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Good Vibrations!

Eun Sok Kim, chair of the Ming Hsieh Department of Electrical Engineering - Electrophysics, and Ph.D. candidate Qian Zhang discover a new way to convert the natural vibrational energy of bridges into electrical power.
By: Conrad Wilton
April 19, 2013 —
Professor Eun Sok Kim, chair of the Ming   Hsieh Department of Electrical Engineering - Electrophysics

We’ve all heard of harvesting wheat, corn, and barley, but what about vibrations? Professor Eun Sok Kim, chair of the Ming Hsieh Department of Electrical Engineering - Electrophysics, and fourth-year Ph.D. candidate, Qian Zhang, have discovered a groundbreaking method to harvest vibrational energy and convert it into electricity that can power complex sensor networks without any batteries.

Kim and Zhang's approach is to place multiple magnets and metal coils into a tiny apparatus that can then be bolted to moving objects such as cars or planes. As the car moves, the magnets vibrate against the coils and spark an electric current that can be used to power sensors, which monitor the car’s tire pressure or engine temperature. The device can also be installed on vibrating structures like a bridge. There, vibrational energy can power pressure sensors that detect cracks and voids in the structure before they become dangerous.

“If a sensor network relies on battery power, once the battery runs out, replacing that battery can be expensive,” Kim said. “Also, once the sensor’s battery fails, that sensor can’t gather any more information, so you could be lacking valuable data.”

Kim and Zhang's vibrational-energy harvesters provide sensors with “permanent power,” drastically reducing maintenance costs.

“Harvesting vibrational energy goes back to the time of (Michael) Faraday, where traditionally a single magnet with a coil was used,” Kim said. “Our new approach is multi-magnet and multi-coil, all arranged uniquely with the inventive idea to maximize (magnetic) flux change for a given vibrational amplitude.”

Diagram of a Vibrational-Energy Harvester

Using multiple magnets and coils to harvest vibrational energy is not a novel notion. What makes Kim and Zhang's approach unique is a specific orientation of magnets and coils that they currently keep under wraps. Nevertheless, this special arrangement can generate approximately ten times as much power as the conventional method, making it a more reliable and less expensive source of renewable energy.

The maximum amount of power one of Kim and Zhang's vibrational-energy harvesters can generate is .27 watts, enough to light an incandescent bulb. Additionally, that is more than enough energy to power a wireless sensor network on a bridge, in an automobile, or inside a home.

"VIbrational-energy harvesters can replace traditional power sources and provide for more efficient power generation over longer periods of time," Zhang said.

Ultimately, Zhang and Kim are confident that in three to five years vibrational-energy harvesters will become available to consumers. In addition, various government departments, including the Department of Defense, have expressed interest in their innovation.

“Soldiers have to carry lots of electrical devices that require battery power, but those batteries can weigh them down,” Kim said. “They don’t have to carry batteries anymore if they use a vibrational-energy harvester, which can power all their equipment without the extra weight.”