U.S. patent application number 12/523146 was filed with the patent office on 2010-01-14 for electrochemical energy cell system.
This patent application is currently assigned to Primus Power Corporation. Invention is credited to Rick Winter.
Application Number | 20100009243 12/523146 |
Document ID | / |
Family ID | 39636667 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100009243 |
Kind Code |
A1 |
Winter; Rick |
January 14, 2010 |
ELECTROCHEMICAL ENERGY CELL SYSTEM
Abstract
A metal halogen electrochemical energy cell system that
generates an electrical potential. One embodiment of the system
includes at least one cell including at least one positive
electrode and at least one negative electrode, at least one
electrolyte, a mixing venturi that mixes the electrolyte with a
halogen reactant, and a circulation pump that conveys the
electrolyte mixed with the halogen reactant through the positive
electrode and across the metal electrode. Preferably, the positive
electrode comprises porous carbonaceous material, the negative
electrode comprises zinc, the metal comprises zinc, the halogen
comprises chlorine, the electrolyte comprises an aqueous
zinc-chloride electrolyte, and the halogen reactant comprises a
chlorine reactant. Also, variations of the system and a method of
operation for the systems.
Inventors: |
Winter; Rick; (Orinda,
CA) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
Primus Power Corporation
|
Family ID: |
39636667 |
Appl. No.: |
12/523146 |
Filed: |
January 16, 2008 |
PCT Filed: |
January 16, 2008 |
PCT NO: |
PCT/US08/51111 |
371 Date: |
July 14, 2009 |
Current U.S.
Class: |
429/51 ; 429/72;
429/81 |
Current CPC
Class: |
H01M 12/04 20130101;
Y02E 60/50 20130101; H01M 2300/0002 20130101; H01M 4/8605 20130101;
H01M 10/0472 20130101; H01M 4/96 20130101; H01M 10/0413 20130101;
H01M 50/30 20210101; H01M 50/572 20210101; H01M 8/08 20130101; H01M
4/42 20130101; H01M 12/085 20130101; H01M 8/04186 20130101; Y02E
60/10 20130101; H01M 50/138 20210101; H01M 50/77 20210101 |
Class at
Publication: |
429/51 ; 429/72;
429/81 |
International
Class: |
H01M 2/38 20060101
H01M002/38 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 16, 2007 |
US |
11654380 |
Claims
1-74. (canceled)
75. A metal halogen electrochemical energy generation system,
comprising: (A) a pressure containment vessel that contains: (a) at
least one cell, that comprises: at least one positive electrode; at
least one negative electrode; and a reaction zone between the
positive electrode and the negative electrode; and (b) an
electrolyte mixture comprising (i) at least one aqueous electrolyte
comprising a metal and a halogen and (ii) a pressurized halogen
reactant; and (B) a circulation pump that is configured to convey a
flow of the electrolyte mixture through the reaction zone so that
the halogen reactant is reduced at the positive electrode to form a
halogen ion rich electrolyte mixture, which passes by the negative
electrode.
76. The system of claim 75, wherein the positive electrode
comprises a porous carbonaceous material.
77. The system of claim 75, wherein the negative electrode
comprises zinc; the metal comprises zinc; the halogen comprises
chlorine; the aqueous electrolyte comprises a zinc chloride
electrolyte, and the halogen reactant comprises a chlorine
reactant.
78. The system of claim 75, wherein the circulation pump is located
in the pressure containment vessel.
79. The system of claim 75, wherein the halogen reactant is
supplied from a source internal to the system.
80. The system of claim 75, wherein the vessel contains an
electrolyte storage reservoir below the at least one cell.
81. The system of claim 75, wherein each of the at least one cell
comprises a cell frame that comprises distribution channels, that
are configured to introduce the electrolyte mixture to the reaction
zone, wherein said distribution channels are formed by splitting
nodes, each splitting the flow of the electrolyte mixture into two,
so that each of said distribution channels has the same length and
the same number and radius of bends.
82. The system of claim 75, wherein the at least one cell comprises
a horizontally positioned cell.
83. The system of claim 82, wherein an inlet of the electrolyte
mixture to the reaction zone and an outlet of the electrolyte
mixture from the reaction zone are each located at or above the
bottom of the positive electrode within the reaction zone.
