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Tiny, artificial trees could form the next generation of windmills

Wind power inspired by nature.

DAVID NIELD
4 MAR 2016
 

Researchers in the US have proposed a new form of wind power: small, artificial, mechanical trees capable of producing energy from their vibrations. Working with the natural breeze, or small movements caused by other factors, the scientists hope that new forms of renewable energy can be developed in the future.

The idea is to create a device that can convert random forces – whether that's from the footfall of pedestrians on a bridge, or a passing gust of wind – into electricity that can be used to power devices. And the researchers have found that tree-like structures made from electromechanical materials are perfect for the task.

 

"Buildings sway ever so slightly in the wind, bridges oscillate when we drive on them and car suspensions absorb bumps in the road," said project leader Ryan Harne from Ohio State University. "In fact, there's a massive amount of kinetic energy associated with those motions that is otherwise lost. We want to recover and recycle some of that energy."

Harne and his team used a mathematical model to determine that a steady source of electricity could be produced from the intermittent oscillations you would typically get from random gusts of wind. Using a process known as internal resonance, the researchers found it would be possible to coax an artificial, electromagnetic tree to vibrate with large amplitudes at a consistent low frequency.

To test their hypothesis, the scientists constructed a tree-like device from two small steel beams (one representing the trunk and the other a branch). A small voltage was produced even when the tree didn't visibly appear to be shaking at all, and the voltage increased as a series of intermittent nudges were introduced, proving the team's hypothesis that random energies can produce vibrations useful for generating electricity.

Even when "massive amounts of noise" were added to the simulation, the tree still produced a robust and reliable voltage output.

Now Harne and his team are going to continue their research and build on the proof-of-concept they've created, to see if it could form the basis of a viable, long-term renewable energy source. To begin with, Harne says, the technology could be used to power the sensors monitoring certain types of civil infrastructure, such as roads and bridges.

As picturesque as windmills can be, they're huge in size, have a tendency to get very loud, and struggle in very cold conditions. A small forest of mechanical trees could one day provide an alternative way of harnessing the kinetic energy around us all the time.

The results have been published in the Journal of Sound and Vibration.

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