U.S. patent application number 14/626478 was filed with the patent office on 2015-06-11 for control system for a flow cell battery.
The applicant listed for this patent is Imergy Power Systems, Inc.. Invention is credited to Binod Kumar Agrawal, Jagat Banerjee, Ali Firouzi, Gopalakrishnan R. Parakulam, Saroj Kumar Sahu, PandariNath Siddineni, Rick Winter.
Application Number | 20150162635 14/626478 |
Document ID | / |
Family ID | 43223406 |
Filed Date | 2015-06-11 |
United States Patent
Application |
20150162635 |
Kind Code |
A1 |
Parakulam; Gopalakrishnan R. ;
et al. |
June 11, 2015 |
CONTROL SYSTEM FOR A FLOW CELL BATTERY
Abstract
A controller for controlling a flow cell battery system is
provided. The controller operates the flow cell battery system in a
plurality of states including a plating state, a charging state and
a discharge state.
Inventors: |
Parakulam; Gopalakrishnan R.;
(Fremont, CA) ; Sahu; Saroj Kumar; (Mountain
House, CA) ; Firouzi; Ali; (Los Altos, CA) ;
Winter; Rick; (Orinda, CA) ; Banerjee; Jagat;
(Campbell, CA) ; Agrawal; Binod Kumar; (Gurgaon,
IN) ; Siddineni; PandariNath; (Bangalore,
IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Imergy Power Systems, Inc. |
Fremont |
CA |
US |
|
|
Family ID: |
43223406 |
Appl. No.: |
14/626478 |
Filed: |
February 19, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14083266 |
Nov 18, 2013 |
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14626478 |
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12790793 |
May 28, 2010 |
8587255 |
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14083266 |
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61182079 |
May 28, 2009 |
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61182660 |
May 29, 2009 |
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Current U.S.
Class: |
429/418 |
Current CPC
Class: |
H02J 3/387 20130101;
Y02E 60/50 20130101; Y02E 10/56 20130101; H02J 3/383 20130101; Y02E
10/566 20130101; H02J 2300/30 20200101; Y02E 10/763 20130101; H02J
3/381 20130101; H02J 7/0068 20130101; Y02E 10/563 20130101; H01M
8/20 20130101; H01M 8/22 20130101; H02J 2300/20 20200101; Y02E
10/76 20130101; H02J 2300/24 20200101; H01M 8/04858 20130101; Y02E
60/528 20130101; H02J 3/32 20130101; H01M 8/0432 20130101; H01M
8/0438 20130101; H01M 8/188 20130101; H01M 8/04537 20130101; H02J
3/386 20130101; H01M 8/04955 20130101; H02J 3/382 20130101; H01M
8/04992 20130101; H02J 2300/28 20200101 |
International
Class: |
H01M 8/18 20060101
H01M008/18; H01M 8/20 20060101 H01M008/20 |
Claims
1. A controller for controlling a flow cell battery system,
comprising: one or more processors operating the flow cell battery
system in multiple states, the multiple states comprising: a
charging state, wherein in the charging state, at least a portion
of the electrolytes in the flow cell battery system are brought to
a charged chemical state; a discharge state, wherein power is
supplied to a load coupled to the flow cell battery system in the
discharge state; and a shutdown state; wherein the controller
switches the flow cell battery system from any state to the
shutdown state when a fault is detected.
2. The controller of claim 1, wherein: the flow cell battery system
further comprises a plating state; in the plating state at least a
portion of electrodes in the flow cell battery system are plated
with a plating material; and the controller switches the flow cell
battery system to the charging state if the when plating of the
electrodes is complete.
3. The controller of claim 1, wherein the controller switches the
flow cell battery system from the charging state to the discharge
state when power to the flow cell battery system is disconnected
and the load is coupled to the flow cell battery system.
4. The controller of claim 1, wherein the flow cell battery system
further comprises a float state, wherein in the float state power
supplied to electrodes of a flow cell battery in the flow cell
battery system is reduced with respect to power supplied to the
electrodes during the charging state, and wherein the controller
switches the flow cell battery system from the charging state to
the float state when a state of charge of the flow cell battery is
greater than a predetermined charged set point and power is
supplied to the flow cell battery system.
5. The controller of claim 4, wherein the controller switches the
flow cell battery system from the float state to the discharge
state when the supplied power to the flow cell battery system is
disconnected and the load is coupled to the flow cell battery
system.
6. The controller of claim 1, wherein the flow cell battery system
further comprises a hibernation state, and wherein the controller
switches the flow cell battery system from the discharge state to
the hibernation state when a state of charge of a flow cell battery
in the flow cell battery system is less than a predetermined
discharged set point and no power is being supplied to the flow
cell battery system.
7. The controller of claim 6, wherein the controller switches the
flow cell battery system from the hibernation state to the charging
state when power is supplied to the flow cell battery system.
8. The controller of claim 1, wherein the controller switches the
flow cell battery system from the discharge state to the charging
state when power is supplied to the flow cell battery system during
the discharge state and a state of charge of the flow cell battery
system is less than a predetermined charged set point.
9. (canceled)
10. The controller of claim 9, wherein the flow cell battery system
further comprises an initialization state, wherein the controller
switches the flow cell battery system to the initialization state
when power is supplied to the flow cell battery system operating in
the shutdown state and switches the flow cell battery system to the
plating state when the initialization state is complete.
11. (canceled)
12. (canceled)
13. The controller of claim 1, wherein the processors are
configured to control pump flow based on levels of electrolyte
tanks and a state of charge of the electrolytes.
14. (canceled)
15. The controller of claim 1, further comprising one or more
processors operating a rebalance cell and wherein the one or more
processors operating the flow cell battery system in multiple
states are in communication with the one or more processors
operating the rebalance cell.
16. A method of operating a flow cell battery system, comprising:
operating the flow cell battery system using a controller capable
of transitioning the flow cell battery system into a plurality of
operating states, the plurality of operating states comprising: a
charging state, wherein in the charging state, at least a portion
of the electrolytes in the flow cell battery system are brought to
a charged chemical state; a discharge state, wherein power is
supplied to a load coupled to the flow cell battery system in the
discharge state; and a shutdown state; wherein transitioning the
flow cell battery system comprises switching the flow cell battery
system from any state to the shutdown state when a fault is
detected.