84. The system of claim 82, wherein the at least one cell comprises
a vertical stack of horizontally positioned cells.
85. The system of claim 84, further comprising an upward flowing
return manifold configured to collect the electrolyte mixture from
the cells of the stack.
86. The system of claim 84, wherein the stack maintains a cell-to
cell electrical continuity and does not maintain a cell-to cell
electrolyte continuity when the flow of the electrolyte mixture
stops.
87. The system of claim 75, wherein each of the at least one cell
comprises a cell frame.
88. The system of claim 75, wherein the positive electrode and the
negative electrode are arranged to maintain contact with a pool of
the electrolyte when the flow of the electrolyte mixture stops.
89. A method of using a metal halogen electrochemical energy
generation system, comprising: (A) providing a system comprising:
(a) a pressure containment vessel that contains at least one cell,
the at least one cell comprises: at least one positive electrode;
at least one negative electrode; and a reaction zone between the
positive electrode and the negative electrode; (B) mixing (i) at
least one aqueous electrolyte comprising a metal and a halogen and
(ii) a pressurized halogen reactant to form an electrolyte mixture,
and (C) delivering a flow of the electrolyte mixture to the
positive electrode of the cell, reducing the halogen reactant at
the positive electrode to form a halogen ion rich electrolyte
mixture, and passing the halogen ion rich electrolyte mixture by
the negative electrode.
90. The method of claim 89, wherein the positive electrode
comprises a porous carbonaceous material so that said delivered
electrolyte mixture passes through said positive electrode.
91. The method of claim 89, wherein the negative electrode
comprises zinc; the metal comprises zinc; the halogen comprises
chlorine; the aqueous electrolyte comprises a zinc chloride
electrolyte, and the halogen reactant comprises a chlorine
reactant.
92. The method of claim 89, wherein said delivering is provided by
a circulation pump located in the pressure containment vessel.
93. The method of claim 89, wherein the halogen reactant is
supplied from a source internal to the system.
94. The method of claim 89, wherein the vessel contains an
electrolyte storage reservoir below the at least one cell.
95. The method of claim 89, wherein the system further comprises an
upward flowing return manifold and wherein the method further
comprises collecting the electrolyte mixture from the at least one
cell through said manifold.
96. The method of claim 89, wherein the at least one cell comprises
a horizontally positioned cell.
97. The method of claim 96, wherein said horizontally positioned
cell has an inlet of the electrolyte mixture to the reaction zone
and an outlet of the electrolyte mixture from the reaction zone
that are each located at or above the bottom of the positive
electrode within the reaction zone.
98. The method of claim 96, wherein the at least one cell comprises
a vertical stack of horizontally positioned cells.
99. The method of claim 98, wherein each of the at least one cell
comprises a cell frame that comprises distribution channels having
the same flow resistance and wherein said delivering comprises
delivering the electrolyte mixture to the positive electrode
through the distribution channels.
100. The method of claim 98, wherein the stack maintains a cell-to
cell electrical continuity and does not maintain a cell-to cell
electrolyte continuity when the flow of the electrolyte mixture
stops.
101. The method of claim 89, wherein the positive electrode and the
negative electrode are arranged to maintain contact with a pool of
the electrolyte when the flow of the electrolyte mixture stops.
102. The method of claim 89, further comprising applying a
balancing voltage to the at least one cell to prevent a
self-discharge of the system when the flow of the electrolyte
mixture stops.
103. The method of claim 89, wherein the system has a first intake
conduit for the electrolyte and a second intake conduit for the
halogen reactant, which is separate from the first intake
conduit.
104. A metal halogen electrochemical energy generation system
comprising: (A) a pressure containment vessel that contains: (a) at
least one cell, that comprises: at least one positive electrode; at
least one negative electrode; and a reaction zone between the
positive electrode and the negative electrode; and (b) an
electrolyte mixture comprising (i) at least one aqueous electrolyte
comprising a metal and a halogen and (ii) a pressurized halogen
reactant; and (B) a circulation pump that is configured to convey a
flow of the electrolyte mixture through the reaction zone when the
pump is on, and wherein the positive electrode and the negative
electrode are arranged to maintain contact with a pool of the
electrolyte when the pump is off.
