U.S. patent application number 11/654380 was filed with the patent office on 2009-09-24 for electrochemical energy cell system.
Invention is credited to Richard Otto Winter.
Application Number | 20090239131 11/654380 |
Document ID | / |
Family ID | 39636667 |
Filed Date | 2009-09-24 |
United States Patent
Application |
20090239131 |
Kind Code |
A1 |
Winter; Richard Otto |
September 24, 2009 |
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 negative
electrodes are made of zinc, the metal is zinc, the positive
electrodes are made of porous carbonaceous material, the halogen is
chlorine, the electrolyte is an aqueous zinc-chloride electrolyte,
and the halogen reactant is a chlorine reactant. Also, variations
of the system and a method of operation for the systems.
Inventors: |
Winter; Richard Otto;
(Orinda, CA) |
Correspondence
Address: |
SWERNOFSKY LAW GROUP PC
548 MARKET ST.
SAN FRANCISCO
CA
94104
US
|
Family ID: |
39636667 |
Appl. No.: |
11/654380 |
Filed: |
January 16, 2007 |
Current U.S.
Class: |
429/51 ; 429/105;
429/199 |
Current CPC
Class: |
H01M 50/572 20210101;
H01M 8/08 20130101; H01M 12/085 20130101; H01M 50/138 20210101;
H01M 10/0413 20130101; H01M 10/0472 20130101; H01M 12/04 20130101;
H01M 2300/0002 20130101; Y02E 60/10 20130101; H01M 4/96 20130101;
H01M 4/8605 20130101; H01M 50/77 20210101; Y02E 60/50 20130101;
H01M 8/04186 20130101; H01M 50/30 20210101; H01M 4/42 20130101 |
Class at
Publication: |
429/51 ; 429/199;
429/105 |
International
Class: |
H01M 6/04 20060101
H01M006/04; H01M 2/38 20060101 H01M002/38 |
Claims
1. A metal halogen electrochemical energy system whereby an
electrical potential is generated, comprising at least one cell
that includes: at least one positive electrode; 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.
2. A system as in claim 1, wherein the positive electrode comprises
porous carbonaceous material.
3. A system as in claim 1, wherein 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.
4. A system as in claim 1, further comprising a mixing venture that
mixes the electrolyte and the halogen reactant.
5. A system as in claim 1, wherein before being conveyed through
the reaction zone, a flow of the electrolyte undergoes concurrent
first, second, and third order binary splits to provide a same flow
resistance for different paths to the reaction zone.
6. A system as in claim 1, further comprising a reservoir from
which the electrolyte is conveyed by the circulation pump to the
cell and to which the electrolyte returns from the cell.
7. A system as in claim 6, further comprising an upward-flowing
electrolyte return manifold to facilitate purging of gas from the
cell.
8. A system as in claim 6, further comprising a return pipe through
which the electrolyte returns from the cell to the reservoir.
9. A system as in claim 6, wherein the halogen reactant is supplied
from an external source.
10. A system as in claim 6, wherein the halogen reactant is
supplied under pressure, and wherein an enthalpy of expansion of
the halogen from the external source acts to cool the system.
11. A system as in claim 1, further comprising a metering valve or
positive displacement pump that controls flow of the halogen
reactant.
12. A system as in claim 1, further comprising plural such
cells.
13. A system as in claim 12, wherein plural horizontal such cells
are stacked vertically in the system.
14. A system as in claim 12, wherein the plural cells further
comprise plural cell frames.
15. A system as in claim 14, wherein the cell frames are circular
to facilitate insertion of the plural cells into a pressure
containment vessel.
16. A system as in claim 14, further comprising the pressure
containment vessel.
17. A system as in claim 14, wherein each of the cell frames
further comprises a feed manifold element, distribution channels,
flow splitting nodes, spacer ledges, flow merging nodes, collection
channels, and a return manifold element.
18. A system as in claim 17, wherein 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; 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; 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; 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 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.
19. A system as in claim 17, wherein each of the cell frames
further comprise bypass conduit elements for fluid flow and
electrical wires or cables.
20. A system as in claim 17, wherein each of the cell frames
further provides a pass-through for an alignment and clamping
element to align and to hold the cell frames together, and further
comprises the alignment and clamping element.
21. A system as in claim 12, wherein vertical steps in cell
geometry 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.
