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.
“The next generation of wearable computing will have power generation coming from the garment itself,” he says.
In fact, modern warriors require approximately 240 watt-hours per day of power to charge all of their electronic devices – too heavy a load for any batteries available today, says Rupert Pengelley, group technical editor at military analyst firm Jane’s Information Group.
Pengelley says portable solar power technology is most useful in producing a trickle charge to top off batteries, but it is not as potent for recharging empty batteries.
“Solar has its place for static applications, such as being used [by soldiers] on a mountaintop” or being integrated into uniforms or the skins of vehicles, he says.
The Army is also testing shelters made of solar panels that can provide electricity for recharging laptops, satellite phones, lights, and ventilation equipment, according to Mike Coon, chief operation officer for Iowa Thin Film Technologies.
Coon says his company will deliver hundreds of tents to the Army as part of a $3.2 million contract announced on May 13. Iowa Thin Film has developed shelters in three sizes, providing from 190 watts to 2 kilowatt of power, says Coon. For example, one hour of full sun for the smallest shelter (Quadrant) would be enough to power a laptop for five hours or a cell phone for 24 hours.
Furthermore, the solar shelters do not leave a heat signature, making it harder for an enemy to track troop movements, and they also reduce the “logistical tail” of delivering generators to remote locations, says Coon.
Coon says that Iowa Thin Film has also developed a proprietary laser scribing process for integrating the solar cells onto a flexible plastic substrate. Advances in the process can now laminate the material 24 times faster than a year ago.
The Army is also evaluating a solar battery charger from Iowa Thin Film as part of a “one-two approach” to deploying photovoltaic power sources, according to Army chemist Samuelson.
“Whatever fits the application will be pursued,” Samuelson says.
According to Samuelson, the goal of the four-year project is to develop materials that can generate power for under $1 per peak watt-hour.
“We have come a long way from large rigid panels to lightweight flexible materials.”
Both Iowa Thin Film and Konarka intend to commercialize their technologies after they produce products in quantity for the military. Konarka’s McGahn says solar materials could be coated onto laptops or cell phones, or “iPod clothing” could recharge music players.
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