Indian Patents
Title of Invention

A FUEL CELL POWER SYSTEM
Abstract Fuel cell power systems (10) and methods of controlling a fuel cell power system are provided. According to one aspect, a fuel cell power system includes a plurality of fuel cells (14) electrically coupled with plural terminals and individually configured to convert chemical energy into electricity; and a digital control system (30) configured to at least one of control and monitor an operation of the fuel cells. Another aspect provides a method of controlling a fuel cell power system including providing a plurality of fuel cells individually configured to convert chemical energy into electricity ; electrically coupling the plurality of fuel cells; providing first and second terminals coupled with the fuel cells and coupling a digital control system with the fuel cells to at least one of monitor and control an operation of the fuel cells.
Full Text A FUEL CELL POWER SYSTEM
Technical Field.
The present invention relates to a fuel cell power system and methods of
controlling a fuel cell power system.
Background Art
Fuel cells are known in the art. The fuel cell is an
electrochemical device which reacts hydrogen, and oxygen, which is
usually supplied from the ambient air, to produce electricity and water.
The basic process is highly efficient and fuel cells fueled directly by
hydrogen are substantially pollution free. Further, since fuel cells can
be assembled into stacks of various sizes, power systems have been
developed to produce a wide range of electrical power output levels
and thus can be employed in numerous industrial applications.
Although the fundamental electrochemical processes involved in all
fuel cells are well understood, engineering solutions have proved elusive
for making certain fuel cell types reliable, and for others economical.
In the case of polymer electrolyte membrane (PEM) fuel cell power
systems reliability has not been the driving concern to date, but rather
the installed cost per watt of generation capacity has. In order to
further lower the PEM fuel cell cost per watt, much attention has been
directed to increasing the power output of same. Historically, this has
resulted in additional sophisticated balance-of-plant systems which are
necessary to optimize and maintain high PEM fuel cell power output.
A consequence of highly complex balance-of-plant systems is that they
do not readily scale down to low capacity applications. Consequently,
cost, efficiency, reliability and maintenance expenses are all adversely
effected in low generation applications.
It is well known that single PEM fuel cells produce a useful
voltage of only about 0.45 to about 0.7 volts D.C. per cell under a
load. Practical PEM fuel cell plants have been built from multiple
cells stacked together such that they are electrically connected in series.
It is further well known that PEM fuel cells can operate at higher
power output levels when supplemental humidification is made available
to the proton exchange membrane (electrolyte). In this regard,
humidification lowers the resistance of proton exchange membranes to
proton flow. To achieve this increased humidification, supplemental
water can be introduced into the hydrogen or oxygen streams by various
methods, or more directly to the proton exchange membrane by means
of the physical phenomenon known as of wicking, for example. The
focus of investigations, however, in recent years has been to develop
membrane electrode assemblies (MEA) with increasingly improved power
output when running without supplemental humidification. Being able
to run an MEA when it is self-humidified is advantageous because it
decreases the complexity of the balance-of-plant with its associated costs.
However, self-humidification heretofore has resulted in fuel cells running
at lower current densities and thus, in turn, has resulted in more of
these assemblies being required in order to generate a given amount
of power.
While PEM fuel cells of various designs have operated with
varying degrees of success, they have also had shortcomings which have
detracted from their usefulness. For example, PEM fuel cell power
systems typically have a number of individual fuel cells which are
serially electrically connected (stacked) together so that the power
system can have a increased output voltage. In this arrangement, if
one of the fuel cells in the stack fails, it no longer contributes voltage
and power. One of the more common failures of such PEM fuel cell
power systems is where a membrane electrode assembly (MEA) becomes
less hydrated than other MEAs in the same fuel cell stack. This loss
of membrane hydration increases the electrical resistance of the effected
fuel cell, and thus results in more waste heat being generated. In
turn, this additional heat drys out the membrane electrode assembly.
This situation creates a negative hydration spiral. The continual
overheating of the fuel cell can eventually cause the polarity of the
effected fuel cell to reverse such that it now begins to dissipate
electrical power from the rest of the fuel cells in the stack. If this
condition is not rectified, excessive heat generated by the failing fuel
cell may cause the membrane electrode assembly to perforate and
thereby leak hydrogen. When this perforation occurs the fuel cell stack
must be completely disassembled and repaired. Depending upon the
design of fuel cell stack being employed, this repair or replacement may
be a costly, and time consuming endeavor.
Further, designers have long sought after a means by which
current densities in self-humidified PEM fuel cells can be enhanced
while simultaneously not increasing the balance-of-plant requirements for
these same devices.
Accordingly, the present invention provides:
a fuel cell power system, comprising:
a housing defining a cavity;
a plurality of terminals borne by the housing and electrically coupled with a load
which has a voltage demand;
a plurality of fuel cells received in the cavity of the housing and electrically
coupled to the plurality of terminals, and wherein the plurality of fuel cells convert
chemical energy into electricity which is supplied to the terminals to meet, at least in part,
the electrical current demand of the load, and wherein the fuel cells are configured to be
individually selectively deactivated, and can be physically removed, by hand, from the
housing while the remaining ones of the fuel cells continue to operate and supply
electricity to the terminals; and
a digital control system which is electrically coupled with the plurality of fuel
cells and is configured to control and monitor an operation of the plurality of fuel cells
and the fuel cell power system.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Preferred embodiments of the invention are described below with
reference to the following accompanying drawings.
