U.S. patent application number 10/977017 was filed with the patent office on 2005-06-09 for electrochemical cell cooling system.
This patent application is currently assigned to GREENLIGHT POWER TECHNOLOGIES, INC.. Invention is credited to Lamont, Gordon John, Martin, Benjamin William, Piotrowski, Jacek.
Application Number | 20050120731 10/977017 |
Document ID | / |
Family ID | 34549517 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050120731 |
Kind Code |
A1 |
Lamont, Gordon John ; et
al. |
June 9, 2005 |
Electrochemical cell cooling system
Abstract
An electrochemical cell cooling system includes a closed loop
for circulating coolant through an electrochemical cell. The loop
includes a pump for pumping the coolant from a container through a
filter and a heat exchanger. Pressure in the container and loop is
selectively adjusted upwardly for a positive pressure condition or
downwardly for a negative pressure condition using a
pressure-adjusting flow line. The flow line includes a venturi in
fluid communication with the container and a shut-off valve
downstream of the venturi which is opened to induce
depressurization of the loop or closed to cause pressurization. A
variable-flow valve upstream of the venturi enables fine adjustment
of the pressurization or depressurization. Alternatively, a
flow-restricted bypass and a second variable-flow valve can be
introduced to facilitate coolant temperature control.
Inventors: |
Lamont, Gordon John; (New
Westminster, CA) ; Martin, Benjamin William; (North
Vancouver, CA) ; Piotrowski, Jacek; (North Saanich,
CA) |
Correspondence
Address: |
OGILVY RENAULT
1981 MCGILL COLLEGE AVENUE
SUITE 1600
MONTREAL
QC
H3A2Y3
CA
|
Assignee: |
GREENLIGHT POWER TECHNOLOGIES,
INC.
Mississauga
CA
|
Family ID: |
34549517 |
Appl. No.: |
10/977017 |
Filed: |
November 1, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60516285 |
Nov 3, 2003 |
|
|
|
Current U.S.
Class: |
62/259.2 ;
62/268 |
Current CPC
Class: |
H01M 8/04029 20130101;
H01M 8/04089 20130101; Y02E 60/50 20130101 |
Class at
Publication: |
062/259.2 ;
062/268 |
International
Class: |
F25D 023/12; F25B
019/00 |
Claims
I/We claim:
1. A system for cooling an electrochemical cell, the system
comprising: a) a coolant circulation loop for supplying a coolant
to an electrochemical cell for absorbing heat from the cell, the
coolant circulation loop having: a coolant container; a pump for
circulating the coolant through the coolant circulation loop; and a
heat exchanging portion for cooling the coolant; and b) a
pressure-adjusting flow line having a pressure-adjustment device in
fluid communication with the coolant container for selectively
increasing or decreasing fluid pressure in the container thereby
selectively enabling either positive-pressure cooling or
negative-pressure cooling of the electrochemical cell.
2. The system as claimed in claim 1 wherein the pressure adjustment
device is a venturi.
3. The system as claimed in claim 2 wherein the pressure-adjusting
flow line further comprises a valve disposed downstream of the
venturi, the valve being operable between an open position, in
which fluid exhausts to atmosphere through the venturi, thus
inducing a depressurization in the coolant container, and a closed
position, in which fluid is forced to vent through a bottom port of
the venturi into the coolant container, thus causing a
pressurization of the coolant container.
4. The system as claimed in claim 3 wherein the pressure-adjusting
flow line further comprises a shut-off valve disposed downstream of
the venturi and operable between an open position permitting fluid
to exhaust to atmosphere, thus inducing a depressurization of the
coolant container, and a closed position, wherein fluid is forced
to vent into the container, thus causing a pressurization of the
coolant container.
5. The system as claimed in claim 4 wherein the shut-off valve is a
solenoid valve.
6. The system as claimed in claim 4 wherein the pressure-adjusting
flow line further comprises a variable-flow valve disposed upstream
of the venturi and operable to variably throttle the fluid flow
passing through the flow line, thereby finely adjusting the
pressurization or depressurization of the coolant container.
