Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Patent
1997-06-04
1999-09-14
Bell, Bruce F.
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
429 18, 429 30, 429 34, 429 38, 429 39, H01M 810
Patent
active
059521180
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a PEM fuel cell consisting of strip membranes and plates assembled to both sides of the membrane, with the plates featuring conductive and nonconductive regions.
BACKGROUND OF THE INVENTION
PEM fuel cells (polymer electrolyte membrane fuel cells) are electrochemical cells consisting, simplified, of anode, cathode and interposed polymeric solid electrolytes. To operate such cells, fuels are continuously supplied externally to both electrodes, where they are electrochemically converted so that a voltage can be tapped on the electrodes. It is not possible, however, to convert the entire energy supplied. A certain part is always lost as heat in the operation of the fuel cell. Especially higher-output fuel cells require therefore measures for heat dissipation. According to the prior art, this is effected with the use of electrically conductive heat exchanger plates through which a coolant is passed (literature: A. J. Appley, E. B. Yeager, Energy 11,
Both sides of the membrane-electrode unit are in contact with the electrically conductive plates, with interposed gaskets being used to achieve cell tightness. The conductive plates are configured as heat exchangers, that is, they contain ducts through which flows as coolant. The coolant is introduced and drained by way of openings contained in the plate. Integrated in the electrically conductive plates are also feed and drain ducts for the fuels, with the fuels then being supplied to the electrodes via suitable structures. For such fuel cell structure according to the prior art it is necessary, however, that the plates consist of electrically conductive material, since each plate must bear down on the respective eletrode area so as to establish the outward electrical connection of the cell. In the case of a stacked design, the plates may be fashioned also as bipolar plates.
To achieve higher outputs, and especially for achieving a higher voltage, it is known also to combine several membrane-electrode units, as described above, to a so-called fuel cell stack (U.S. Pat. No. 4,175,165 "Fuel cell system utilizing ion exchange membranes and bipolar plates"). To that end, a plurality of such cells, as described above, have so far been constructed separately, arranged successively and electrically wired in series, making the voltages of the individual cells additive. The design-related expense of such a series circuit is very high, however, since each membrane-electrode unit requires a separate fuel supply. This makes for a very high engineering expense for such cells.
SUMMARY OF THE INVENTION
Basing thereon, the objective underlying the present invention is to provide a PEM fuel cell which in addition to high output voltages features a very simple and low-cost structure.
According to the invention it is thus proposed to construct a PEM fuel cell of so called strip membranes and plates in contact with them on both sides. The design of the plates is such that they possess both conductive and nonconductive regions, the arrangement of the regions being such that a short circuit between the individual electrodes of a membrane side will be avoided. Inventionally essential is thus the use of novel strip membranes and their joining to plates of a configuration such that they possess both conductive and nonconductive regions. The inventional plates serve at the same time as heat exchangers and as a fuel gas supply system. Realized thereby are PEM fuel cells with a simple structure and a high output voltage. The voltage can be boosted once again when realizing so-called fuel cell stacks by series wiring of several strip membranes structured as described above. According to the invention it is also possible to employ no individual strip membranes, so-called one dimensional strip membranes, but to arrange several such strip membranes in parallel as so-called two-dimensional strip membranes. The structure of the two-dimensional strip membranes may be such that the individual strip membranes are disposed either parallel to one ano
REFERENCES:
patent: 4175165 (1979-11-01), Adlhart
patent: 4833045 (1989-05-01), Pollack et al.
patent: 5169731 (1992-12-01), Yoshimura et al.
patent: 5171646 (1992-12-01), Rohr
patent: 5219673 (1993-06-01), Kaun
patent: 5258240 (1993-11-01), Di Croce et al.
patent: 5470671 (1995-11-01), Fletcher et al.
patent: 5686197 (1997-11-01), Nishida et al.
A.J. Apley, E.B. Yeager, Energy 11, 137-152 (1986) No month available.
Ledjeff Konstantin
Nolte Roland
Bell Bruce F.
Fraunhofer-Gesellschaft Zur Foerderung der Angewandten
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