U.S. patent application number 09/834673 was filed with the patent office on 2001-12-27 for four-way valve for battery circulation system.
Invention is credited to Eidler, Phillip A., Jonshagen, Bjorn, Lex, Peter J., Rixford, Robert R..
Application Number | 20010055713 09/834673 |
Document ID | / |
Family ID | 22184647 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010055713 |
Kind Code |
A1 |
Eidler, Phillip A. ; et
al. |
December 27, 2001 |
Four-way valve for battery circulation system
Abstract
A circulation system for a flowing-electrolyte battery having at
least one electrochemical cell, an anolyte reservoir, and a
catholyte reservoir. The circulation system includes an anolyte
pump coupled in fluid flowing relationship to the anolyte reservoir
which pumps anolyte from the anolyte reservoir to the at least one
electrochemical cell. A catholyte pump is coupled in fluid flowing
relationship to the catholyte reservoir and also pumps catholyte to
the at least one electrochemical cell. A second phase pump is
coupled in fluid flowing relationship to the catholyte reservoir
and is used to introduce second phase electrolyte into the aqueous
catholyte pumped by the catholyte pump. The second phase pump is
controlled by a controller so that the second phase is introduced
into the catholyte stream in a metered fashion. A controllable
four-way valve is coupled in fluid flowing relationship to the
catholyte pump and operable to direct the flow of catholyte through
the electrochemical cell in a first direction, and periodically
reverse the flow of the catholyte in a second direction. Metering
the amount of second phase injected into the catholyte stream and
reversing catholyte flow improve battery efficiency.
Inventors: |
Eidler, Phillip A.;
(Muskego, WI) ; Lex, Peter J.; (Wauwatosa, WI)
; Rixford, Robert R.; (Shebovgan Falls, WI) ;
Jonshagen, Bjorn; (South Fremantle, AU) |
Correspondence
Address: |
GODFREY & KAHN S.C.
780 NORTH WATER STREET
MILWAUKEE
WI
53202
US
|
Family ID: |
22184647 |
Appl. No.: |
09/834673 |
Filed: |
April 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09834673 |
Apr 13, 2001 |
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09305218 |
May 4, 1999 |
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6242125 |
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60084386 |
May 6, 1998 |
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Current U.S.
Class: |
429/81 ;
251/304 |
Current CPC
Class: |
H01M 12/085 20130101;
H01M 50/77 20210101; Y02E 60/10 20130101 |
Class at
Publication: |
429/81 ;
251/304 |
International
Class: |
H01M 002/38; F16K
005/00 |
Claims
What is claimed is:
1. A four-way valve for use in a circulation system, the valve
comprising: a main body having a hollow interior portion; a valve
body housed within the hollow interior portion, the valve body
having a valve stem, a first U-shaped chamber with two axially
positioned legs, a second U-shaped chamber having two axially
positioned legs, each leg of the first and second U-shaped members
terminating in a port; and an end cap having four ports mounted on
the main body; wherein the valve body is rotatable within the main
body such that the ports of the first and second U-shaped chambers
may be aligned with the ports in the end cap.
2. A valve as in claim 1, wherein each of the ports in the legs of
the first and second U-shaped chambers includes a compressible ring
topped by a substantially non-compressible, low-friction ring.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 60/084,386, filed May 6, 1998 and is a
division of U.S. Application Ser. No. 09/305,218 filed May 4,
1999.
FIELD OF THE INVENTION
[0002] The present invention relates generally to energy storage
systems. More particularly, the present invention relates to
improvements in the electrolyte circulation systems of the energy
storing devices (such as batteries) used in energy storage
systems.
BACKGROUND OF THE INVENTION
[0003] Electric power utility companies use a variety of techniques
to meet fluctuating power demand while maintaining a relatively
constant level of electric power production. One way to handle
short lived, irregularly occurring electric power demand increases
is to electrically couple an electric energy storage system to an
electric power transmission system so that the energy storage
system may be utilized, or turned on, to provide additional
electric power during peak demand.
[0004] While some systems such as the one shown in U.S. Pat. No.