17. The method of claim 16, wherein: the operating states further
comprise a plating state; and the method further comprises: plating
at least a portion of electrodes in the flow cell battery system
with a plating material when the flow cell battery system is in the
plating state; and switching the flow cell battery system to the
charging state when plating of electrodes of a flow cell battery of
the flow cell battery system is complete.
18. The method of claim 16, further comprising switching the flow
cell battery system from the charging state to the discharge state
when power to the flow cell battery system is disconnected and the
load is coupled to the flow cell battery system.
19. The method of claim 16, wherein the operating states further
comprise a float state, wherein in the float state power supplied
to electrodes of a flow cell battery in the flow cell battery
system is reduced with respect to power supplied to the electrodes
during the charging state, and wherein the method further comprises
switching the flow cell battery system from the charging state to
the float state when a state of charge of the flow cell battery is
greater than a predetermined charged set point and power is
supplied to the flow cell battery system.
20. The method of claim 19, further comprising switching the flow
cell battery system from the float state to the discharge state
when the supplied power to the flow cell battery system is
disconnected and the load is coupled to the flow cell battery
system.
21. The method of claim 16, wherein the operating states further
comprise a hibernation state, and wherein the method further
comprises switching the flow cell battery system from the discharge
state to the hibernation state when a state of charge of the flow
cell battery system is less than a predetermined discharged set
point and no power is being supplied to the flow cell battery
system.
22. The method of claim 16, further comprising switching the flow
cell battery system from the hibernation state to the charging
state when power is supplied to the flow cell battery system.
23. The method of claim 16, further comprising switching the flow
cell battery system from the discharge state to the charging state
when power is supplied to the flow cell battery system during the
discharge state and a state of charge of a flow cell battery of the
flow cell battery system is less than a predetermined charged set
point.
24. (canceled)
25. The method of claim 24, wherein the operating states further
comprise an initialization state, and wherein the method further
comprises switching the flow cell battery system to the
initialization state when power is supplied to the flow cell
battery system operating in the shutdown state and switching the
flow cell battery system to the plating state when the
initialization state is complete.
26. (canceled)
Description
PRIORITY CLAIM
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/182,079 entitled "Control System for a Flow Cell
Battery," filed on May 28, 2009 and U.S. Provisional Application
No. 61/182,660 entitled "Control System for a Flow Cell Battery,"
filed on May 29, 2009.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments disclosed herein generally relate to control
systems, and more specifically, to a control system for a flow cell
battery.
[0004] 2. Description of the Relevant Art
[0005] There is an increasing demand for novel and innovative
electric power storage systems. Redox flow cell batteries have
become an attractive means for such energy storage. In particular,
redox batteries can be utilized as energy backup supplies in areas
where power from the grid is unreliable, for energy load shifting
where energy can be stored at low demand times and supplied at peak
demand times, and for storage in alternative energy systems to
supply power when the alternative energy source (e.g. solar, wind,
tidal, or other source) is unavailable or low in production.
[0006] In a redox flow cell battery system, for example, a battery
cell may include two electrodes, each immersed in an electrolyte.
The two electrolytes are separated by a membrane. The battery is
discharged when current flows between the terminals and a charged
ion is transported across the membrane. The electrolytes are flowed
through the battery so that the amount of stored energy is not
determined by the size of the cell itself. The battery is charged
when a current is supplied between the terminals and the charged
ion is transported back across the membrane, charging the two
separated electrolytes in the cell. The electrical energy is
thereby stored by appropriately charging the two electrolytes.
[0007] In order to provide a consistent supply of energy, it is
important that many of the components of the flow cell battery
system are performing properly. Flow cell performance, for example,
can change based on parameters such as the state of charge,
temperature, electrolyte level, concentration of electrolyte and
fault conditions such as leaks, pump problems, and power supply
failure for powering electronics. To be useful as an electric power
storage system, it is desirable that the flow cell battery system
requires a minimal amount of maintenance and monitoring. Therefore,
there is a need for efficient control systems for controlling and
monitoring a flow cell battery system.
SUMMARY OF THE INVENTION
[0008] In accordance with some embodiments, a controller for
controlling a flow cell battery system is disclosed. In some
embodiments, the controller includes one or more processors
executing a state machine, the state machine including a shutdown
state; an initialization state that is transitioned to when the
flow cell battery system is turned on; a plating state transitioned
to from the initialization state; a charging state transitioned to
from the plating state; a float state that can be transitioned to
from the charging state if charging is complete; a discharge state
that can be transitioned to from the charging state or from the
float state if a discharge condition is detected; and a hibernate
state that can be transitioned to from the discharge state when the
flow cell battery is discharged below a threshold level, and
wherein the hibernate state can transition to the charge state when
a charging condition is detected.
[0009] In one embodiment, in the plating state, at least a portion
of the electrodes are plated with a plating metal. In the charging
state at least a portion of the electrolytes in the flow cell
battery are brought to a charged chemical state. In the discharge
state power is supplied to a load coupled to the flow cell battery
system in the discharge state.
[0010] In one embodiment, the controller switches the flow cell
battery system to the charging state if the plating of the
electrodes is complete. The controller further switches the flow
cell battery system from the charging state to the discharge state
when power to the flow cell battery system is disconnected and a
load is coupled to the flow cell battery system.
[0011] The flow cell battery system may also be operated in a float
state. In the float state power to electrodes of the flow cell
battery system is reduced with respect to the power supplied to the
electrodes during the charging state. The controller switches the
flow cell battery system from the charging state to the float state
when a state of charge of the flow cell battery system is greater
than a predetermined charged set point and when power is supplied
to the flow cell battery system. In some embodiments, the
predetermined charged set point is a state of charge greater than
80%, greater than 85%, greater than 90%, greater than 95%, or
greater than 99%. The controller may also switch the flow cell
battery system from the float state to the discharge state when
power to the flow cell battery system is disconnected and a load is
coupled to the flow cell battery system.
[0012] The flow cell battery system may also be operated in a
hibernation state. The controller switches the flow cell battery
system from the discharge state to the hibernation state when a
state of charge of the flow cell system is less than a
predetermined discharged set point and when no power is being
supplied to the flow cell battery system. In some embodiments, the
predetermined discharged set point is a state of charge less than
20%, less than 15%, less than 10%, less than 5%, or less than 1%.