7. The system as claimed in claim 6 wherein the pressure-adjusting
flow line further comprises a fluid supply exhausting to atmosphere
through the variable valve, pressure-adjustment device and shut-off
valve.
8. The system as claimed in claim 7 wherein the fluid flowing in
the pressure-adjusting flow line is an inert gas.
9. The system as claimed in claim 8 wherein the inert gas is
nitrogen.
10. The system as claimed in claim 1 wherein the heat exchanging
portion is a heat exchanger.
11. The system as claimed in claim 9 wherein the coolant
circulation loop further comprises a filter.
12. The system as claimed in claim 1 wherein the coolant
circulation loop further comprises a bypass line that bypasses the
electrochemical cell from a bypass point upstream of the
electrochemical cell, thus dividing the coolant circulation loop
into an inner bypass loop and an outer loop.
13. The system as claimed in claim 12 wherein the bypass line
comprises a flow constriction.
14. The system as claimed in claim 13 wherein the outer loop
comprises a second variable-flow valve disposed between the bypass
point and the electrochemical cell.
15. A method of cooling an electrochemical cell, the method
comprising the steps of: circulating a coolant through a loop that
includes the electrochemical cell and a coolant container; flowing
a fluid through a pressure-adjusting flow path in fluid
communication with the container for selectively increasing or
decreasing pressure in the container and thus in the loop.
16. The method as claimed in claim 15 wherein the step of flowing
the fluid through the pressure-adjusting flow path comprises the
step of flowing the fluid through a venturi.
17. The method as claimed in claim 16 further comprising the step
of selectively operating a shut-off valve downstream of the
venturi, whereby the valve is operated between an open position
permitting fluid to exhaust to atmosphere, thus inducing a
depressurization of the coolant container, and a closed position,
wherein fluid is forced to vent into the container, thus causing a
pressurization of the coolant container.
18. The method as claimed in claim 17 further comprising the step
of variably adjusting a variable-flow valve disposed upstream of
the venturi, thereby finely adjusting the pressurization or
depressurization of the coolant container.
19. The method as claimed in claim 18 further comprising the step
of partially bypassing the electrochemical cell whereby a portion
of the coolant flows through a bypass while a remainder of the
coolant flows through the electrochemical cell.
20. The method as claimed in claim 19 wherein the step of partially
bypassing the electrochemical cell comprises the step of
constricting coolant flow through the bypass.
21. The method as claimed in claim 20 wherein the step of partially
bypassing the electrochemical cell further comprises the step of
throttling coolant flow with a variable-flow valve disposed between
a bypass point and the electrochemical cell.
22. The method as claimed in claim 21 further comprising the step
of filtering the coolant.
23. A system for cooling an electrochemical cell, the system
comprising: a) a coolant circulation loop for supplying a coolant
to an electrochemical cell for absorbing heat from the cell, the
coolant circulation loop having: a coolant container; a pump for
circulating the coolant through the coolant circulation loop; and a
heat exchanger for cooling the coolant; and b) a pressure-adjusting
flow line having: a venturi in fluid communication with the coolant
container for selectively increasing or decreasing fluid pressure
in the container; and a valve downstream of the venturi, the valve
adapted to be opened to depressurize the coolant circulation loop
or to be closed to pressurize the coolant circulation loop.
24. The system as claimed in claim 23 wherein the
pressure-adjusting flow line further comprises a variable valve
disposed upstream of the venturi to vary a flow rate of fluid
through the venturi.
25. The system as claimed in claim 24 further comprising a pressure
controller for controlling the variable valve in response to a
pressure feedback signal from a pressure transducer in the coolant
circulation loop.
26. The system as claimed in claim 24 further comprising a
temperature controller for controlling a cooling rate of the heat
exchanger in response to a temperature feedback signal from a
temperature sensor in the coolant circulation loop.
27. The system as claimed in claim 25 further comprising a
temperature controller for controlling a cooling rate of the heat
exchanger in response to a temperature feedback signal from a
temperature sensor in the coolant circulation loop.