22. A system as in claim 12, further comprising: a feed manifold
and a distribution zone for the electrolyte to the plural cells; a
collection zone and a return manifold for the electrolyte from the
plural cells.
23. A system as in claim 22, wherein the positive electrode and the
negative 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.
24. A system as in claim 22, further comprising a reservoir from
which the electrolyte is conveyed by the circulation pump to the
feed manifold and to which the electrolyte returns from the return
manifold.
25. A system as in claim 24, further comprising an upward-flowing
electrolyte return manifold to facilitate purging of gas from the
cell.
26. A system as in claim 24, further comprising a return pipe that
is internal to the cell frames through which the electrolyte
returns from the cell to the reservoir.
27. A metal halogen electrochemical energy cell system, comprising
at least one cell that includes a positive electrode, a negative
electrode, a reaction zone between the positive electrode and the
negative electrode, and flow distribution zones; an aqueous
electrolyte that includes the metal and the halogen; a reservoir
where the electrolyte is collected; and a circulation pump that
conveys the electrolyte through the system; wherein the flow
distribution zones contain flow-splitting nodes in which flow
channels are concurrently and repeatedly divided in two to provide
a same flow resistance for different paths to the reaction
zone.
28. A system as in claim 27, wherein the negative electrode
comprises zinc, the halogen comprises chlorine, the positive
electrode comprises porous carbonaceous material, the electrolyte
comprises an aqueous zinc-chloride electrolyte, and the halogen
reactant comprises a chlorine reactant.
29. A metal halogen electrochemical energy cell system, comprising
at least one cell that includes a positive electrode, a negative
electrode, and a reaction zone between the positive electrode and
the negative electrode; an aqueous electrolyte that includes the
metal and the halogen; a reservoir where the electrolyte is
collected; a circulation pump that conveys the electrolyte through
the system; and a halogen metering element by which the halogen is
replenished from an external source.
30. A system as in claim 29, wherein the negative electrode
comprises zinc, the metal comprises zinc, the halogen comprises
chlorine, the positive electrode comprises carbonaceous material,
the electrolyte comprises an aqueous zinc-chloride electrolyte, and
the halogen reactant comprises a chlorine reactant.
31. A system as in claim 29, wherein the halogen metering element
is a valve or a positive displacement pump.
32. A system as in claim 29, wherein chlorine is fed to the halogen
metering element from the external source.
33. A system as in claim 29, wherein an enthalpy of expansion of
the halogen from the external source cools the system.
34. A metal halogen electrochemical energy cell system, comprising
at least one cell that includes a positive electrode, a negative
electrode, and a reaction zone between the positive electrode and
the negative electrode; an aqueous electrolyte that includes a
metal and a halogen; a reservoir where the electrolyte is
collected; and a circulation pump that conveys the electrolyte
through the system; wherein a balancing voltage is applied to
inhibit electrochemical reactions and thereby maintain system
availability when the system is in a standby or stasis mode.
35. A system as in claim 34, wherein the negative electrode
comprises zinc, the halogen comprises chlorine, the positive
electrode comprises carbonaceous material, the electrolyte
comprises an aqueous zinc-chloride electrolyte, and the halogen
reactant comprises a chlorine reactant.
36. A metal halogen electrochemical energy cell system, comprising
at least one cell that includes a positive electrode, a negative
electrode, and a reaction zone between the positive electrode and
the negative electrode; an aqueous electrolyte that includes the
metal and the halogen; a halogen reactant that is mixed with the
electrolyte; a reservoir where the electrolyte is collected; a
circulation pump that conveys the electrolyte through the system;
output terminals connected to at least the cell; and a blocking
diode that is applied to the output terminals to inhibit reverse
current flow within the system.
37. A system as in claim 36, wherein the negative electrode
comprises zinc, the metal comprises zinc, the halogen comprises
chlorine, the positive electrode comprises carbonaceous material,
the electrolyte comprises an aqueous zinc-chloride electrolyte, and
the halogen reactant comprises a chlorine reactant.
38. A method of generating an electrical potential using a metal
halogen electrochemical energy system, comprising the steps of:
mixing an electrolyte with a halogen reactant, with the electrolyte
including a metal and a halogen; and conveying the electrolyte
through at least one cell that includes at least one positive
electrode and at least one negative electrode, wherein the
electrolyte passes through the positive electrode and across the
negative electrode.
