Researchers at the U.S. Army Soldier Systems Center in Natick,
Mass., are developing prototypes of battery chargers and shelters
that would harness solar energy through nanocomposite thin-film
photovoltaics.
“It’s really an exciting time right now, because there
are a number of new photovoltaic technologies out there trying to
drive down costs, allowing you to use them in ways that couldn’t
be used before,” said Lynne Samuelson, a research chemist
at Natick.
Photovoltaic technology has advanced from the large, heavy and
expensive glass panels into smaller, lightweight and cheaper devices.
“Up until the last few years, those technologies weren’t
of interest to the military,” said Samuelson. But now, she
said, power is a number one priority for soldiers who carry an increasing
amount of electronic equipment. They need something lightweight
and portable to charge those devices, she said.
Her research team has produced thin-film photovoltaics, or PVs,
that could eventually answer that call.
The thin-film PVs are made by coating nanoparticles of titanium
dioxide with a light-harvesting dye and sandwiching them between
two plastic-based electrodes, said Samuelson. The resulting device
has the thickness of three sheets of paper. When light comes through
the device, it hits the dye and an electron gets shuttled through
the titanium dioxide to the other electrode. A redux mediator keeps
the process running, she said.
The sheets of PVs can be cut to any length or width, she said.
The longer the device, the more current it will produce. If you
need to charge up a radio, for example, you know the watts and amps
required, and you could design a PV to meet that specific requirement,
she said.
The goal for these devices is to generate 30 watts per pound, said
Samuelson. Soldiers currently use a battery, BA5590, that produces
about 22 watts per pound. With the nanocomposite thin-film PVs,
“you’re providing a higher density, and it’s renewable,”
said Samuelson.
Within the next year, these films will be incorporated into handheld
battery-charger prototypes capable of recharging four AA batteries
in two hours, said Samuelson. In the next two years, the team will
incorporate the films into shelters as well.
“What’s nice about this technology is you can do some
unique things with it that you can’t do with traditional materials,”
said Samuelson. For example, making a camouflage-pattern photovoltaic.
“Because we’re using a light-harvesting dye, we can
make colored patterns,” she explained. “We can inkjet-print
these dyes easily to make camouflage-colored PVs without having
to put a mesh over it,” she added.
Her team is also working on converting the thin-film PVs into fibers
that could be weaved directly into textiles.
“It would make all the applications we’re already going
after even better,” she said.