Powerful millimeter-scale energy harvester generates electricity from vibrations

Electrical engineers at the University of Michigan have built a device that can harness energy from vibrations and convert it to electricity with five to 10 times greater efficiency and power than other devices in its class. And it's smaller than a penny.

"In a tiny amount of space, we've been able to make a device that generates more power for a given input than anything else out there on the market," said Khalil Najafi, one of the system's developers and chair of Electrical and Computer Engineering.

This new vibration energy harvester is specifically designed to turn the cyclic motions of factory machines into energy to power wireless sensor networks. These sensor networks monitor machines' performance and let operators know about any malfunctions.

The sensors that do this today get their power from a plug or a battery. They're considered "wireless" because they can transmit information without wires. Being tethered to a power source drastically increases their installation and maintenance costs, said Erkan Aktakka, one of the system's developers and a doctoral student in Electrical and Computer Engineering.

Long-lasting power is the greatest hurdle to large-scale use of pervasive information-gathering sensor networks, the researchers say.

"If one were to look at the ongoing life-cycle expenses of operating a wireless sensor, up to 80 percent of the total cost consists solely of installing and maintaining power wires and continuously monitoring, testing and replacing finite-life batteries," Aktakka said. "Scavenging the energy already present in the environment is an effective solution."