University of Michigan electrical engineers have built a piezoelectric generator 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. It’s smaller than a penny.

University of Michigan Piezoelectric Energy Harvester. Click image for the largest view. Image Credit: Erkan Aktakka

The UM team has 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.)

Called a micro machining piezoelectric or MEMS the unit is packaged with its MEMS together with tiny circuit elements that form a complete vibration energy harvester in just 27 cubic millimeters. The tiny unit harvests vibrational energy between 14-and-155 cycles-per-second (155 Hz is similar to the vibration you’d feel if you put your hand on top of a running microwave oven) and produces about 200 microWatts from 1.5g vibrations.

The energy harvester sends the charge to a supercapacitor up to 1.85 volts, which powers the load. The researchers estimate the energy harvester could repeat this cycle for 10-to-20 years without degradation.

Khalil Najafi, one of the system’s developers and chair of Electrical and Computer Engineering at UM said, “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.”

The 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.

Erkan Aktakka, one of the system’s developers and a doctoral student in Electrical and Computer Engineering explains, 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.

Aktakka thinks the wireless sensor networks can be expected to grow to $450 million by 2015, “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.”

Perhaps most interesting is the team as come up with a novel silicon micro machining technique that allows the engineers to fabricate the harvesters in bulk with a high-quality piezoelectric material, unlike other competing devices.

Najafi believes 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.

The team will present the new harvester at the 16th International Conference on Solid-State Sensors, Actuators, and Microsystems (TRANSDUCERS 2011) in Beijing in June. The research was funded by the Defense Advanced Research Projects Agency and National Nanotechnology Infrastructure Network.

The University of Michigan is pursuing patent protection for the intellectual property, and is seeking commercialization partners to help bring the technology to market.

Stacked up to say nine units would get well past 12 volts, enough for battery charging, or 1000 would get to 2 hundredths of watt, a worthwhile amount of power.

This design is fascinating in its completeness at the diminutive size.  Its quite good voltage and should production get to scale perhaps the price might be low enough that really noticeable wattage production could get to market.  The team’s work might not drive resistance heating or other power hungry loads, but for fast low power needs, remote or high maintenance positions, bursting messaging from low draw sensors, even some micro processors and memory chips, there will be a huge market – if the price can plunge far enough fast enough.

It’s a very interesting engineering effort – but please UM, tell us more about the team’s micro machining technique!  We want to see the rest of the iceberg.


3 Comments so far

  1. Salvatore Peres on October 27, 2011 6:17 AM

    I am agree that a way for wireless sensor in that thay have autogenerate elctricity. The energy from vibration open new vision also in automotive e industrial site. Please give me information about application that we could utilize.

  2. concrete tanks ballarat on January 13, 2012 3:50 PM

    Reliable information you. Many thanks for sharing.

  3. my on January 25, 2014 12:26 PM

    Where can i buy this? Article is from 2011 so now should be possibility of buying it.

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