U.S. patent application number 16/246874 was filed with the patent office on 2019-07-18 for water electrolysis system.
The applicant listed for this patent is HONDA MOTOR CO., LTD.. Invention is credited to Tadashi NISHIYAMA, Akihiro NODA, Hiroshi SHINKAI.
Application Number | 20190218676 16/246874 |
Document ID | / |
Family ID | 67212738 |
Filed Date | 2019-07-18 |
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United States Patent
Application |
20190218676 |
Kind Code |
A1 |
NODA; Akihiro ; et
al. |
July 18, 2019 |
WATER ELECTROLYSIS SYSTEM
Abstract
A water electrolysis system includes a water electrolysis stack,
a gas-liquid separator, a water supply path, a water introduction
unit, a water lead-out unit, a water discharge path, and a
circulation pump. The water lead-out unit includes a first water
lead-out unit and a second water lead-out unit, which are provided
in the water electrolysis stack. The water introduction unit is
positioned in a stacking direction between the first water lead-out
unit and the second water lead-out unit, together with being
disposed in a water electrolysis cell which is positioned between
both ends in the stacking direction among a plurality of the water
electrolysis cells.
Inventors: |
NODA; Akihiro; (WAKO-SHI,
JP) ; NISHIYAMA; Tadashi; (WAKO-SHI, JP) ;
SHINKAI; Hiroshi; (WAKO-SHI, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONDA MOTOR CO., LTD. |
TOKYO |
|
JP |
|
|
Family ID: |
67212738 |
Appl. No.: |
16/246874 |
Filed: |
January 14, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25B 15/02 20130101;
C25B 9/20 20130101; C25B 15/08 20130101; C25B 1/08 20130101 |
International
Class: |
C25B 15/08 20060101
C25B015/08; C25B 9/20 20060101 C25B009/20; C25B 1/08 20060101
C25B001/08; C25B 15/02 20060101 C25B015/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 15, 2018 |
JP |
2018-003968 |
Claims
1. A water electrolysis system equipped with a water electrolysis
stack provided with a water introduction unit and a water lead-out
unit, and in which a plurality of water electrolysis cells, which
produce hydrogen and oxygen by electrolysis of water, are stacked
together mutually, and a circulation pump through which water is
circulated in a manner so that water which is stored in a
gas-liquid separator is supplied from the water introduction unit
into the water electrolysis stack via a water supply path, and so
that unreacted water which was not subjected to electrolysis inside
the water electrolysis stack is discharged from the water lead-out
unit into the gas-liquid separator via a water discharge path;
wherein the water lead-out unit comprises: a first water lead-out
unit provided on one end side of the water electrolysis stack in a
stacking direction of the water electrolysis cells; and a second
water lead-out unit provided on another end side of the water
electrolysis stack in the stacking direction; wherein the water
introduction unit is positioned in the stacking direction between
the first water lead-out unit and the second water lead-out unit,
together with being disposed in a water electrolysis cell which is
positioned between both ends in the stacking direction among the
plurality of water electrolysis cells.
2. The water electrolysis system according to claim 1, wherein the
water introduction unit is disposed in a water electrolysis cell
which is located in a central region in the stacking direction
among the plurality of water electrolysis cells.
3. The water electrolysis system according to claim 1, wherein, in
each of the water electrolysis cells, there are formed: a water
introducing communication passage adapted to allow the water
introduced from the water introduction unit to flow in the stacking
direction; and a water lead-out communication passage adapted to
allow the unreacted water which was not subjected to electrolysis
to flow in the stacking direction, and to guide the unreacted water
to the first water lead-out unit and the second water lead-out
unit.
4. The water electrolysis system according to claim 1, wherein each
of the first water lead-out unit and the second water lead-out unit
is disposed at a position which is shifted in phase from the water
introduction unit by 180.degree. in a circumferential direction of
the water electrolysis stack.
5. The water electrolysis system according to claim 1, wherein: the
first water lead-out unit is provided in a water electrolysis cell
positioned at one end in the stacking direction among the plurality
of water electrolysis cells; and the second water lead-out unit is
provided in a water electrolysis cell position at another end in
the stacking direction among the plurality of water electrolysis
cells.
6. The water electrolysis system according to claim 1, further
comprising: a drain flow passage connected to a lowermost part of
the water discharge path; and an opening-closing valve adapted to
open and close the drain flow passage; wherein the water
electrolysis stack is installed in a manner so that the stacking
direction is arranged along a vertical direction; and the second
water lead-out unit is positioned lower than the first water
lead-out unit and the water introduction unit.
