U.S. patent application number 14/936491 was filed with the patent office on 2016-05-12 for fuel cell stack.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Norishige KONNO, Hiroki Okabe.
Application Number | 20160133957 14/936491 |
Document ID | / |
Family ID | 55802974 |
Filed Date | 2016-05-12 |
United States Patent
Application |
20160133957 |
Kind Code |
A1 |
KONNO; Norishige ; et
al. |
May 12, 2016 |
FUEL CELL STACK
Abstract
A fuel cell stack 11 includes a cell laminate 21 composed of a
plurality of stacked cells 20, and air is introduced from an anode
end part 21a of the cell laminate 21. The cell laminate 21 has two
end cells 24 installed adjacently to a cathode end part 21b side,
thereby providing the cathode end part 21b with high thermal
insulation properties.
Inventors: |
KONNO; Norishige;
(Toyota-shi, JP) ; Okabe; Hiroki; (Okazaki-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
55802974 |
Appl. No.: |
14/936491 |
Filed: |
November 9, 2015 |
Current U.S.
Class: |
429/452 |
Current CPC
Class: |
H01M 2008/1095 20130101;
Y02E 60/50 20130101; Y02P 70/50 20151101; H01M 8/04067 20130101;
H01M 8/2483 20160201; H01M 8/241 20130101; H01M 8/04731
20130101 |
International
Class: |
H01M 8/04 20060101
H01M008/04; H01M 8/24 20060101 H01M008/24 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 10, 2014 |
JP |
2014-228191 |
Claims
1. A fuel cell stack comprising: a cell laminate composed of a
plurality of stacked cells, wherein an oxygen gas is introduced
from a gas introduction end part on one side of the cell laminate,
and the cell laminate has relatively higher thermal insulation
properties at least at an end part on a far side from the gas
introduction end part than at an end part closer thereto.
2. The fuel cell stack according to claim 1, wherein the cell
laminate includes a non-power-generating end cell which has thermal
insulation properties that are higher than those of other cells and
which is located at least at the end part on the far side from the
gas introduction end part.
3. The fuel cell stack according to claim 1, wherein the cell
laminate has the end cells at both ends thereof, and a greater
number of the end cells is provided at the end part on the far side
from the gas introduction end part than the number of the end cells
provided at the gas introduction end part.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a fuel cell stack
constituting a fuel cell.
[0003] 2. Background Art
[0004] A fuel cell stack includes a cell laminate composed of a
plurality of stacked cells. Each cell of the cell laminate
generates power from the electrochemical reaction between a
hydrogen gas and the oxygen contained in air when the hydrogen gas
and the air are supplied from one end of the cell laminate (refer
to, for example, Patent Document 1).
CITATION LIST
Patent Document(s)
[0005] [Patent Document 1] JP2009-158349A
[0006] A cell located on a far side from an oxygen gas inlet,
through which air containing an oxygen gas is introduced into a
cell laminate, receives less oxygen gas due to a pressure loss than
a cell located adjacent to the oxygen gas inlet. Further, the cells
at both ends of the cell laminate radiate heat more easily than the
cells at a central part of the cell laminate and therefore more
easily cool, causing water, which is produced during power
generation, to be apt to remain in the cells. For this reason,
especially in a cell on the far side from the oxygen gas inlet, at
which the volume of the oxygen gas reduces due to the pressure
loss, the water produced during the power generation blocks the
flow of the oxygen gas in a flow path. This may lead to the
shortage of the oxygen gas, resulting in deteriorated efficiency of
power generation.
SUMMARY OF THE INVENTION
[0007] The present invention has been made in view of the
background described above, and an object of the invention is to
provide a fuel cell stack capable of suppressing a temperature
difference in a cell laminate thereby to achieve higher efficiency
of power generation.
[0008] To this end, a fuel cell stack in accordance with the
present invention is a fuel cell stack including: a cell laminate
composed of a plurality of stacked cells,
[0009] wherein an oxygen gas is introduced from a gas introduction
end part on one side of the cell laminate, and
[0010] the cell laminate has relatively higher thermal insulation
properties at least at an end part on a far side from the gas
introduction end part than at an end part closer thereto.
[0011] According to the fuel cell stack configured as described
above, the thermal insulation properties at the end part on the far
side from the gas introduction end part are set to be relatively
higher than the thermal insulation properties at the end part
closer thereto. This makes it possible to prevent the relative
decrease in the temperature of the cell at the end part on the far
side, thus preventing the volume of water, which is generated by
the gas and which is carried away, from becoming smaller than those
of the other cells. Thus, it is possible to control the volume of
the generated water that remains in the cell at the end part on the
far side from the gas introduction end part of he cell
laminate.
