Artificial, leafless trees could turn nature's vibrations into electricity

leafless tree
CC BY-SA 2.0 端木月明

We've covered quite a few small-scale wind turbines over the years -- some made to resemble trees, others just small, vertical-axis versions -- and universally they would provoke some heated comments. You all would respond, rightly so, that these designs will just never be effective sources of energy generation, but we cover them because we're always wanting to discuss new ideas in clean technology and generally feel like these ideas, even if unfeasible, are worth mentioning because they may inspire the next new technology that is feasible and effective.

Luckily, this new artificial tree is not a wind turbine. It is inspired by tree swaying and does harness energy from the wind, but it doesn't rely on the wind rotating or spinning anything, it instead harnesses the vibrations caused by the wind, or traffic, or seismic activity, or the swaying of a tall building or anything else that may cause it to shake.

Researchers at The Ohio State University are developing this new technology that resembles a tree with no leaves and only a few branches. The team is using a tree design because they discovered that tree-like structures made with electromechanical materials can convert random forces like wind or footsteps on a bridge into strong structural vibrations that can then be converted into electricity.

The researchers don't imagine groves of tall artificial trees placed everywhere, they actually believe this technology is best suited for small scale applications, requiring little power, where other clean energy sources won't work. One possible early use could be tiny trees powering bridge and building sensors that monitor the integrity of the structures. Today, these types of sensors rely on batteries or being plugged into the grid.

The researchers point out that there are constant vibrations all around us from nature, like wind and seismic activity, and human movements that these trees could turn into electricity.

“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, assistant professor of mechanical and aerospace engineering and director of the Laboratory of Sound and Vibration Research. “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.”

Tree-like designs have been used for a long time in energy generating technologies, but this is the first time that random vibrations, like those in reality, have been proven to be a reliable and consistent energy source.

Through computer modeling and then small-scale testing, the researchers were able to show that they could "exploit internal resonance to coax an electromechanical tree to vibrate with large amplitudes at a consistent low frequency, even when the tree was experiencing only high frequency forces...It reached a tipping point where the high frequency energy was suddenly channeled into a low frequency oscillation. At this point, the tree swayed noticeably back and forth, with the trunk and branch vibrating in sync."

These tiny tree produced around 2 volts of electricity at this stage, which is low, but this was just a proof-of-concept. The team will now work on scaling up the experiment and increasing the voltage, but they believe this design will be a reliable source of renewable energy for low power applications around the world.

Tags: Biomimicry | Renewable Energy | Technology

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