Imagine wearing your own electricity source: it brings a whole new meaning to the idea of portable power. But for soldiers in danger of outpacing their supply lines, having a lightweight power source can be essential, and can ease logistics burdens and fuel costs for the military. The U.S. Army last month announced a new round of funding for product development at Konarka Technologies, a Lowell, Mass.-based solar company that makes lightweight, flexible photovoltaic units on sheets of plastic that can generate electricity from indoor, artificial light, as well as sunlight.
Though solar clothing may be a ways off, the military is feeling the pinch now of powering more sophisticated soldier electronics systems. Batteries are heavy to carry already and the backup power supplies needed to recharge them present further transport obstacles, while disposable batteries leave traces that enemy armies can track. Early applications of the solar units will allow soldiers to unroll the units from their packs when needed and stow them away when on the move. Consisting of parallel strips of PV material connected in series, the units will also continue to work if punctured by bullets or shrapnel, Dr. Russell Gaudiana, Konarka vice president of research and development, told Prospects.
The new funding announced by the Army, which will pay for prototype development and demonstrations of battery charging and military equipment operation, brings the total funding Konarka has received from government agencies including the Army, the Navy and the Defense Advanced Research Projects Agency to $1.3 million. Gaudiana said the amounts of individual contracts are confidential, but that eventually every soldier could be equipped with some type of PV technology.
Konarka is targeting early 2005 for the commercial release of its first products, which will serve similar nonmilitary applications as well. Konarka has strategic partnerships with chemical giants such as ChevronTexaco and Eastman Chemical, who advise the company on materials development. The solar technology may be well suited to power remote sensors at chemical plants, oil refineries and pipelines. Konarka also plans to market the same type of soldier roll-out recharging units to civilian campers. While the ultimate goal is building-integrated rooftop applications, Gaudiana says the units may not be able to meet the temperature and durability requirements of that market until around 2007.
The technology uses dye-coated titania nanocrystals sintered onto either a flexible metallic foil base through a high-temperature process, or onto a plastic base using a low-temperature process. The dye acts like a catalyst for absorbing light and moving electrons. For indoor applications such as department store displays, the dye can be tuned to the color wavelength of the indoor light source. In military applications, the color flexibility can help with camouflage.
The foil-based units attain efficiencies of about 7 percent and will most likely be used for early commercial products, but they are more expensive to produce than those using the low-temperature process, which yield efficiencies above 5 percent, Gaudiana said.
The technology is still in its early stages, howeverthe low-temperature sintering process that led to the formation of Konarka was just discovered fewer than four years ago in a project between the University of Massachusetts, Lowell, and the Army Natick Soldier Center. Last year the company demonstrated an actual PV fiber, initiating the possibility of cloth photovoltaics within a year or two of commercial launch. The application goes beyond just the existing units tailored in the shape of a shirt. This fiber actually breathes as normal cloth does, using titania-coated wire encapsulated in plastic and woven with cotton or nylon. [B.G.]
Konarka Technologies (www.konarkatech.com)
Defense Advanced Research Projects Agency (www.darpa.mil)
Issue 23: September 5, 2003