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Wireless, MEMS advancements boost energy harvesting

Posted: 06 Apr 2009 ?? ?Print Version ?Bookmark and Share

Keywords:energy harvesting? wireless application? MEMS? sensor?

Technologies that scavenge energy have been in development for the last 20 years. They enable so-called "perpetual devices" to monitor buildings, to gauge tools and machines installed in inaccessible places, or to sense structural integrity or movement.

The key to such perpetual devices is that they perform these tasks indefinitely, thereby eliminating the need to replace batteries. Energy harvesting is increasingly becoming a hot topic. But "what has really changed energy harvesting in the last two decades?" asked Patrick Mannion, editorial director of TechOnline, who moderated the energy harvesting panel at Embedded Systems Conference March 31.

The answer, in sum, is a confluence of the development of wireless and lower power electronics, along with advancements in sensors and MEMS. The result is a combination of factors that is fundamentally changing today's energy-harvesting market.

The development of low-power electronics and wireless technologies made it "viable" to use harvested energy for a number of applications, said Dave Freeman, engineering manager at Texas Instruments Inc.

Patrick Chapman, associate professor at University of Illinois, agreed. "The power of wireless communication devices has become so low that we can finally start doing something about small, harvested energy," he said.

Eugene You, application engineering manager at EnOcean, added, "Don't forget the price of wireless devices." With a steady decrease in the cost of wireless devices, he said, "We can now put [perpetual devices] everywhere for sending data wirelessly, and forget about it."

Nonetheless, you still need a power storage device, said Steve Grady, VP of marketing at Cymbet Corp. Some systems are required to occasionally handle a large burst of energy. If you can store energy, such as in a thin-film battery Cymbet is developing, "you can respond to it faster," Grady added. And that energy storage device "needs to hold charge long-term."

Quest for killer app
Every new technology often needs a hot mass market that can help lower the cost of the technology and push it to a broadly penetrated mainstream technology. What's the killer app for energy harvesting technology?

"Wireless is the killer app for energy harvesting," said Keith Abate, director of business development, at Perpetuum.

TI's Freeman agreed. Wireless sensor networks used in so many different applications will drive the acceptance of energy harvesting, he explained.

Cymbet's Grady chooses smart buildings and intelligent monitoring as killer apps. "I see the stimulus package helping to create a lot of access to energy harvesting," he added.

A new wrinkle is that MEMS sensors themselves may become energy harvesting devices, said the University of Illinois' Chapman. Further, "Things like medical sensor devices that could be flown into blood could be also killer apps, for example," he added.

The Holy Grail for energy harvesting applications lies in the use of the technology when combined with wireless and sensors.

With the help of energy harvesting devices, one can collect data, process it, transport it and analyze it. What's lacking is interoperability among such data.

The use of Internet Protocols is ideal for that purpose, said Cymbet's Grady, so that data collected from different wireless sensor networks can be pulled together. The problem of using IP is that it's power-hungry when used in wireless devices. Further, if using IPs, one needs a whole new address space for billions of sensors.

Developing the standard protocol for a variety of wireless sensor networks is still "a few years off," said Grady.

One can use a variety of wireless technologies, including Wi-Fi, Bluetooth, Zigbee or others. But without interoperability, a killer wireless/sensor application for energy is hardly a sure thing, Grady acknowledged.

- Junko Yoshida
EE Times

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