U.S. patent application number 17/362490 was filed with the patent office on 2021-10-21 for redox flow battery.
This patent application is currently assigned to Sumitomo Electric Industries, Ltd.. The applicant listed for this patent is Sumitomo Electric Industries, Ltd.. Invention is credited to Atsuo IKEUCHI.
Application Number | 20210328242 17/362490 |
Document ID | / |
Family ID | 1000005684802 |
Filed Date | 2021-10-21 |
United States Patent
Application |
20210328242 |
Kind Code |
A1 |
IKEUCHI; Atsuo |
October 21, 2021 |
REDOX FLOW BATTERY
Abstract
A redox flow battery includes a battery cell; a positive
electrolyte tank and a negative electrolyte tank configured to
store therein a positive electrolyte and a negative electrolyte,
respectively; a positive electrolyte circulation path and a
negative electrolyte circulation path each configured to allow a
corresponding one of the electrolytes to circulate between a
corresponding one of the tanks and the battery cell; and a
communicating tube including a tube immersed at one open end
thereof in the positive electrolyte, stretched at an intermediate
portion thereof above levels of both the electrolytes, and immersed
at the other open end thereof in the negative electrolyte.
Inventors: |
IKEUCHI; Atsuo; (Osaka-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sumitomo Electric Industries, Ltd. |
Osaka-shi |
|
JP |
|
|
Assignee: |
Sumitomo Electric Industries,
Ltd.
Osaka-shi
JP
|
Family ID: |
1000005684802 |
Appl. No.: |
17/362490 |
Filed: |
June 29, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16060286 |
Jun 7, 2018 |
11081708 |
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PCT/JP2017/042652 |
Nov 28, 2017 |
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17362490 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 8/04753 20130101;
H01M 8/188 20130101; H01M 8/04186 20130101; H01M 8/04082 20130101;
H01M 8/04201 20130101 |
International
Class: |
H01M 8/04186 20060101
H01M008/04186; H01M 8/04082 20060101 H01M008/04082; H01M 8/04746
20060101 H01M008/04746; H01M 8/18 20060101 H01M008/18 |
Claims
1. A redox flow battery comprising: a battery cell; a positive
electrolyte tank and a negative electrolyte tank; a positive
electrolyte circulation path and a negative electrolyte circulation
path each configured to allow an electrolyte to circulate between a
corresponding one of the tanks and the battery cell; and a
communicating tube configured to allow an interior of the positive
electrolyte tank to communicate with an interior of the negative
electrolyte tank, wherein the communicating tube has one open end
located in the interior of the positive electrolyte tank and the
other open end located in the interior of the negative electrolyte
tank; a height of an intermediate portion of the communicating tube
is higher than a height of the one open end, the intermediate
portion being disposed between the one open end and the other open
end; and the height of the intermediate portion of the
communicating tube is higher than a height of the other open
end.
2. The redox flow battery according to claim 1, wherein the
positive electrolyte tank and the negative electrolyte tank each
have a top, a bottom, and a side; and the communicating tube has a
first extending portion extending from the one open end to the top
of the positive electrolyte tank, the intermediate portion located
in an outside region between the positive electrolyte tank and the
negative electrolyte tank, and a second extending portion extending
from the top of the negative electrolyte tank to the other open
end.
3. The redox flow battery according to claim 2, wherein the first
extending portion has a first end corresponding to the one open end
of the communicating tube; a distance from the top of the positive
electrolyte tank to the first end is greater than a distance from
the bottom of the positive electrolyte tank to the first end; the
second extending portion has a second end corresponding to the
other open end of the communicating tube; and a distance from the
top of the negative electrolyte tank to the second end is greater
than a distance from the bottom of the negative electrolyte tank to
the second end.
4. The redox flow battery according to claim 3, further comprising:
a positive electrolyte stored in the positive electrolyte tank; and
a negative electrolyte stored in the negative electrolyte tank,
wherein the first end is located below a level of the positive
electrolyte stored in the positive electrolyte tank; the first end
is located at a distance of h/2 or less from the bottom of the
positive electrolyte tank, where h is a height from the bottom of
the positive electrolyte tank to the level of the positive
electrolyte; the second end is located below a level of the
negative electrolyte stored in the negative electrolyte tank; and
the second end is located at a distance of H/2 or less from the
bottom of the negative electrolyte tank, where H is a height from
the bottom of the negative electrolyte tank to the level of the
negative electrolyte.
5. The redox flow battery according to claim 2, wherein the first
extending portion extends substantially in a height direction; and
the second extending portion extends substantially in the height
direction.
6. The redox flow battery according to claim 1, wherein at least a
portion of the communicating tube is made of a transparent material
to make an interior of the communicating tube visible from
outside.
7. The redox flow battery according to claim 1, wherein the
communicating tube has a window in a highest region thereof, and
the window is made of a transparent material.
8. The redox flow battery according to claim 1, wherein a length L
from the one open end to the other open end of the communicating
tube is 10 m or less.
9. The redox flow battery according to claim 1, wherein the
communicating tube has an inside diameter d of 10 mm or more and
150 mm or less.
10. The redox flow battery according to claim 1, wherein a length L
from the one open end to the other open end of the communicating
tube is 10 m or less; an inside diameter d of the communicating
tube is 10 mm or more and 150 mm or less; and the length L is less
than or equal to 100 times the inside diameter d.
