Direct methanol fuel cells integrated with fuel reservoirs have been proposed as power sources in applications that involve power demands up to about 50 W. A prior concept of direct methanol fuel cells as alternatives to re- chargeable batteries in such applications was reported previously in “Miniature Fuel Cells for Small, Portable Electronic Devices” (NPO-21066), NASA Tech Briefs, Vol. 26, No. 8 (August 2002), page 30. The prior concept called for the fuel (a methanol/water solution) to be supplied from reservoirs outside the fuel cells. The present concept would eliminate the need for separate reservoirs, thereby reducing bulk and complexity and increasing convenience of use.
A fuel-cell assembly according to the present proposal would include a stack of fuel cells either above or surrounded by a fuel reservoir, all contained within a single housing. Wicks would protrude from the anodes in the stack into the reservoir. The wicks would deliver the methanol/water fuel solution to the anodes by capillary action. Oxygen in the air would be accessible to the cathodes.
The water produced in the fuel-cell chemical reactions could be discharged as a liquid into the reservoir to maintain the required relative concentrations of water and methanol; alternatively, this water could be emitted as a gas along with carbon dioxide, which is also produced in the fuel-cell chemical reactions. Refueling could be accomplished by injecting or pouring additional methanol or methanol/water solution into the reservoir from a syringe, a container similar to a cigarette-lighter-fuel container, or other suitable vessel.
This work was done by Gerald Halpert, Harvey Frank, and Sekharipuram Narayanan of Caltech for NASA’s Jet Propulsion Laboratory.
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Refer to NPO-30331, volume and number of this NASA Tech Briefs issue, and the page number.