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Battery free TENG alarm monitors forest fires

Technology News |
By Nick Flaherty


Researchers at Michigan State University have built a battery-free remote forest fire detection and alarm system powered by the movement of the trees in the wind.

The alarm is based around a multilayered cylindrical triboelectric nanogenerator (MC-TENG) that generates power by harvesting energy from the sporadic movement of the tree branches.

“As far as we know, this is the first demonstration of such a novel MC-TENG as a forest fire detection system,” said Changyong Cao, directors of the Laboratory of Soft Machines and Electronics in MSU’s School of Packaging and is an assistant professor in the Packaging School and Departments of Mechanical Engineering, and Electrical and Computer Engineering.

“The self-powered sensing system could continuously monitor the fire and environmental conditions without requiring maintenance after deployment,” he said.

Early and quick response to forest fires will make the task of extinguishing them easier, significantly reducing the damage and loss of property and life. Traditional forest fire detection methods include satellite monitoring, ground patrols, watch towers, among others, which have high labour and financial costs in return for low efficiency.

Current remote sensor technologies are becoming more common, but primarily rely on battery technology for power. “Although solar cells have been widely used for portable electronics or self-powered systems, it is challenging to install these in a forest because of the shading or covering of lush foliage,” said Yaokun Pang, co-author and postdoc associate at Cao’s lab.

The simplest version of the TENG device consists of two cylindrical sleeves of unique material that fit within one another. The core sleeve is anchored from above while the bottom sleeve is free to slide up and down and move side to side, constrained only by an elastic connective band or spring. As the two sleeves move out of sync, the intermittent loss of contact generates electricity. The MC-TENG are equipped with several hierarchical triboelectric layers, increasing the electrical output.

The MC-TENG stores its sporadically generated electrical current in a carbon-nanotube-based micro supercapacitor. The researchers selected this technology for its rapid charge and discharge times, allowing the device to adequately charge with only short but sustained gusts of wind. The MC‐TENG produces a peak power of 2.9 mW and a maximum average power of 1.2 mW at a low frequency of 1.25 Hz.

“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 researchers built the initial prototype with both carbon monoxide (CO) and temperature sensors. The addition of a temperature sensor was intended to reduce the likelihood of a false positive carbon dioxide reading.

Cao hopes the team will be able to field test a production device to monitor forest environmental conditions and test scenarios, making use of materials that mimic a real fire. The team also aims to add additional functions, presumably wireless links, allowing the device to be adapted for the weather and environmental conditions where it is deployed.

The paper is at onlinelibrary.wiley.com/doi/10.1002/adfm.202003598

msu.edu/

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