most powerful millimeter-scale energy harvester
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.
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, Long-lasting power is the greatest hurdle to large-scale use of pervasive information-gathering sensor networks, the researchers say.
The researchers have built a complete system that integrates a high-quality energy-harvesting piezoelectric material with the circuitry that makes the power accessible. (Piezoelectric materials allow a charge to build up in them in response to mechanical strain, which in this case would be induced by the machines' vibrations.)
The active part of the harvester that enables the energy conversion occupies just 27 cubic millimeters. The packaged system, which includes the power management circuitry, is in the size of a penny. The system has a large bandwidth of 14 Hertz and operates at a vibration frequency of 155 Hertz, similar to the vibration you'd feel if you put your hand on top of a running microwave oven.
A novel silicon micromachining technique allows the engineers to fabricate the harvesters in bulk with a high-quality piezoelectric material, unlike other competing devices. The market for power sources for wireless sensor networks in industrial settings is expected to reach $450 million by 2015.
These new devices could have applications in medicine and the auto industry too. They could possibly be used to power medical implants in people or heat sensors on vehicle motors.