Today's soldiers are more power hungry than ever, and the army believes flexible solar cells can provide the extra juice. The military is testing lightweight materials that harness the sun's rays and feed electronic devices wherever mobile warriors travel.

Keeping the power on for soldiers -- who rely on night vision goggles, laptops, communications devices, and GPS units -- requires 150 tons of batteries per year, according to Lynn Samuelson, a research chemist at the U.S. Army Soldier Systems Center, in Natick, Massachusetts.

Batteries are frequently airlifted to remote troops and distributed to soldiers, who carry two dozen spares and must also make sure they are not discarded so that their movements can be tracked. The Army is transitioning to rechargeable batteries that can gain new life from solar-powered chargers, according to Samuelson.

"Using photovoltaics can offer tremendous advantages in logistics," Samuelson says.

The Army is now field testing portable battery chargers, tents, and sensor systems containing flexible solar cell materials that can be rolled up or folded for easy storage. The new materials "allow someone to go farther, stay longer, and be more self sufficient," says Samuelson.

Earlier this month, Konarka Technologies of Lowell, Massachusetts, announced that it is supplying the Army with solar-powered battery chargers as part of a $1.6 million contract. The prototype devices use polymer photovoltaic plastic that can be rolled out to soak up the sun's rays and generate approximately six watts of electricity, according to Dan McGahn, Konarka's executive vice president.

McGahn says that unlike traditional rigid photovoltaic panels that are fabricated from layers of semiconductor material, Konarka's nano-based solar material is printed on a roll of polymer plastic similar to the way photographic film is created. The plastics are injected with chemicals that become active when exposed to sunlight or indoor light, and electrodes convert the chemical energy to electricity.

"We are manufacturing solar materials similar to traditional printing and coating processes," says McGahn. "The target is to get to one-half or one-third the price of traditional solar materials cost," he says. Photovoltaic cells run about $5 per watt of power generated, according to solar consultancy Solarbuzz.

Konarka is also developing a device that integrates its solar material with sensors that could enable soldiers to monitor locations without being in harm's way.  A plastic mat of solar material would power motion- or sound-detection sensors and would wirelessly broadcast the data to the soldiers, McGahn says.

"We are looking to extend the sensors' ability to operate unattended so that [soldiers] can go places they couldn't before and stay longer," he says.

In the future, soldiers may be getting a charge out of their uniforms, too. Konarka's McGahn says the solar material can be colored to match fatigues and woven into fabric.