New tools for harvesting wind energy may soon look less like giant windmills and more like tiny leafless trees. A project at The Ohio State University is testing whether high-tech objects that look a bit like artificial trees can generate renewable power when they are shaken by the wind--or by the sway of a tall building, traffic on a bridge or even seismic activity.

In a recent issue of the Journal of Sound and Vibration, researchers report that they've uncovered something new about the vibrations that pass through tree-shaped objects when they are shaken. 

Specifically, they've demonstrated that tree-like structures made with electromechanical materials can convert random forces--such as winds or footfalls on a bridge--into strong structural vibrations that are ideal for generating electricity.

The idea may conjure images of fields full of mechanical trees swaying in the breeze. But the technology may prove most valuable when applied on a small scale, in situations where other renewable energy sources such as solar are not an option, said project leader Ryan Harne, assistant professor of mechanical and aerospace engineering at Ohio State, and director of the Laboratory of Sound and Vibration Research.

The "trees" themselves would be very simple structures: think of a trunk with a few branches--no leaves required.

Early applications would include powering the sensors that monitor the structural integrity and health of civil infrastructure, such as buildings and bridges. Harne envisions tiny trees feeding voltages to a sensor on the underside of a bridge, or on a girder deep inside a high-rise building.

The project takes advantage of the plentiful vibrational energy that surrounds us every day, he said. Some sources are wind-induced structural motions, seismic activity and human activity.

"Buildings sway ever so slightly in the wind, bridges oscillate when we drive on them and car suspensions absorb bumps in the road," he said. "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."