The controller may also switch the flow cell battery system from a
hibernation state to a charging state when power is supplied to the
flow cell battery system. In some embodiments, the controller
switches switch the flow cell battery system from the discharge
state to the charging state when power is supplied to the flow cell
battery system during the discharge state and when a state of
charge of the flow cell battery system is less than a predetermined
charged set point.
[0013] The flow cell battery system may also be operated in a
shutdown state. The controller may switch the flow cell battery
system from any state to the shutdown state when a fault is
detected. The flow cell battery system may come out of the shutdown
state after a predetermined amount of time, if the shutdown is due
to a short circuit at the output of the flow cell battery system,
or within the flow cell battery system.
[0014] The flow cell battery system may also be operated in
initialization state. The controller switches the flow cell battery
system to the initialization state when power is supplied to the
flow cell battery system operating in the shutdown state. The
controller switches the flow cell battery system to a plating state
when the initialization state is complete.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Advantages of the present invention will become apparent to
those skilled in the art with the benefit of the following detailed
description of embodiments and upon reference to the accompanying
drawings in which:
[0016] FIG. 1 illustrates a particular example of a flow cell
battery system according to some embodiments;
[0017] FIG. 2 illustrates a flow cell battery coupled to a control
system according to some embodiments;
[0018] FIG. 3 illustrates a cabinet that houses the flow cell
battery along with temperature control systems that are coupled to
a control system according to some embodiments;
[0019] FIG. 4 illustrates an example external environment for a
flow cell battery system according to some embodiments;
[0020] FIG. 5 illustrates a controller system according to some
embodiments;
[0021] FIG. 6 illustrates a state function map for operation by a
controller system;
[0022] FIGS. 7 and 8 illustrate a communication system that can be
utilized with a flow cell battery system;
[0023] FIG. 9 illustrates a schematic of control board system
having a relay control board;
[0024] FIG. 10 depicts a schematic of an embodiment of a relay
control board
[0025] FIG. 11 depicts DAC vs. no load output voltage curve;
[0026] FIG. 12 depicts a schematic of a pump control algorithm;
and
[0027] FIG. 13 depicts a pump control correction scheme for a
rebalance cell.
[0028] While the invention may be susceptible to various
modifications and alternative forms, specific embodiments thereof
are shown by way of example in the drawings and will herein be
described in detail. The drawings may not be to scale. It should be
understood, however, that the drawings and detailed description
thereto are not intended to limit the invention to the particular
form disclosed, but to the contrary, the intention is to cover all
modifications, equivalents, and alternatives falling within the
spirit and scope of the present invention as defined by the
appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] It is to be understood the present invention is not limited
to particular devices or systems, which may, of course, vary. It is
also to be understood that the terminology used herein is for the
purpose of describing particular embodiments only, and is not
intended to be limiting. As used in this specification and the
appended claims, the singular forms "a", "an", and "the" include
singular and plural referents unless the content clearly dictates
otherwise.
[0030] FIG. 1 illustrates a redox flow cell battery system 100 that
includes a redox flow cell 202. As shown in FIG. 1, power is
received from several sources, including an external power line 152
or a generator 154 (e.g., a diesel or gas powered generator). In
general, external power line may supply energy from any source,
including a power grid or dedicated generator such as a solar,
tidal, wind, or other form of generator. AC power is received in a
rectifier 102, which is coupled to provide DC power to load 164. DC
power is provided to flow cell battery system 100 from rectifier
102 when AC power is supplied to rectifier 102. In the embodiment
shown in FIG. 1, DC power supplied to redox flow cell battery
system 100, and to load 164, is supplied between a reference bus
and a Bbus.
[0031] As shown in FIG. 1, redox flow cell battery system 100
includes a redox flow cell 202 and a rebalance cell 228. Redox flow
cell 202 provides or receives DC power through a CBus to a
buck-boost circuit 110, when switch 167 is closed. An example of
buck-boost circuit 110, is described in U.S. patent application
entitled "Buck-Boost Control Circuit", filed concurrently herewith,
which claims priority to U.S. Provisional Patent Application No.
61/182,082 entitled "Buck-Boost Control Circuit", filed May 28,
2009, both of which are incorporated herein by reference. During
charging, buck-boost circuit 110 provides charging current from
rectifier 102 to redox flow cell 202 in order to recharge redox
flow cell battery system 100. During discharge, buck-boost circuit
provides power across load 164 when no power is provided by
rectifier 102. Power is supplied or received by buck-boost circuit
110 when switch 166 is closed.
[0032] Rebalance cell 228 is coupled to redox flow cell 202 to
rebalance the electrolytes during operation. Rebalance cell 228 is
controlled by a rebalance control board 120. Some embodiments of
rebalance cell 228 and rebalance control board 120 are further
described in U.S. patent application entitled "Flow Cell
Rebalancing", filed concurrently herewith, which claims priority to
U.S. Provisional Patent Application No. 61/182,099 entitled "Flow
Cell Rebalancing", filed May 28, 2009, both of which are
incorporated herein by reference. As shown in FIG. 1, when switch
168 is closed, power can be supplied to rebalance cell 228 by
rebalance control board 120.
[0033] Electronics 130 monitors and controls operation of flow cell
battery system 100. As shown in FIG. 1, electronics 130 is coupled
to rebalance control board 120, and monitors the Bbus and the Cbus.
Electronics 130 is also coupled to control the flow of electrolytes
in redox flow cell 202. Electronics 130 gets power from either the
C-Bus or B-Bus, as shown in FIG. 1, to ensure that power is
maintained to the control electronics.
[0034] FIG. 2 illustrates a redox flow cell battery 212 that
includes redox flow cell 202 and rebalance cell 228. Redox flow
cell battery includes one or more redox flow cells 202, each cell
having a cathode side and an anode side separated by a membrane
205. The ends of the cells are defined by electrodes 256 and 258.
In redox flow cell battery 212, electrode 256 is the anode battery
terminal and electrode 258 is the cathode battery terminal.
Electrolyte for the anode is stored in tank 204, electrolyte for
the cathode is stored in tank 206, and flowed through redox flow
cell 202. Energy, therefore, is converted between chemical energy
stored in the electrolytes and electricity of redox flow cell 202.