11. The redox flow battery according to claim 1, further comprising
a gas vent pipe configured to allow air bubbles to escape from
inside the communicating tube, wherein the gas vent pipe is
connected at one end thereof to the communicating tube and
connected at the other end thereof to at least one of the positive
electrolyte circulation path and the negative electrolyte
circulation path.
12. The redox flow battery according to claim 1, further
comprising: a positive electrolyte stored in the positive
electrolyte tank; and a negative electrolyte stored in the negative
electrolyte tank, wherein the communicating tube is immersed at
both ends thereof in the respective electrolytes, and an interior
of the communicating tube is filled with the positive electrolyte
and the negative electrolyte.
13. The redox flow battery according to claim 12, wherein the
height of the intermediate portion of the communicating tube is
higher than a level of the positive electrolyte stored in the
positive electrolyte tank and a level of the negative electrolyte
stored in the negative electrolyte tank.
14. The redox flow battery according to claim 12, wherein at least
a portion of the communicating tube is made of a transparent
material to make an interior of the communicating tube visible from
outside.
15. The redox flow battery according to claim 12, wherein the
communicating tube has a window in a highest region thereof, and
the window is made of a transparent material.
Description
TECHNICAL FIELD
[0001] The present invention relates to a redox flow battery.
BACKGROUND ART
[0002] As a large-capacity storage battery, a redox flow battery
(which may hereinafter be referred to as "RF battery") is known,
which performs charge and discharge by circulating positive and
negative electrolytes through a battery cell (see, e.g., Patent
Literatures 1 and 2). The RF battery includes the battery cell, a
positive electrolyte tank and a negative electrolyte tank
configured to store therein a positive electrolyte and a negative
electrolyte, respectively, and a positive electrolyte circulation
path and a negative electrolyte circulation path each configured to
allow a corresponding one of the electrolytes to circulate between
a corresponding one of the tanks and the battery cell. Patent
Literatures 1 and 2 each describe an RF battery that includes a
communicating tube configured to allow communication between the
positive electrolyte tank and the negative electrolyte tank.
CITATION LIST
Patent Literature
[0003] PTL 1: Japanese Unexamined Patent Application Publication
No. 2013-25964
[0004] PTL 2: Japanese Unexamined Patent Application Publication
No. 2013-37814
SUMMARY OF INVENTION
[0005] A redox flow battery of the present disclosure includes a
battery cell; a positive electrolyte tank and a negative
electrolyte tank configured to store therein a positive electrolyte
and a negative electrolyte, respectively; a positive electrolyte
circulation path and a negative electrolyte circulation path each
configured to allow a corresponding one of the electrolytes to
circulate between a corresponding one of the tanks and the battery
cell; and a communicating tube including a tube immersed at one
open end thereof in the positive electrolyte, stretched at an
intermediate portion thereof above levels of both the electrolytes,
and immersed at the other open end thereof in the negative
electrolyte.
BRIEF DESCRIPTION OF DRAWINGS
[0006] FIG. 1 is a schematic diagram of a redox flow battery
according to an embodiment.
[0007] FIG. 2 is a schematic diagram of a cell stack.
[0008] FIG. 3 illustrates dimensions of a communicating tube
included in the redox flow battery according to the embodiment.
[0009] FIG. 4 illustrates a modified open end of the communicating
tube included in the redox flow battery according to the
embodiment.
[0010] FIG. 5 is a schematic diagram of a redox flow battery
according to a first modification.
[0011] FIG. 6 is a schematic diagram of a redox flow battery
according to a second modification.
DESCRIPTION OF EMBODIMENTS
Problems to be Solved by the Present Disclosure
[0012] When charge and discharge cycles are repeated during
operation of a redox flow battery (RF battery), a phenomenon called
"electrolyte crossover" may occur, in which positive and negative
electrolytes are each transferred from one side to the other
through a membrane interposed between a positive electrode and a
negative electrode inside a battery cell. This may create a
difference between the volumes of the electrolytes in a positive
electrolyte tank and a negative electrolyte tank and lead to
reduced battery capacity (discharge capacity).
[0013] As a solution to such problems associated with the
electrolyte crossover, Patent Literatures 1 and 2 each disclose a
technique in which the positive electrolyte tank and the negative
electrolyte tank are connected by a communicating tube and when a
difference occurs between the volumes of the electrolytes in the
tanks, the levels of the electrolytes in the tanks are adjusted to
the same height using the communicating tube. In the techniques
disclosed in Patent Literatures 1 and 2, however, the communicating
tube is connected and positioned at a level substantially the same
as, or lower than, the levels of the electrolytes in the tanks.
This may cause electrolyte to leak through a connection of each
tank with the communicating tube, or may cause electrolyte to flow
out of the communicating tube in the event of breakage of the
communicating tube.
[0014] Accordingly, the present disclosure aims to provide a redox
flow battery that is capable not only of adjusting the volumes of
the electrolytes in the positive electrolyte tank and the negative
electrolyte tank, but also of preventing each electrolyte from
flowing out of the tank.
Advantageous Effects of the Present Disclosure
[0015] The present disclosure provides a redox flow battery that is
capable not only of adjusting the volumes of the electrolytes in
the positive electrolyte tank and the negative electrolyte tank,
but also of preventing each electrolyte from flowing out of the
tank.