7. The water electrolysis system according to claim 6, wherein the
second water lead-out unit is positioned lower than each of the
gas-liquid separator, the water supply path, and the circulation
pump.
8. The water electrolysis system according to claim 6, wherein the
opening-closing valve is a solenoid valve, the water electrolysis
system further comprising: an air supply path through which air is
supplied to the gas-liquid separator; an air supplying device
provided in the air supply path; a freeze prediction unit adapted
to predict freezing of the water inside the water electrolysis
system; and a control unit adapted to control the solenoid valve
and the air supplying device; wherein, when performing a process to
stop driving of the water electrolysis system, in the case it is
predicted by the freeze prediction unit that there is a possibility
that the water inside the water electrolysis system may become
frozen, the control unit controls the solenoid valve in a manner so
as to open the drain flow passage, and controls driving of the air
supplying device in a manner so that air is supplied to the
gas-liquid separator via the air supply path.
9. The water electrolysis system according to claim 2, wherein the
central region is a middle region obtained by dividing the
plurality of water electrolysis cells into three equal parts in the
stacking direction.
10. The water electrolysis system according to claim 6, wherein the
second water lead-out unit is connected to a lowermost part of the
water discharge path.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2018-003968 filed on
Jan. 15, 2018, the contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a water electrolysis system
equipped with a water electrolysis stack in which a plurality of
water electrolysis cells that generate hydrogen and oxygen by
electrolysis of water are stacked.
Description of the Related Art
[0003] In this type of water electrolysis system, for example, in
Japanese Laid-Open Patent Publication No. 2015-113496, a structure
is disclosed in which water is supplied to an end plate positioned
at an end portion in a stacking direction of the plurality of water
electrolysis cells in the water hydrolysis stack.
SUMMARY OF THE INVENTION
[0004] Incidentally, the water electrolysis cells generate heat due
to carrying out electrolysis of water therein. Therefore, during a
time when the water electrolysis stack is in operation, it is
likely for the water electrolysis cells (hereinafter referred to as
central water electrolysis cells) which are located at a central
portion in the stacking direction of the plurality of water
electrolysis cells to be heated to a higher temperature than the
water electrolysis cells that are positioned at the ends.
[0005] However, in the above-described conventional technique,
since the water is supplied to the end plate, it is impossible to
effectively cool the central water electrolysis cells. Accordingly,
a temperature difference between the plurality of water
electrolysis cells becomes large, and there is a concern that
variations may occur in the performance and durability of the
respective water electrolysis cells.
[0006] The present invention has been devised taking into
consideration the aforementioned problem, and has the object of
providing a water electrolysis system in which, by reducing a
difference in temperature between a plurality of water electrolysis
cells, it is possible to suppress variations in the performance and
durability of the respective water electrolysis cells.
[0007] In order to achieve the aforementioned object, a water
electrolysis system according to the present invention is equipped
with a water electrolysis stack provided with a water introduction
unit and a water lead-out unit, and in which a plurality of water
electrolysis cells, which produce hydrogen and oxygen by
electrolysis of water, are stacked together mutually, and a
circulation pump through which water is circulated in a manner so
that water which is stored in a gas-liquid separator is supplied
from the water introduction unit in the water electrolysis stack
via a water supply path, and so that unreacted water which was not
subjected to electrolysis inside the water electrolysis stack is
discharged from the water lead-out unit into the gas-liquid
separator via a water discharge path, wherein the water lead-out
unit comprises a first water lead-out unit provided on one end side
of the water electrolysis stack in a stacking direction of the
water electrolysis cells, and a second water lead-out unit provided
on another end side of the water electrolysis stack in the stacking
direction, wherein the water introduction unit is positioned in the
stacking direction between the first water lead-out unit and the
second water lead-out unit, together with being disposed in a water
electrolysis cell which is positioned between both ends in the
stacking direction among the plurality of water electrolysis
cells.
[0008] In accordance with such a configuration, since the water is
introduced from the water introduction unit into the water
electrolysis cell which is positioned in the stacking direction
between the end portions of the plurality of water electrolysis
cells, it is possible for the centrally located water electrolysis
cells to be cooled effectively. Further, unreacted water which has
not been subjected to electrolysis, and to which heat has been
imparted accompanying the occurrence of electrolysis taking place
in each of the water electrolysis cells, is led out from the first
water lead-out unit and the second water lead-out unit positioned
at both end sides in the stacking direction of the water
electrolysis stack. Therefore, since the temperature difference
between the plurality of water electrolysis cells can be reduced,
variations in the performance and durability of the respective
water electrolysis cells can be suppressed.
