Oct 01 2013
The U.S. Army’s Natick Soldier Research, Development and Engineering Center (NSRDEC) and the University of Massachusetts Dartmouth are working together to develop an electricity-generating fabric that can be incorporated into tents and backpacks.
The Army Contracting Command-Aberdeen Proving Ground division awarded a $1.8 million contract to the University of Massachusetts Dartmouth for the Photovoltaics Fabrics Program to develop an electrical power-producing fabric that could be used to make backpacks, tents, and even clothing. Such fabrics also might have the potential to generate electricity to power other gear — surveillance systems or communications equipment.
Yong K. Kim, Ph.D., a researcher at the university’s College of Engineering Textile Sciences Department, creates the fabric by embedding photovoltaic yarns in it so, when exposed to sunlight, the yarns serve as the engine for power generation. Kim notes he and his team first tried 250 dernier filament yarn but were not pleased with the structural integrity of the finished fabric.
“We now are trying a cotton-nylon blend yarn,” he says. “The twill gives the fabric pretty good stability and about 70- to 75-percent exposure (for the photovoltaic yarn).”
And while photovoltaic fabric yarn is as flexible as a monofilament fishing line, Kim observes if too many photovoltaic wire yarns are used, the fabric would be very stiff and won’t conform to the structure to be covered.
“It would be difficult to wear,” Kim says, “so the compromise is maybe every other or every third time we’ll include the photovoltaic yarn between the textural fibers.”
Barry DeChristofano, a NSRDEC chemical engineer, says the first uses the Army is looking at are helmet covers and backpack covers.
“As far as weight goes of the fabric, it’s a little bit heavier than a traditional helmet cover, but the trade-off is that it will be providing power where none had been provided before,” DeChristofano says. “The slight weight gain, if any, is not a penalty.”
Tents and shade shelters are possible future uses for the photovoltaic fabric, DeChristofano points out.
However, he says, “It would be challenging to put on a soldier’s uniform, although that might be a long term goal. Flexibility is a key because we want it flexible enough but not so much that it might crack the photovoltaic wires.”
Kim points out the fabric’s power generating efficiency at 5 percent is “a pretty good goal to start with, but we might end up with 7 percent or larger efficiency. With one square meter of sunlight, you get around one kilowatt, but it all can’t be converted, so 5 percent of 1,000 watts of solar radiation per square meter equals 50 watts of power efficiently produced.”
Kim envisions the photovoltaic fabric first being able to recharge AA batteries that the troops carry.
“As efficiency rises and we increase the exposure of the wires on the fabric surface,” Kim says, “we can optimize the fabric’s use with the 1.5-volt lithium-ion batteries.”
About the author: Alan M. Petrillo is a Tucson, Ariz., freelance journalist who works in a variety of fields, writing for national and regional magazines and newspapers. He’s also the author of the historical mystery, Full Moon, several books on historical military small arms, and the nonfiction work, Ice Hockey in the Desert.