Vibration &Energy Harvesting:

Powering Up

the Battery-Free World

Oct 31, 2010 23:58 ideyoshi Kume

The amount of electricity generated by vibration is proportional to the frequency and amplitude of the vibrator, which means that maximizing both will easily increase output. Because of the way vibration-based generators work, however, fine adjustment is needed to ensure they resonate at a particular frequency, and the inherent vibrational frequency must be matched to the application.

A look at the vibration parameters for the announced prototypes reveals just what application each firm is aiming at. Sanyo Electric, for example, plans to having people wear its device and set the frequency to 2Hz Note 8). Murata Manufacturing chose 10Hz to 20Hz, which is a neat fraction of the 50Hz/60Hz frequency of commercial power. Their decision, explains a source at the firm, was that the large number of vibration sources in that range would provide a wide range of applications. Omron, on the other hand, comments that “about 30Hz is common in factories, vehicles and bridges, for example.”

Note 8) Sanyo Electric is now developing a prototype measuring 23mm x 42mm x 6mm, capable of generating 120?W.

Omron is planning to wait until the market scale becomes a little clearer, and ship product in 2011, according to Masashi Doi, manager, core technology centerof the firm. The company has already shifted its development target from boosting generating performance to assuring reliability. Many wireless sensor networks are expected to be “plug and forget,” capable of running for at least five years without needing anything, so reliability assurance is critical.

Troubling Patents

Patents could pose a thorny problem for practical applications, though. Basic patents do exist for energy harvesting, and some people in the industry have warned that care will be needed when launching business in the field. They are held by EnOcean Note 9), and already eighteen key patents in energy harvesting have been identified in the firm’s portfolio.

Note 9) EnOcean began research into energy harvesting in 1995, when it was still a research arm of Siemens AG of Germany. It became an independent venture business in 2001, acquiring all related patents from Siemens in return for 19% of its issued stock.

Fig. 10 Patents held by EnOcean
The patents are for “transmitting collected data using power acquired through energy harvesting technology,” which covers a wide range of applications.

Of these, the strongest is said to be international patent WO 98/36395 (Fig. 10), which covers a very wide scope. It has been granted in a number of nations already, including Germany, the US and China. The patent was filed in Japan in 1998, but patent examination was refused and as a result the patent has not been granted. EnOcean refused to accept the judgment, requesting reconsideration in 2008.

A number of manufacturers planning to ship products using energy harvesting technology as early as 2011 are worried about possible patent issues, but EnOcean Chief Executive Officer (CEO) Markus Brehler has said “Our business is shipping products, not arguing about patents.” In any case, though, care will be needed in export sale.

1) Harrop, P. et al., Energy Harvesting and Storage for Electronic Devices 2010-2020, IDTechEx Ltd., July 2010.


3) Roundy, S. et al., “A study of low level vibrations as a power source for wireless sensor nodes,” Computer Communications 26, Issue 11, pp. 1131-1144, July 2003.

Sourced & published by Henry Sapiecha

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