Therefore, the charge on redox flow cell battery 212 is limited
only by the storage capacity of tanks 204 and 206. The operation of
flow cell stack and the composition of a membrane is further
described in U.S. patent application Ser. No. 12/217,059, entitled
"Redox Flow Cell," filed on Jul. 1, 2008, which is incorporated
herein by reference. Construction of a flow cell stack is described
in U.S. patent application Ser. No. 12/577,134, entitled "Common
Module Stack Component Design" filed on Oct. 9, 2009, which is
incorporated herein by reference. Tanks 204 and 206 may include
fluid level sensors to determine the level of fluid in the tanks
Example of fluid level sensors are described in U.S. patent
application Ser. No. 12/577,147, entitled "Level Sensor for
Conductive Liquids" filed on Oct. 9, 2009, which is incorporated
herein by reference. Examples of electrodes 256 and 258 are
described in U.S. patent application Ser. No. 12/576,235, entitled
"Magnetic Current Collector" filed on Oct. 8, 2009, which is
incorporated herein by reference.
[0035] As shown in FIG. 2, electrolyte from tank 206 can be pumped
by pump 218 through pipe 220 into redox flow cell 202 and returned
through pipe 248 to tank 206. Further, electrolyte from tank 204
can be pumped by pump 216 through pipe 214 into redox flow cell 202
and returned to tank 204 through pipe 268. In some embodiments,
pumps 216 and 218 may be located inside tanks 204 and 206,
respectively.
[0036] In some embodiments, during operation of flow cell stack 202
hydrogen gas is produced and electrolytes in each half-cell of
redox flow cell 202 become unbalanced. Rebalance cell 228 functions
to rebalance electrolytes. As shown in FIG. 2, rebalance cell 228
includes electrodes 232 and 236 separated by membrane 234.
Electrolyte can be transferred through pipe 222 into compartment
230 and returned through pipe 254 to tank 204. Further, compartment
238 may be partially filed with electrolyte transferred through
pipe 224 from tank 204. Further, compartment 238 may be drained
into tank 204 through pipe 252 when valve 250 is open. Valve 250
may be a pump as well in order to move fluid from compartment 238
into tank 204.
[0037] As shown in FIG. 2, the level of electrolyte 208 in
compartment 238 can be controlled utilizing lower level sensor 248
and upper level sensor 246. Because there is a loss of electrolyte
during the rebalance process in compartment 238, when the level of
fluid reaches lower level sensor 248, fluid from tank 204 may be
used to refill compartment 238 until fluid reaches upper level
sensor 246. After some number of refills, electrolyte in
compartment 238 may need to be completely replaced. In which case,
when the electrolyte level in compartment 238 reaches lower level
sensor 248 valve, 250 may be opened to allow the fluid to drain
into tank 204, or be pumped back into tank 204, and then
compartment 238 is refilled from tank 204. In some embodiments,
electrolyte may be allowed to flow through compartment 238 for a
set period of time in order to flush fluid out of compartment 238
before refilling with fresh electrolyte.
[0038] As shown in FIG. 2, hydrogen gas may be flowed into
compartment 238 from tank 206 through pipe 212. When power is
applied between electrodes 232 and 236, and compartment 238 is
partially filed with electrolyte 208, chlorine gas is produced so
that a mixture of chlorine gas and hydrogen gas accumulates above
the fluid level in compartment 238. UV light source 244 is mounted
in the gas area of compartment 238. Light from UV light source 244
facilitates the formation of HCl from the hydrogen and chlorine
gas, which is absorbed into the fluid of electrolyte 208 in
compartment 238. Hydrogen ions can pass through membrane 234 to
interact with the constituents of electrolyte 238 being flowed
through compartment 230.
[0039] Both hydrogen gas and chlorine gas are problematic in
concentration, especially in the presence of UV radiation. In order
to monitor the process, and ultimately to control the process,
sensors 240 and 242 are provided in compartment 238. Sensor 240 may
include temperature and pressure sensors. If, for example, the
temperature or pressure exceed a set threshold value, certain steps
such as shutting down redox flow cell battery 212 may be taken.
Sensor 242 measures the relative concentrations of chlorine and
hydrogen gas. The ratio of chlorine concentration to hydrogen
concentration may be kept at a particular level, for example
between one and two, in order to safely control the formation of
HCl. Some embodiments of sensor 242 are further described in U.S.
patent application entitled "Hydrogen Chloride Level Detector",
filed concurrently herewith, which claims priority to U.S.
Provisional Patent Application No. 61/182,076 entitled "Hydrogen
Chloride Level Detector", filed May 28, 2009, both of which are
incorporated herein by reference.
[0040] FIG. 3 illustrates an enclosure 312 that houses redox flow
cell 212. As shown in FIG. 3, enclosure 312 includes a lower
section 306 and an upper section 308. Lower section 306 houses
holding tanks 206 and 204. Upper section 308 houses flow cell stack
202, rebalance cell 228, control electronics 302, and all other
wiring, plumbing, valves, pumps, and other components of redox flow
cell battery 212. Redox flow cell battery 212 may be of any size,
so enclosure 312 can be of any dimensions or shape capable of
housing redox flow cell battery 212.
[0041] A redox flow cell battery efficiently operates within a
range of temperatures, for example between about 30.degree. C. and
about 50.degree. C. However, the redox flow cell battery may be in
thermal environmental conditions that vary widely over time. For
example, the redox flow cell battery may be placed in a sunny
location in a hot environment, or in the shade in a cold
environment. Nonetheless, the temperature of the electrolyte in
holding tanks 206 and 204 and the temperature of the electronics
302, redox flow cell 202, and rebalance cell 228 should be
maintained within the efficient operating range of redox flow cell
battery 212. Thermal management of redox flow cell battery 212 is
disclosed in U.S. patent application Ser. No. 12/577,127, entitled
"Thermal Control of a Flow Cell Battery" filed on Oct. 9, 2009,
which is incorporated herein by reference.
[0042] Enclosure 312 can be part of the thermal management of redox
flow cell battery 212. As shown in FIG. 3, a fluid blanket 316 is
created about holding tanks 206 and 204 in lower section 306.