[0009] In the above-described water electrolysis system, the water
introduction unit may be disposed in a water electrolysis cell
which is located in a central region in the stacking direction
among the plurality of water electrolysis cells.
[0010] In accordance with such a configuration, the difference in
temperature between the plurality of water electrolysis cells can
be further reduced.
[0011] In the above-described water electrolysis system, in each of
the water electrolysis cells, there may be formed a water
introducing communication passage adapted to allow the water
introduced from the water introduction unit to flow in the stacking
direction, and a water lead-out communication passage adapted to
allow the unreacted water which was not subjected to electrolysis
to flow in the stacking direction, and to guide the unreacted water
to the first water lead-out unit and the second water lead-out
unit.
[0012] In accordance with such a configuration, it is possible to
cause the water to flow and circulate efficiently in each of the
water electrolysis cells.
[0013] In the above-described water electrolysis system, each of
the first water lead-out unit and the second water lead-out unit
may be disposed at a position which is shifted in phase from the
water introduction unit by 180.degree. in a circumferential
direction of the water electrolysis stack.
[0014] In accordance with such a configuration, it is possible to
cause the water to flow and circulate more efficiently in each of
the water electrolysis cells.
[0015] In the above-described water electrolysis system, the first
water lead-out unit may be provided in a water electrolysis cell
positioned at one end in the stacking direction among the plurality
of water electrolysis cells, and the second water lead-out unit may
be provided in a water electrolysis cell position at another end in
the stacking direction among the plurality of water electrolysis
cells.
[0016] In accordance with such a configuration, the difference in
temperature between the plurality of water electrolysis cells can
be even further reduced.
[0017] In the above-described water electrolysis system, there may
further be provided a drain flow passage connected to a lowermost
part of the water discharge path, and an opening-closing valve
adapted to open and close the drain flow passage, wherein the water
electrolysis stack may be installed in a manner so that the
stacking direction is arranged along a vertical direction, and the
second water lead-out unit is positioned lower than the first water
lead-out unit and the water introduction unit.
[0018] In accordance with such a configuration, by opening the
opening-closing valve, the water in the water electrolysis stack
can be discharged to the exterior of the water electrolysis system
via the drain flow passage. Consequently, when driving of the water
electrolysis system is shut down, it is possible to prevent water
inside the water electrolysis stack from freezing and damaging the
water electrolysis stack.
[0019] In the above-described water electrolysis system, the second
water lead-out unit may be positioned lower than each of the
gas-liquid separator, the water supply path, and the circulation
pump.
[0020] In accordance with such a configuration, by opening the
opening-closing valve, water in the gas-liquid separator, the water
supply path, the circulation pump, and the water discharge path
(hereinafter referred to as a water circulation circuit) can be
discharged to the exterior of the water electrolysis system.
Consequently, when driving of the water electrolysis system is shut
down, it is possible to prevent water inside the water circulation
circuit from freezing and causing damage to the members that
constitute the water circulation circuit.
[0021] In the above-describe water electrolysis system, the
opening-closing valve may be a solenoid valve, and the water
electrolysis system may further comprise an air supply path through
which air is supplied to the gas-liquid separator, an air supplying
device provided in the air supply path, a freeze prediction unit
adapted to predict freezing of the water inside the water
electrolysis system, and a control unit adapted to control the
solenoid valve and the air supplying device, wherein, when
performing a process to stop driving of the water electrolysis
system, in the case it is predicted by the freeze prediction unit
that there is a possibility that the water inside the water
electrolysis system may become frozen, the control unit may control
the solenoid valve in a manner so as to open the drain flow
passage, and may control driving of the air supplying device in a
manner so that air is supplied to the gas-liquid separator via the
air supply path.
[0022] In accordance with such a configuration, by the air that is
supplied from the air supplying device, the water inside the water
circulation circuit and the water electrolysis stack can be
discharged efficiently to the exterior of the water electrolysis
system via the drain flow passage. Further, it is possible to
shorten the time required for the process to stop driving of the
water electrolysis system.