105. The system of claim 104, wherein the positive electrode
comprises a porous carbonaceous material.
106. The system of claim 104, wherein the negative electrode
comprises zinc; the metal comprises zinc; the halogen comprises
chlorine; the aqueous electrolyte comprises a zinc chloride
electrolyte and the halogen reactant comprises a chlorine
reactant.
107. The system of claim 104, wherein the circulation pump is
located in the pressure containment vessel.
108. The system of claim 104, wherein the halogen reactant is
supplied from a source internal to the system.
109. The system of claim 104, wherein the vessel contains an
electrolyte storage reservoir below the at least one cell.
110. The system of claim 104, further comprising an upward flowing
return manifold configured to collect the electrolyte mixture from
the at least one cell.
111. The system of claim 104, wherein each of the at least one cell
comprises distribution channels that are configured to introduce
the electrolyte mixture to the reaction zone, wherein each of said
distribution channels has the same flow resistance.
112. The system of claim 104, wherein the at least one cell
comprises a horizontally positioned cell.
113. The system of claim 112, wherein an inlet of the electrolyte
mixture to the reaction zone and an outlet of the electrolyte
mixture from the reaction zone are each located at or above the
bottom of the positive electrode within the reaction zone.
114. The system of claim 112, wherein the at least one cell
comprises a vertical stack of horizontally positioned cells.
115. The system of claim 114, wherein the stack maintains a cell-to
cell electrical continuity and does not maintain a cell-to cell
electrolyte continuity when the flow of the electrolyte mixture
stops.
116. The system of claim 104, wherein each of the at least one cell
comprises a cell frame.
117. A metal halogen electrochemical energy generation system
comprising: (A) a pressure containment vessel that contains: (a) a
vertical stack of a plurality of horizontal cells, each of the
plurality of horizontal cells comprising: at least one positive
electrode; at least one negative electrode; and a reaction zone
between the positive electrode and the negative electrode; and (b)
an electrolyte mixture comprising (i) at least one aqueous
electrolyte comprising a metal and a halogen and (ii) a pressurized
halogen reactant; and (B) a circulation pump that is configured to
convey a flow of the electrolyte mixture through the reaction zone
of each of the cells of the stack.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to metal halogen
electrochemical energy systems.
[0003] 2. Related Art
[0004] One type of electrochemical energy system uses a halogen
component for reduction at a normally positive electrode, and an
oxidizable metal adapted to become oxidized at a normally negative
electrode during the normal dispatch of the electrochemical system.
An aqueous electrolyte is used to replenish the supply of halogen
component as it becomes reduced at the positive electrode. The
electrolyte contains the dissolved ions of the oxidized metal and
reduced halogen and is circulated between the electrode area and a
reservoir area and an elemental halogen injection and mixing area,
to be consumed at the positive electrode. One example of such a
system uses zinc and chlorine system.
[0005] Such electrochemical energy systems are described in prior
patents including U.S. Pat. Nos. 3,713,888, 3,993,502, 4,001,036,
4,072,540, 4,146,680, and 4,414,292. Such systems are also
described in EPRI Report EM-1051 (Parts 1-3) dated April 1979,
published by the Electric Power Research Institute. The specific
teachings of the aforementioned cited references are incorporated
herein by reference.
SUMMARY OF THE INVENTION
[0006] There are certain weaknesses or disadvantages in prior
electrochemical energy systems for standby applications. These
include, but are not limited to, the following: [0007] an inability
to store sufficient energy without requirement to charge the
system, precluding availability while in a discharged condition;
[0008] complexity and inefficiency of requiring active cooling
systems during discharge, which can further reduce capacity; [0009]
ambiguities in diagnosing symptoms of failure, which can
significantly increase a probability of failure; and [0010]
hydrogen generation, which can be a significant and costly safety
issue.
[0011] Specific weaknesses or disadvantages in prior metal halogen
systems for standby applications also include, but are not limited
to, the following: [0012] inability to maintain a state of
readiness without significant capacity loss due to self-discharge;
[0013] mal-distribution of zinc metal from internal shunt currents
between cells of differing potential further reduces available
capacity; [0014] a long length of small diameter channels required
for minimizing shunt currents during operation further reduce
system capacity due to pumping losses; [0015] metallic dendritic
growth during the charge mode can permanently damage a metal
halogen system and lead to premature and hazardous failure
conditions.