39. A method as in claim 38, wherein the positive electrode
comprises porous carbonaceous material.
40. A method as in claim 38, wherein 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.
41. A method as in claim 38, wherein the electrolyte and the
halogen reactant are mixed by a mixing venturi.
42. A method as in claim 38, further comprising the step of
subjecting a flow of the electrolyte to concurrent first, second,
and third order splits before being conveyed through the positive
electrode, thereby providing a same flow resistance for different
paths to a reaction zone between the positive electrode and the
negative electrode.
43. A method as in claim 38, wherein the electrolyte is circulated
from a reservoir to the cell and returns from the cell to the
reservoir.
44. A method as in claim 43, further comprising the step of
upward-flowing the electrolyte in a return manifold to facilitate
purging gas from the cell.
45. A method as in claim 43, further comprising the step of
returning the electrolyte to the reservoir through a pipe.
46. A method as in claim 43, further comprising the step of
supplying the halogen reactant to the system from an external
source.
47. A method as in claim 43, wherein an enthalpy of expansion of
the halogen from the external source acts to cool the system.
48. A method as in claim 38, further comprising the step of
controlling flow of the halogen reactant using a metering valve or
positive displacement pump.
49. A method as in claim 38, wherein conveying the electrolyte
through at least one cell further comprises conveying the
electrolyte through plural such cells.
50. A method as in claim 49, wherein the plural horizontal cells
are stacked vertically in the system.
51. A method as in claim 49, wherein the plural cells further
comprise plural cell frames.
52. A method as in claim 51, wherein the cell frames are circular
to facilitate insertion of the plural cells into a pressure
containment vessel.
53. A method as in claim 51, wherein the plural cells are contained
in a pressure containment vessel.
54. A method as in claim 51, wherein conveying the electrolyte
through the plural cell frames further comprises conveying the
electrolyte through a feed manifold element, distribution channels,
flow splitting nodes, spacer ledges, flow merging nodes, collection
channels, and a return manifold element.
55. A method as in claim 54, wherein 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; 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; 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; 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 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.
56. A method as in claim 54, wherein each of the cell frames
further comprise bypass conduit elements for fluid flow and
electrical wires or cables.
57. A method as in claim 54, wherein each of the cell frames
further provides a pass-through for an alignment and clamping
element to align and to hold the cell frames together, and further
comprises the alignment and clamping element.
58. A method as in claim 49, further comprising the step of using
vertical steps in cell geometry to interrupt flow paths of the
electrolyte within each of the plural cells to interrupt shunt
currents that otherwise would continue to occur after electrolyte
flow stops.
59. A method as in claim 49, wherein conveying the electrolyte
through the plural cells further comprises conveying the
electrolyte through a feed manifold and a distribution zone to the
plural cells and through a collection zone and a return manifold
from the plural cells.
60. A method as in claim 59, further comprising the step of
maintaining 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.
61. A method as in claim 59, wherein conveying the electrolyte
through the plural cells further comprises conveying the
electrolyte from a reservoir to the feed manifold and from the
return manifold to the reservoir.
62. A method as in claim 61, further comprising the step of
upward-flowing electrolyte in the return manifold to facilitate
purging gas from the cell.
63. A method as in claim 61, further comprising the step of
returning the electrolyte to the reservoir through a pipe that is
internal to the cell frames.
64. A method of generating an electrical potential using a metal
halogen electrochemical energy system, comprising the steps of:
conveying an aqueous electrolyte that includes the metal and the
halogen through at least one cell that includes a positive
electrode, a negative electrode, a reaction zone between the
positive electrode and the negative electrode, and flow
distribution zones; and collecting the electrolyte in a reservoir;
wherein the flow distribution zones contain flow-splitting nodes in
which flow channels are concurrently and repeatedly divided in two
to provide a same flow resistance for different paths to the
reaction zone.
65. A method as in claim 64, wherein the negative electrode
comprises zinc, the metal comprises zinc, the halogen comprises
chlorine, the positive electrode comprises carbonaceous material,
the electrolyte comprises an aqueous zinc-chloride electrolyte, and
the halogen reactant comprises a chlorine reactant.