Further, a fluid blanket 318 exists about flow cell stack 202,
electronics 302, and rebalance cell 228 in upper portion 308. Fluid
blanket 316 and fluid blanket 318 may be air blankets, which are
utilized to thermally control the temperatures. In some
embodiments, however, fluid blanket 316 or fluid blank 318 may be
water, oil, or other fluid that can be utilized to thermally
regulate the interior of enclosure 312.
[0043] Temperature sensors 320 and 322 can be utilized to monitor
the temperature of electrolyte in tanks 206 and 204. A temperature
sensor 324 can be utilized to monitor the temperature of upper
portion 308. Further, a temperature sensor 326 can be utilized to
monitor ambient temperature. Control electronics 302, receiving
temperature readings from temperature sensors 320, 322, 324, and
326, can then control fans, blowers, or fluid pumps and heaters in
order to control the operating temperature of battery 112. For
example, in FIG. 3 blowers 330 and 328 can control air flow in
blanket 316. Fans 332 and 334 can control the air flow of blanket
318.
[0044] FIG. 4 illustrates example inputs and outputs to some
embodiments of redox flow cell battery system 100 disposed in an
enclosure 312. As shown in FIG. 4, DC power is received by flow
cell battery system 100 from rectifier 102. A user display panel
410 can include indicators 412 and a digital display 414 for
communicating the status of redox flow cell battery system 100 to a
user. Additionally, a user display panel 416 may include an input
panel 416 to receive input commands from a user. Such input
commands can include a power-up command, shut-down command, and
various requests for information, the results of which may be
displayed on indicators 412 or display 414. An interface 420 may be
provided to communicate with flow cell battery system 100 with an
external device. Interface 420 may also be coupled to allow flow
cell battery system 100 to communicate over the internet, or phone,
either wired or wirelessly, with monitoring and control systems
separated from flow cell battery system 100.
[0045] FIG. 5 shows an embodiment of electronics 160. Electronics
160 includes the control systems that control all aspects of system
100. As shown in FIG. 5, electronics 160 includes a system
controller 510. System controller 510 includes one or more
processors 512, volatile and non-volatile memory 514, and signal
processors 516 that receives and processes various input signals
and drives output signals.
[0046] As shown in FIG. 5, controller 510 receives the voltage and
current on the Bbus in sensors 532 and 534, respectively.
Additionally, the voltage and current of flow to or from cell stack
202 is provided in sensors 536 and 538, respectively. Leaks
detector inputs 540, 542, and 544 provide information regarding
fluid leaks in redox flow cell battery system 100. Embodiments of
leak detectors that, for example, can distinguish electrolyte leaks
are further described in U.S. patent application entitled "Optical
Leak Detection Sensor", filed concurrently herewith, which claims
priority to U.S. Provisional Patent Application No. 61/182,077
entitled "Optical Leak Detection Sensor", filed May 28, 2009, both
of which are incorporated herein by reference. Leak sensors may be
placed in various portions of cabinet 312, and may be provided in
pumps 216 and 218. Controller 510 also receives signals from
temperature sensors 546, 548, 550, 552, 554, 556, and 558, for
example, which are temperature sensors at various locations
throughout the system. Further, signals may be received from
pressure sensor 558.
[0047] Signals are also received from electrolyte pumps 216 and
218. For example, as shown in FIG. 5, the rpm of each pump and the
current drawn from each pump is received. Controller 510 provides a
signal to each pump to control the rpm, which in turn controls how
fast electrolyte is pumped.
[0048] Controller 510 also receives and provides signals to various
fans and blowers 560 in order to provide thermal control of flow
cell battery system 100. Use of temperature sensors 546 through 556
and fans and blowers 560 in order to thermally manage flow cell
battery system 100 is further disclosed in U.S. patent application
Ser. No. 12/577,127, entitled "Thermal Control of a Flow Cell
Battery" filed on Oct. 9, 2009, which is incorporated herein by
reference.
[0049] Level sensor 562 provides information regarding the level of
electrolyte and the condition of electrolyte stored in tanks 204
and 206. Embodiments of level sensors that can be utilized for
level sensors 562 are described in U.S. patent application Ser. No.
12/577,147, entitled "Level Sensor for Conductive Liquids" filed on
Oct. 9, 2009, which is incorporated herein by reference.
[0050] System voltage monitoring 564 provides controller 510 with
signals related to the voltages supplied to control circuitry.
These voltages include, for example, the 5V, 10V, 15V, and 3.3V
supplies.
[0051] In some embodiments, controller 510 can monitor rebalance
cell 228. In which case, controller 510 receives signals from the
rebalance cell system voltage monitors 566, the rebalance cell
thermisters 568 in sensors 240, which monitor temperature at
various locations in rebalance cell 228, the rebalance cell LED
570, rebalance cell level switches 572, rebalance cell voltage
supplied across electrodes 232 and 236 (574), rebalance cell
current between electrodes 232 and 236 (576), and provides controls
for rebalance cell valves 226 and 250 (578). Rebalance cell 228,
and rebalance control board 120, are further disclosed in U.S.
patent application entitled "Flow Cell Rebalancing", filed
concurrently herewith, which claims priority to U.S. Provisional
Patent Application No. 61/182,099 entitled "Flow Cell Rebalancing",
filed May 28, 2009, both of which are incorporated herein by
reference.
[0052] In some embodiments, controller 510 can communicate to
devices through a device interface 530, which may be an I2C
interface. For example, controller 510 may communicate with
rebalance control board 120 and buck-boost 110 through the I2C
interface. Further, controller 510 may communicate with a global
monitoring system 520 through a communication device 580, which may
be wireless or may be directly coupled to a network.
[0053] FIG. 6 illustrates a state diagram that can be executed on
controller 510 for operation of flow cell battery system 100. As
shown in FIG. 6, state machine 600 starts in initialization state
602. Controller 510 transitions to a system initialization state
602 when a main switch, switch 166, is turned on or after a
predetermined period of time has passed after a short condition is
experienced. In some embodiments, switch 168 is closed along with
switch 166. In initialization state 602, load 164 is available and
flow cell battery system 100 is powered on. Further, software
parameters are initialized. Once initialization step 602 is
complete, controller 510 transitions to plating step 603.