28. The system as claimed in claim 27 wherein the pressure
controller and temperature controller are both PID controllers
adapted to receive pressure and temperature setpoints,
respectively, for comparison with the pressure and temperature
feedback signals, respectively.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Patent Application Ser. No. 60/516,285 filed Nov. 3, 2003.
FIELD OF THE INVENTION
[0002] The present invention relates generally to an
electrochemical cell system and, more particularly, to a cooling
system for an electrochemical cell system.
BACKGROUND OF THE INVENTION
[0003] A fuel cell is an electrochemical device that produces an
electromotive force by bringing the fuel (typically hydrogen) and
an oxidant (typically air) into contact with two suitable
electrodes and an electrolyte. A fuel, such as hydrogen gas, for
example, is introduced at a first electrode where it reacts
electrochemically in the presence of the electrolyte to produce
electrons and cations in the first electrode. The electrons are
circulated from the first electrode to a second electrode through
an electrical circuit connected between the electrodes. Cations
pass through the electrolyte to the second electrode.
Simultaneously, an oxidant, such as oxygen or air is introduced to
the second electrode where the oxidant reacts electrochemically in
the presence of the electrolyte and a catalyst, producing anions
and consuming the electrons circulated through the electrical
circuit. The cations are consumed at the second electrode. The
anions formed at the second electrode or cathode react with the
cations to form a reaction product. The first electrode or anode
may alternatively be referred to as a fuel or oxidizing electrode,
and the second electrode may alternatively be referred to as an
oxidant or reducing electrode. The half-cell reactions at the first
and second electrodes respectively are:
H.sub.2.fwdarw.2H.sup.++2e.sup.- (1)
1/2O.sub.2+2H.sup.++2e.sup.-.fwdarw.H.sub.2O (2)
[0004] The external electrical circuit withdraws electrical current
and thus receives electrical power from the fuel cell. The overall
fuel cell reaction produces electrical energy as shown by the sum
of the separate half-cell reactions shown in equations 1 and 2.
Water and heat are typical by-products of the reaction.
[0005] In practice, fuel cells are not operated as single units.
Rather, fuel cells are connected in series, either stacked one on
top of the other or placed side by side. The series of fuel cells,
referred to as a fuel cell stack, is normally enclosed in a
housing. The fuel and oxidant are directed through manifolds in the
housing to the electrodes. The fuel cell is cooled by either the
reactants or a cooling medium. The fuel cell stack also comprises
current collectors, cell-to-cell seals and insulation while the
required piping and instrumentation are provided external to the
fuel cell stack.
[0006] As fuel cell reactions are exothermic, heat generated within
the fuel cell stack has to be dissipated to ensure that the fuel
cells operate within an optimal temperature range. One of the
commonly used methods of cooling a fuel cell stack is providing
coolant flow passages within the fuel cells stack having a coolant
inlet and a coolant outlet, and running liquid coolant through the
fuel cell stack. A coolant circulation loop is typically provided,
which includes a circulation pump and a heat exchanger. The
circulation pump supplies the coolant to the coolant inlet of the
fuel cell stack and draws the coolant from the coolant outlet. The
coolant absorbs heat generated in the fuel cell stack, as the
coolant flows through the fuel cell stack. Outside the fuel cell
stack, the coolant temperature is readjusted by a heat exchanger to
within a predetermined temperature range. Depending on the system
configuration and operation conditions, the coolant may be cooled
or heated. Typical coolant includes deionized water, pure water,
any non-conductive water, ethylene glycol, or a mixture
thereof.
[0007] The coolant in the coolant circulation loop is usually
pumped into the fuel cell stack. Hence, the fuel cell stack is
usually referred to as operating under positive pressure of
coolant. Alternatively, the circulation pump may be disposed
downstream of the fuel cell stack and draws coolant therefrom. In
this case, the fuel cell stack is referred to as operating under
negative pressure of coolant. A fuel cell cooling system that can
operate under both positive and negative pressure conditions was
disclosed in U.S. patent application Ser. No. 10/184,104. However,
the fuel cell cooling system uses two coolant circulation loops,
two circulation pumps and various control valves. The system
configuration is complex, which results in high parasitic load and
low system efficiency.
