Scientists harvest energy from beam's self-induced, self-sustaining vibrations in airflow

July 27, 2015 by Lisa Zyga, Phys.org feature

The energy harvester consists of a carbon fiber beam with a piezoelectric sensor and stepper motor to adjust the angle of attack of the airflow in the wind tunnel. Unlike previous designs, the system does not require a secondary vibrating structure because the beam itself vibrates, reducing the volume of the harvester and increasing its efficiency. Credit: Zakaria, et al. ©2015 AIP Publishing
(Phys.org)—In an attempt to harvest the kinetic energy of airflow, researchers have demonstrated the ability to harvest energy directly from the vibrations of a flexible, piezoelectric beam placed in a wind tunnel. While the general approach to harvesting energy from these "aeroelastic" vibrations is to attach the beam to a secondary vibrating structure, such as a wing section, the new design eliminates the need for the secondary vibrating structure because the beam is designed so that it produces self-induced and self-sustaining vibrations. As a result, the new system can be made very small, which increases its efficiency and makes it more practical for applications, such as self-powered sensors.

The researchers, Mohamed Y. Zakaria, Mohammad Y. Al-Haik, and Muhammad R. Hajj from the Center for Energy Harvesting Materials and Systems at Virginia Tech, have published a paper on the new energy-harvesting method in a recent issue of Applied Physics Letters.

"The greatest significance of the work is the reduction of the volume of the harvester, which translates to an increase in the power density, by eliminating the need for a secondary structure to be attached to the beam," Zakaria said. "This reduction is important in the design of very small harvesters that can be used to develop self-powered sensors."

The research shows that subjecting a flexible beam to wind at the right angle of attack can cause the beam to bend so much that the beam's "flutter speed" is significantly reduced. A large degree of bending also induces a change in the beam's natural frequencies that basically results in a synchronization of the beam's bending and twisting frequencies. Specifically, the beam's second bending frequency and torsional frequency coalesce, resulting in "self-induced flutter" of the beam. Complex aerodynamic effects ensure that the vibrations are self-sustaining, allowing for continuous energy harvesting.

The researchers demonstrated the design using a flexible cantilever beam with a piezoelectric transducer, which they hung from the ceiling in a . They found that the amount of energy harvested depends on a combination of factors, including the wind speed and the angle at which the wind hits the . At a wind speed of 10 m/s and 5.4° angle, the method can harvest approximately 0.3 mW of power. Although the researchers plan to improve the power levels, even this small value can be used to power individual sensors, which, as Zakaria explained, have a wide variety of applications.

"Future monitoring of different systems and platforms such as air and water systems, structures, vehicles, infrastructure, etc., as well as secure data transmission and reception from these sensors, will require the use of hundreds or thousands of sensors, data loggers and hardware components," Zakaria said. "The ability to integrate harvesters within these sensors or data loggers to develop such self-powered instruments is very much needed to enable their use without the need to replace batteries on a regular basis."

In the future, the researchers plan to design even smaller beams with specific geometries and capabilities, as well as to improve the performance of the piezoelectric elements.

Explore further: UK scientists develop optimum piezoelectric energy harvesters

More information: Mohamed Y. Zakaria, et al. "Experimental analysis of energy harvesting from self-induced flutter of a composite beam." Applied Physics Letters. DOI: 10.1063/1.4926876

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11 comments

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SciTechdude
5 / 5 (1) Jul 27, 2015
All types of motion, energy, or heat exchange are valuable options for recapture! Good work!
denglish
1 / 5 (1) Jul 27, 2015
Yes, this is very hopeful in our quest for clean energy.
allum
5 / 5 (1) Jul 27, 2015
- I am making a bet that one of the 1st applications is measuring air flow to brake rotors on race cars

With formula one cars worth $600,000.oo ensuring that brake rotor heat does not compromise bearins or cause tire beed failures and weighing in in grams this is a natural !
ab3a
1 / 5 (1) Jul 27, 2015
At 10 Meters/second it makes 0.0003 Watts of power? It would take a lot of those just to make a single LED light up. Even windmills could do better than that.
24volts
not rated yet Jul 27, 2015
If I'm not mistaken so did the kid with the magnet mounted on a ribbon fluttering in the wind with a coil mounted to the frame of the ribbon a few years ago. Other than the fact this version can be made really small I don't see much difference.
inorg_lsc
5 / 5 (1) Jul 28, 2015
The energy harvesting output of clear glass windows is already a few orders of magnitude higher: https://www.youtu...eXLtoKKU
The next step is to see what a huge building will generate, estimated to be few hundred MW-hrs per year
EnricM
not rated yet Jul 28, 2015
At 10 Meters/second it makes 0.0003 Watts of power? It would take a lot of those just to make a single LED light up. Even windmills could do better than that.


You didn't read the text, did you?
It clearly state that the aim is to be used in small self powered sensors not to power an aircraft carrier.
ab3a
1 / 5 (1) Jul 28, 2015
It clearly state that the aim is to be used in small self powered sensors not to power an aircraft carrier.


An embedded lithium battery could do that for months or even years and it would be a fraction of that size --nor would it need a 10 m/s breeze. Energy harvesting devices are commonplace. This does not strike me as one of the better ones.
SciTechdude
5 / 5 (1) Jul 29, 2015
It clearly state that the aim is to be used in small self powered sensors not to power an aircraft carrier.


An embedded lithium battery could do that for months or even years and it would be a fraction of that size --nor would it need a 10 m/s breeze. Energy harvesting devices are commonplace. This does not strike me as one of the better ones.


This is the smallest of tests, of course it's not better than what's already on the market. You don't strike me as one of the better ones either. >.>
katesisco
not rated yet Aug 02, 2015
Well, there has to be some way that the Bosnian pyramids made energy. They have tunnels and water. Seems like that would create a draft. Possible energy source.
The Giza pyramid has been shown to have a water based--http://sentinelke...--energy system.
Macrocompassion
not rated yet Aug 03, 2015
By taking the vibrational energy of a turbulent boundary layer from a wing or body of an air-vehicle (or water borne one for that matter), by this means, it would not only be possible to harvest energy buy to reduce the associated aerodynamic skin-frictional drag. Such a method using mechanical means has previously been proposed without good results to date, but it appears that this idea is even better!

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