[0012] With this arrangement, the blockage of the oxygen gas flow
caused by the generated water can be suppressed, and therefore, the
shortage of the oxygen gas at the cell on the far side from the gas
introduction end part can be restrained. Hence, variations in the
supply of the oxygen gas in the cell laminate can be restrained,
permitting higher efficiency of power generation.
[0013] In the fuel cell stack in accordance with the present
invention, the cell laminate may include a non-power-generating end
cell which has thermal insulation properties that are higher than
those of other cells and which is located at least at the end part
on the far side from the gas introduction end part.
[0014] According to the fuel cell stack configured as described
above, providing the end cell at the end part on the far side from
the gas introduction end part in the cell laminate restrains the
radiation of heat at the end part on the far side from the gas
introduction end part, resulting in higher thermal insulation
properties. This suppresses the volume of the generated water
remaining in the cell at the end part on the far side from the gas
introduction end part of the cell laminate thereby to restrain the
blockage of the flow of the oxygen gas by the generated water, thus
making it possible to restrain the shortage of the oxygen gas at
the cell on the far side from the gas introduction end part.
[0015] In the fuel cell stack in accordance with the present
invention, the cell laminate may have the end cells at both ends
thereof, and a greater number of the end cells may be provided at
the end part on the far side from the gas introduction end part
than the number of the end cells provided at the gas introduction
end part.
[0016] According to the fuel cell stack configured as described
above, the end cells provided at the gas introduction end part and
at the end part on the far side from the gas introduction end part
in the cell laminate restrain the radiation of heat at the gas
introduction end part and at the end part on the far side from the
gas introduction end part, resulting in higher thermal insulation
properties. This makes it possible to suppress the volume of the
generated water remaining in the cell at the gas introduction end
part and at the end part on the far side from the gas introduction
end part of the cell laminate, thereby restraining the blockage of
the flow of the oxygen gas by the generated water and therefore
restraining the shortage of the oxygen gas.
[0017] Furthermore, the thermal insulation properties at the end
part on the far side from the gas introduction end part, at which
there are more end cells, are higher than those at the gas
introduction end part. This makes it possible to suppress the
volume of the generated water remaining especially in the cell at
the end part on the far side from the gas introduction end part of
the cell laminate, thereby restraining the blockage of the flow of
the oxygen gas by the generated water and therefore restraining the
shortage of the oxygen gas. Further, the operational advantages
described above are achieved by the end cells, which are common
parts, so that an increase in cost or size can be restrained, as
compared with the case where a heater, a cooling component or the
like is used to achieve the same operational advantages.
[0018] The fuel cell stack in accordance with the present invention
permits higher efficiency of power generation by suppressing a
temperature difference in a cell laminate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a side view of a fuel cell according to a present
embodiment;
[0020] FIG. 2 is a schematic exploded perspective view of a fuel
cell stack constituting the fuel cell according to the present
embodiment;
[0021] FIG. 3 is a sectional view of a cell constituting a cell
laminate of the fuel cell stack;
[0022] FIGS. 4A and 4B present graphs illustrating the moisture
content and the cell temperature in a cell laminate without any end
cells;
[0023] FIG. 5 is a graph illustrating the cell temperature in the
cell laminate; and
[0024] FIG. 6 is a graph illustrating the relationship between the
number of the end cells and the temperature difference of a cathode
end part from a central part.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] The following will describe an embodiment of a fuel cell
stack in accordance with the present invention with reference to
the accompanying drawings.
[0026] FIG. 1 is a side view of a fuel cell according to the
present embodiment. FIG. 2 is a schematic exploded perspective view
of a fuel cell stack constituting the fuel cell according to the
present embodiment. FIG. 3 is a sectional view of a cell
constituting a cell laminate of the fuel cell stack.
[0027] As illustrated in FIG. 1, a fuel cell stack 11 according to
the present embodiment has end plates 12 at both ends thereof. The
end plates 12 are connected with each other by being fastened by a
fastening rod (not illustrated). The fuel cell stack 11 is
pressurized under a predetermined load from both ends by the
fastening force of the end plates 12. The fuel cell stack 11
constitutes a fuel cell used by being installed in a mobile body,
such as a vehicle.
[0028] As illustrated in FIG. 2, the fuel cell stack 11 has a cell
laminate 21, current-collecting plates 22, and a rust-proof plate
23. The cell laminate 21 is formed by stacking a plurality of cells
20, and end cells 24 are provided on both ends thereof. The cell
laminate 21 has one end serving as a gas introduction end part and
the other end serving as a gas return end part.