[0054] During plating state 603, power is applied across electrodes
256 and 258 of flow stack 202 (shown in FIG. 2) in order to provide
plating of the electrodes using a plating metal added to the
electrolytes for the electrodes in flow stack 202 (e.g., bismuth
metal). In some embodiments, a small current at a nominal voltage
is provided across electrodes 256 and 258. When the current drops
below a current threshold value or the voltage increases above a
voltage threshold value, plating is completed. For example, in some
embodiments the plating voltage is set at 18.5 V with a current of
8 amps. Plating is completed if the current crops below 4 amps or
the voltage increases about 18.5 volts. Once plating is completed,
controller 510 transitions to charging state 604.
[0055] In some embodiments, especially when a new flow cell battery
112 is placed in service, a small amount of plating metal is added
to electrolytes 208 and 210 and is plated onto the electrodes of
flow cell stack 202 during plating state 603. When flow cell stack
202 has been plated, in some embodiments plating state 603 can be
bypassed. In some embodiments, plating state 603 operates on each
transition from initialization state 602. Plating is done at low
voltage and low current. In order that plating state 603 completes,
even with systems that have already been plated, controller 510 is
capable of detecting completion in order to transition to charging
state 604.
[0056] Several states of state machine 600 transition to shutdown
state 601 upon detection of a fault. Fault conditions include, for
example, detection of a leak, detection of a high temperature
situation, detection of a pump problem, detection of a power supply
failure for powering electronics, and detection of a low
electrolyte level. Other fault conditions may also be detected.
Controller 510 transitions from plating state 603 to shutdown state
601 upon detection of a fault or if a buck state in buck-boost 110
is not enabled. In shutdown state 601, all pumps are off and all
buck-boosts are off. Sensor monitoring is on and controller 510 may
be sampling data. Further, a genset request may be on. Essentially,
flow cell battery system 100 is off. Switches 166 as shown in FIG.
1, may be open, isolating flow cell battery system 100 from load
164, as shown in FIG. 1.
[0057] If shutdown state 601 was transitioned to due to the
presence of a short at the load or at the Bbus, controller 510 is
configured to transition the system to the initialization state
after a predetermined time. This sequence is guided by a short
circuit latch release algorithm. The Power good signal from the
Buck boost board is tied to the interrupt line INT1 When the
interrupt occurs the system should generate a Bbuss fault and
should go into shutdown state Initially INT1 should be configured
to trigger on the falling edge. When the interrupt occurs this
signifies that there is a short on the Bbus. This error is
reported. Interrupt routines set a flag to shutdown the system. The
interrupt should be reconfigured to get an interrupt on the rising
edge. When the interrupt occurs on the rising edge reset the error
code. Send a 200 msec wide latch release signal and restart the
state machine from the Initial state. Blank the Error checking for
the next 1 sec.
[0058] As suggested, during charging state 604 flow cell battery
112 is charged. Generally, charging involves supplying a current
between terminals 256 and 258 while flowing electrolytes through
flow cell stack 202 in order to restore the charged chemical state
of electrolytes 208 and 210. Charging electrolytes 208 and 210 is
generally discussed in U.S. application Ser. No. 12/074,110, filed
on Feb. 28, 2008, which is incorporated herein by reference.
[0059] During charge state 604, power is supplied from either
generator 154 or power source 152 through rectifier 102. In some
embodiments, voltage on the Bbus when rectifier 102 is active can
be about 54 V. Buck-boost circuit 110 is on in buck mode and
provides power to C-bus, which is utilized to charge flow cell
stack 202. Pump controls are active to control pumps 216 and 218,
the level sensors are active to monitor electrolyte levels in tanks
206 and 204, state-of-charge monitoring is active, and thermal
control is on.
[0060] FIG. 12 depicts a pumping control algorithm.
[0061] 1. Stoichiometric Flow Rate ("SFR") based control voltage
calculation
In DISCHARGING, SFR=3*(I*NumCells)/(C*SOC*1608) a.
In CHARGING, SFR=3*(I*NumCells)/(C*(1-SOC)*1608) b.
[0062] where C is concentration of electrolyte.
[0063] 2. Compensation for Tank level difference
Compute level tolerance=ABS(L1-L2)/2*H a.
[0064] L1 and L2 level of electrolyte form the bottom of the tank,
where L1 is the right side of the tank, L2 is the left side of the
tank, and H is the total height of the tank.
Compute compensation
voltage(Vdelta)=PUMP_GAIN*tolerance*tolerance*Vmin. b.
[0065] 3. Compute pump control voltage
PumpVf=Vmin
PumpVc=Vmin+Vdelta
[0066] An algorithm for computing the pump control correction for
the rebalance flow cell is set forth below with reference to FIG.
13. In the following equations: Qf is the flow rate through the Fe
side of the redox flow cell; Qc is the flow rate through the Cr
side of the redox flow cell; Qr is the flow through the rebalance
cell; Vf is the pump control voltage for the pump on the Fe side of
the redox flow cell; Vc is the pump control voltage for the pump on
the Cr side of the redox flow cell; Pf is the pressure of the Fe
side of the redox flow cell; Pc is the pressure of the Cr side of
the redox flow cell and k, .alpha., .beta. are constants.
Correction control may be determined as follows [0067] If Qf=k*Vf,
Qc=k*Vc and Qr=.alpha.*Vf
[0067] Q'=Qf-Qr
Q'=(k-.alpha.)*Vf [0068] If Pf=.beta.*Q' and Pc=.beta.*Qc
[0068] Pf=.beta.*(k-.alpha.)*Vf
Pc=.beta.*k*Vc [0069] If Pf=Pc
[0069] .beta.*(k-.alpha.)*Vf=.beta.*k*Vc
Vf=k/(k-.alpha.)*Vc [0070] Thus, If Qc is 15 L/min and Qr is 1.5
L/min, the base voltage to start pump control is:
[0070] Vf=1.1 Vc
[0071] Further, the state of charge ("SOC") of electrolytes 208 and
210 are monitored and reported during the charging process.
Descriptions of measurements of the state of charge are provided in
U.S. patent application Ser. No. 11/674,101, filed on Feb. 12,
2007, which is herein incorporated by reference. During charging,
thermal monitoring and control is accomplished, for example as U.S.
patent application Ser. No. 12/577,127, entitled "Thermal Control
of a Flow Cell Battery" filed on Oct. 9, 2009, which is
incorporated herein by reference.
