Energy Harvesting Smackdown: ZigBee vs. EnOcean

Read between the lines of the ZigBee Alliance’s announcement last month of its intention to draft a standard for energy-harvesting devices — which can capture and store energy from external sources like the sun and movement — and here’s what you’ll find: The market for such devices, which includes the likes of battery-free sensors for wireless networks, is rapidly heating up and the ZigBee Alliance, which promotes the ZigBee standard, needs to move quickly if it wants to be part of it.

Quickly, but carefully. The group’s announcement has already ruffled the feathers of the lesser-known EnOcean Alliance, which has developed an energy-harvesting standard based on technology from Siemens spinoff EnOcean and is protected by dozens of patents. “Our lawyers are waiting to evaluate anything ZigBee puts out related to energy harvesting very closely,” EnOcean Alliance Chairman and CEO Graham Martin told us.

The Market for Battery-Free

At stake is control of a market that is set to explode in the coming years. As
the smart grid
is built out, utilities, building owners and consumers will look to wireless sensors and networks in buildings to deliver increasingly granular data about energy use. The sheer scale of these projects can be enormous. EnOcean has one project with 10,000 wireless sensors installed on a single building site. The MGM Center in Las Vegas has about 70,000 ZigBee radios installed.

That’s a heck of a lot of sensors and wireless nodes. If every sensor and node uses a battery, that means the added expense of replacing the batteries every few years. Sustainability directors also won’t be too keen on explaining why their energy-efficiency strategy is actually resulting in the disposal of tons of batteries per year in landfills.

The ZigBee standard 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. But it’s been largely dependent on batteries — hence why the ZigBee Alliance is amending its standard to work with more energy-harvesting devices.

The EnOcean Alliance, like the ZigBee Alliance, is a consortium of companies (currently 110 of them) whose energy-harvesting standard, also like ZigBee, is open, interoperable with existing standards — from TCP/IP to ZigBee itself, it claims. It has applied to the IEC to become an official global standard for energy-harvesting devices and has started to gain traction in North America, with manufacturers such as Masco Corp., Philips and Osram Sylvania embracing its technology.

The Smackdown

For its part the ZigBee Alliance sees EnOcean’s reaction as proof that the EnOcean Alliance’s standard is not really open. “It’s a proprietary user group masquerading as an alliance,” ZigBee Alliance Chairman Bob Heile told us this week. “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.”

EnOcean President Jim O’Callaghan, however, disagrees. “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.”

The competition between the two is clear in company materials, too. An internal ZigBee Alliance document says: “To bridge the gap with EnOcean a marketing campaign should be considered, with the announcement of a batteryless, maintenance free solution compatible with the current ZigBee standard.”

Regardless of how the groups view each other, Heile said that nothing the ZigBee Alliance is working on flies in the face of EnOcean’s intellectual property. “We are not standardizing or developing harvested energy techniques,” he said. “There are plenty of suppliers for that, EnOcean being one of them. What we are doing is creating extensions to the existing ZigBee stack that would permit OEMs to use a greater selection of available energy-harvesting solutions.”

Nonetheless, Martin said that while nothing the ZigBee Alliance is working on is in violation of its IP as soon as any of its OEM partners release an energy-harvesting ZigBee product to market, EnOcean lawyers will go to work protecting the company’s 40-odd patent families.

The Differences

Above and beyond any IP concerns, ZigBee will face some hurdles developing an energy-harvesting standard, namely that there won’t be a completely battery-free ZigBee option. “You can’t get enough power from energy harvesting to do all of the things that make ZigBee ZigBee,” said Martin. On this point Heile agrees.

The EnOcean Alliance says 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. But ZigBee’s Heile contends that’s 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.

EnOcean’s O’Callaghan retorts that because the 2.4 GHz band is so widely used there is way too much traffic in that space. “Devices in the 315 MHz band only have to deal with the occasional garage door or remote keyless entry for a car,” he said.

Still, what ZigBee has is traction. The standard is widely thought to be the de facto choice for energy-related wireless products and has spent years making headway in the smart grid space. And if the history of standards battles has taught us anything, it’s that the most advanced technology isn’t always the one that wins out.


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