Description of Embodiment of the Invention of the Present
Application
[0016] First, aspects of an embodiment of the invention of the
present application will be listed.
[0017] (1) A redox flow battery according to an aspect of the
invention of the present application includes a battery cell; a
positive electrolyte tank and a negative electrolyte tank
configured to store therein a positive electrolyte and a negative
electrolyte, respectively; a positive electrolyte circulation path
and a negative electrolyte circulation path each configured to
allow a corresponding one of the electrolytes to circulate between
a corresponding one of the tanks and the battery cell; and a
communicating tube including a tube immersed at one open end
thereof in the positive electrolyte, stretched at an intermediate
portion thereof above levels of both the electrolytes, and immersed
at the other open end thereof in the negative electrolyte.
[0018] In the redox flow battery described above, the one and other
open ends of the communicating tube are immersed in the positive
electrolyte and the negative electrolyte, and the intermediate
portion of the communicating tube is stretched above the levels of
both the electrolytes. The communicating tube becomes a siphon by
being filled with electrolyte. Then, when a difference occurs
between the volumes of the electrolytes in the tanks, the levels of
the electrolytes are adjusted to the same height through the
communicating tube using the siphon principle. The volumes of the
electrolytes are thus automatically adjusted to maintain the levels
of the electrolytes in the tanks. If the communicating tube is
broken, the resulting entry of air into the communicating tube
terminates the siphon. As described above, the intermediate portion
of the communicating tube is disposed above the levels of both the
electrolytes. Therefore, even in the event of breakage, the
electrolyte in the communicating tube is returned to either of the
tanks by termination of the siphon. That is, even if the
communicating tube is broken, the electrolyte in the communicating
tube is prevented from flowing out of the tank. The redox flow
battery described above is thus capable not only of adjusting the
volumes of the electrolytes in the positive electrolyte tank and
the negative electrolyte tank, but also of preventing each
electrolyte from flowing out of the tank.
[0019] (2) Another aspect of the redox flow battery may include an
introducing tube configured to connect at least one of the positive
electrolyte circulation path and the negative electrolyte
circulation path to the communicating tube, and an open-close valve
configured to open and close the introducing tube.
[0020] To serve as a siphon, the communicating tube needs to be
filled with electrolyte. In this aspect of the redox flow battery,
which includes the introducing tube, the electrolyte is introduced
through the introducing tube into the communicating tube when the
redox flow battery starts, and this allows the communicating tube
to be filled with the electrolyte. Also, with the open-close valve,
a siphon can be created when the open-close valve closes the
introducing tube to block the flow between the circulation path and
the communicating tube, with the communicating tube being filled
with the electrolyte.
[0021] (3) In another aspect of the redox flow battery, the open
ends of the communicating tube may each be located on a bottom side
in a corresponding one of the tanks.
[0022] Entry of a gas into the communicating tube may terminate the
siphon. Gas bubbles may be produced in the vicinity of the surface
of the electrolyte in each tank. Therefore, if an open end of the
communicating tube is located near the surface of the electrolyte
in the tank, gas bubbles are easily drawn in through the open end.
In this aspect of the redox flow battery, where each open end of
the communicating tube is located on the bottom side in the tank,
gas bubbles are not easily drawn in through the open end. This
makes it easier to keep the communicating tube in a siphon
state.
[0023] (4) In another aspect of the redox flow battery, the open
ends of the communicating tube may be formed to face upward.
[0024] In this aspect of the redox flow battery, where the open
ends of the communicating tube are formed to face upward, gas
bubbles are not easily drawn in through the open ends. This also
makes it easier to keep the communicating tube in a siphon
state.
[0025] (5) In another aspect of the redox flow battery, the
communicating tube may be provided with a flow control valve.
[0026] In this aspect of the redox flow battery, where the
communicating tube is provided with a flow control valve, it is
possible to control, with the flow control valve, the flow rate (or
the amount of transfer) of the electrolyte passing through the
communicating tube when the volumes of the electrolytes in the
tanks are adjusted through the communicating tube using the siphon
principle.
[0027] (6) Another aspect of the redox flow battery may include a
gas vent pipe configured to allow gas bubbles to escape from inside
the communicating tube, and the gas vent pipe may be connected at
one end thereof to the communicating tube and connected at the
other end thereof to at least one of the positive electrolyte
circulation path and the negative electrolyte circulation path.
[0028] In this aspect of the redox flow battery, which includes the
gas vent pipe, gas bubbles accumulated in the communicating tube
can be discharged through the gas vent pipe to the circulation
path. This makes it possible to keep the communicating tube in a
siphon state.
Details of Embodiment of the Invention of the Present
Application
[0029] Examples of a redox flow battery (RF battery) according to
an embodiment of the invention of the present application will now
be described with reference to the drawings. The same reference
numerals in the drawings denote the same or corresponding parts.
The invention of the present application is not limited to the
examples described below, and is defined by the appended claims.
All changes that fall within meanings and scopes equivalent to the
claims are therefore intended to be embraced by the claims.
