EE Times - 6 Oct 08

Prof. Robert B. Laughlin
Department of Physics
Stanford University, Stanford, CA 94305
(Copied 4 Jun 09)

Direct-Methanol Fuel Cell Takes DoD Prize

R. Colin Johnson
October 6, 2008

PORTLAND, Ore. - DuPont Fuel Cells and German partner Smart Fuel Cell (SFC) AG have grabbed a $1 million first prize in the Defense Department's Wearable Power Prize competition.

DuPont (Wilmington, Del.) and SFC AG (Brunnthal, Germany) entered an advanced prototype of SFC's direct-methanol fuel cell (DMFC) called the M-25 Land Warrior Soldier Power Generator.

Second place went to Adaptive Materials Inc. (Ann Arbor, Mich.) for a vest-mounted version of its Amie25, a solid-oxide fuel cell. Third place went to Capitol Connections LLC (Middleburg, Va.) for its DMFC based on SFC's commercial Jenny Portable Power System.

All three used a hybrid approach, in which the fuel cell charged batteries, which in turn provided electrical power to devices.

"The fact that hybrid fuel cells won all three prizes is a strong endorsement for that technology over conventional batteries," said James Stephens, founder of Capitol Connections.

DoD launched the Wearable Power Prize competition in July 2007, offering $1 million first prize for wearable power systems that provided 20 watts of electrical power for 96 hours. Entries had to weigh less than 4 kilograms (8.8 pounds) and could attach to a standard military vest. From the initial 169 entries, the field was narrowed to 20.

Only six survived the next phase: a 92-hour bench test that discharged 1,840 W/hour. The last four hours tested the six finalists in field tests using real loads on the already partially discharged power packs.

"The last four hours was the survivor-mode competition, where the six teams went head-to-head with the vests being worn by a team member going through a field test consisting of nine different stations where they powered machinery and equipment that simulated various loads that the military might use," said U.S. Navy Commander Darryn James.

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.