The Ohio State University is conducting a research project to understand howyou can generate renewable energy from environmental vibrations generated bynatural atmospheric forces, by natural events or human activities. In a recent issue of the Journal of Sound and Vibration, OSU researchers say they have discovered something new on the propagation of vibrations using particular structures that can remember the schema of a leafless tree elementary.
In particular, the researchers were able to prove that these structures, built withelectromechanical materials, are able to convert random forces, such as those performed by the wind or by the steps of the crowd on a bridge, in strongstructural vibrations that are suitable to the production of electricity. Although the idea may bring to mind wide open spaces where these particulars"electromechanical trees" swaying in the wind professor Ryan Harne, head of research at the Laboratory of Sound and Vibration of OSU, explains that thistype of technology is showing its effectiveness when applied on a small scale, in those situations where the generation of energy from renewable sources is not aviable approach.
"The buildings sway slightly in the wind, the bridges we cross them swaying and suspension of the car absorb the disconnections of the road. There is a large amount of kinetic energy related to these movements is lost. We want to recoverand recycle a portion of this energy, "said Harne. In a first step, the idea of usingsimilar devices to trees to catch the wind or vibration energy seemed logicalenough, since real trees dissipate energy when sway. Already other groups havehad the opportunity to test the effectiveness of similar structures using vibrationideals, that is different from the random generated in the real world.
The assumption was that random natural forces were not suitable to generatethat kind of homogeneous oscillations that allow themselves to generate electricity. Using the mathematical modelling Harne has determined that for the trees you can manage to keep vibrations to a homogeneous random input, so that despite many frequency energy can be effectively captured and preserved.In particular Harne identified the possibility of inducing a tree low frequency and large amplitude electromagnetic vibrate, even when the structure is stressed only by high frequency forces. Mathematical modelling has determined that thissystem can work even when the forces are greatly overwhelmed by randominterference, as the natural vibrations of the environment.
Harne and colleagues then tested the mathematical model with an experimentby building a device similar to a tree using two small steel stems (stems andbranches) connected by a strip of the electromechanical material polyvinylidene fluoride (PVDF) that converts the structural vibrations into electricity. This structure was installed on a device rocked back and forth at high frequenciesthat have made it possible to generate a small voltage to 0.8 volts.
At this point the researchers added "noise" to the system, as if the tree wasstruck accidentally in various directions. At this point the structure showed whatHarne called "saturation phenomenon": at one point the high frequency energyis suddenly channeled into a swing at low frequency. At this point the tree variesconsiderably and perceptibly back and forth, with a synchronized vibration oftrunk and branches. The low-frequency allowed to generate a voltage more than double, to almost 2 volts.
It is of low voltage, but the experiment represented the so-called "proof of concept" or failed to demonstrate that random energies can produce usefulvibration to generate electricity. "We created a lot of noise and discovered that the phenomenon of saturation is quite strong and the output voltage is reliable.This is something that was not previously known, "said Harne.
One of the first practical applications there might be feeding of sensors suitable for structural health monitoring of civil infrastructure, such as bridges and buildings. Harne you imagine these little trees to fuel sensors placed at the bottom of a bridge or in the supporting structures of a building. Sensors monitorthe integrity of the building by detecting vibrations that they run through. The initial goal of the project is to transform the vibrations into electric energy sothat structural monitoring systems can be powered by the same vibrationsranging to monitor.
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