5,610,802 have been developed to address peak demand needs, ever
increasing demand for power requires that such systems operate very
efficiently, with little need for human supervision, be designed to
minimize leaks or other releases of potentially hazardous
materials, and be relatively inexpensive. Of particular importance
to the efficient operation of such systems is the effective and
efficient operation of the energy storing devices used in them.
Often these devices are liquid electrolyte batteries, particularly
zinc-bromine batteries.
[0005] Zinc-bromine batteries are a type of bipolar, metal-halogen
battery with a stack of cells made from a series of alternating
electrodes and separators. An electrolyte flows through the stack
of cells and conducts electricity ionically. In a bipolar,
zinc-bromine battery each cell includes a bipolar electrode upon
which an anodic and a cathodic reaction occurs.
[0006] The electrolyte used in a zinc-bromine battery is a fluid
containing aqueous zinc-bromide and quaternary ammonium salts. It
is circulated through the cells to and from external reservoirs.
For each cell, one half cell contains an anolyte and the other half
cell contains a catholyte. The anolyte flows through a common
anolyte manifold to each anodic half cell and the catholyte flows
through a parallel common catholyte manifold to each cathodic half
cell. The alternating separators and electrodes are sealed together
in a manner that prevents communication between the anolyte and
catholyte systems.
[0007] A zinc-bromine battery may be in various states including a
charged state and a discharged state. In addition, the battery may
cycle through these states. When a zinc-bromine battery is in a
discharged state, the anolyte is chemically identical to the
catholyte. When a zinc-bromine battery is charged the following
reaction takes place. 1 2
[0008] Zinc is plated on the anode, and bromine is evolved on the
cathode. The bromine is immediately complexed by quaternary
ammonium ions in the electrolyte to form a dense second phase that
is removed from the battery stack with the flowing electrolyte.
When the battery is charged, zinc is stored on one side of each
electrode and complex bromine is stored in a catholyte
reservoir.
[0009] During discharge, the following reaction takes place. 3
[0010] Zinc is oxidized and the released electrons pass through the
electrode where they combine with molecular bromine to form bromide
ions. Positively charged zinc ions travel through the separator and
remain in solution, and at the same time, bromide ions pass through
the separator in the opposite direction and remain in solution.
[0011] As discussed above, the electrolyte used in most
zinc-bromine batteries is circulated within the battery.
Circulation of the electrolyte has several advantages. First it
removes and externally stores bromine that is produced during
charge. Thus, the active materials of the battery, which are zinc
and bromine, are separated from each other. Second, circulation of
the electrolyte ensures uniform zinc metal deposition and deplating
during charge and discharge, respectively. Third, circulation of
the electrolyte removes excess heat from the system.
[0012] While all these advantages are achieved with present
circulation systems, there are still several problems that known
circulation systems fail to address. One of the more significant
problems is the entrapment of gas and vapor in the electrolyte as
it circulates through the battery. A possible side reaction in such
batteries could cause the formation of small amounts of hydrogen
gas during the charging process and the hydrogen may accumulate in
the stack of cells hindering the flow of electrolyte in the
battery. Of less importance, but still problematic, is the
entrapment of other gases and vapors that often infiltrate the
battery through its pressure equalization and release valves. The
presence of these gases and vapors may also hinder the flow of
electrolyte.
[0013] In addition to those already noted, present electrolyte
circulation systems have several other shortcomings. The
circulation of electrolyte through a conventional battery is
controlled through one anolyte pump/motor and one catholyte
pump/motor. The catholyte pump introduces a mixture of second phase
and aqueous phase electrolyte (catholyte) into the battery during
discharge. Conventional technology uses one of two techniques to
produce this mixture. A first technique uses a single pump inlet
tube that has two branches on one end. One branch is positioned at
the bottom of the reservoir tank and serves as the inlet for the
dense second phase. The other branch has a pickup positioned higher
in the reservoir tank and serves as the inlet for the aqueous
catholyte phase. In this design, the amount of second phase
introduced into the battery can not be adjusted during discharge.
Also, this design requires the second phase to be circulated during
both discharge and charge.