RF Battery
[0030] An RF battery according to the embodiment is typically
connected through an AC/DC converter to an electric system and
performs charge and discharge. The charge and discharge process
involves using a positive electrolyte and a negative electrolyte
each containing, as active materials, metal ions whose valences are
changed by oxidation-reduction. The charge and discharge process is
performed using a difference between the oxidation-reduction
potential of the ions contained in the positive electrolyte and the
oxidation-reduction potential of the ions contained in the negative
electrolyte.
[0031] An RF battery 1 according to the embodiment will now be
described with reference to FIGS. 1 and 2. As illustrated in FIG.
1, the RF battery 1 of the embodiment includes a battery cell 100,
a positive electrolyte tank 106 and a negative electrolyte tank
107, and a positive electrolyte circulation path 120 and a negative
electrolyte circulation path 130. A feature of the RF battery 1 is
that it includes a communicating tube 40 for an adjustment which is
made using the siphon principle such that electrolytes 10P and 10N
stored in the positive electrolyte tank 106 and the negative
electrolyte tank 107, respectively, have the same level.
Hereinafter, the configuration of the RF battery 1 will be
described in detail.
Battery Cell
[0032] As illustrated in FIG. 1, the battery cell 100 includes a
positive electrode 104, a negative electrode 105, and a membrane
101 interposed between the electrodes 104 and 105, and a positive
electrode cell 102 and a negative electrode cell 103 are formed
with the membrane 101 therebetween. The membrane 101 is, for
example, an ion-exchange membrane that allows hydrogen ions to pass
therethrough. The battery cell 100 (i.e., the positive electrode
cell 102 and the negative electrode cell 103) has the positive
electrolyte circulation path 120 and the negative electrolyte
circulation path 130 connected thereto, and allows the positive
electrolyte 10P and the negative electrolyte 10N to circulate
therethrough. The electrolytes 10P and 10N may be ones that
contain, as active materials, metal ions of the same type. For
example, the electrolytes 10P and 10N may each be an electrolyte
containing vanadium ions, an electrolyte containing either
manganese ions or titanium ions, or an electrolyte containing both
manganese ions and titanium ions.
[0033] The battery cell 100 may be configured either as a single
cell including one battery cell 100, or as a multicell including a
plurality of battery cells 100. In the case of a multicell, a
structure called a cell stack 2 (see FIG. 2) is used, which is
formed by stacking a plurality of battery cells 100. The cell stack
2 includes a substack 200 sandwiched on both sides by two end
plates 220, which are fastened with a fastening mechanism 230 (see
the lower part of FIG. 2). FIG. 2 illustrates a structure including
a plurality of substacks 200. The substacks 200 are each formed by
sequentially stacking a cell frame 3, the positive electrode 104,
the membrane 101, and the negative electrode 105 in layers (see the
upper part of FIG. 2) and sandwiching the resulting layered body
between supply/drainage plates 210 on both sides. The number of
battery cells 100 stacked in layers to form the cell stack 2 can be
appropriately determined.
[0034] As illustrated in the upper part of FIG. 2, each cell frame
3 includes a bipolar plate 31 disposed between the positive
electrode 104 and the negative electrode 105, and a frame body 32
disposed around the bipolar plate 31. The positive electrode 104 is
disposed on one side of the bipolar plate 31, and the negative
electrode 105 is disposed on the other side of the bipolar plate
31. The bipolar plate 31 is disposed inside the frame body 32, and
a recessed portion 32o is defined by the bipolar plate 31 and the
frame body 32. The recessed portion 32o is provided on each side of
the bipolar plate 31. The positive electrode 104 and the negative
electrode 105 are housed in the respective recessed portions 32o,
with the bipolar plate 31 interposed therebetween, and a first side
of the frame body 32 of each cell frame 3 and a second side of the
frame body 32 of an adjacent cell frame 3 are joined opposite each
other. In the substack 200 (cell stack 2), the positive electrode
104 and the negative electrode 105, with the membrane 101
therebetween, are arranged between the bipolar plates 31 of
adjacent cell frames 3 to form one battery cell 100. To prevent
leakage of electrolyte, the frame bodies 32 of adjacent cell frames
3 are each provided with an annular sealing member 37, such as an O
ring or flat gasket, therebetween.
[0035] For example, the bipolar plate 31 is made of plastic carbon,
and the frame body 32 is made of plastic, such as vinyl chloride
resin (PVC), polypropylene, polyethylene, fluorine resin, or epoxy
resin. In this example, each cell frame 3 includes the bipolar
plate 31 and the frame body 32 therearound that are integrally
formed, for example, by injection molding.
[0036] The circulation of electrolyte into the battery cell 100 is
made through the supply/drainage plates 210 (see the lower part of
FIG. 2) and also through liquid supply manifolds 33 and 34 and
liquid discharge manifolds 35 and 36 passing through the frame body
32 of each cell frame 3 (see the upper part of FIG. 2) and liquid
supply slits 33s and 34s and liquid discharge slits 35s and 36s
formed in the frame body 32. In the case of the cell frame 3 (frame
body 32) of this example, the positive electrolyte is supplied from
the liquid supply manifold 33 in the lower part of the frame body
32, through the liquid supply slit 33s on the first side of the
frame body 32, to the positive electrode 104, and then discharged
through the liquid discharge slit 35s in the upper part of the
frame body 32 to the liquid discharge manifold 35. Similarly, the
negative electrolyte is supplied from the liquid supply manifold 34
in the lower part of the frame body 32, through the liquid supply
slit 34s on the second side of the frame body 32, to the negative
electrode 105, and then discharged through the liquid discharge
slit 36s in the upper part of the frame body 32 to the liquid
discharge manifold 36. A flow-guiding portion (not shown) may be
formed along the lower and upper inner edges of the frame body 32
having the bipolar plate 31 therein. The flow-guiding portions have
the function of diffusing the electrolytes supplied through the
liquid supply slits 33s and 34s along the lower edges of the
electrodes 104 and 105, and collecting the electrolytes discharged
from the upper edges of the electrodes 104 and 105 into the liquid
discharge slits 35s and 36s.
