Regulating a flow through a fuel cell

Details Regulating a flow through a fuel cell Regulating a flow through a fuel cell

1999-08-24

2001-04-17

Kalafut, Stephen (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

With pressure equalizing means for liquid immersion operation

C429S010000, C429S010000, C429S006000, C429S006000, C429S006000, C429S006000, C429S006000

Reexamination Certificate

active

06218038

ABSTRACT:

BACKGROUND
The invention relates to regulating a flow through a fuel cell.
A fuel cell is an electrochemical device that converts chemical energy produced by a reaction directly into electrical energy. For example, one type of fuel cell includes a proton exchange membrane (PEM), a membrane that may permit only protons to pass between an anode and a cathode of the fuel cell. At the anode, diatomic hydrogen (a fuel) is oxidized to produce hydrogen protons that pass through the PEM. The electrons produced by this oxidation travel through circuitry that is external to the fuel cell to form an electrical current. At the cathode, oxygen is reduced and reacts with the hydrogen protons to form water. The anodic and cathodic reactions may be described by the following equations:
H
2
→2H
+
+2e
−
at the anode of the cell, and
O
2
+4H
+
+4e
−
→2H
2
O at the cathode of the cell.
Because a single fuel cell typically produces a relatively small voltage (around 1 volt, for example), several serially connected fuel cells may be formed out of an arrangement called a fuel cell stack to produce a higher voltage. The fuel cell stack may include different plates that are stacked one on top of the other in the appropriate order, and each plate may be associated with more than one fuel cell of the stack. The plates may be made from a metal or graphite composite material (as examples) and include various channels and orifices to, as examples, route the above-described reactants and products through the fuel cell stack. Several PEMs (each one being associated with a particular fuel cell) may be dispersed throughout the stack between the anodes and cathodes of the different fuel cells. The anode and the cathode may each be made out of an electrically conductive gas diffusion material, such as a carbon cloth or paper material, for example.
Referring to
FIG. 1
, as an example, a fuel cell stack
10
may be formed out of repeating units called plate modules
12
. In this manner, each plate module
12
includes a set of composite plates that may form several fuel cells. For example, for the arrangement depicted in
FIG. 1
, an exemplary plate module
12
a
may be formed from a cathode cooler plate
14
, a bipolar plate
16
, a cathode cooler plate
18
, an anode cooler plate
20
, a bipolar plate
22
and an anode cooler plate
24
that are stacked from bottom to top in the listed order. The cooler plate functions as a heat exchanger by routing a coolant through flow channels in either the upper or lower surface of the cooler plate to remove heat from the plate module
12
a
. The surface of the cooler plate that is not used to route the coolant includes flow channels to route either hydrogen (for the anode cooler plates
20
and
24
) or oxygen (for the cathode cooler plates
14
and
28
) to an associated fuel cell. The bipolar plates
16
and
22
include flow channels on one surface (i.e., on the top or bottom surface) to route hydrogen to an associated fuel cell and flow channels on the opposing surface to route oxygen to another associated fuel cell. Due to this arrangement, each fuel cell may be formed in part from one bipolar plate and one cooler plate, as an example.
For example, one fuel cell of the plate module
12
a
may include an anode-PEM-cathode sandwich, called a membrane-electrode-assembly (MEA), that is located between the anode cooler plate
24
and the bipolar plate
22
. In this manner, tipper surface of the bipolar plate
22
includes flow channels to route oxygen near the cathode of the MEA, and the lower surface of the anode cooler plate
24
includes flow channels to route hydrogen near the anode of the MEA.
As another example, another fuel cell of the plate module
12
a
may be formed from another MEA that is located between the bipolar plate
22
and the cathode cooler plate
20
. The lower surface of the bipolar plate
22
includes flow channels to route hydrogen near the anode of the MEA, and the upper surface of the cathode cooler plate
24
includes flow channels to route oxygen near the cathode of the MEA. The other fuel cells of the plate module
12
a
may be formed in a similar manner.
During the course of its lifetime, one or more of the fuel cells of the fuel cell stack
10
may fail. When this occurs, the entire fuel cell stack
10
typically must be shut down, and thus, the power that the fuel cell stack
10
furnishes (to a house, for example) is turned off.
SUMMARY
In one embodiment of the invention, an assembly includes fuel cell plates and a valve. The fuel cell plates arc arranged to form at least one fuel cell, and the plates establish a manifold passageway to communicate a fluid for the fuel cell. At least one of the plates includes flow channels to communicate the fluid through the fuel cell. The valve selectively regulates communication of the fluid between the manifold passageway and the flow channels.
Advantages and other features of the invention will become apparent from the following description, from the drawing and from the claims.


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