[0008] There remains a need for a simplified cooling system that
can provide an electrochemical cell with both positive and negative
coolant pressure conditions in an efficient manner.
SUMMARY OF THE INVENTION
[0009] It is therefore an object of the invention to provide a
simplified cooling system that can provide an electrochemical cell
with both positive and negative coolant pressure conditions in an
efficient manner.
[0010] The invention therefore provides a system for cooling an
electrochemical cell, the system including a coolant circulation
loop for supplying a coolant to an electrochemical cell for
absorbing heat from the cell. The coolant circulation loop has a
coolant container; a pump for circulating the coolant through the
coolant circulation loop; and a heat exchanging portion for cooling
the coolant. The system also includes a pressure-adjusting flow
line having a pressure-adjustment device in fluid communication
with the coolant container for selectively increasing or decreasing
fluid pressure in the container thereby selectively enabling either
positive-pressure cooling or negative-pressure cooling of the
electrochemical cell.
[0011] In one embodiment, the flow line includes a venturi in fluid
communication with the container and a shut-off valve downstream of
the venturi for selectively pressurizing or depressurizing the
container and loop. When the shut-off valve is open, the fluid
flows through an inlet and outlet of the venturi and exhausts to
atmosphere, causing the venturi to induce a negative pressure
condition in the container and loop. When the shut-off valve is
closed, the fluid is forced to flow through a bottom port of the
venturi into the container, thus causing a positive pressure
condition in the loop. As a refinement, a variable-flow valve can
be provided upstream of the venturi to regulate the fluid pressure
in the flow line, thus enabling fine adjustment of the
pressurization or depressurization of the container and loop. As a
further refinement, a bypass with a flow constriction can be
provided to facilitate coolant temperature control.
[0012] The invention further provides a method of cooling an
electrochemical cell. The method includes the step of circulating a
coolant through a loop having the electrochemical cell and a
coolant container. The method also includes the step of flowing a
fluid through a pressure-adjusting flow path in fluid communication
with the container for selectively increasing or decreasing
pressure in the container and thus in the loop.
[0013] In one embodiment, the step of flowing the fluid through the
pressure-adjusting flow path includes the step of flowing the fluid
through a venturi.
[0014] In another embodiment, the step of flowing the fluid through
the pressure-adjusting flow path includes the step of selectively
operating a shut-off valve downstream of the venturi, whereby the
valve is operated between an open position permitting fluid to
exhaust to atmosphere, thus inducing a depressurization of the
coolant container, and a closed position, wherein fluid is forced
to vent into the container, thus causing a pressurization of the
coolant container.
[0015] In another embodiment, the step of flowing the fluid through
the pressure-adjusting flow path further includes the step of
variably adjusting a variable-flow valve disposed upstream of the
venturi, thereby finely adjusting the pressurization or
depressurization of the coolant container.
[0016] In yet another embodiment, the method also includes the step
of partially bypassing the electrochemical cell whereby a portion
of the coolant flows through a bypass while a remainder of the
coolant flows through the electrochemical cell.
[0017] The present invention further provides a system for cooling
an electrochemical cell that includes a coolant circulation loop
for supplying a coolant to an electrochemical cell for absorbing
heat from the cell. The coolant circulation loop has a coolant
container; a pump for circulating the coolant through the coolant
circulation loop; and a heat exchanger for cooling the coolant. The
system further includes a pressure-adjusting flow line that has a
venturi in fluid communication with the coolant container for
selectively increasing or decreasing fluid pressure in the
container; and a valve downstream of the venturi, the valve adapted
to be opened to depressurize the coolant circulation loop or to be
closed to pressurize the coolant circulation loop.
[0018] In one embodiment, the system further includes a pressure
controller for controlling a variable valve located upstream of the
venturi in response to a pressure feedback signal from a pressure
transducer in the coolant circulation loop and a temperature
controller for controlling a cooling rate of the heat exchanger in
response to a temperature feedback signal from a temperature sensor
in the coolant circulation loop.