Positive Electrolyte Tank and Negative Electrolyte Tank
[0037] As illustrated in FIG. 1, the positive electrolyte tank 106
and the negative electrolyte tank 107 store therein the positive
electrolyte 10P and the negative electrolyte 10N, respectively. The
tanks 106 and 107 are of the same shape and capacity. The upper
part of the interior of each of the tanks 106 and 107 (i.e., upper
part above the level of each of the electrolytes 10P and 10N) is a
gas-phase portion. The positive electrolyte tank 106 has an outlet
61 and an inlet 62 connected to a supply pipe 108 and a return pipe
110, respectively, of the positive electrolyte circulation path
120. The negative electrolyte tank 107 has an outlet 71 and the
inlet 72 connected to a supply pipe 109 and a return pipe 111,
respectively, of the negative electrolyte circulation path 130. In
this example, the outlets 61 and 71 and the inlets 62 and 72 are
located above the levels of the electrolytes 10P and 10N in the
tanks 106 and 107, or specifically, at the tops of the tanks 106
and 107. The outlet 61 and the inlet 62 are each provided with an
open-close valve 66, and the outlet 71 and the inlet 72 are each
provided with an open-close valve 76.
[0038] The tanks 106 and 107 have openings 64 and 74, respectively,
to which the communicating tube 40 is connected. The openings 64
and 74 are disposed above the levels of the electrolytes 10P and
10N in the tanks 106 and 107. In this example, the openings 64 and
74 are located at the tops of the tanks 106 and 107. The openings
64 and 74 are provided with open-close valves 67 and 77,
respectively.
Positive Electrolyte Circulation Path and Negative Electrolyte
Circulation Path
[0039] As illustrated in FIG. 1, the positive electrolyte
circulation path 120 connects the positive electrolyte tank 106 to
the battery cell 100, whereas the negative electrolyte circulation
path 130 connects the negative electrolyte tank 107 to the battery
cell 100, thereby allowing the electrolytes 10P and 10N to
circulate between the tanks 106 and 107 and the battery cell 100.
The positive electrolyte circulation path 120 includes the supply
pipe 108 configured to supply the positive electrolyte 10P from the
positive electrolyte tank 106 to the positive electrode cell 102,
and the return pipe 110 configured to return the positive
electrolyte 10P from the positive electrode cell 102 to the
positive electrolyte tank 106. The negative electrolyte circulation
path 130 includes the supply pipe 109 configured to supply the
negative electrolyte 10N from the negative electrolyte tank 107 to
the negative electrode cell 103, and the return pipe 111 configured
to return the negative electrolyte 10N from the negative electrode
cell 103 to the negative electrolyte tank 107. The supply pipes 108
and 109 of the circulation paths 120 and 130 are connected to the
outlets 61 and 71, respectively, of the tanks 106 and 107, and the
return pipes 110 and 111 of the circulation paths 120 and 130 are
connected to the inlets 62 and 72, respectively, of the tanks 106
and 107.
[0040] End portions of the respective supply pipes 108 and 109 are
inserted through the outlets 61 and 71, respectively, into the
tanks 106 and 107, and open ends 81 and 91 of these end portions
are disposed below the levels of the electrolytes 10P and 10N in
the tanks 106 and 107. That is, the open ends 81 and 91 of the
supply pipes 108 and 109 are immersed in the electrolytes 10P and
10N, respectively, which are drawn in through the open ends 81 and
91. In this example, the open ends 81 and 91 of the supply pipes
108 and 109 are each located on the bottom side in the
corresponding one of the tanks 106 and 107. Note that "located on
the bottom side in the tank" refers to being located below the
level of the electrolyte 10P or 10N, that is, h/2 or less from the
bottom of the tank 106 or 107, where h is a height from the bottom
of the tank 106 or 107 to the surface of the electrolyte 10P or
10N.
[0041] The supply pipes 108 and 109 are provided with pumps 112 and
113, respectively, configured to suck up the electrolytes 10P and
10N from the tanks 106 and 107 and pressure-feed them. During
charge and discharge operation, the pumps 112 and 113 circulate the
electrolytes 10P and 10N, respectively, through the battery cell
100 (i.e., the positive electrode cell 102 and the negative
electrode cell 103). In standby mode where neither charge nor
discharge takes place, the pumps 112 and 113 are off and the
electrolytes 10P and 10N are not circulated.