[0016] The invention attempts to address some or all of these
weaknesses and disadvantages. The invention is not limited to
embodiments that do, in fact, address these weaknesses and
disadvantages.
[0017] Some embodiments of the invention that attempts to address
some or all of these weaknesses and disadvantages are metal halogen
electrochemical energy cell systems. These embodiments preferably
include at least at least one positive and at least one negative
electrode, a reaction zone between the positive electrode and the
negative electrode, at least one electrolyte that includes a metal
and a halogen, and a circulation pump that conveys the electrolyte
through the reaction zone, wherein the electrolyte and a halogen
reactant are mixed before, at, or after the pump. Preferably, the
positive electrode is made of porous carbonaceous material, the
negative electrode is made of zinc, the metal include zinc, the
halogen includes chlorine, the electrolyte includes an aqueous
zinc-chloride electrolyte, and the halogen reactant includes a
chlorine reactant. One effect of this arrangement is generation of
an electrical potential.
[0018] A preferred embodiment further includes a mixing venture
that mixes the electrolyte and the halogen reactant, as well as a
metering valve or positive displacement pump that controls flow of
the halogen reactant to the mixing venturi.
[0019] A flow of the electrolyte preferably undergoes concurrent
first, second, and third order binary splits before being conveyed
through the reaction zone, thereby providing a same flow resistance
for different paths to the reaction zone.
[0020] Preferred embodiments of the systems also include a
reservoir from which the electrolyte is conveyed by the circulation
pump to the cell and to which the electrolyte returns from the
cell, an upward-flowing electrolyte return manifold to facilitate
purging of gas from the cell, and a return pipe through which the
electrolyte returns from the cell to the reservoir.
[0021] The halogen reactant preferably is supplied from an external
source and preferably is supplied under pressure. In this context,
"external" refers to external to the system. An enthalpy of
expansion of the halogen from the external source tends to act to
cool the system. Alternatively, the halogen reactant can be
supplied from a source internal to the system.
[0022] The systems preferably include plural such cells, each of
which is horizontal and plural of which are stacked vertically in
the system. Vertical steps in cell geometry tend to result in
interrupted electrolyte flow paths within each of the plural cells,
thereby interrupting shunt currents that otherwise would continue
to occur after electrolyte flow stops.
[0023] The plural cells preferably include plural cell frames. The
cell frames can be circular to facilitate insertion of the plural
cells into a pressure containment vessel. The preferred form of the
cell frames each include a feed manifold element, distribution
channels, flow splitting nodes, spacer ledges, flow merging nodes,
collection channels, and a return manifold element. When cell
frames having this form are stacked, these structures form
additional structures within the system. In particular: [0024] the
feed manifold element in each of the plural cells frames aligns
with the feed manifold element in another of the cell frames,
thereby forming a feed manifold; [0025] the distribution channels
and the flow splitting nodes in each of the cell frames align with
the distribution channels and the flow splitting nodes in another
of the cell frames, thereby forming a distribution zone; [0026] the
positive electrode for each cell sits above or below the negative
electrode for each cell on the spaces ledges of the cell frames,
thereby forming alternating layers of positive electrodes and
negative electrodes; [0027] the flow merging nodes and the
collection channels in each of the plural cells frames align with
the flow merging nodes and the collection channels in another of
the cell frames, thereby forming a collection zone; and [0028] the
return manifold element in each of the cell frames aligns with the
return manifold element in another of the cell frames, thereby
forming a return manifold.
[0029] The cell frames can include bypass conduit elements for
fluid flow and electrical wires or cables and preferably provide a
pass-through for a alignment and clamping element to align and to
hold the cell frames together.
[0030] The invention is not limited to systems with cells that
include cell frames.
[0031] Whether or not cell frames are used, preferred embodiments
of the systems include a feed manifold and a distribution zone for
the electrolyte to the plural cells, and a collection zone and a
return manifold for the electrolyte from the plural cells. The
positive electrode and the negative electrode in each cell
preferably are arranged to maintain contact with a pool of
electrolyte in each cell when electrolyte flow stops and the feed
manifold, distribution zone, collection zone, and return manifold
drain.