[0019] The present invention thereby provides a system and method
for simple and efficient cooling of an electrochemical cell under
either positive or negative coolant pressure conditions. This
invention therefore enables efficient and cost-effective cooling of
electrochemical cells, such as those utilized in fuel cell
stacks.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Having thus generally described the nature of the invention,
reference will now be made to the accompanying drawings, in
which:
[0021] FIG. 1 shows a simplified schematic of an electrochemical
cell cooling system in accordance with a first embodiment of the
present invention;
[0022] FIG. 2 shows a simplified schematic of an electrochemical
cell cooling system in accordance with a second embodiment of the
present invention; and
[0023] FIG. 3 is a schematic of an electrochemical cell cooling
system with pressure and temperature feedback control loops in
accordance with a third embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] FIG. 1 shows, in schematic form, an electrochemical cell
cooling system, generally designated by reference numeral 10, in
accordance with a first embodiment of the present invention.
Although the present invention can be used to efficiently cool fuel
cell systems, it is not limited to application in fuel cell
systems. Rather, it is applicable to any electrochemical cell
system where liquid coolant is needed to control the operating
temperature of the electrochemical cell.
[0025] As shown in FIG. 1, the cooling system 10 includes a coolant
circulation loop 100 for circulating a coolant through or past an
electrochemical cell 50 for absorbing heat from the exothermic
reaction of a working electrochemical cell 50. The coolant
circulation loop 100 includes a coolant container 140, which is
also known as an overflow tank or storage tank. The coolant
container 140 stores an excess volume of coolant at a nominal
operating pressure, which can be adjusted in a manner to be
described below.
[0026] As illustrated in FIG. 1, the coolant circulation loop 100
includes a pump 120, e.g. a variable speed pump, which drives the
coolant through the loop 100. The coolant circulation loop 100 also
includes a heat exchanging portion, such as a heat exchanger 70,
e.g. a radiator, but which is preferably a high-efficiency plate
heat exchanger. Where ambient conditions suffice to cool the
coolant, the heat exchanging portion can simply be an exposed
section of the coolant circulation loop itself.
[0027] Optionally, as shown in FIG. 1, the coolant circulation loop
100 further includes a filter 60. As is known in the art, as
coolant flows along conduits and pipes, it may pick up impurities
and ions. To keep the coolant non-conductive so that the coolant
does not short the electrochemical cell 50 when flowing
therethrough, the filter 60 may be provided to filter out the
impurities and ions. For example, a de-ionizing filter is provided
when de-ionized water is used as the coolant. Different types of
filters can be provided, as is known in the art, depending on the
type of coolant being used and the piping used to construct the
loop. The filter 60 may be omitted altogether where filtration is
considered unnecessary or where the effects of impurities on system
performance are negligible.
[0028] In order to adjust the pressure in the coolant container 140
and hence in the loop 100, a pressure-adjusting flow line 170 is
provided. The pressure-adjusting flow line 170 includes a fluid
supply source 180, a variable-flow valve 200, and a
pressure-adjustment device 160, e.g. a venturi. As shown in FIG. 1,
the venturi is located downstream of the fluid supply source 180
and the variable-flow valve 200. The venturi 160 has an inlet 161,
an outlet 162, and a bottom port 163. The bottom port 163 is in
fluid communication with the coolant container 140 via a pressure
line 190. The pressure-adjusting flow line also includes a shut-off
valve 300 located downstream of the venturi 160.
[0029] The pressure-adjusting flow line utilizes, preferably, an
inert gas, such as nitrogen which can be exhausted to atmosphere
without raising concerns about pollution. Thus, in one embodiment,
the fluid supply source 180 is a nitrogen storage tank.
[0030] In operation, the fluid (e.g., the nitrogen gas) flows along
a pressure-adjusting flow line 170 from the fluid supply source 180
(e.g., the nitrogen storage tank) through the variable-flow valve
200 to an inlet 161 of the venturi 160. Then the fluid (e.g.,
nitrogen) flows through the venturi 160 to the shut-off valve 300.
In one embodiment, the shut-off valve is a solenoid valve.
Thereafter, the fluid (nitrogen gas) is vented into the
environment, i.e., it is exhausted to atmosphere. As is known in
the art, as the nitrogen flows through the venturi 160, a negative
pressure or vacuum is generated therein at the bottom port 163.
