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Walk Around in the Sun to Power Wearables With This Cloth

Fabric woven from fiber-based solar cells and kinetic energy harvesters generates power day and night

2 min read
A patch of energy harvesting fabric combines solar-cell threads and triboelectric energy generator fibers
Photo: Xing Fan/Chongqing University

A new wearable fabric that generates electricity from both sunlight and motion could let you power your cell phone or smart watch by walking around outside. Researchers made the textile by weaving together plastic fiber solar cells and fiber-based generators that produce electricity when rubbed against each other.

The 0.32-millimeter-thick fabric is lightweight, flexible, breathable, and uses low-cost materials, its creators say. It could be integrated into clothes, tents, and curtains, turning them into power sources when they flap or are exposed to the sun. By harvesting solar and mechanical energy, the power-generating cloth could work day and night, its inventors say.

“The hybrid power textile could be extensively applied not only to self-powered electronics but also possibly to power generation on a larger scale,” Zhong Lin Wang at Georgia Tech, Xing Fan at Chongqing University in Chongqing, China, and their colleagues write in a research published today in the journal Nature Energy.

Wang and his colleague report that a patch of the power textile wrapped on a person’s hand charged a cell phone and a watch when the person stood in daylight in ambient wind conditions and moved their hand.

Wang has made many motion-harvesting devices before, from energy-generating flags to biodegradable power sources for medical implants. The underlying phenomenon is the triboelectric effect, which causes static electricity. When two different materials repeatedly touch each other, one grabs electrons from the other so that opposite charges build up on the two surfaces.

img Photo: Xing Fan/Chongqing University

In the new hybrid energy textile, thin flat strips of copper coated with a Teflon-like polymer act as triboelectric generators. The other power-generating component is the fiber solar cells, which the researchers make by growing light-sensitive zinc oxide nanowires on manganese and copper-coated plastic wires.

They use an industrial weaving machine to interlace the triboelectric strips and fiber solar cells with copper-coated plastic threads that serve as electrodes. When the fabric bends, the copper threads brush against the Teflon strips and generate electricity.

A flexible, wearable 4 centimeter x 5 cm power patch made by mixing wool fibers with the triboelectric and photovoltaic component charged a 2-millifarad commercial capacitor up to 2 Volt in one minute. Wang says they can make textiles as large as 20 cm x 30 cm, and it should be easy to scale up with a larger weaving machine.

Although they haven’t tested the fabric’s durability extensively, Fan says the output doesn’t drop even after it is bent 500 times. It works well in a temperature range humans can endure, he adds. And it should be able to withstand rain with proper encapsulation. “If the textile gets wet, any drop in performance can be recovered if the device is dried,” he says.

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Smokey the AI

Smart image analysis algorithms, fed by cameras carried by drones and ground vehicles, can help power companies prevent forest fires

7 min read
Smokey the AI

The 2021 Dixie Fire in northern California is suspected of being caused by Pacific Gas & Electric's equipment. The fire is the second-largest in California history.

Robyn Beck/AFP/Getty Images

The 2020 fire season in the United States was the worst in at least 70 years, with some 4 million hectares burned on the west coast alone. These West Coast fires killed at least 37 people, destroyed hundreds of structures, caused nearly US $20 billion in damage, and filled the air with smoke that threatened the health of millions of people. And this was on top of a 2018 fire season that burned more than 700,000 hectares of land in California, and a 2019-to-2020 wildfire season in Australia that torched nearly 18 million hectares.

While some of these fires started from human carelessness—or arson—far too many were sparked and spread by the electrical power infrastructure and power lines. The California Department of Forestry and Fire Protection (Cal Fire) calculates that nearly 100,000 burned hectares of those 2018 California fires were the fault of the electric power infrastructure, including the devastating Camp Fire, which wiped out most of the town of Paradise. And in July of this year, Pacific Gas & Electric indicated that blown fuses on one of its utility poles may have sparked the Dixie Fire, which burned nearly 400,000 hectares.

Until these recent disasters, most people, even those living in vulnerable areas, didn't give much thought to the fire risk from the electrical infrastructure. Power companies trim trees and inspect lines on a regular—if not particularly frequent—basis.

However, the frequency of these inspections has changed little over the years, even though climate change is causing drier and hotter weather conditions that lead up to more intense wildfires. In addition, many key electrical components are beyond their shelf lives, including insulators, transformers, arrestors, and splices that are more than 40 years old. Many transmission towers, most built for a 40-year lifespan, are entering their final decade.

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