[0023] In the above-described water electrolysis system, the
central region may be a middle region obtained by dividing the
plurality of water electrolysis cells into three equal parts in the
stacking direction.
[0024] In the above-described water electrolysis system, the second
water lead-out unit may be connected to a lowermost part of the
water discharge path.
[0025] According to the present invention, since the water is
introduced from the water introduction unit into a water
electrolysis cell which is positioned between both ends in the
stacking direction among the plurality of water electrolysis cells,
the difference in temperature between the plurality of water
electrolysis cells can be made small, so that variations in the
performance and durability of the respective water electrolysis
cells can be suppressed.
[0026] The above and other objects, features, and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings, in which a preferred embodiment of the present invention
is shown by way of illustrative example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a schematic configuration explanatory diagram of a
water electrolysis system according to an embodiment of the present
invention;
[0028] FIG. 2 is a flowchart for explaining the freezing
preventative operation at a time that the driving of the water
electrolysis system is stopped; and
[0029] FIG. 3 is an explanatory diagram of operations of the water
electrolysis system shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Preferred embodiments of a water electrolysis system
according to the present invention will be presented and described
below with reference to the accompanying drawings. In FIGS. 1 and
3, the direction of the arrow A1 indicates the direction of
gravity, and the direction of the arrow A2 indicates a direction
opposite to the direction of gravity.
[0031] As shown in FIG. 1, a water electrolysis system 10 according
to an embodiment of the present invention is equipped with a water
electrolysis stack 12, which performs electrolysis on pure water
(hereinafter, also simply referred to as water) to thereby produce
oxygen (at a normal pressure) and hydrogen (at a higher pressure
than that of the oxygen).
[0032] The water electrolysis stack 12 has a plurality of mutually
stacked water electrolysis cells 14. The water electrolysis cells
14 are formed, for example, in a disk-like shape. Although detailed
illustration thereof is omitted, each of the water electrolysis
cells 14 includes an electrolyte electrode assembly, for example, a
membrane electrode assembly (MEA), and an anode separator and a
cathode separator disposed on both sides of the membrane electrode
assembly. The membrane electrode assembly includes a solid polymer
electrolyte membrane and an anode power supplying member and a
cathode power supplying member provided on both sides of the solid
polymer electrolyte membrane.
[0033] The water electrolysis stack 12 is installed in a manner so
that the stacking direction of the water electrolysis cells 14 lies
along the vertical direction (in the direction of the arrow A). An
electrolytic power supply 16 which is a DC power source is
connected to the water electrolysis stack 12. End plates 18a, 18b
are disposed at both ends of the plurality of water electrolysis
cells 14 in the stacking direction. A hydrogen lead-out path 20
which communicates with the cathode sides (high-pressure hydrogen
generating side) of the respective water electrolysis cells 14 is
connected to the upper end plate 18a.
[0034] A water introduction unit 22 and a water lead-out unit 24
are provided in the water electrolysis stack 12. A water inlet port
22a through which water is introduced into the water electrolysis
stack 12 is formed in the water introduction unit 22. The water
inlet port 22a communicates with a water introducing communication
passage 25 which is provided so as to penetrate through the water
electrolysis cells 14 in the stacking direction. The water
introducing communication passage 25 allows water introduced from
the water inlet port 22a of the water introduction unit 22 to flow
in the stacking direction. The water introducing communication
passage 25 communicates with anode inlet sides (water supply inlet
sides) of each of the water electrolysis cells 14.
[0035] The water introduction unit 22 is disposed in a water
electrolysis cell 14 which is positioned between both ends
(centrally) in the stacking direction among the plurality of water
electrolysis cells 14. More specifically, the water introduction
unit 22 is disposed in a water electrolysis cell 14 which is
positioned in a central region in the stacking direction among the
plurality of water electrolysis cells 14. The central region, for
example, is a middle region obtained by dividing the plurality of
water electrolysis cells 14 into three equal parts in the stacking
direction. However, the central region, for example, may be a
middle region obtained by dividing the plurality of water
electrolysis cells 14 into three parts at a ratio of 1:2:1 in the
stacking direction.
[0036] The water lead-out unit 24 includes a first water lead-out
unit 26 and a second water lead-out unit 28. The first water
lead-out unit 26 is provided in the water electrolysis cell 14 (on
an upper end side of the water electrolysis stack 12) located at
the upper end (one end) of the plurality of water electrolysis
cells 14 in the stacking direction. More specifically, the first
water lead-out unit 26 is positioned more upwardly (in the
direction of the arrow A2) than the water introduction unit 22. A
first water outlet port 26a through which unreacted water (surplus
water) which has not been subjected to electrolysis is led out from
the interior of the water electrolysis stack 12 is formed in the
first water lead-out unit 26.
