The ZigBee Alliance announced in July 2009 that it will draft a standard for energy harvesting devices. ZigBee is a short range wireless protocol that uses less power than alternatives such as WiFi and Bluetooth but it has two serious limitations for energy harvesting. Firstly, the devices are rarely interoperable and secondly, the power consumed is too high for most of the potential in Wireless Sensor Networks (WSN), where energy harvesting is most desperately needed. Twenty year life with no maintenance is a typical target specification for the biggest potential applications. For this reason, other, lower power standards have gained traction in WSN as detailed in the IDTechEx report Wireless Sensor Networks 2009-2019. Other standards organisations in Europe and the USA are progressing standards that encompass such things as piezoelectric and vibration harvesting. Meanwhile, it seems that the ZigBee Alliance intends to wrestle with second generation energy harvesting where there is no battery though that seems a distant dream. Here the only major success has been the EnOcean Alliance with about 150 companies involved with interoperable devices, mainly for use in buildings, and well over 500,000 of them installed.
ZigBee is already the leading standard for parts of the smart grid and the in-building wireless network market, and it already has the International Electrotechnical Commission (IEC) seal of approval. Almost all ZigBee applications rely on batteries. This is why the ZigBee Alliance will amend its standard to work with more energy-harvesting devices, possibly battery free ones if they can crack the technical problems.
The EnOcean Alliance, like the ZigBee Alliance, is a consortium of companies whose energy-harvesting standard, also like ZigBee, is open, interoperable with existing standards — from TCP/IP to ZigBee itself. EnOcean has applied to the IEC to become an official global standard for energy-harvesting devices and, following great success in Europe, has started to gain traction in North America, with manufacturers such as Masco Corporation, Philips and Osram Sylvania embracing its technology.
Much at stake
A great deal is at stake, not least the potentially huge market for WSN with billions of sensors needed on trees for forest fires, utility assets, including the planned US smart grid, buildings, pollution monitors and so on. EnOcean has one project with 10,000 wireless, battery-less sensors installed on a single building site. The MGM Center in Las Vegas has about 70,000 ZigBee radios installed but they are not solely reliant on energy harvesting.
Not surprisingly, the ZigBee announcement has not been welcomed by the EnOcean Alliance. Even if ZigBee cannot lead to such low power long life devices, it can muddy the water and, in the view of EnOcean, perhaps infringe patents. "Our lawyers are waiting to evaluate anything ZigBee puts out related to energy harvesting very closely," EnOcean Alliance Chairman and CEO Graham Martin announced.
ZigBee Alliance sees EnOcean's reaction as proof that the EnOcean Alliance's standard is not yet really open. "It's a proprietary user group masquerading as an alliance," said ZigBee Alliance Chairman Bob Heile. "What they've got is not a standard," he added. "They've got a single-company proprietary solution and their alliance is their customer base. So you've got our open, publicly available solution with over 300 manufacturers involved vs. one company, one company, one company."
In response, EnOcean President Jim O'Callaghan, says, "There is a published specification and about 100 companies make products that communicate with other company's products using that spec," he said, adding that the EnOcean Alliance is an open, non-discriminatory organization. "One need not purchase product from EnOcean to be part of the EnOcean Alliance," he said. "And in fact, many members offer software or services to either OEMs, installers or end users."
However, we are not seeing direct competition here. Zigbee Alliance is not standardizing or developing harvested energy techniques. It is only creating extensions to the existing ZigBee stack that would permit OEMs to use a greater selection of available energy-harvesting solutions. Both sides agree that you cannot get enough power from energy harvesting to do all of the things that make ZigBee ZigBee.
The EnOcean Alliance notes that its standard can operate with less power than ZigBee because, rather than using the 2.4 GHz band like ZigBee does, EnOcean's standard operates at either 315 MHz or 868 MHz, where less power is required. Indeed, the 2.4 GHz band is massively crowded with microwave ovens, real time locating systems, non-stop road tolling, WiFi, Bluetooth and so on beaming it at each other and it can be greatly affected by water and metal. On the other hand ZigBee's Heile argues that its frequencies are a downside of EnOcean's technology, because those are regional bands, while ZigBee's 2.4GHz is a global band, which makes it more user-friendly all over the world. IDTechEx would note that this has not stopped UHF RFID, which uses the roughly 850-950 MHz variously approved bands across the world becoming the fastest growing form of RFID. Indeed, EnOcean's O'Callaghan has noted that there is less interference in his bands, particularly the 315 MHz.
IDTechEx believes that energy harvesting can only become a multibillion dollar business if standards are created and interoperable equipment becomes more widely available. We see highest volume potential for multiple energy harvesting in single devices without batteries and offering twenty year life. For example, affordable, long-lived WSN networks with much more than 10,000 nodes are sorely needed. ZigBee does not seem appropriate to this and EnOcean does not yet offer WSN ie mesh networks, though it does have impressive two way, battery-less wireless sensor systems. For more attend the co-located Wireless Sensor Networks & RTLS and Energy Harvesting USA events in Denver Colorado 3-4 November. EnOcean Alliance will present its case, and several companies present on their developments with ZigBee. Particular emphasis will be on what the potentially large customers want. NASA, Lockheed Martin, Northrop Grumman, SPAWAR Systems Center San Diego, the US Navy, Adidas, BP, Hospital Corporation of America, GE Global Research and Texas Instruments are among those speaking.