[0072] In some embodiments, a particular voltage and current are
applied across electrodes 256 and 258 in order to charge
electrolytes 208 and 210. Applying power to electrodes 256 and 258
while electrolytes flow through the flow cell battery brings at
least a portion of the electrolytes from a discharged chemical
state to a charged chemical state. In some embodiments, charging
may stop at a predetermined charged set point. For example,
charging may be stopped when the SOC reaches substantially 100%. In
other embodiments, the predetermined charged set point is reached
when an SOC is greater than 80%, greater than 85%, greater than
90%, greater than 95%, or greater than 99%. If, at that time, power
from power source 152 is still available, controller 510
transitions to a float state 605. In some embodiments, for example,
charging may occur at a voltage across electrodes 256 and 258 of
about 30 volts and a current through flow cell stack 202 of about
100 amps, although more complicated charging algorithms can be
employed by controller 510.
[0073] An alternate charging algorithm is designed to reach the
target charged current quickly. The algorithm includes:
[0074] 1. Read the Cbus voltage (Vcell).
[0075] 2. If the ESR Value of the Cell is know use it, otherwise
assume a nominal value of 27 mOhms.
[0076] 3. The Vcharge=Vcell+Icharge*ESR. In the above equation
Icharge is the charge current required.
[0077] 4. From the calibration curves for each of the units use the
equation for the DAC voltage VS. Vcharge. (Sample curve and
equation is depicted in FIG. 11, DACvalue=-0.0792x+2.9822. x is the
desired Vcharge voltage.
[0078] 5. Apply the DAC voltage and wait for the system to
settle.
[0079] If a fault is detected during the charge process that occurs
in charge state 604, controller 510 transitions to shutdown state
601 to shut system 100 down. Otherwise, once a SOC of about 100% is
achieved, controller 510 transitions to float state 605 if buck is
still enabled. Controller 510 transitions from charge state 604 to
discharge state 606 if buck-boost 110 switches from buck to boost,
indicating that power is no longer being received from rectifier
102.
[0080] During float state 605, buck is enabled and provides an
output voltage at a particular value. In some embodiments, the
value is about 25 Volts. During this state, flow cell battery 112
is standing by and ready to provide power to load 164 should power
at rectifier 102 be reduced. During the float state, pump control
is on and pumps 216 and 218 may be run to provide a small flow of
electrolyte through flow cell stack 202. Further, in some
embodiments, power utilized for providing voltage on buck-boost 110
and for running pumps and other system may be supplied by charging
rectifier 102 instead of drawing on the charged electrolyte of
battery 112. Further, monitoring of the SOC can be turned off.
Again, if a fault is detected, controller 510 transitions to shut
down state 601.
[0081] If power to rectifier 102 fails, then controller 510
transitions from float state 605 to discharge state 606. Controller
510 can also transition from charge state 604 to discharge state
606 before SOC is about 100% if the signal En_Buck indicates that
power to rectifier 102 has been interrupted. In discharge state
606, power from flow cell battery 112 is supplied to load 164. In
that case, pumps 216 and 218 are activated and controlled, buck
boost 110 is in boost mode, electrolyte levels in tanks 208 and 210
are monitored, and the SOC is monitored and reported. In some
embodiments, the Bbus voltage can be held at about 50 V. Once the
SOC drops below a certain value, for example 10%, or available
power on the Cbus drops, for example below about 20 V, which
indicates that flow cell battery 112 is in a substantially
discharged state, then controller 510 can transition from discharge
state 606 to a hibernation state 607. If, during discharge, a fault
is detected, then controller 510 can transition from discharge
state 606 to shutdown state 601. Further, if power, for example
from power source 152 or from generator 154, is supplied to
rectifier 102 then controller 510 can transition from discharge
state 606 back to charge state 604, buck-boost 110 switches from
boost mode to buck mode, so that flow cell battery 112 can be
recharged.
[0082] Controller 510 transitions into hibernate state 607 from
discharge state 606 when flow cell battery 112 is reaches a
predetermined discharged set point. For example, flow cell battery
may be transitioned to a hibernation state when the SOC is less
than 10%. In other embodiments, the predetermined discharged set
point is reached when an SOC is less than 20%, less than 15%, less
than 10%, less than 5%, or less than 2%. In hibernate state 607,
pumps 216 and 218 are off and buck boost 110 is turned off.
Controller 510 monitors flow cell battery system 100 until the
charge on flow cell stack 202 is depleted. Controller 510 can
transitioned out of hibernate state 607 if power returns to
rectifier 102, in which case controller 510 transitions to charge
state 604 to recharge flow cell battery 112. Controller 510 can
also transition from hibernate state 607 to shutdown state 701 if a
fault condition is detected.
[0083] Controller 510 can transition from hibernate state 607 to
charge state 604 if power appears on the Bbus. In some embodiments,
generator 154 may be activated in discharge state 606 if SOC is
reduced below a threshold level. In some embodiments, generator 154
may be activated in hibernate state 607. In some embodiments,
controller can transition the system from the hibernation state to
the plating state (not shown).
[0084] In handling any fault state that occurs throughout state
machine 700, the first fault can be latched for later review and
state machine 600 transitions to shutdown state 601. In some cases,
multiple cascading fault conditions result from the initial fault
condition, so capturing the first fault condition can help a
servicer to determine what caused the system to go to shutdown
mode.
[0085] As shown in FIG. 5, controller 510 is coupled to
communication device 520. FIG. 7 illustrates a networking
environment 800 for flow cell battery systems 100. As shown in FIG.
7, any number of flow cell battery systems 100, systems 100-1
through 100-N are shown, can be networked to a server 808. As
illustrated in FIG. 5, each system 100-1 through 100-N includes a
corresponding communication device 520-1 through 520-N, coupled to
a corresponding controller 510-1 through 510-N. In some
embodiments, communications devices 520-1 through 520-N can be
coupled to communication devices 802-1 through 802-N, respectively.
Communication devices 802-1 through 802-N can be coupled to
transmit and receive data with a server 808. FIG. 7 shows
communication devices 802-1 through 802-N coupled to wireless
transceivers 804-1 through 804-N, but any networking connection may
be utilized. For example, transceivers 804-1 through 804-N may be
wired connections, internet connections, or any other connection
for transmitting data.