[0029] As illustrated in FIG. 3, each of the cells 20 has a
membrane electrode assembly (hereinafter referred to as "the MEA")
5, which includes electrodes 4 provided on both sides of an
electrolyte film 1, each of the electrodes 4 being composed of a
catalyst layer 2 and a diffusion layer 3. Separators 6 are provided
on both surfaces of the MEA 5. The separators 6 are formed of
stainless plates. Each of the cells 20, which is a unit module
generating power in the fuel cell stack 11, generates power by the
electrochemical reaction between a hydrogen gas and the oxygen
contained in the air.
[0030] Each of the current-collecting plates 22 is formed of an
electrically conductive metal material, such as aluminum or
stainless steel. The current-collecting plates 22 are provided with
output terminals (not illustrated), and the electric power
generated by the fuel cell stack 11 is taken out through the output
terminals. The current-collecting plate 22 adjacent to the gas
introduction end part of the cell laminate 21 is defined as the
electrode on the anode side, while the current-collecting plate 22
adjacent to the gas return end part of the cell laminate 21 is
defined as the electrode on the cathode side. In other words, the
cell laminate 21 has the gas introduction end part serving as an
anode (An) end part 21a and the gas return end part serving as a
cathode (Ca) end part 21b. The rust-proof plate 23 is provided
between the cell laminate 21 and the current-collecting plate 22 on
the cathode end part 21b side of the cell laminate 21.
[0031] Air containing the oxygen gas is supplied to the cell
laminate 21 from the anode end part 21a, which is the gas
introduction end part. The air supplied from the anode end part 21a
turns around at the cathode end part 21b, which is the gas return
end part, and is exhausted from the anode end part 21a. This passes
the air through each of the cells 20. As with the air, the hydrogen
gas is supplied from the anode end part 21a of the cell laminate
21, turns around at the cathode end part 21b, and is exhausted from
the anode end part 21a. Thus, in the cell laminate 21, each of the
cells 20 generates electric power by the electrochemical reaction
between the hydrogen gas and the oxygen contained in the air.
[0032] The both ends of the cell laminate 21, namely, the anode end
part 21a and the cathode end part 21b, are provided with the end
cells 24. The anode end part 21a has one of the end cells 24, while
the cathode end part 21b has two of the end cells 24. The end cells
24 have the same configuration, which is similar to the
configuration of the cells 20. For example, the end cell 24 does
not have the electrolyte film, but has the assembly in which the
catalyst layer and the diffusion layer are bonded, and both
surfaces of the assembly are provided with separators similar to
the separators 6 of the cells 20.
[0033] Each of the end cells 24 is a non-power-generating cell
configured as described above.
[0034] Providing the anode end part 21a and the cathode end part
21b of the cell laminate 21 with the end cells 24 causes the
hydrogen gas, air and cooling water, which are supplied to the cell
laminate 21, to pass through the flow paths in the end cells 24. At
this time, even when the air and the hydrogen gas are supplied, the
oxygen gas in the air and the hydrogen gas do not contribute to
power generation and bypass the end cells 24 without being
consumed. Meanwhile, the thermal capacity of cooling water is high,
and the cooling water flowing through the end cells 24 causes the
thermal capacity of the entire end cells 24 to become relatively
high, so that the thermal insulation properties thereof become
relatively higher than those of the cells 20. This suppresses or
shuts off the radiation of heat to the outside from the cells 20
adjacent to the end cells 24.
[0035] As illustrated in FIGS. 4A and 4B, generally, in a fuel cell
stack configured to distribute a gas from the anode end part 21a of
the cell laminate 21, the cathode end part 21b of the cell laminate
21 is influenced by heat radiation and the cell temperature tends
to become lower than that at the central part or the anode end part
21a throughout power generation and discharge, leading to the
occurrence of a temperature difference .DELTA.T from the central
part. As a result, especially when the load is low at the time of
idling or the like in a low temperature environment, the volume of
water generated by the power generation which is contained in the
air increases in the flow path at the cathode end part 21b, thus
frequently blocking the air flow. In addition, the flow quantity of
the air is reduced due to the pressure loss at the cathode end part
21b, as compared with the anode end part 21a. This may lead to an
air distribution failure at the cathode end part 21b in the cell
laminate 21.
[0036] As the preventive measures, therefore, the fuel cell stack
11 according to the present embodiment includes the two end cells
24 installed adjacently to the cathode end part 21b on the far side
from the anode end part 21a, which is the gas introduction end
part. This makes it possible to enhance the thermal insulation
properties of the cathode end part 21b of the cell laminate 21.
