The mesmerizing flutter of a quaking aspen's leaves has inspired a new kind of energy harvester that could one day provide backup power to future rovers scouring the surface of Mars.
In a paper published in the journal Applied Physics Letters, researchers at the University of Warwick in Coventry, England, say they looked to the aspen because of the way its leaves dramatically oscillate even under extremely low-wind conditions. By studying the mechanisms behind this natural quiver, they were able to engineer a new kind of wind harvester capable of operating in the harshest of environments.
"What's most appealing about this mechanism is that it provides a mechanical means of generating power without the use of bearings, which can cease to work in environments with extreme cold, heat, dust or sand," lead author Sam Tucker Harvey, a University of Warwick PhD engineering researcher, said in a statement.
While the energy generated would be small, Harvey says it would be more than enough to power autonomous electrical devices.
"These networks could be utilized for applications such as providing automated weather sensing in remote and extreme environments," he adds.
A backup lifeline on Mars
Beyond applications on Earth, the scientists say their "galloping energy harvester" could also be used to help sustain rovers on Mars. One of the key obstacles faced by robots operating on the red planet is surviving extreme nighttime temperatures in excess of minus 146 degrees Fahrenheit. Adding a low-wind quiver to future rover designs could utilize Mars' winds to generate enough power to keep internal systems warm and avoid the frosty fate suffered by the Opportunity rover last summer.
"The performance of the Mars rover Opportunity far exceeded its designers' wildest dreams but even its hard-working solar panels were probably eventually overcome by a planetary-scale dust storm," co-author Dr. Petr Denissenko said. "If we could equip future rovers with a backup mechanical energy harvester based on this technology, it may further the lives of the next generation of Mars rovers and landers."
This curved blade was inspired by aspen leaves. According to researchers, this design creates enough sustained self-oscillation in low-wind environments to generate power. (Photo: University of Warwick)
As for the design of their mechanical blade, the researchers said they stopped short of incorporating all of the clever natural engineering behind the aspen leaf.
"In nature, the propensity of a leaf to quiver is also enhanced by the thin stem's tendency to twist in the wind in two different directions," the press release states. "However, the researchers modeling and testing found that they did not need to replicate the additional complexity of a further degree of movement in their mechanical model."
In an interview with Sky and Telescope, the team says their next step will be to scale the system to something that could be deployed in larger arrays; in particular for regions where solar energy potential is low. According to Denissenko, the design of the aspen leaf will likely inform blade design going forward.
"We reckon most of the actual wind energy harvesters will be blade-shaped like ours," he said.
The video below will help you understand more about the ecology of these beautiful — and insightful — trees: