Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Patent
1997-06-04
1999-01-26
Skapars, Anthony
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
429 32, 429 33, 429 34, H01M 804, H01M 810
Patent
active
058636722
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a PEM fuel cell comprising strip membranes and plates made of non-conductive material, the current being derived via separate electrically conductive structures.
BACKGROUND OF THE INVENTION
PEM fuel cells (Polymer Electrolyte Membrane fuel cells) are electrochemical cells which, to simplify, comprise anode and cathode with interposed polymeric solid electrolyte. In order to operate such cells, fuels are continuously applied to both electrodes from the exterior, said fuel being there electrochemically converted, so that a current can be derived at the electrodes. It is now at present however, impossible to convert all of the chemical energy supplied. During operation of the fuel cell a certain proportion is always lost as heat. For this reason, higher-performance fuel cells require measures for heat removal. This is effected according to prior art by electrically conductive heat exchanger plates through which a cooling fluid flows (Literature: A. J. Appley, E.
In this case both sides of the membrane-electrode unit are in contact with the electrically conductive plates, interposed seal rings being used in order to achieve a tightness of the cell. The conductor plates are designed as heat exchangers, i.e. they contain ducts through which a cooling fluid flows. The cooling fluid is fed in and out through openings in the plate. Furthermore, feed and return ducts for the fuels are integrated in the electrically conductive plates, the fuels then being supplied through suitable structures to the electrodes. It is however necessary for such a fuel cell construction according to prior art for the plates to consist of electrically conductive material, as each plate must press against the respective electrode surface in order to produce the outward electrical contact of the cell. In the case of a stack structure, the plates can also be constructed as bipolar plates.
In order to achieve higher performance and particularly in order to achieve a higher voltage, it is also known to incorporate together a plurality of membrane-electrode units as described above to form a so-called fuel cell stack (U.S. Pat. No. 4,175,165 "Fuel cell system utilizing ion exchange membranes and bipolar plates"). For this purpose until now a plurality of cells as described above were separately constructed, disposed one behind the other and incorporated electrically in series, so that the voltages of the individual cells are added to one another. The constructive outlay for such an in-series incorporation is however extremely high, as each membrane-electrode unit must have a separate fuel supply. The result is an extremely high constructive outlay for these cells.
SUMMARY OF THE INVENTION
Proceeding from this point, the object of the present invention is to indicate a PEM fuel cell which in addition to having high output voltages, has an extremely simple and cost-effective structure.
This object is achieved by the characterising features of claim 1. The sub-claims illustrate advantageous further developments.
Thus it is proposed according to the invention to construct a PEM fuel cell from so-called membranes and plates contacted thereon on both sides of electrically non-conductive material, the current being derived through separate conductive structures passing to the exterior.
By means of using electrically non-conductive plates a situation is achieved in which strip membranes can be used in a PEM cell without the occurrence of a short circuit of the individual cells of a strip membrane between one another. Thus an essential feature of the invention is the use of novel strip membranes and their contacting with plates which serve as heat exchangers and as a fuel gas supply device, from electrically non-conductive material. In this way now PEM fuel cells may be produced with a simple structure and a high output voltage. The voltage can be further increased if so-called fuel cell stacks are produced by incorporating one behind the other a plurality of individual cells with the structure des
REFERENCES:
patent: 3507704 (1970-04-01), Webb
patent: 4649091 (1987-03-01), McElroy
patent: 4826741 (1989-05-01), Aldhart et al.
patent: 5045169 (1991-09-01), Feduska et al.
patent: 5262249 (1993-11-01), Beal et al.
Ledjeff Konstantin
Nolte Roland
Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung
Skapars Anthony
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