[0037] The second water lead-out unit 28 is provided in the water
electrolysis cell 14 (on a lower end side of the water electrolysis
stack 12) located at the lower end (other end) of the plurality of
water electrolysis cells 14 in the stacking direction. More
specifically, the second water lead-out unit 28 is positioned more
downwardly (in the direction of the arrow A1) than the water
introduction unit 22 and the first water lead-out unit 26. A second
water outlet port 28a through which unreacted water (surplus water)
which has not been subjected to electrolysis is led out from the
interior of the water electrolysis stack 12 is formed in the second
water lead-out unit 28.
[0038] The first water lead-out unit 26 and the second water
lead-out unit 28 are disposed at positions, respectively, which are
shifted in phase from the water introduction unit 22 by 180.degree.
in a circumferential direction of the water electrolysis stack 12.
The first water outlet port 26a and the second water outlet port
28a communicate respectively with a water lead-out communication
passage 30 which is provided so as to penetrate through the water
electrolysis cells 14 in the stacking direction. The water lead-out
communication passage 30 communicates with anode outlet sides
(water and oxygen discharge sides) of each of the water
electrolysis cells 14, allows the unreacted water which has not
been subjected to electrolysis to flow in the stacking direction,
and guides the unreacted water to the first water lead-out unit 26
and the second water lead-out unit 28.
[0039] The water electrolysis system 10 includes a pure water
producing device 32, a pure water supply path 34, a water
circulation circuit 36, an air blower 38, an air supply path 40, an
air discharge path 42, a drain flow passage 44, and an
opening-closing valve 46.
[0040] The pure water producing device 32 produces pure water from
city water (tap water). The pure water supply path 34 guides the
pure water produced by the pure water producing device 32 to the
water circulation circuit 36. The water circulation circuit 36
includes a gas-liquid separator 48, a water supply path 50, a water
discharge path 52, and a circulation pump 54. The pure water supply
path 34 is connected to an upper part of the gas-liquid separator
48. The gas-liquid separator 48 functions as a tank in which water
is stored.
[0041] The water supply path 50 mutually interconnects the bottom
portion of the gas-liquid separator 48 and the water introduction
unit 22. The water supply path 50 guides the water stored in the
gas-liquid separator 48 to the water introduction unit 22. The
water discharge path 52 mutually interconnects the first water
lead-out unit 26 and the second water lead-out unit 28 respectively
to the upper part of the gas-liquid separator 48. The water
discharge path 52 guides a mixed fluid, in which unreacted water
which has not been subjected to electrolysis, oxygen generated by
the reaction, and hydrogen that has permeated from the cathode
sides to the anode sides are mixed, into the interior of the
gas-liquid separator 48.
[0042] The water discharge path 52 includes a first flow passage
portion 52a extending from the first water lead-out unit 26, a
second flow passage portion 52b extending from the second water
lead-out unit 28, and a third flow passage portion 52c to which the
first flow passage portion 52a and the second flow passage portion
52b are respectively connected. The second flow passage portion 52b
is positioned lower than the first flow passage portion 52a and the
third flow passage portion 52c. Stated otherwise, the second flow
passage portion 52b is positioned at a lowermost location of the
water discharge path 52.
[0043] The circulation pump 54 is provided in the water supply path
50. The circulation pump 54 circulates the water in a manner so
that the water that is stored in the gas-liquid separator 48 is
supplied into the interior of the water electrolysis stack 12 from
the water introduction unit 22 via the water supply path 50 and
further unreacted water which has not been subjected to
electrolysis inside the water electrolysis stack 12 is discharged
from the water lead-out unit 24 into the gas-liquid separator 48
via the water discharge path 52.
[0044] In the water circulation circuit 36 which is configured in
the foregoing manner, the second water lead-out unit 28 is
positioned lower than each of the gas-liquid separator 48, the
water supply path 50, and the circulation pump 54, together with
being connected to the lowermost part (second flow passage portion
52b) of the water discharge path 52.
[0045] The air blower 38 is an air supplying device that guides
diluting air into the gas-liquid separator 48 via the air supply
path 40. The air supply path 40 and the air discharge path 42 are
connected to the upper part of the gas-liquid separator 48. Oxygen
and hydrogen inside the gas-liquid separator 48 are discharged into
the air discharge path 42 together with the air introduced from the
air blower 38.
