allows the reliable parallel operation of hundreds of wireless switches and sensors in close proximity to one another.
Statistics show that, even in a situation where you have 200 wireless sensors each sending their signals once a minute, the probability of a data collision is only one in every ten thousand transmissions.
A Technology for Every Need
Self-powered wireless modules are suitable for use in many different surroundings, in applications ranging from room thermostats with preset temperatures to maintenance-free wireless window contacts and handles. The range of typical batteryless wireless sensors is around 1000’ (300m) in the open and up to 100’ (30m) inside buildings.
To prevent the possibility of overlap with other wireless switches, modules typically come with a unique 32-bit identification number that allows them to function reliably without “stepping on the toes” of other nearby wireless devices.
The energy that powers these devices is produced by the pressing of a button, the turning of a handle, or from tiny solar cells.
Another form of energy harvesting now under development is the generation of operating power from the difference between two temperatures. As Buck Rogers as this may sound, we will soon see sensors that generate the current they need to wirelessly transmit signals by sensing the difference in temperature between, for example, the radiator heating a room and the surrounding air.
Flexibility Made to Measure
In this brave new world of the greener facility, intelligent building automation will continue to provide the key to future sustainability advancements, as new strides are made in cutting operating costs and reducing the energy consumed during normal building operations.
Self-powered wireless switches and sensors, whose developers include EnOcean Alliance, will continue to greatly simplify cabling requirements while, at the same time, increase flexibility.
No minor advantage, this technology allows the ability to attach and re-attach sensors, switches and other devices wherever they provide optimum benefit and, by so doing, the complexity and cost of internal building retrofitting is greatly reduced.
Another spot of good news, the inherent interoperability of batteryless wireless technology, products and systems ensures easy integration with leading building automation systems, including LonWorks, KNX, BACnet, TCP/IP and Ethernet.
At the bottom line, batteryless wireless sensors may be viewed as an enabling technology that will help sustainable facility professionals to implement high-performance energy-management strategies with less effort and expense.
Graham Martin, chairman and CEO of EnOcean Alliance, is an electronics industry veteran with more than 25 years' experience in analog and RF solutions. The EnOcean Alliance is a global consortium of 150 companies working to develop and promote self-powered wireless monitoring and control systems for sustainable buildings by formalizing an interoperable wireless standard.
Images courtesy of EnOcean.