Communicating Tube
[0042] As illustrated in FIG. 1, the communicating tube 40 is a
tube immersed at one open end 41 thereof in the positive
electrolyte 10P, stretched at an intermediate portion 43 thereof
above the levels of the electrolytes 10P and 10N, and immersed at
the other open end 42 thereof in the negative electrolyte 10N. The
communicating tube 40 is configured to allow liquid-phase portions
in the tanks 106 and 107 to communicate with each other. The
communicating tube 40 is connected to the openings 64 and 74 of the
tanks 106 and 107. In this example, the communicating tube 40 is
inserted at both end portions thereof through the openings 64 and
74 of the tanks 106 and 107 into the tanks 106 and 107, and the
open ends 41 and 42 of both the end portions are disposed below the
levels of the electrolytes 10P and 10N in the tanks 106 and 107.
The intermediate portion 43 is placed above the tanks 106 and 107.
In this example, the open ends 41 and 42 of the communicating tube
40 are each located on the bottom side in a corresponding one of
the tanks 106 and 107.
[0043] The communicating tube 40 becomes a siphon by being filled
with electrolyte. Thus, when a difference occurs between the
volumes of the electrolytes 10P and 10N in the tanks 106 and 107,
the levels of the electrolytes 10P and 10N are adjusted to the same
height using the siphon principle. When the tube forming the
communicating tube 40 (or the intermediate portion 43 in
particular) is made of a transparent material, it is possible to
visually recognize from the outside that the communicating tube 40
is filled with electrolyte. The intermediate portion 43 may have a
window at the top (or highest portion) thereof, and the window may
be made of a transparent material. Examples of the transparent
material include transparent resin, such as vinyl chloride resin,
and glass.
[0044] The communicating tube 40 may be appropriately designed to
satisfy the siphon principle. Dimensions of the communicating tube
will now be described with reference primarily to FIG. 3.
[0045] If a height H from the level of the electrolytes 10P and 10N
in the tanks 106 and 107 to the top of the communicating tube 40 is
too high, the transfer of electrolyte based on the siphon principle
fails. The maximum height H.sub.max that satisfies the siphon
principle is determined by the following equation:
H.sub.max=P0/.rho.g
where P0 (N/m.sup.2) is pressure in the tank, .rho. (kg/m.sup.3) is
an electrolyte density, and g (m/s.sup.2) is the acceleration of
gravity.
[0046] When the pressure P0 is equal to the atmospheric pressure
(1.013.times.10.sup.5 N/m.sup.2) and the electrolyte density .rho.
is 1400 kg/m.sup.3, then H.sub.max is 7.38 m. Therefore, the
installation level of the intermediate portion 43 (corresponding to
the height H) is less than 7.38 m from the level of the
electrolytes 10P and 10N in the tanks 106 and 107.
[0047] If a length L of the communicating tube 40 is too long, the
resulting increase in frictional resistance in the communicating
tube 40 leads to an increased flow friction loss and lowers the
flow rate of the electrolyte passing through the communicating tube
40. This means that it takes time to adjust the electrolyte levels.
The adjustment of the electrolyte levels is preferably completed
within 10 minutes (or 600 seconds). Therefore, the length L of the
communicating tube 40 is preferably set to ensure that the flow
rate of the electrolyte passing through the communicating tube 40
is above a certain level. For example, the length L may be 15 m, or
more preferably 10 m or less.
[0048] An inside diameter d of the communicating tube 40 may also
be appropriately set. For example, the inside diameter d may range
from 10 mm to 150 mm, or more preferably from 20 mm to 100 mm. The
flow friction loss varies depending also on the inside diameter d
of the communicating tube 40. That is, the smaller the inside
diameter d, the greater the flow friction loss. Therefore, it is
preferable to appropriately set the length L of the communicating
tube 40 in accordance with the inside diameter d. Specifically, it
is preferable to set the length L of the communicating tube 40 such
that when a difference occurs between the volumes of the
electrolytes 10P and 10N in the tanks 106 and 107, it takes 10
minutes (or 600 seconds) or less until the levels of the
electrolytes 10P and 10N reach the same height. In this case, for
example, the length L of the communicating tube 40 may be less than
or equal to 100 times the inside diameter d (L.ltoreq.100d).
Specifically, the length L may be 10 m or less if the inside
diameter d is 100 mm, L may be 4.5 m or less if d is 50 mm, and L
may be 1.7 m or less if d is 20 mm.
Introducing Tube
[0049] The RF battery 1 illustrated in FIG. 1 includes an
introducing tube 50 configured to connect the positive electrolyte
circulation path 120 to the communicating tube 40, and an
open-close valve 51 configured to open and close the introducing
tube 50. In this example, the introducing tube 50 is connected at
one end thereof in such a manner as to branch off the supply pipe
108 of the positive electrolyte circulation path 120 and is
connected at the other end thereof to the intermediate portion 43
of the communicating tube 40. Also, in this example, the supply
pipe 108 has an open-close valve 69 downstream of its connection
with the introducing tube 50 (i.e., located closer to the battery
cell 100 than the connection is).
[0050] The introducing tube 50 and the open-close valve 51 are used
to form a siphon, when the RF battery 1 starts, by filling the
communicating tube 40 with electrolyte. Specifically, when the RF
battery 1 starts, the open-close valve 51 is opened to start the
pump 112, with the supply pipe 108 and the communicating tube 40
communicating with each other through the introducing tube 50, and
circulate the positive electrolyte 10P through the communicating
tube 40. This makes it possible to introduce the positive
electrolyte 10P into the communicating tube 40 and fill the
communicating tube 40 with the electrolyte. Then, with the
communicating tube 40 being filled with the electrolyte, the
open-close valve 51 closes the introducing tube 50 to block the
flow between the supply pipe 108 and the communicating tube 40.