66. A method of generating an electrical potential using a metal
halogen electrochemical energy system, comprising the steps of:
conveying an aqueous electrolyte that includes the metal and the
halogen through at least one cell that includes a positive
electrode, a negative electrode, and a reaction zone between the
positive electrode and the negative electrode; collecting the
electrolyte in a reservoir; and replenishing the halogen from an
external source using a halogen metering element.
67. A method as in claim 66, wherein the negative electrode
comprises zinc, the metal comprises zinc, the halogen comprises
chlorine, the positive electrode comprises carbonaceous material,
the electrolyte comprises an aqueous zinc-chloride electrolyte, and
the halogen reactant comprises a chlorine reactant.
68. A method as in claim 66, wherein the halogen metering element
is a valve or positive displacement pump.
69. A method as in claim 66, wherein chlorine is fed to the halogen
metering element from the external source.
70. A method as in claim 66, wherein an enthalpy of expansion of
the halogen from the external source acts to cools the system.
71. A method of generating an electrical potential using a metal
halogen electrochemical energy system, comprising the steps of:
conveying an aqueous electrolyte that includes a metal and a
halogen through at least one cell that includes a positive
electrode, a negative electrode, and a reaction zone between the
positive electrode and the negative electrode; collecting the
electrolyte in a reservoir; and applying a balancing voltage to
inhibit electrochemical reactions and thereby maintain system
availability when the system is in a standby or stasis mode.
72. A method as in claim 71, wherein the negative electrode
comprises zinc, the metal comprises zinc, the halogen comprises
chlorine, the positive electrode comprises carbonaceous material,
the electrolyte comprises an aqueous zinc-chloride electrolyte, and
the halogen reactant comprises a chlorine reactant.
73. A method of generating an electrical potential using a metal
halogen electrochemical energy cell system, comprising the steps
of: conveying an aqueous electrolyte that includes a metal and a
halogen through at least one cell that includes a positive
electrode, a negative electrode, and a reaction zone between the
positive electrode and the negative electrode; mixing a halogen
reactant with the electrolyte; collecting the electrolyte in a
reservoir; and applying a blocking diode to output terminals of the
system to inhibit reverse current flow within the system.
74. A method as in claim 73, wherein the negative electrode
comprises zinc, the metal comprises zinc, the halogen comprises
chlorine, the positive electrode comprises carbonaceous material,
the electrolyte comprises an aqueous zinc-chloride electrolyte, and
the halogen reactant comprises a chlorine reactant.
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 an 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 positive porous electrode
and at least one negative 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] Alternatively, different types of positive and/or negative
electrodes can be used. In addition, the halogen reactant can be
supplied from an internal source instead of or in addition to an
external source. Furthermore, the mixing venture can be replaced
with a different type of mixing element, and the metering valve can
be replaced with a different type of metering element such as a
positive displacement pump.
[0046] 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
[0047] 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. The electrolyte preferably is conveyed by the circulation pump
from the reservoir to these paths and returns from these paths to
the reservoir. One feature of these paths is that the return
manifold preferably is upward-flowing return manifold, which can
facilitate purging of gas from the cell during electrolyte
flow.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] Before being conveyed through the porous electrode, the
electrolyte mixed with the halogen reactant preferably undergoes
concurrent first, second, and third order splits to provide a same
flow resistance for different paths to the porous electrode. In
this context, "concurrent" indicates that splits are aligned with
other splits of the same order. 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
[0052] 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.
[0053] 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: [0054] 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; [0055] 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; [0056] 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;
[0057] 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; [0058] 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
[0059] 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, a return pipe,
and/or electrical wires or cables.
[0060] The cell frames preferably are circular to facilitate
insertion of the plural cells into a pressure containment vessel
such as vessel 11. In a preferred embodiment, each of the cell
frames also provides a pass-through for an alignment and clamping
element to align and to hold the cell frames together.
[0061] 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.
[0062] 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
[0063] 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.
[0064] 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
help inhibit reverse current flow through the system via any
external voltage sources.
[0065] 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.
[0066] 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,
thereby inhibiting electrochemical reactions and maintaining system
availability.
[0067] 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.
[0068] 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
[0069] This application should be read in the most general possible
form. This includes, without limitation, the following: [0070]
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. [0071]
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. [0072] References to contemplated causes and effects
for some implementations do not preclude other causes or effects
that might occur in other implementations. [0073] 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.
[0074] 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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