[0086] Data is received by a server 808 coupled through
communication devices 812-1 through 812-N and transceivers 806-1
through 806-N, respectively. Server 808 can receive data from
systems 100-1 through 100-N and can transmit data and instructions
to systems 100-1 through 100-N. A computer 810 coupled to server
808 can provide a user interface, through which individual ones of
systems 100-1 through 100-N can be monitored and controlled.
[0087] FIG. 8 further illustrates system 800. As shown in FIG. 8,
system 100 includes control electronics, which includes a
controller and communications device. As discussed above, the
controller monitors various aspects of system 100, and especially
the flow cell battery, and provides operating information,
including fault information, for transmission to server 808. Server
808 receives information from system 100 through transceivers. As
shown in block 822, the data received from system 100 may be
processed and stored. As is further shown, server 808 may include a
tracking system 824 and a performance system 826 and tracks the
performance of system 100 over time. Further, a user 810 coupled to
server 808 (see FIG. 7) can be alerted to alarms, can initiate
software updates, and otherwise may monitor and control system 100.
In some embodiments, system 100 communicates with server 808
utilizing any communication scheme, for example SMS messaging. In
some embodiments, data encryption may be utilized. In some
embodiments, system 100 may utilized a particular phone number for
reporting of alarms resulting from faults. In some embodiments, a
SMS message length is typically 256 bytes. For example, 40 bytes
may be utilized for sending data related to analog inputs to DAS
520. Binary fault flags can be sent in further bytes of the SMS
message. Monitored parameters may include, for example, the leak
detectors, temperature, voltage and current from flow cell battery
112, voltage and current across load, pump currents and rotational
frequencies, hour meters, availability of power source and/or
generator. Any of this data may be stored in databases, for example
in a spreadsheet, in server 808.
[0088] Server 808 may perform alarm processing, status reports,
software updates, phone number updates, and other functions. Alarm
processing can include processing, authentication, recordation,
transmission of alarm message to critical personal, acknowledging
the alarm to system 100, and providing an estimated time for
service to system 100.
[0089] The time to service is the amount of time estimated for
service personnel to arrive and repair the problem that resulted in
the alarm. In some embodiments, system 100 may ignore the alarm
once the time to service is received, provided the alarm is not the
result of a critical functionality. In some embodiments, if the
time of service is not received system 100 can continue to provide
the alarm at subsequent intervals until a time of service is
provided.
[0090] In some embodiments, server 808 may submit a status request
to a system 100. In response, system 100 may process the status
request and provide the requested data, in addition to its
reporting functions. In some embodiments, messages to and from
system 100 can be encrypted. In some embodiments, server 808 may
also maintain service functions such as client billings, client
reports, and other functions.
[0091] An example of a relay control board that may be used with a
controller system 130 as disclosed herein is depicted schematically
in FIG. 9. In an embodiment, it is desired to operate a normally
off mechanical relay to isolate the output of our 48V DC B-Bus from
powering the external load in BTS in the event of any faults such
as a short circuited B-Bus output or if there is any under voltage
at the Boost converter output which will affect the functioning of
customer side BTS power supply. As shown in FIG. 9, the customer
side power supply 910 is also connected to the B-Bus. If there is
short circuit or under voltage of less than 30V DC at BTS on
account of any fault in the customer's power supply, the controller
is designed so that the relay contacts will open and isolate the
Boost output. An indication that there is a fault at their side of
the power supply may be displayed.
[0092] The relay control board 920 includes an electronic control
board and an electromechanical relay. Relay control board 920 may
be mounted on the main control board 930 and the electromechanical
relay is mounted on the bus bar which connects the B-Bus to the
customer side BTS. A cut may be provided in the bus bar to mount
the contacts of the mechanical relay so that if a fault, such as an
output short circuit or output under voltage occurs in the output
of the Boost converter of the Buck/Boost regulator, the contacts of
the mechanical relay will open up and isolate the Buck/Boost from
the BTS.
[0093] When the Buck/Boost converter turns on, a nominal 48V, in
one embodiment, will be available at the output of the Boost
converter. The same 48V from the Buck/Boost would also be available
in the Control Board. This B-Bus voltage is sensed by the relay
control board and will turn on the mechanical relay whose N/O
contacts will close and connect the Boost output to the BTS.
[0094] If there is any short circuit at the output of the Boost
converter or if the output of the Boost converter goes down to
30V+/-2V (in certain embodiments where the nominal is 48V), the
fault will be sensed by the Relay Control board and switch off the
relay, its contacts will open; thus isolating the Boost converter
output from the BTS. On the other hand, when the output voltage of
the Boost recovers to 40V+/-2V DC the relay will be energized by
the Relay Control board and its contacts will close thus allowing
the Boost converter output to be connected back to the BTS.
[0095] FIG. 10 depicts a schematic of an embodiment of a relay
control board. The relay Control Board depicted in FIG. 10 requires
a 12V DC, however this voltage is coming from the 24V C-Bus, rather
than using the 12V from the 12V regulator in the Control Board. 5V
DC voltage taken from the 5V regulator in the Control Board is
connected to the Relay Control Board to provide a reference voltage
the comparator circuit. The mechanical relay has 12V DC coil
voltage but may use a 24V DC relay. A regulator U2 is used to
convert 24V to 12V for this purpose.
[0096] In this patent, certain U.S. patents, U.S. patent
applications, and other materials (e.g., articles) have been
incorporated by reference. The text of such U.S. patents, U.S.
patent applications, and other materials is, however, only
incorporated by reference to the extent that no conflict exists
between such text and the other statements and drawings set forth
herein. In the event of such conflict, then any such conflicting
text in such incorporated by reference U.S. patents, U.S. patent
applications, and other materials is specifically not incorporated
by reference in this patent.
[0097] Further modifications and alternative embodiments of various
aspects of the invention will be apparent to those skilled in the
art in view of this description. Accordingly, this description is
to be construed as illustrative only and is for the purpose of
teaching those skilled in the art the general manner of carrying
out the invention. It is to be understood that the forms of the
invention shown and described herein are to be taken as examples of
embodiments. Elements and materials may be substituted for those
illustrated and described herein, parts and processes may be
reversed, and certain features of the invention may be utilized
independently, all as would be apparent to one skilled in the art
after having the benefit of this description of the invention.
Changes may be made in the elements described herein without
departing from the spirit and scope of the invention as described
in the following claims.
* * * * *