This creates a liquid-tight state in the communicating tube 40 and
thereby forms a siphon. After the RF battery 1 starts, the
open-close valve 51 is always in a closed state during the
operation.
[0051] When, for example, the communicating tube 40 is removed from
the tanks 106 and 107 for maintenance of the RF battery 1, the pump
112 is stopped and the open-close valve 51 is opened. This
terminates the siphon, causes the electrolyte in the communicating
tube 40 to return to the tanks 106 and 107, and thereby facilitates
the maintenance work. After the communicating tube 40 is removed
from the tanks 106 and 107, the open-close valves 67 and 77 are
closed to prevent air from entering the tanks 106 and 107 through
the openings 64 and 74. This inhibits oxidation of the electrolytes
10P and 10N during the maintenance work.
[0052] Although the introducing tube 50 is connected and attached
to the positive electrolyte circulation path 120 (supply pipe 108)
in this example, the introducing tube 50 may be attached to the
negative electrolyte circulation path 130 (supply pipe 109) or may
be attached to both the circulation paths 120 and 130.
Gas-Phase Communicating Tube
[0053] The RF battery 1 illustrated in FIG. 1 includes a gas-phase
communicating tube 45 that allows the gas-phase portions in the
tanks 106 and 107 to communicate with each other. With the
gas-phase communicating tube 45, it is possible to equalize
pressures in the tanks 106 and 107. The gas-phase communicating
tube 45 is stretched over the tanks 106 and 107. In this example,
the gas-phase communicating tube 45 is connected to openings 65 and
75 at the tops of the tanks 106 and 107. The openings 65 and 75 are
provided with open-close valves 68 and 78, respectively.
Advantageous Effects of Embodiment
[0054] The RF battery 1 according to the embodiment described above
has the following operational advantages.
[0055] With the communicating tube 40, when a difference occurs
between the volumes of the electrolytes 10P and 10N in the tanks
106 and 107 during operation of the RF battery 1, the levels of the
electrolytes 10P and 10N can be automatically adjusted to the same
level through the communicating tube 40 using the siphon principle.
As described above, the intermediate portion 43 of the
communicating tube 40 is disposed above the levels of the
electrolytes 10P and 10N. Therefore, even if the communicating tube
40 is broken, the electrolyte in the communicating tube 40 is
returned to either of the tanks 106 and 107 by termination of the
siphon. Thus, even in the event of breakage of the communicating
tube 40, it is possible to prevent the electrolyte in the
communicating tube 40 from flowing out of the tanks 106 and 107.
Additionally, since the openings 64 and 74 of the tanks 106 and 107
to which the communicating tube 40 is connected are located above
the levels of the electrolytes 10P and 10N, the electrolytes 10P
and 10N are prevented from leaking through the openings 64 and 74.
Therefore, it is possible to effectively prevent the electrolytes
10P and 10N from flowing out of the positive electrolyte tank 106
and the negative electrolyte tank 107 while automatically adjusting
the volumes of the electrolytes 10P and 10N in the tanks 106 and
107.
[0056] With the introducing tube 50 and the open-close valve 51, a
siphon can be created by filling the communicating tube 40 with
electrolyte when the RF battery 1 starts.
[0057] Since the open ends 41 and 42 of the communicating tube 40
are located on the bottom side in the tanks 106 and 107, gas
bubbles are not easily drawn in through the open ends 41 and 42.
This makes it easier to keep the communicating tube 40 in a siphon
state.
[0058] As illustrated in FIG. 4, the communicating tube 40 may be
bent into a J shape at both end portions thereof to allow the open
ends 41 and 42 to face upward. In this case, gas bubbles are not
easily drawn in through the open ends 41 and 42, and this makes it
easier to maintain the siphon state.
[0059] Modifications of the RF battery 1 according to the
aforementioned embodiment will now be described with reference to
FIGS. 5 and 6.
First Modification
[0060] The RF battery 1 according to a first modification
illustrated in FIG. 5 differs from the aforementioned embodiment
illustrated in FIG. 1 in that the communicating tube 40 is provided
with a flow control valve 44. Other configurations of the first
modification are the same as those of the aforementioned
embodiment.
Flow Control Valve
[0061] The flow control valve 44 is disposed in the communicating
tube 40 and configured to control the flow rate of the electrolyte
passing through the communicating tube 40. In this example, as
illustrated in FIG. 5, the flow control valve 44 is disposed in the
intermediate portion 43 of the communicating tube 40. When, in the
RF battery 1 of the first modification, the volumes of the
electrolytes 10P and 10N in the tanks 106 and 107 are adjusted
through the communicating tube 40, the flow rate (or the amount of
transfer) of the electrolyte can be controlled by the flow control
valve 44. In some cases, the transfer of the electrolyte may be
stopped by closing the flow control valve 44. In this example, the
flow control valve 44 is a motor-operated valve.