[0032] In some embodiments, a balancing voltage can be applied to
inhibit electrochemical reactions and thereby maintain system
availability when the system is in a standby or stasis mode. A
blocking diode also can be applied to output terminals of the
system to inhibit reverse current flow within the system.
[0033] The basic operation of preferred embodiment of the system is
as follows: aqueous electrolyte is sucked up from a reservoir and
through a mixing venturi where halogen such as elemental chlorine
is metered into an electrolyte. The halogen mixes with and
dissolves into the electrolyte while its latent heat of
liquefaction also cools the mixture. The cooled and halogenated
aqueous electrolyte passes through the pump and is delivered to
positive electrodes in a stack assembly. The positive electrodes
preferably are made of porous carbonaceous material such as porous
graphite-chlorine. The electrolyte passes through the positive
electrodes, reducing the dissolved halogen. The halogen-ion rich
electrolyte then passes by one or more a negative electrode
preferably made of a metal such as zinc, where electrode
dissolution occurs. These reactions yield power from the electrode
stack terminals and metal-halogen is formed in the electrolyte by
reaction of the metal and the halogen.
[0034] The invention also encompasses processes performed by
embodiments of the metal halogen electrochemical energy cell system
according to the invention, as well as other systems and
processes.
[0035] This brief summary has been provided so that the nature of
the invention may be understood quickly. Other objects, features,
and advantages of the invention will become apparent from the
description herein, from the drawings, which show a preferred
embodiment, and from the appended claims.
BRIEF DESCRIPTION OF THE FIGURES
[0036] FIG. 1 illustrates a metal halogen electrochemical energy
cell system according to the invention.
[0037] FIG. 2 illustrates flow paths of an electrolyte through the
cell plates of an embodiment of the system illustrated in FIG.
1.
[0038] FIG. 3 illustrates cell frames that can be used in the
system illustrated in FIGS. 1 and 2.
DETAILED DESCRIPTION OF THE INVENTION
Electrolyte Energy Cell System
[0039] FIG. 1 illustrates a metal halogen electrochemical energy
cell system according to the invention.
[0040] One embodiment of the invention that attempts to address
some or all of these weaknesses and disadvantages is a metal
halogen electrochemical energy cell system. This embodiment
includes at least at least one positive and at least one negative
electrode, a reaction zone between the positive electrode and the
negative electrode, at least one electrolyte that includes a metal
and a halogen, and a circulation pump that conveys the electrolyte
through the reaction zone. The electrolyte and a halogen reactant
can be mixed before, at, or after the pump, for example using a
mixing venture. Preferably, the positive electrode is made of
porous carbonaceous material, the negative electrode is made of
zinc, the metal include zinc, the halogen includes chlorine, the
electrolyte includes an aqueous zinc-chloride electrolyte, and the
halogen reactant includes a chlorine reactant. One effect of this
arrangement is generation of an electrical potential.
[0041] The basic operation of this embodiment is as follows:
aqueous electrolyte is sucked up from a reservoir and through a
mixing venturi where halogen such as elemental chlorine is metered
into an electrolyte. The halogen mixes with and dissolves into the
electrolyte while its latent heat of liquefaction also cools the
mixture. The cooled and halogenated aqueous electrolyte passes
through the pump and is delivered to positive electrodes in a stack
assembly. The positive electrodes preferably are made of porous
carbonaceous material such as porous graphite-chlorine. The
electrolyte passes through the positive electrodes, reducing the
dissolved halogen. The halogen-ion rich electrolyte then passes by
one or more a negative electrode preferably made of a metal such as
zinc, where electrode dissolution occurs. These reactions yield
power from the electrode stack terminals and metal-halogen is
formed in the electrolyte by reaction of the metal and the
halogen.
[0042] FIG. 1 shows an electrochemical energy system housed in
containment vessel 11 designed to achieve the foregoing. The system
in FIG. 2 includes two basic parts: stack assembly 12 and reservoir
19, as shown in FIG. 1.
[0043] Stack assembly 12 is made up of a plurality of cells or cell
assemblies 13 that include at least one porous electrode and at
least one metal electrode. The cells preferably are stacked
vertically. Pressurized halogen reactant is supplied via feed pipe
15 from a source external to the system through metering valve 17
to mixing venturi 18. Circulation pump 16 circulates the
electrolyte from reservoir 19 through mixing venturi 18, through
stack assembly 12, and back to reservoir 19 through a return pipe.