Thus, the temperature difference .DELTA.T of the cathode end part
21b from the central part of the cell laminate 21 can be minimized,
making it possible to suppress the volume of the generated water at
the cathode end part 21b of the cell laminate 21 so as to suppress
the blockage of the air flow by the generated water, thereby
restraining the shortage of the oxygen gas at the cathode end part
21b.
[0037] Further, a decrease in the flow quantity of the air due to
the pressure loss does not take place at the anode end part 21a,
which is the gas introduction end part of the cell laminate 21.
However, as with the cathode end part 21b, the anode end part 21a
tends to radiate heat and therefore, the cell temperature thereof
tends to become lower than that at the central part. Hence, the
present embodiment has the single end cell 24 located adjacently to
the anode end part 21a so as to enhance the thermal insulation
properties of the anode end part 21a of the cell laminate 21, thus
making it possible to minimize the temperature difference .DELTA.T
of the anode end part 21a from the central part in the cell
laminate 21. With this arrangement, the volume of the generated
water at the anode end part 21a of the cell laminate 21 can be
suppressed so as to suppress the blockage of the air flow by the
generated water, thereby restraining the shortage of the oxygen gas
at the anode end part 21a.
[0038] As illustrated in FIG. 5, providing the single end cell 24
adjacently to the anode end part 21a and the two end cells 24
adjacently to the cathode end part 21b as in the present embodiment
makes it possible to suppress a decrease in the cell temperature at
both ends (the temperature indicated by the solid line in FIG. 5)
in contrast to the case where the end cells 24 are not provided and
the cell temperature decreases at both ends (the temperature
indicated by the dashed One in FIG. 5).
[0039] As described above, the fuel cell stack 11 according to the
present embodiment makes it possible to maximize the suppression of
the temperature difference .DELTA.T of the cell temperature in the
cell laminate 21 by providing the anode end part 21a and the
cathode end part 21b of the cell laminate 21 with the end cells 24
without using any special heat insulation members or the like. This
arrangement permits smooth supply of the oxygen gas to the entire
cell laminate 21 to achieve efficient power generation.
Furthermore, the end cells 24, which are common parts, are used,
thus making it possible to avoid an increase in cost or size caused
by using a heater or a cooling component for suppressing the
temperature difference .DELTA.T of the cell temperature.
[0040] The temperature difference .DELTA.T between the cathode end
part 21b and the central part was measured using several different
numbers of the end cells 24 provided adjacently to the cathode end
part 21b of the cell laminate 21. The measurement of the
temperature difference .DELTA.T was carried out at a cooling water
temperature of 60.degree. C., a current value of 15 A, and an
outside temperature of -20.degree. C.
[0041] As illustrated in FIG. 6, which shows the measurement
results, the temperature difference .DELTA.T is still large in the
case where the single end cell 24 is provided, whereas the
temperature difference .DELTA.T can be markedly reduced by
providing the two end cells 24. Theoretically, it is ideal to
eliminate the temperature difference .DELTA.T to prevent the air
distribution failure. It has been found, however, installing the
two end cells 24 is effective for nearly eliminating the air
distribution failure. Further, adding more of the end cells 24
(three, five and seven) permits a reduction in the temperature
difference .DELTA.T, but results in an inconvenient increase in the
size of the cell laminate 21.
[0042] Based on the measurement results, it has been concluded that
providing two of the end cells 24 is appropriate for achieving a
sufficiently reduced temperature difference .DELTA.T while
restraining the cell laminate 21 from becoming larger.
[0043] The number of the end cells 24 to be provided at the anode
end part 21a and the cathode end part 21b of the cell laminate 21
is not limited to that in the foregoing embodiment, and is to be
selected according to a required reduction in the temperature
difference .DELTA.T between the anode end part 21a and the cathode
end part 21b and the central part of the cell laminate 21. For
example, the number of the end cells 24 to be provided at the anode
end part 21a and the cathode end part 21b of the cell laminate 21
is preferably changed, as necessary, according to the shape or the
material of the cell laminate 21, the position of the flow path of
a gas or cooling water, the environment in which the fuel cell
stack 11 housed in a case or the like is installed, or the
like.
DESCRIPTION OF REFERENCE NUMERALS
[0044] 11 fuel cell stack [0045] 20 cell [0046] 21 cell laminate
[0047] 21a anode end part (gas introduction end part) [0048] 21b
cathode end part (end part on the far side from the gas
introduction end part) [0049] 24 end cell
* * * * *