[0046] The drain flow passage 44 is a flow passage for discharging
to the exterior the water in the water circulation circuit 36 and
the water electrolysis stack 12, and is connected to the lowermost
part (second flow passage portion 52b) of the water discharge path
52. The opening-closing valve 46 is configured in the form of a
solenoid valve that opens and closes the drain flow passage 44.
[0047] The water electrolysis system 10 is equipped with a
controller 55 that carries out control of operations of the water
electrolysis system 10 as a whole. The controller 55 is a
computation device including a microcomputer, which includes a CPU
(central processing unit), and a ROM, a RAM, and the like, serving
as memories. The CPU, by reading and executing programs recorded in
the ROM, functions as various function realizing units (function
realizing means). The various function realizing units can also be
constituted by function realizing devices in the form of
hardware.
[0048] Output signals from a temperature detecting unit 56
(temperature sensor) that detects the system environmental
temperature are input to the controller 55. The temperature
detecting unit 56, for example, detects the temperature of the
water in the water supply path 50. However, the temperature
detecting unit 56 may also detect the temperature of the water
stored in the gas-liquid separator 48.
[0049] The controller 55 comprises a control unit 58, a freeze
prediction unit 60, and a drainage determination unit 62. The
control unit 58 controls driving and stopping of the circulation
pump 54, controls driving and stopping of the air blower 38, and
controls the opening and closing operations of the opening-closing
valve 46. On the basis of the temperature detected from the
temperature detecting unit 56, the freeze prediction unit 60
predicts whether or not there is a possibility that the water
inside the water electrolysis system 10 may become frozen. The
drainage determination unit 62 determines whether or not all of the
water inside the water circulation circuit 36 and the water
electrolysis stack 12 has been drained.
[0050] The water electrolysis system 10 which is configured as
described above operates in the following manner.
[0051] Under the action of the circulation pump 54, the pure water
inside the gas-liquid separator 48 is supplied to the water
introduction unit 22 (into the water electrolysis cell 14
positioned roughly in the center in the stacking direction) via the
water supply path 50. The pure water supplied to the water
introduction unit 22 flows into the water introducing communication
passage 25, flows in upward and downward directions (in the
stacking direction), and is distributed to the anode inlet sides of
each of the water electrolysis cells 14.
[0052] At this time, a voltage is applied to the water electrolysis
stack 12 via the electrolytic power supply 16 which is electrically
connected thereto. Therefore, in each of the respective water
electrolysis cells 14, on the anode sides thereof, pure water is
subjected to electrolysis to thereby generate hydrogen ions,
electrons, and oxygen. Accordingly, on the cathode sides, hydrogen
ions are combined with electrons to obtain hydrogen, and the
hydrogen is taken out to the hydrogen lead-out path 20 to thereby
become dry hydrogen (product hydrogen), which is supplied to a
non-illustrated fuel cell electric vehicle or the like.
[0053] On the other hand, on the anode outlet sides, oxygen
produced by the reaction, unreacted water which has not been
subjected to electrolysis, and furthermore, the permeated hydrogen
flow, and a mixed fluid made up therefrom is led out into the water
lead-out communication passage 30, and flows in upward and downward
directions (in the stacking direction). The mixed fluid that has
flowed upwardly through the water lead-out communication passage 30
is guided into the first flow passage portion 52a via the first
water lead-out unit 26. The mixed fluid that has flowed downwardly
through the water lead-out communication passage 30 is guided into
the second flow passage portion 52b via the second water lead-out
unit 28.
[0054] The mixed fluid in the first flow passage portion 52a and
the mixed fluid in the second flow passage portion 52b are joined
together in the third flow passage portion 52c, are guided into the
upper part of the gas-liquid separator 48, and are separated into a
liquid (water) and gases (oxygen and hydrogen). Moreover, at this
time, the opening-closing valve 46 closes the drain flow passage
44.
[0055] The water that is separated from the mixed fluid is stored
in the gas-liquid separator 48, and by action of the circulation
pump 54, is guided into the water supply path 50. By action of the
air blower 38, the oxygen and hydrogen that are separated from the
mixed fluid are discharged to the exterior from the air discharge
path 42.
