Simplified direct oxidation fuel cell system

Abstract

A simplified direct oxidation fuel cell system is provided. The fuel cell is constructed in such a manner that fuel is added to the cell anode as it is consumed and water is evaporated off at cell cathode so that there is no need for recirculation of unreacted fuel at the cell anode or water at the cell cathode. In addition, carbon dioxide generated from the anodic reaction is passively vented out of the system by using a CO2 gas permeable membrane material integrated as part of the anode chamber construction. Other embodiments of the invention include a fuel container and delivery assembly.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates generally to the field of fuel cells, and more specifically, to a simplified direct oxidation fuel cell device containing a direct oxidation fuel cell stack with a fuel container, fuel delivery and reaction product release system. [0003] 2. Background Information [0004] Fuel cells are devices in which electrochemical reactions are used to generate electricity. A variety of materials may be suited for use as a fuel depending upon the materials chosen for the components of the cell. Organic materials, such as methanol or natural gas, are attractive choices for fuel due to their high specific energy. [0005] Fuel cell systems may be divided into “reformer-based” systems (i.e., those in which the fuel is processed in some fashion to extract hydrogen from the fuel before it is introduced into the fuel cell system) or “direct oxidation” systems in which the fuel is fed directly into the cell w...

AI Technical Summary

Benefits of technology

[0016] These and other advantages are provided by the present invention in which a simplified direct oxidation fuel cell system is provided. In one embodiment of the invention, the fuel cell includes a membrane electrode assembly which has a gas permeable layer disposed generally parallel to the anode face of the membrane electrode assembly. The gas permeable layer includes a gas-permeable material, disposed generally parallel to, and in close proximity to, an anode diffusion layer, and it removes the CO2 gas generated in the anoxic reaction, and separates it away from the anode compartment. The CO2 is thus simply vented out of the system, preventing accumulation, which may hinder the anode reaction.

[0017] In addition, a fuel delivery assembly coupled with an associated fuel source has a pressure-applying member that places the fuel mixture under pressure and thus delivers fuel to the anode. Thus, as the electricity generating reactions occur, the combination of the CO2 separation and the fuel being consumed creates a void in the anode compartment. The void created is immediately filled with fresh fuel from the pressurized fuel cell delivery system. In this manner, only the amount of fuel that has been consumed is added, thereby avoiding the need to recirculate unreacted fuel back into the fuel cell system. This also minimizes or eliminates the needs for pumps and valves, and other recirculation devices In accordance with another aspect of this embodiment of the invention, there is essentially no recovery of liquid water from the cathode face of the fuel cell, and no recirculation of water. This further simplifies the DMFC system. The anode fluid recirculation is required, as revealed in previous patents for an active DMFC system design including, but not limited to those described in U.S. Pat. Nos. 5,599,638; 5,992,008; and 5,945,231, in order to vent the CO2 and control the methanol concentration in such an active system design.

Problems solved by technology

Thus, as the electricity generating reactions occur, the combination of the CO2 separation and the fuel being consumed creates a void in the anode compartment.

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