Since the bottom port 163 is in fluid communication with the
coolant container 140 via the pressure line 190, a negative
pressure condition (i.e., a depressurization) is created in the
coolant container 140. This in turn results in a negative pressure
in the coolant circulation loop 100. Accordingly, the cooling
system 10 provides the electrochemical cell 50 with a negative
coolant pressure. During testing, Applicant has been able to obtain
a pressure range of -3 psig to 60 psig. This range could be
increased or decreased by modifying the fluid dynamic properties of
the venturi.
[0031] The shut-off valve, e.g., the solenoid valve 300, must be in
an open position to allow the nitrogen to flow through the venturi
160. In other words, the shut-off valve 300 must be open for the
venturi 160 to induce depressurization of the container 140 and of
the loop 100. When the solenoid valve 300 is closed, the nitrogen
enters the venturi 160 via the inlet port 161 and is forced to flow
out via the bottom port 163. The nitrogen is thus directed
downwardly into the coolant container 140 via the pressure line
190. This results in increased pressure in the coolant container
140 and hence increased pressure in the coolant circulation loop
100. In this case, the cooling system 10 provides the
electrochemical cell 50 with a positive pressure condition.
[0032] The pressure in the loop can thus be adjusted upwardly
(positive pressure condition) or downwardly (negative pressure
condition) by simply opening and closing the shut-off valve 300. By
simply opening and closing the shut-off valve 300, the
electrochemical cell 50 can operate under either positive or
negative pressure condition.
[0033] The pressurization or depressurization of the container 140
and loop 100 can be finely adjusted by operating the variable-flow
valve 200 located upstream of the venturi 160. This is useful where
a precise positive or negative pressure condition is sought, e.g.,
for optimal system performance. Alternatively, the variable-flow
valve 200 can be used to control the rate of pressurization or
depressurization. In one embodiment, a microprocessor control
system can receive signals from sensors or transducers and adjust
the opening or closing of the variable-flow valve 200 according to
a performance-optimizing algorithm. In other words, the
variable-flow valve 200 can be used to variably regulate, or
throttle, the fluid flow through the pressure-adjusting flow line
170 so that a desired flow pressure (or flow rate) is achieved in
the flow line 170 which, in turn, finely adjusts the pressurization
or depressurization of the loop.
[0034] For fine tuning of the positive pressure condition, the
solenoid valve 300 is closed, thus diverting the flow of fluid
(nitrogen) through the bottom port 163, through the pressure line
190 and into the container 140, thus pressurizing the container
140. The variable-flow valve 200 can be partially closed to
diminish the fluid pressure in the flow line 170 and thus diminish
the pressurization, or rate of pressurization, as the case may be,
of the loop 100. Conversely, for fine tuning of the negative
pressure condition, the solenoid valve 300 is opened, thus inducing
a negative pressure condition in the container and loop due to the
venturi effect. The degree or rate of depressurization can then be
finely tuned by adjusting the variable-flow valve 200.
[0035] FIG. 2 shows an electrochemical cell cooling system 20 in
accordance with a second embodiment of the present invention. Same
reference numbers are used herein to indicate same or similar
components. In this second embodiment, the pressure-adjusting flow
line 170 includes the same components as in the previous
embodiment, namely a fluid supply source 180, a variable-flow valve
200, a venturi 160, and a shut-off valve 300. The flow line 170 is
fluidly connected to the container as already described to provide
either pressurization or depressurization of the container
depending on whether the shut-off valve is open or closed.
[0036] As shown in FIG. 2, the coolant circulation loop 100 further
includes a bypass line 220 that bypasses the electrochemical cell
50 from a bypass point 155 in the coolant circulation loop 100
which is upstream of the electrochemical cell 50. This forms an
inner bypass loop 230 starting from the container (or storage tank)
140 along the bypass line 220 and back to the container 140.
Coolant flowing through an outer loop (i.e., the coolant that does
not traverse the bypass) flows through an optional filter 60, the
electrochemical cell 50 and a heat exchanging portion, e.g., the
heat exchanger 70. In one embodiment, a second variable-flow valve
150, such as a solenoid valve, is disposed in the outer loop
between the bypass point 155 and the electrochemical cell 50.
