Electrical engineers from the University of Michigan claim to have invented a technique for micro-machining piezoelectric MEMS that generate 10-times more energy than conventional energy harvesters. The research team said a penny-sized piezoelectric MEMS could generate enough electricity to power medical implants in the body and wireless sensors on motor vehicles.
It is the most powerful millimeter-scale energy harvester.
'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.'
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.)
'There are lots of energy sources surrounding us. Lightning has a lot of electricity and power, but it's not useful,' Najafi said. 'To be able to use the energy you harvest you have to store it in a capacitor or battery. We've developed an integrated system with an ultracapacitor that does not need to start out charged.'
...In theory, these devices could be left in place for 10 or 20 years without regular maintenance. 'They have a limitless shelf time, since they do not require a pre-charged battery or an external power source,' Aktakka said."