[0014] Another known design uses an outlet at the bottom of the
reservoir tank and gravity to introduce the second phase into the
aqueous catholyte. This technique can adjust the amount of second
phase allowed into the aqueous catholyte input and even shut it off
during charge. However, a major drawback to this system is that the
second phase is drawn from the bottom of the tank requiring a hole
to be placed at the lowest point in the tank. With a hole in this
position, any compromise (puncture, break, etc.) of the outlet has
the potential risk of a large electrolyte leak.
[0015] Accordingly, it would be desirable to have a system that
eliminated or reduced the amount of gas and vapors entrapped in a
liquid electrolyte battery. It would also be desirable to have a
system where the amount of second phase circulated through the
battery could be readily controlled, but with a design that would
minimize the amount and effect of electrolyte leaks.
SUMMARY OF THE INVENTION
[0016] Therefore, an object of the present invention is to provide
a circulation system that aids in removing entrapped gas and vapor
from the battery stack. Another object of the present invention is
to provide a pump-based circulation system that permits increased
control over electrolyte flow in the battery, particularly of the
second phase. These and other objects and advantages are achieved
in a battery having at least one electrochemical cell, an anolyte
reservoir coupled to the cell, an anolyte pump, a catholyte
reservoir coupled to the cell, a catholyte pump, a second phase
pump mounted on the catholyte cell, and a controllable four-way
valve for reversing the flow of electrolyte through the system. The
improved pump configuration and other features permit better
control of electrolyte flow in the batteries and improve
efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Throughout the following views, reference numerals will be
used on the drawings, and the same reference numerals will be used
throughout the several views and in the description to indicate
same or like parts of the invention.
[0018] FIG. 1 is a perspective view of a battery module employing
the four-way valve and circulation system of the present
invention;
[0019] FIG. 1A is a schematic diagram of the controller used in the
present invention.
[0020] FIG. 2 is a top plan view of the battery module shown in
FIG. 1;
[0021] FIG. 3 is a schematic view of the circulation system used in
the present invention;
[0022] FIG. 3A is another schematic view of the circulation system
used in the present invention showing flow of electrolyte through
the four-way valve in a reverse direction;
[0023] FIG. 4 is a perspective view of the four-way valve used in
the circulation system of the present invention;
[0024] FIG. 5 is an exploded view of the four-way valve used in the
present invention;
[0025] FIG. 6 is an end view of the four-way valve used in the
present invention;
[0026] FIG. 7 is a cross-sectional view of the four-way valve used
in the present invention.
[0027] FIG. 8 is a cross-sectional view of an electrolyte reservoir
used in the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0028] A battery module 10 having a circulation system 11 made in
accordance with the teachings of the present invention is shown in
FIG. 1. The battery module 10 includes a container 13 in which an
anolyte reservoir 15, a catholyte reservoir 17, and a plurality of
batteries 19 are positioned. The container 13 has a lid (not shown)
which seals the entire module. The container 13 includes a cabinet
20 for housing a module controller 21 (FIG. 1A) used to monitor the
batteries and control the system's pumps (discussed below). Each of
the batteries 19 includes a stack of electrochemical cells that
store and release energy in a manner essentially as discussed
above. When the batteries 19 are operating, electrolyte flows to
and from the reservoirs 15 and 17 through plumbing 22. Plumbing
suitable for use in the present invention includes VITON.RTM.
tubing. Barbed fittings and spring clamps may be used to couple the
tubing to the various components of the module 10. Connections made
may be wrapped with a TEFLON.RTM. tape.
[0029] The circulation system 11 is best seen by reference to FIGS.
2 and 3. The system 11 includes an anolyte pump 30 mounted near the
top of the anolyte reservoir 15, a catholyte pump 32 mounted near
the top of the catholyte reservoir 17, and a second phase pump 36
also mounted near the top of the catholyte reservoir 17. In one
embodiment of the present invention, each of the pumps 30, 32, and
36 is operated by a variable, high-efficiency, DC motor. The
benefits of using such motors include a reduction in the amount of
energy needed to operate them and reduced maintenance and support
compared to conventional brushed DC or AC motors.
[0030] When the battery is charged, the anolyte pump 30 pumps
anolyte from the anolyte reservoir 15 to the anodic half cells
(represented by the half cell 40 in FIG. 3) in the batteries 19.