It should be noted that some halogen reactant could be left in the
electrolyte when it returns back to the reservoir from the
cell.
[0044] In a preferred embodiment, the porous electrodes include
carbonaceous material, the metal includes zinc, the metal electrode
includes zinc, the halogen includes chlorine, the electrolyte
includes an aqueous zinc-chloride electrolyte, and the halogen
reactant includes a chlorine reactant.
[0045] In a preferred embodiment, this arrangement results in cells
that each has an electrical potential of two volts, giving a stack
arrangement with 21 cells a potential of 42 volts. An enthalpy of
expansion of the halogen from the external source preferably cools
the system. Thus, a strong potential can be provided without
generating excessive heat.
Electrolyte Flows
[0046] FIG. 2 illustrates flow paths of an electrolyte through the
cell plates of an embodiment of the system illustrated in FIG. 1.
In this figure, the electrolyte flow paths 28 are represented by
arrows. These paths are from feed manifold 21, to distribution zone
22, through porous electrodes 23, over metal electrodes 25, to
collection zone 26, through return manifold 27, and to return pipe
29.
[0047] In a preferred embodiment, membranes 24 on a bottom of metal
electrodes 25 screen the flows of electrolyte from contacting the
metal electrodes before passing through the porous electrodes.
These membranes preferably are plastic membranes secured to bottoms
of the metal electrodes with adhesive. Other types of membranes
secured in other ways also can be used. Alternatively, the
membranes could be omitted.
[0048] With the arrangement shown in FIG. 2, the porous electrode
and the metal electrode in each cell are arranged to maintain
contact with a pool of electrolyte in each cell when electrolyte
flow stops and the feed manifold, distribution zone, collection
zone, and return manifold drain.
[0049] Furthermore, the vertically stacked cells and the geometry
of the cells result in flow paths of the electrolyte within each of
the plural cells that tend to interrupt shunt currents that
otherwise would occur when electrolyte flow stops. These shunt
currents are not desired because they can lead to reactions between
the plates that corrode the metal plates without generating any
usable potential.
[0050] Before being conveyed through the porous electrode, the
electrolyte mixed with the halogen reactant preferably undergoes
first, second, and third order splits to provide a same flow
resistance for different paths to the porous electrode. Each split
preferably divides the flow by two, although this need not be the
case. FIG. 3 illustrates one possible cell design that can achieve
these splits.
Cell Frames
[0051] FIG. 3 illustrates a cell design that uses cell frames to
achieve the structures and flows shown in FIG. 2. These cell frames
preferably include feed manifold element 31, distribution channels
32, flow splitting nodes 33, spacer ledge 35, flow merging nodes
36, collection channels 37, return manifold element 38, and bypass
conduit elements 34.
[0052] When these cell frames are stacked vertically with the
electrodes in place, these elements combine to form the elements
shown in FIG. 2 as follows: [0053] the feed manifold element in
each of the plural cells frames aligns with the feed manifold
element in another of the cell frames, thereby forming a feed
manifold; [0054] the distribution channels and the flow splitting
nodes in each of the cell frames align with the distribution
channels and the flow splitting nodes in another of the cell
frames, thereby forming a distribution zone; [0055] the porous
electrode for each cell sits above or below the metal electrode for
each cell on the spaces ledges of the cell frames, thereby forming
alternating layers of porous electrodes and metal electrodes;
[0056] the flow merging nodes and the collection channels in each
of the plural cells frames align with the flow merging nodes and
the collection channels in another of the cell frames, thereby
forming a collection zone; [0057] the return manifold element in
each of the cell frames aligns with the return manifold element in
another of the cell frames, thereby forming a return manifold; and
[0058] the bypass conduit elements in each of the cell frames align
with the bypass conduit elements in another of the cell frames,
thereby forming bypass conduits for fluid flow and/or electrical
wires or cables.
[0059] The cell frames preferably are circular to facilitate
insertion of the plural cells into a pressure containment vessel
such as vessel 11.
[0060] The cell frame based design facilitates low-loss electrolyte
flow with uniform distribution, bipolar electrical design, ease of
manufacture, internal bypass paths, and elements by which the
operational stasis mode (described below) can be achieved.