[0037] As shown in FIG. 2, the bypass line 220 is preferably
provided with a flow constriction 210. The solenoid valve 150 also
functions as a flow constriction. Hence, the coolant in the portion
of the coolant circulation loop upstream of the electrochemical
cell 50 and in the bypass line 220 is pressurized. This provides a
relative fast flow rate in the bypass loop 230. This is beneficial
in terms of coolant temperature control. The coolant temperature
can be maintained at a stable level in the bypass loop 230. This in
turn helps to control the temperature of the coolant supplied to
the electrochemical cell 50 from the bypass point 155 via the
solenoid valve 150, as the coolant temperature at the bypass point
155 is relatively stable. In comparison with the first embodiment,
the second embodiment provides better control of coolant
temperature. However, it is more complex and more expensive due to
the bypass and the additional valve.
[0038] It can be understood by those skilled in the art that heat
exchangers, heaters, flow meters, temperature sensors, pressure
gauges, etc can be disposed at various locations in the coolant
circulation loop 100. However, these are not essential to the
present invention, and hence are not described herein in
detail.
[0039] It is to be appreciated that the fluid used in the
pressure-adjusting flow line 170 is not limited to nitrogen or
inert gas. It can be any fluid that is compatible with the
electrochemical cell environment. The pressure adjustment device is
not limited to a venturi and can be any device that provides a
similar function. The flow constriction means 210 in the bypass
line 220 can be any suitable device, such as a valve.
Alternatively, the bypass line 220 can simply have a smaller
cross-sectional area than the line in the coolant circulation loop
100. This also achieves flow constriction in the bypass line 220.
Other components in the present invention may also be replaced with
other devices having similar function.
[0040] FIG. 3 shows an electrochemical cell cooling system 30 in
accordance with a third embodiment of the present invention. Again,
same reference numbers are used herein to indicate same or similar
components. In this third embodiment, the pressure-adjusting flow
line 170 includes the same components as in the previous
embodiment, namely a fluid supply source 180, a variable-flow valve
200, a venturi 160, and a shut-off valve 300. The flow line 170 is
fluidly connected to the container 140 as already described to
provide either pressurization or depressurization of the container
140 depending on whether the shut-off valve 300 is open or
closed.
[0041] As shown in FIG. 3, the coolant circulation loop 100 further
includes a de-ionizing filter 700 and a particulate filter 900.
Although the de-ionizing filter is shown to be located in a second
bypass line that is parallel to and upstream of the main bypass
220, the de-ionizing filter may be located elsewhere as would be
known by those of ordinary skill in the art. Similarly, while the
particulate filter 900 is shown between the container 140 and the
pump 120, the particulate filter 900 can also be located elsewhere
in the coolant circulation loop 100. Optionally, as shown in FIG.
3, a heater 800 can be provided to heat the coolant to ensure that
the coolant remains in the optimal temperature range.
[0042] As shown in FIG. 3, the electrochemical cell cooling system
30 further includes a pressure transducer 450 and a temperature
sensor, e.g. a thermocouple 650. While the pressure transducer 450
and the thermocouple 650 are shown between the second variable-flow
valve 150 and the electrochemical cell 50, these sensors may be
located elsewhere in the coolant circulation loop 100 as would be
known by those of ordinary skill in the art.
[0043] The pressure transducer 450 generates a pressure feedback
signal which is sent to a PID (Proportional-Integral-Derivative)
pressure controller 400. A Proportional-Integral-Derivative
controller is a standard component in industrial control
applications which reads a sensor, subtracts the measurement from a
desired "setpoint" to determine an "error", and then drives the
output toward the setpoint. As PID controllers are very well known
in the art, their operation will not be described herein.
[0044] In addition to receiving the pressure feedback signal from
the pressure transducer 450, the PID pressure controller 400 also
receives a pressure setpoint from a user or overall system control
unit. The PID pressure controller 400 compares the pressure
setpoint to the feedback signal from the pressure transducer 450
and then adjusts the first variable-flow valve 200 accordingly.