The anolyte is circulated in a direction shown by arrow L.sub.1 and
the amount of electrolyte circulated is adjusted in order to
maintain a relatively constant volume level of electrolyte in the
anolyte reservoir 15. More specifically, the rate of circulation is
adjusted to accommodate changes in volume caused by changes in the
density, temperature, and viscosity of the electrolyte which occur
while the battery is operating.
[0031] As discussed above, each battery 19 is fabricated with a
microporous (or in some cases an ion permeable) separator (not
shown) so the electrolyte has the ability to gradually migrate into
the other electrolyte circulation loop in the event of a slight
pressure imbalance. To correct this imbalance, some previous
systems simply used a valve to reduce the flow of one electrolyte
circulation loop. It is known that this type of restriction will
increase pressure losses reducing the efficiency of the system. In
the present invention, the speed of the anolyte pump is simply
raised or lowered depending on the level of electrolyte in the
anolyte reservoir 15.
[0032] The catholyte pump 32 draws aqueous catholyte from the top
of the catholyte reservoir 17 through an intake 42. The catholyte
is pumped from the reservoir 17 to the cathodic half cells
(represented by the half cell 44 in FIG. 3) in the batteries 19.
The catholyte is circulated in a direction shown by arrow L.sub.2
with the electrolyte flowing from the top to the bottom of each
cathodic half cell.
[0033] The second phase electrolyte generated during charge will
settle to the bottom of the reservoir 17. Since the intake 42 is
positioned high (at the mid-point or higher) within the reservoir
17, the pump 32 does not take in any of the dense second phase.
Rather, circulation of the second phase is controlled through the
second phase pump 36 which draws the second phase from intake 48.
The intake 48 has a mouth 49 which is positioned adjacent to the
bottom of the reservoir 17. So positioned, no aqueous electrolyte
is drawn by the pump 36 and by controlling the activity of the pump
36 (i.e., on/off and pump rate) the amount of second phase
circulated through the batteries 19 may be controlled. Desired
control may be achieved through the module controller 21 which can
adjust the pump 36 so that the amount of second phase injected into
the aqueous catholyte stream can be varied according to the
discharge rate of the batteries 19. Controlling the amount of
second phase in the catholyte is important because it contains the
bromine needed for the discharge reaction. At high current
discharge rates, more bromine is needed for the reaction to take
place. Therefore, more second phase is needed, and the pump speed
is increased. The opposite occurs at lower current discharge rates.
Less second phase is needed, and the pump speed is decreased.
[0034] Flow from the catholyte pump 32 is directed to the catholyte
half cells in the batteries 19 through a four-way valve 50.
Preferably, the valve 50 is manufactured from a
chemically-resistant material such as polyvinyl chloride (PVC),
polyethylene, polypropylene, polyvinyldifluoride (PVDF) or
polytetrafluoroethylene (PTFE). As shown in FIG. 3, the valve 50 is
normally positioned so that electrolyte is circulated through the
cathodic half cells from top to bottom. However, periodically the
valve is rotated 90.degree. (FIG. 3A) so that flow through the
cathodic half-cells is reversed and follows the path generally
indicated by the arrow L.sub.3. When reversed, flow is directed
from bottom to top. Reversing the flow pushes gas and vapors
trapped at the top of the half cells out of each of the half cells
to the catholyte reservoir. Once in the reservoirs, the gases are
released to the atmosphere through one or more release valves
55.
[0035] Although manual operation is possible, in one embodiment of
the present invention movement of the valve 50 is controlled by the
module controller 21 or similar programmable controller. In
particular, the four-way valve 50 is coupled to an actuator 58
(FIGS. 1 and 2) which is controlled by the module controller 21.
The actuator 58 is turned on periodically to reverse catholyte
flow. An actuator suitable for use in the present invention is the
EL-O-MATIC ELS-8 actuator, which is commercially available from
Tubemakers Piping System, North Fremantle, Western Australia, with
the following specifications: rotation: 90 degrees; torque: 8 Nm;
voltage: 240V AC; materials: steel base plate, cover, drive
spindle, and fastenings; finish: all external steel parts zinc
plated, cover has a two part polyurethane finish. The inventors
have found that a periodic schedule where rotation occurs every
hour for one minute is effective to increase the efficiency of the
battery and prevent the build up of gases in the batteries.
