The final tests consumed an additional 80 W/hours of power, and included powering a laptop, the Army's Land Warrior system that included a helmet-mounted display, radio, GPS and thermal scope, a cooled vest, a heated vest, a ventilator, a water purification device and a pump for an inflatable boat.
Survivors of the field test were then ranked by weight and declared the winners. The DuPont/SFC entry weighed 8.29 pounds, AMI's entry weighed 8.35 pounds and Capitol Connection's entry weighed 8.52 pounds. All three systems weighed up to 80 percent less than traditional batteries.
"DoD is interested in giving the warfighter a reliable source of power that is lighter weight than the batteries they have to carry today," said James.
DMFC technology is simpler than the hydrogen fuel cells being developed for transport applications. DMFC uses methanol, a widely available liquid which can more easlily be converted to electricity in a fuel cell.
Methanol's energy density is relatively high and is much easier to store than hydrogen since as it does not require high pressures or low temperatures. Unfortunately, DMFCs do not produce enough instantaneous energy for powering heavy objects like a car. Also, methanol produces both water and carbon dioxide as waste products, making it less clean than hydrogen-based fuel cells.
Despite these drawbacks, DMFCs can store a lot of power in a smaller space and with a lighter mechanisms than traditional batteries. They are also well suited to supplying small amounts of power over long periods of time, making them ideal for powering small devices.
The second place winner, AMI, was the only winning entry using solid-oxide fuel cells, a technology that produces electricity directly from oxidizing almost any hydrocarbon fuel. AMI used a higher-density hydrocarbon, albeit one that needed to be kept in a pressurized tank since it is a gas at room temperature.
"The main advantage of our solid-oxide fuel cell is that it can run on pretty much any hydrocarbon, but our fuel of choice is propane," said Miguel Tovar, a mechanical engineer and team leader for the AMI entry.