[0056] Next, a description will be given with reference to the
flowchart shown in FIG. 2 concerning an operation to prevent
freezing at a time that driving of the water electrolysis system 10
is stopped.
[0057] In step S1, the controller 55 receives a signal to stop
driving of the water electrolysis stack 12. Upon doing so, the
controller 55 stops the application of voltage to the water
electrolysis stack 12. Further, in step S2, the freeze prediction
unit 60 determines whether there is a possibility that the water
inside the water electrolysis system 10 may become frozen. More
specifically, the freeze prediction unit 60 determines that there
is a possibility of freezing in the case that the temperature
(detected temperature) detected by the temperature detecting unit
56 is less than a predetermined temperature (for example, 4.degree.
C.), and determines that there is not a possibility of freezing in
the case that the detected temperature is greater than or equal to
the predetermined temperature.
[0058] If the freeze prediction unit 60 determines that there is
not a possibility that the water inside the water electrolysis
system 10 may become frozen (step S3: NO), the process to stop
driving of the water electrolysis system 10 for the present time is
brought to an end. If the freeze prediction unit 60 determines that
there is a possibility that the water inside the water electrolysis
system 10 may become frozen (step S3: YES), the control unit 58
opens the opening-closing valve 46 (step S4), and turns on the air
blower 38 (step S5). Consequently, by the air that is led in from
the air blower 38, the water that exists inside the water
circulation circuit 36 and the water electrolysis stack 12 is
discharged to the exterior via the drain flow passage 44.
[0059] Thereafter, in step S6, the drainage determination unit 62
determines whether or not all of the water inside the water
circulation circuit 36 and the water electrolysis stack 12 has been
drained. More specifically, the drainage determination unit 62 is
provided, for example, with a non-illustrated flowmeter disposed in
the drain flow passage 44, and determines that all of the water has
been discharged when the flow rate of the water detected by the
flowmeter becomes zero. However, the drainage determination unit 62
may determine that all of the water has been discharged after a
predetermined time has elapsed from starting of the drainage
process (after the processes of steps S4 and S5 have been
started).
[0060] In the case that the drainage determination unit 62 has
determined that all of the water has not been discharged (step S6:
NO), the process of step S6 is repeated. In the case that the
drainage determination unit 62 has determined that all of the water
has been discharged (step S6: YES), the control unit 58 closes the
opening-closing valve 46 (step S7), and stops driving of the air
blower 38 (step S8). Thereafter, the process to stop driving of the
water electrolysis system 10 for the present time is brought to an
end.
[0061] In this case, the water electrolysis system 10 according to
the present embodiment achieves the following advantageous
effects.
[0062] The first water lead-out unit 26 is provided on the one end
side (the upper end side) in the stacking direction of the water
electrolysis cells 14 in the water electrolysis stack 12. The
second water lead-out unit 28 is provided on the other end side
(the lower end side) in the stacking direction of the water
electrolysis cells 14 in the water electrolysis stack 12. The water
introduction unit 22 is positioned in the stacking direction
between the first water lead-out unit 26 and the second water
lead-out unit 28, together with being disposed in a water
electrolysis cell 14 which is positioned between both ends in the
stacking direction among the plurality of water electrolysis cells
14.
[0063] In accordance with such features, since the water is
introduced from the water introduction unit 22 into a water
electrolysis cell 14 which is positioned between both ends in the
stacking direction from among the plurality of water electrolysis
cells 14, it is possible to effectively cool the water electrolysis
cell 14 (the central water electrolysis cell 14) that is positioned
centrally in the stacking direction among the plurality of water
electrolysis cells 14. Further, the unreacted water which has not
been subjected to electrolysis, and to which heat has been imparted
accompanying the occurrence of electrolysis taking place in each of
the water electrolysis cells 14, is led out from the first water
lead-out unit 26 and the second water lead-out unit 28 positioned
at both end sides in the stacking direction of the water
electrolysis stack 12.
[0064] Therefore, since the temperature difference between the
plurality of water electrolysis cells 14 can be reduced, variations
in the performance and durability of the respective water
electrolysis cells 14 can be suppressed.
[0065] The water introduction unit 22 is disposed in a water
electrolysis cell 14 which is positioned substantially centrally in
the stacking direction among the plurality of water electrolysis
cells 14. Therefore, the difference in temperature between the
plurality of water electrolysis cells 14 can be further
reduced.