[0036] As best seen by reference to FIGS. 4-7, the valve 50
includes a main body 62 which has a hollow interior portion 64 and
toroidal channel 66 for receiving a sealing ring 68. The interior
portion 64 houses a valve body 70 and is closed by an endcap 72
having four ports 73, 74, 75, and 76. The endcap 72 is fastened to
the main body 70 by screws or similar mechanisms.
[0037] The valve body 70 is spaced from the main body 62 by a
spacer 86, such as a TEFLON.RTM. (spacer, and has a valve stem 90
with a circumferential channel 92 for receiving a sealing ring 94.
The valve stem 90 is coupled to the actuator 58. The valve body 70
has a first U-shaped chamber 100 with two axially positioned legs
102 and 104. Each leg 102 and 104 is substantially identical and
terminates in a port 106 which seats a compressible O-ring 107
topped by a relatively hard, low-friction ring 108, such as a
TEFLON.RTM. ring. The valve body 70 has a second U-shaped chamber
110, which similarly has two legs 112 and 114. Each leg 112 and 114
is substantially identical and terminates in a port 116, which
seats a compressible O-ring 117 topped by a relatively hard,
low-friction ring 118. The ports 106 and 116 are configured to
match the ports 73, 74, 75, and 76. Depending on the rotation of
the valve body 70, the ports 106 may be aligned with the ports 76
and 75 or 75 and 74. Similarly, the ports 116 may be aligned with
the ports 73 and 74 or the ports 76 and 73. Thus, the valve 50 may
direct two input flows along one of two paths.
[0038] A key to the successful operation of the four-way valve 50
is its ability to seal in the electrolyte flowing through it. In
other words, the four-way valve is designed to prevent the
electrolyte from leaking or seeping out of the valve or into
unintended places within the valve. The seals provided by the
compressible O-rings 107, 117 and low friction rings 108, 118
prevent such leaks and seepage while still permitting the valve
body 70 to rotate against the inner surface of the endcap 72. If
any leakage occurs, the seal provided by the sealing ring 68
prevents electrolyte from escaping from the valve 50.
[0039] Another feature of the present invention involves
electrolyte level control. The electrolyte levels in the batteries
19 can be controlled using liquid level sensors 130 (FIG. 8) placed
in each in each reservoir 15, 17, and coupled in data exchange
relation to the controller 21. If an imbalance in levels is sensed,
as indicated by a high liquid level sensor value, the speed of the
anolyte pump 30 may adjust to even out the levels. The change in
the pump speed adjusts the relative electrolyte pressure in the
cell stack by forcing liquid across the microporous separators
between the cells to re-establish a balance in the reservoirs 15
and 17. If both liquid level sensors in the reservoirs 15 and 17
sense "high" levels, the batteries 19 are shut down by the
controller 21. Such a condition would indicate that additional
fluid was entering the reservoirs 15 and 17 from another source,
such as a heat exchanger used to cool the electrolyte. As with a
high level condition, if both liquid level sensors in the
reservoirs 15 and 17 sensed a "low" level, the batteries 19 are
shut down by the controller. Such a condition would indicate a leak
of electrolyte from some location in the system 10. Once shut down
the leak could be investigated and repaired before the battery was
again operated.
[0040] As can be seen from the above, the present invention
provides an improved circulation system where flow of second phase
to zinc-bromine batteries can be readily controlled and metered and
gas entrapped in the cathodic cells of such batteries can be
removed resulting in improved battery performance. Further, liquid
electrolyte level can be controlled. However, while the circulation
system, four-way valve, and other components of the invention were
described by reference to the drawings and examples presented
herein, these examples are not meant to limit the scope of the
invention. It should be understood that many variations and
modifications may be made while remaining within the spirit and
scope of the invention. Further, the invention herein described is
related to the subject matter disclosed in U.S. Pat. Nos.
5,610,802; 5,650,239; 5,626,986; 5,600,534; 5,591,538; 5,605,771;
and 5,601,943. The disclosures of these references are incorporated
by reference herein.
* * * * *