Innovations of the cell frame include, but are not limited to, the
flow-splitting design in the distribution zone that include first,
second, and third order splits in the flow channels to deliver
eight feed channels per cell to the reaction zone. This design
attempts to ensure that each outlet to the reaction zone passes
through the same length of channels, the same number and radius of
bends, with laminar flow throughout and uniform laminar flow prior
to each split. The design encourages division of flow volume
equally, independent of flow velocity, uniformity of viscosity, or
uniformity of density in the electrolyte. These features have been
found to be of particular importance when a mixture of gaseous and
liquid phases is fed through the system.
[0061] Alternatively, the same types of structures and flows (i.e.,
those shown in FIG. 2) can be achieved without using cell
frames.
Modes of Operation
[0062] The energy cell system according to the invention preferably
Cell has three modes of operation: Off Mode, Power Mode, and Stasis
Mode. These modes are described below in the context of a
zinc-chlorine system. However, the modes also can be implemented
using other metal-halogen systems.
[0063] Off Mode is typically used for storage or transportation.
During Off Mode, the circulation pump is off. A small amount of
elemental chlorine in the stack assembly is reduced and combined
with zinc ions to form zinc-chloride. The stack terminals
preferably are connected via a shorting resistor, yielding a stack
potential of zero volts. A blocking diode preferably is used to
prevent reverse current flow through the system via any external
voltage sources.
[0064] During Power Mode the electrolyte circulation pump is
engaged. The catholyte (i.e., electrolyte) containing dissolved
chlorine is circulated through the stack assembly containing the
zinc anode plates. Electrons are released as zinc ions are formed
and captured as chlorine ions are formed, preferably with an
electrical potential of 2.02 volts per cell, thereby creating
electrical power from the terminals of the collector plates
preferably located at each end of the stack assembly. The demand
for power from the system consumes chlorine and reduces pressure
within the reservoir, causing the metering valve to release
higher-pressure chlorine into the mixing venturi. This design
feature aids both in speeding the dissolving of chlorine gas into
the electrolyte, and uniformly cooling the electrolyte without risk
of freezing at the injection point. The injection rate preferably
is determined by the electrochemical reaction rates within the
stack assembly. The metering valve and the circulation pump
preferably provide sufficient response speed to match rapidly
changing instantaneous power demands. As the compressed chlorine is
released into the system, its enthalpy of expansion should absorb
sufficient heat to maintain the energy cell within thermal
operating limits.
[0065] During Stasis or Standby Mode, there should be little or no
electrolyte flow or chlorine injection. The availability of the
system preferably is maintained via a balancing voltage that is
applied to maintain system availability. This balancing voltage
tends to prevent self-discharge by maintaining a precise electrical
potential on the cell stack to counteract the electrochemical
reaction forces that can arise with the circulation pump off. The
particular design of the cell plates tends to interrupt shunt
currents that would otherwise flow through the feed and return
manifolds, while maintaining cell-to-cell electrical continuity
through the bipolar electrode plates.
[0066] While these are preferred modes of operation, the invention
is not limited to these modes or to the details of these modes.
Rather, some embodiments might have some of these modes, none of
these modes, or different modes of operation.
Generality of Invention
[0067] This application should be read in the most general possible
form. This includes, without limitation, the following: [0068]
References to specific techniques include alternative and more
general techniques, especially when discussing aspects of the
invention, or how the invention might be made or used. [0069]
References to "preferred" techniques generally mean that the
inventor contemplates using those techniques, and thinks they are
best for the intended application. This does not exclude other
techniques for the invention, and does not mean that those
techniques are necessarily essential or would be preferred in all
circumstances. [0070] References to contemplated causes and effects
for some implementations do not preclude other causes or effects
that might occur in other implementations. [0071] References to
reasons for using particular techniques do not preclude other
reasons or techniques, even if completely contrary, where
circumstances would indicate that the stated reasons or techniques
are not as applicable.
[0072] Furthermore, the invention is in no way limited to the
specifics of any particular embodiments and examples disclosed
herein. Many other variations are possible which remain within the
content, scope and spirit of the invention, and these variations
would become clear to those skilled in the art after perusal of
this application.
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