[0066] In each of the water electrolysis cells 14, there are formed
the water introducing communication passage 25 through which the
water introduced from the water introduction unit 22 flows in the
stacking direction, and the water lead-out communication passage 30
through which the unreacted water which was not subjected to
electrolysis flows in the stacking direction, and which guides the
unreacted water to the first water lead-out unit 26 and the second
water lead-out unit 28. In accordance with this feature, it is
possible to cause the water to flow and circulate efficiently in
each of the water electrolysis cells 14.
[0067] Each of the first water lead-out unit 26 and the second
water lead-out unit 28 is disposed at a position which is shifted
in phase from the water introduction unit 22 by 180.degree. in the
circumferential direction of the water electrolysis stack 12, and
consequently, the water in each of the water electrolysis cells 14
can be made to flow and circulate more efficiently.
[0068] The first water lead-out unit 26 is provided in the water
electrolysis cell 14 positioned at the one end (upper end) in the
stacking direction among the plurality of water electrolysis cells
14, and the second water lead-out unit 28 is provided in the water
electrolysis cell 14 positioned at the other end (lower end) in the
stacking direction among the plurality of water electrolysis cells
14. In accordance with this feature, the difference in temperature
between the plurality of water electrolysis cells 14 can be further
reduced.
[0069] The water electrolysis system 10 is equipped with the drain
flow passage 44, which is connected to the lowermost part (second
flow passage portion 52b) of the water discharge path 52, and the
opening-closing valve 46 that opens and closes the drain flow
passage 44. The water electrolysis stack 12 is installed in a
manner so that the stacking direction is arranged along the
vertical direction (the direction of gravity), and the second water
lead-out unit 28 is positioned lower than the first water lead-out
unit 26 and the water introduction unit 22.
[0070] In this case, by opening the opening-closing valve 46, the
water inside the water electrolysis stack 12 can be discharged to
the exterior of the water electrolysis system 10 via the drain flow
passage 44. Consequently, when driving of the water electrolysis
system 10 is stopped, it is possible to prevent water inside the
water electrolysis stack 12 from freezing and damaging the water
electrolysis stack 12.
[0071] The second water lead-out unit 28 is positioned lower than
each of the gas-liquid separator 48, the water supply path 50, and
the circulation pump 54. In accordance with this configuration, by
opening the opening-closing valve 46, water (the water inside the
water circulation circuit 36) in the gas-liquid separator 48, the
water supply path 50, the circulation pump 54, and the water
discharge path 52 can be discharged to the exterior of the water
electrolysis system 10 via the drain flow passage 44. Consequently,
when operation of the water electrolysis system 10 is shut down, it
is possible to prevent water inside the water circulation circuit
36 from freezing and causing damage to the members that constitute
the water circulation circuit 36.
[0072] When performing the process to stop driving of the water
electrolysis system 10, in the case it is predicted by the freeze
prediction unit 60 that there is a possibility that the water
inside the water electrolysis system 10 may become frozen, the
control unit 58 controls the opening-closing valve 46 which is a
solenoid valve in a manner so as to open the drain flow passage 44,
and controls driving of the air blower 38 in a manner so that air
is supplied to the gas-liquid separator 48 via the air supply path
40.
[0073] In accordance with these features, by the air that is
supplied from the air blower 38, the water inside the water
circulation circuit 36 and the water electrolysis stack 12 can be
discharged efficiently to the exterior of the water electrolysis
system 10 via the drain flow passage 44. Further, it is possible to
shorten the time required for the process to stop driving of the
water electrolysis system 10.
[0074] The present invention is not limited to the configuration
described above. The first water lead-out unit 26 may be provided
in the upper end plate 18a. The second water lead-out unit 28 may
be provided in the lower end plate 18b. The first water lead-out
unit 26 and the second water lead-out unit 28 may be positioned so
as to be out of phase with each other in the circumferential
direction of the water electrolysis cells 14. The opening-closing
valve 46 may be a manual valve and not a solenoid valve. The water
introduction unit 22 may be disposed in a water electrolysis cell
14 which is positioned upwardly or downwardly from the center in
the stacking direction among the plurality of water electrolysis
cells 14. Stated otherwise, the water introduction unit 22 may be
disposed in a water electrolysis cell 14 other than those at both
ends in the stacking direction among the plurality of water
electrolysis cells 14.
[0075] The water electrolysis system according to the present
invention is not limited to the above-described embodiments, and it
goes without saying that various alternative or additional
configurations could be adopted therein without departing from the
essence and gist of the present invention.
* * * * *