[0045] In addition to implementing control logic based on a generic
PID transfer function, the PID pressure controller 400 can also
include additional control logic designed to regulate the opening
and closing of the shut-off valve 300. However, preferably, the
shut-off valve 300 is controlled by an overall system controller
(not shown) which switches the shut-off valve 300 between the open
and closed positions, i.e. between negative and positive pressure
modes. If the pressure setpoint is less than the pressure measured
by the pressure transducer 450, then the overall system controller
(or the PID pressure controller 400) generates a signal to open the
shut-off valve 300. As explained above, opening the shut-off valve
300 depressurizes the coolant container 140, thus driving the
pressure of the coolant in the first coolant circulation loop
downwardly toward the pressure setpoint. If, on the other hand, the
pressure setpoint is greater than the pressure measured by the
pressure transducer 450, then the overall system controller (or the
PID pressure controller 400) generates a signal to close the
shut-off valve 300. Closing the shut-off valve 300 pressurizes the
coolant container 140, thus driving the pressure of the coolant in
the first coolant circulation loop upwardly toward the pressure
setpoint.
[0046] Similarly, the thermocouple 650 generates a temperature
feedback signal which is sent to a PID temperature controller 610.
The PID temperature controller 610 also receives a temperature
setpoint, which is a temperature value or setting input by a user
or an overall system controller. The PID temperature controller 610
compares the temperature feedback signal from the thermocouple 650
to the temperature setpoint and then accordingly adjusts a third
variable-flow valve 600. The third variable-flow valve 600
regulates the flow of coolant in a second coolant circulation loop
620. The second coolant circulation loop 620 circulates coolant
through the heat exchanger 70 to absorb heat from the coolant
circulating through the first coolant circulation loop 100. Heat
transferred at the heat exchanger 70 from the first coolant
circulation loop 100 to the second coolant circulation loop 620 is
then dissipated to the environment using, for example, an
evaporative condenser 630 with a fan 640. As will be appreciated by
those of ordinary skill in the art, the coolant in the second
coolant circulation loop 620 can be cooled by a variety of means
that are known in the art of heat transfer. By regulating a flow
rate of coolant in the second coolant circulation loop 620, the PID
temperature controller 610 therefore controls a cooling rate of the
heat exchanger 70 and thus adjusts the temperature of the coolant
in the first coolant circulation loop 100.
[0047] Although PID controllers represent the best mode known to
the Applicant of implementing control of the electrochemical cell
cooling system, it should be understood that other controllers or
other control logic can be substituted.
[0048] As alluded to in the foregoing paragraphs, the PID pressure
controller 400 and the PID temperature controller 610 can be
themselves controlled by a master controller and/or an overall
system controller. The master controller and/or the overall system
controller can thus provide pressure and temperature setpoints
based on a power generation requirement for the electrochemical
cell 50 or based on a variety of other factors, e.g. reactant
consumption rates, ambient conditions, etc.
[0049] As would be appreciated by those of ordinary skill in the
art, more than a single pump and/or heat exchanger can be provided
in the embodiments described herein in order to optimize
thermodynamic performance. The location of the pump(s) and heat
exchanger(s) can also be varied without departing from the spirit
and scope of the invention. Furthermore, various sensors and/or
transducers can be provided for measuring parameters of the
coolant, such as temperature and pressure (as shown in FIG. 3) as
well as other process parameters such as flow rate, humidity, etc.
The measured parameters can be sent to one or more processors (like
the PID controllers shown in FIG. 3) which in turn control the
operation of the pump(s), heat exchanger(s) and/or valves. For
example, temperature sensors can be provided at the inlet and
outlet of the electrochemical cell to monitor the temperature rise
of the coolant and hence the amount of heat transferred from the
electrochemical cell to the coolant.
[0050] Modifications and improvements to the above-described
embodiments of the present invention may become apparent to those
skilled in the art. The foregoing description is intended to be
exemplary rather than limiting. The scope of the invention is
therefore intended to be limited solely by the scope of the
appended claims.
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