Soldiers will be carrying more than guns, rations, and letters from home onto future battlefields. They'll also have heads-up tactical displays, laser range finders, thermal weapons sights, and global positioning systems. But all of this high-tech gear, forming a unit known as a soldier system, has to be efficiently powered.
Researchers at the Department of Energy's Pacific Northwest National Laboratory (PNNL) in Richland, Wash., are working on a lightweight fuel processor to power these systems. Developed for the U.S. Army's Communications-Electronics Command, this device is one component in a "man-portable generator" that will generate between 15 and 25 W of power while weighing 10 times less than the batteries soldiers currently carry. This increased power density would reduce the load on individual soldiers while enabling the extension of missions.
PNNL engineers have demonstrated a concept model of a full-size, advanced-design fuel processor that converts methanol into hydrogen. Based on a 1- to 10-kW prototype fuel processor built for use in automobile power systems, it consists of four microtechnologies: a combustor, a vaporizer, a primary conversion reactor, and a gas cleanup device (see the figure). While it uses a proprietary catalyst to produce hydrogen from hydrocarbon fuels, the reactions take place within the small channels of a catalytic converter.
The microchannels within the processor enhance the heat and mass transfer rates. The unit's size is reduced by the speed with which the chemical reactions occur. Since hydrogen doesn't need to be stored or carried, this configuration lessens the weight and risk inherent in a portable power system. Researchers project the creation of hydrogen from liquid fuels, such as methanol, synthetic diesel fuel, and military jet fuels. Each of these materials is more readily available and more portable than hydrogen.
Currently, PNNL engineers are designing a prototype fuel processor that will be tested within the next year. After testing is complete, the engineers will integrate the fuel processor with other components of a complete power system, including a microscale fuel cell, a fuel storage and delivery unit, and a battery for peak power.
Researchers expect the man-portable generator to weigh as little as 2 lbs. Currently, lithium batteries providing equivalent power weigh as much as 20 lbs. Also, the generator's fuel processor allows the system to be refueled so it can be reused. The testing of the complete power system is slated for 2003. The U.S. Army projects the use of electronic gear, including integrated computers and communications devices, by infantry soldiers within this time frame.
For details on the processor and man-portable generator, visit www.pnl.gov.