ChallengeDirect Methanol Fuel Cells (DMFCs) canbe a viable power source in manyapplications if their power density,energy conversion efficiency, and fuelutilization can be increased, while alsoreducing their cost. To realize theseimprovements, two critical challengesmust be resolved: (1) lowering therequired amount, or “loading,” of platinum catalyst while achieving a highcurrent (power density) level, and (2)eliminating the crossover of methanolthrough the membrane, a process thatdecreases the air cathode’s performanceand wastes fuel.
TechnologyDescriptionSimilar to polymer electrolyte membrane (PEM)fuel cells powered directly by hydrogen or by reformate (hydrogen-rich gas produced by reforming liquid fuels), in DMFCs oxygenfrom the surrounding air is reduced at thecathode, but liquid methanol, instead ofhydrogen, is the fuel oxidized directly at theanode. Therefore a DMFC system does notrequire a hydrogen storage tank or reformer,which is why DMFC systems could be anattractive alternative to direct hydrogen orreformate systems.
AccomplishmentsWork on DMFC designs has focused on thetradeoff between reducing platinum catalystloading and peak power. Platinum catalystloadings have been reduced by over a factorof ten, with only a 30% reduction in peakpower. For example, at a platinum loading of2 g Pt/kW, a peak power level of 0.12 W/cm2
was demonstrated.
New hardware developed and used in a 30-cell fuel stack with a 50-cm2 cross-sectionalarea produced 80 W of power at nearambient operating temperature and pressure.The projected output power at higher operating conditions (90° C and 30 psig) is 200 W.
A DMFC system was successfully operatedusing factory-grade methanol without furtherpurification. This indicates that special “fuel cellgrade” fuel will not be required for DMFCs.
BenefitsA Direct Methanol Fuel Cell offers a number ofadvantages, including:
■ Using a liquid fuel for power.
■ A simpler system design, with the potentialfor low-volume, lightweight packaging.
■ Eliminating the requirement for fuelreforming and/or onboard hydrogenstorage.
■ Classification as a zero-emission powersystem.
DirectMethanolFuel Cell
April 2001 http://www.ott.doe.gov/success.html
Technical advances improve thepotential for a fuel cell whicheliminates the need to store orgenerate hydrogen
ContactsJoAnn MillikenManager, Fuel Cells R&D202-586-2480202-586-9811 [email protected]
Robert NowakDARPA703-696-7491703-696-3999 [email protected]
Piotr ZelenayLos Alamos National
Laboratory505-667-0197505-665-4292 [email protected]
DirectMethanolFuel Cell
30-cell 45-cm2 direct methanol fuel cell stack.
CommercializationMotorola and Los Alamos National Laboratory (LANL) collaborated in establishing a DMFCResearch Center at LANL to develop DMFCs for portable power applications, such as cellularphones and laptop computers. Mechanical Technology, Inc. has licensed the LANL DMFC technology and spun off a company to commercialize DMFC for portable power applications.Commercial interest also exists for DMFCs in remote and auxiliary power applications rangingfrom low-power instrumentation to higher power (5 kW) auxiliary units in cars and trucks. Themilitary is also interested in DMFCs as a battery replacement for combat personnel and for battle-field applications. The Defense Advanced Research Projects Agency (DARPA) is collaborating withthe U.S. Department of Energy (DOE) in sponsoring DMFC research and development.
Future ActivitiesResearch and development efforts on DMFC systems will aim at further lowering precious metalrequirements while improving power density. To address water management and system levelissues, fuel cell stacks will be scaled up to 1 kW peak power. Long-term operation and durabilitytesting will be initiated.
Partners in Success■ U.S. Department of Defense - DARPA
■ Los Alamos National Laboratory
http://www.ott.doe.gov/success.html
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