Wind energy could get a makeover now that engineers from Ohio State University have developed new tools for harvesting wind energy that look less like giant windmills and more like tiny leafless trees, taking advantage of the vibrational energy around us daily.
Researchers are working on a project to determine whether high-tech objects that look like artificial trees can generate renewable power when they are shaken by the wind, or even by the sway of a tall building, traffic on a bridge or seismic activity.
In the course of its research, the team demonstrated that tree-like structures made with electromechanical materials can convert random forces, such as wind, into strong structural vibrations capable of generating electricity.
According to project leader Ryan Harne, assistant professor of mechanical and aerospace engineering at Ohio State, the technology would not require forests full of mechanical trees, but instead would be most valuable on a smaller scale, in situations where other renewable energy sources such as solar are unavailable.
The “trees,” which would look like the trunk of an ordinary tree, could find early applications 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. Since sensors monitor how sound a structure is by measuring vibrations, the team’s initial goal is convert those vibrations into electricity – in effect, getting the system to power itself.
“Buildings sway ever so slightly in the wind, bridges oscillate when we drive on them and car suspensions absorb bumps in the road,” says Harne. “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.”
Currently, the only power source for structural sensors are batteries or plugs, which can be costly and difficult to manage in remote locations, but if sensors could capture vibrational energy, they could acquire and wirelessly transmit their data self-sufficiently.
While other teams have toyed with the concept of tree-swaying in energy harvesting, none have done so while making an effort to capture realistic ambient vibrations with a tree-shaped electromechanical device, since many assumed that random forces wouldn’t be suitable for consistent energy generation.
However, after testing, Harne and his team installed a model tree on a device that shook back and forth at high frequencies, and its electromechanical material, polyvinylidene fluoride (PVDF), was able to produce about 0.8 volts from the motion. By adding noise to the system, the tree was able to produce 2 volts.
Although these numbers are low, the proof-of-concept experiment proved that random energy can produce vibrations capable of generating electricity.
Harne plans to continue exploring the concept.