Second Modification
[0062] The RF battery 1 according to a second modification
illustrated in FIG. 6 differs from the aforementioned embodiment
illustrated in FIG. 1 in that it includes a gas vent pipe 55 for
allowing gas bubbles to escape from inside the communicating tube
40. Other configurations of the second modification are the same as
those of the aforementioned embodiment.
Gas Vent Pipe
[0063] The gas vent pipe 55 is used to vent, from the communicating
tube 40, gas bubbles accidentally drawn into the communicating tube
40. The gas vent pipe 55 is connected at one end thereof to the
communicating tube 40 and connected at the other end thereof to at
least one of the positive electrolyte circulation path 120 and the
negative electrolyte circulation path 130. In this example, as
illustrated in FIG. 6, the gas vent pipe 55 is connected at one end
thereof to the intermediate portion 43 in such a manner as to
branch off the communicating tube 40 and connected at the other end
thereof to the supply pipe 109 of the negative electrolyte
circulation path 130 in such a manner as to join the supply pipe
109. More specifically, the gas vent pipe 55 is connected at one
end thereof to the top of the intermediate portion 43 and connected
at the other end thereof to the supply pipe 109 at a location
upstream of the pump 113 in the supply pipe 109 (i.e., closer to
the tank 107 than the pump 113 is).
[0064] The gas vent pipe 55 is provided with a check valve 56. The
check valve 56 is disposed in the gas vent pipe 55 and configured
to block the circulation from the negative electrolyte circulation
path 130 (supply pipe 109) to the communicating tube 40.
Additionally, in this example, an open-close valve 57 is provided
downstream of the check valve 56 (i.e., closer to the supply pipe
109 than the check valve 56 is). The open-close valve 57 is in an
open state when gas bubbles are to be removed from the
communicating tube 40, and is in a closed state when there is no
need to remove gas bubbles from the communicating tube 40.
[0065] In the RF battery 1 of the second modification, if gas
bubbles are accidentally drawn into the communicating tube 40, the
gas bubbles accumulated in the communicating tube 40 can be vented
through the gas vent pipe 55 to the negative electrolyte
circulation path 130 (supply pipe 109) using suction by the pump
113. This allows the communicating tube 40 to be kept in a siphon
state. With the gas vent pipe 55 having the check valve 56, even
when the pump 113 is stopped and the supply pipe 109 is emptied,
the entry of gas from the supply pipe 109 into the communicating
tube 40 can be blocked. Therefore, even when the pump 113 is
stopped, the communicating tube 40 is kept in a siphon state and
the electrolyte in the communicating tube 40 is not returned into
either of the tanks 106 and 107.
[0066] Additionally, by adjusting the degree of opening of the
open-close valve 57, it is possible to control the flow rate of the
electrolyte passing through the gas vent pipe 55 and prevent the
electrolyte from accidentally flowing out of the communicating tube
40 into the supply pipe 109. Specifically, suction by the pump 113
causes the electrolyte to be fed little by little through the gas
vent pipe 55 and the communicating tube 40 to the supply pipe 109,
so that gas bubbles accumulated in the communicating tube 40 are
efficiently removed. When the communicating tube 40 is removed, for
example, for maintenance of the RF battery 1, the entry of air into
the supply pipe 109 is prevented by closing the open-close valve
57.
Application of Embodiment
[0067] The redox flow battery according to the embodiment can be
used for load leveling, compensation for instantaneous voltage
drop, emergency power supply, and smoothing of the output of
natural energy-based power generation (e.g., solar or wind power
generation) which has been introduced at a large scale.
REFERENCE SIGNS LIST
[0068] 1: redox flow battery (RF battery)
[0069] 2: cell stack
[0070] 3: cell frame
[0071] 31: bipolar plate
[0072] 32: frame body
[0073] 32o: recessed portion
[0074] 33, 34: liquid supply manifold
[0075] 35, 36: liquid discharge manifold
[0076] 33s, 34s: liquid supply slit
[0077] 35s, 36s: liquid discharge slit
[0078] 37: sealing member
[0079] 40: communicating tube
[0080] 41, 42: open end
[0081] 43: intermediate portion
[0082] 44: flow control valve
[0083] 45: gas-phase communicating tube
[0084] 50: introducing tube
[0085] 51: open-close valve
[0086] 55: gas vent pipe
[0087] 56: check valve
[0088] 57: open-close valve
[0089] 61, 71: outlet
[0090] 62, 72: inlet
[0091] 64, 74: opening
[0092] 65, 75: opening
[0093] 66, 67, 68, 69, 76, 77, 78: open-close valve
[0094] 81, 91: open end
[0095] 100: battery cell
[0096] 101: membrane
[0097] 102: positive electrode cell
[0098] 103: negative electrode cell
[0099] 104: positive electrode
[0100] 105: negative electrode
[0101] 106: positive electrolyte tank
[0102] 107: negative electrolyte tank
[0103] 108, 109: supply pipe
[0104] 110, 111: return pipe
[0105] 112, 113: pump
[0106] 120: positive electrolyte circulation path
[0107] 130: negative electrolyte circulation path
[0108] 10P: positive electrolyte
[0109] 10N: negative electrolyte
[0110] 200: substack
[0111] 210: supply/drainage plate
[0112] 220: end plate
[0113] 230: fastening mechanism
* * * * *