The beginning of 2020 was marked by horrific wildfires in Australia, brought on by record breaking temperatures and months of severe drought.
Wildfires have become increasingly worse in recent years, not just in Australia but also in places like Brazil, the US, and Portugal. When it comes to forest fires, the faster they can be detected, the less they can spread, and the easier they are to extinguish.
Traditional methods of forest fire detection have included satellite monitoring, ground patrols, and watch towers. These methods were not only labor intensive and expensive, but they were also inefficient.
Past prototypes utilizing tree-mounted sensors were mostly battery-powered. This meant that someone would have to periodically journey into the forest and replace the batteries.
Solar cells aren’t ideal for a forested environment either, where thick foliage blocks sunlight.
A team at the University of Michigan may have just found the solution.
Meet MC-TENG, or the multilayered cylindrical triboelectric nanogenerator. This device can convert mechanical energy from the sporadic movement of tree branches into electricity by way of the triboelectric effect.
Simply put, the triboelectric effect is an electric charge that occurs when two materials that are in contact are separated from each other. If you’ve ever run a comb through your hair and watched your hair stick to the comb afterwards, then you know what I’m talking about.
“As far as we know, this is the first demonstration of such a novel MC-TENG as a forest fire detection system,” says Changyong Cao, the lead author of the study. “The self-powered sensing system could continuously monitor the fire and environmental conditions without requiring maintenance after deployment,”
At its core, the TENG device is made up of two cylindrical sleeves of a unique material that fit within one another. One of these sleeves is anchored in place from above, while the other, bottom, sleeve is attached to a tree limb and can slide up and down and move side to side, constrained only by an elastic connective band or spring. When the wind blows, the bottom sleeve moves out of sync with the anchored sleeve. This temporary loss of contact generates electricity. The MC-TENG device developed by the University of Michigan team is equipped with several hierarchical triboelectric layers, which increases the electrical output.
The electricity generated is stored in a carbon-nanotube-based micro supercapacitor, chosen for its rapid charge and discharge times. This technology allows the device to adequately charge with only short but sustained gusts of wind.
“At a very low vibration frequency, the MC-TENG can efficiently generate electricity to charge the attached supercapacitor in less than three minutes,” Cao said.
The electricity generated is used to power a carbon monoxide sensor and a temperature sensor. By using both, the team hopes to reduce the likelihood of a false positive carbon monoxide reading.
In the future, the team hopes to expand functionality by adapting the device to fit the weather and environmental conditions where it is deployed. The final, weatherproof version of the MC-TENG should be able to detect forest fires and wirelessly transmit alerts to firefighting stations, thereby quickening response time and hopefully preventing more forest destruction from occurring.
The full study by the University of Michigan was published in Advanced Functional Materials and can be found here.