Fig. 1 is a prospective view of one embodiment of a fuel cell
power system according to the present invention.
Fig. 2 is an illustrative representation of a control system coupled
with components of the fuel cell power system.
Fig. 3 is an exploded perspective view of one configuration of a
fuel cell cartridge of the fuel cell power system.
Fig. 4 is. a schematic representation of one embodiment of
circuitry coupled with plural fuel cells of the fuel cell cartridge.
Fig. 5 is a functional block diagram of one configuration of the
control system for the fuel cell power system.
Fig. 6 is a functional block diagram of a cartridge analysis slave
controller of the control system coupled with associated circuitry and
components.
Fig. 7 is a functional block diagram of an auxiliary valve slave
controller of the control system coupled with associated circuitry and
components.
Fig. 8 is a anotional block diagram of a fan slave controller of
the control system coupled with associated circuitry and components.
Fig. 9 is a functional block diagram of an interface slave
controller of the control system coupled with associated circuitry and
components.
Fig. 10 is a functional block diagram of an external port slave
controller of the control system coupled with associated circuitry and
components.
Fig. 11 is a functional block diagram of a system analysis slave
controller of the control system coupled with associated circuitry and
components.
Fig. 12 is a functional block diagram of a sensor slave controller
of the control system coupled with associated circuitry and components.
Fig. 13 is a functional block diagram of an air temperature slave
controller of the control system coupled with associated circuitry and
components.
Fig. 14 is a functional block diagram of a shunt slave controller
of the control system coupled with associated circuitry and components.
Fig. 15 is a functional block diagram of a switch slave controller
of the control system coupled with associated circuitry and components.
Figs. 16-16A are a flow chart illustrating exemplary operations of
a master controller of the control system.
Fig. 17 is a flow chart illustrating an exemplary start-up operation
of the master controller.
Figs. 18-18A are a flow chart illustrating exemplary error
operations of the master controller.
Figs. 19-19B are a flow chart of exemplary operations of the
cartridge analysis slave controller.
Figs. 20-20A are a flow chart illustrating exemplary operations of
the auxiliary valve slave controller of the control system.
Figs. 21-21A are a flow chart illustrating exemplary operations of
the fan slave controller of the control system.
Fig. 22 is a flow chart illustrating exemplary operations of the
interface slave controller of the control system.
Fig. 23 is a flow chart illustrating exemplary operations of the
external port slave controller of the control system.
Figs. 24-24A are a flow chart illustrating exemplary operations of
the system analysis slave controller of the control system.
Fig. 25 is a flow chart illustrating exemplary operations of the
sensor slave controller of the control system.
Fig. 26 is a flow chart illustrating exemplary operations of the air
temperature slave controller of the control system.
Fig. 27 is a flow chart illustrating exemplary operations of the
shunt slave controller of the control system.
Fig. 28 is a flow chart illustrating exemplary operations of the
switch slave controller of the control system.
Best Modes for Carrying Out the Invention and Disclosure of Invention
This disclosure of the invention is submitted in furtherance of the
constitutional purposes of the U.S. Patent Laws "to promote the
progress of science and useful arts" (Article 1, Section 8).
Referring to Fig. 1, one configuration of a fuel cell power
system 10 is illustrated. The depicted configuration of fuel cell power
system 10 is exemplary and other configurations are possible. As
shown, fuel cell power system 10 includes a housing 12 provided about
a plurality of fuel cell cartridges 14. Housing 12 defines a subrack
assembly in the described embodiment.
Fuel cell power system 10 is configured to utilize one or more
of fuel cell cartridges 14. Twelve such fuel cell cartridges 14 are
utilized in the embodiment of fuel cell power 10 described herein. As
described below, individual fuel cell cartridges 14 include a plurality of
fuel cells. In the described configuration, individual fuel cell
cartridges 14 include four fuel cells.
Such fuel cells can comprise polymer electrolyte membrane (PEM)
fuel cells. In the described embodiment, the fuel cells can comprise
membrane electrode assembly (MEA) fuel cells or membrane electrode
diffusion assembly (MEDA) fuel cells. Further details of one
configuration of fuel cells and fuel cell cartridges 14 are described in
a co-pending U.S. Patent Application Serial No. 08/979,853, entitled "A
Proton Exchange Membrane Fuel Cell Power System", filed
November 20, 1997, naming William A. Fuglevand, Dr. Shiblihanna I.
Bayyuk, Ph.D., Greg A. Lloyd, Peter D. Devries, David R. Lott,
John P. Scartozzi, Gregory M. Somers and Ronald G. Stokes as
inventors, assigned to the assignee hereof, having attorney docket
number WA23-002, and incorporated herein by reference.
Housing 12 additionally includes an operator interface 16. In the
present embodiment, operator interface 16 includes a display 18 and
interface switches 20. Operator interface 16 is configured to indicate
operation of fuel cell power system 10 and also enable an operator to
control various functions of fuel cell power system 10.
Display 18 of operator interface 16 is configured to emit a
human perceptible signal, such as visible signals, to indicate operation
of fuel cell power system 10. In the depicted embodiment, display 18
comprises a plurality of light emitting diode (LED) bar graph arrays to
indicate operational conditions of respective fuel cell cartridges 14. In
one configuration, individual bar graph arrays of display 18 indicate high
and low voltages of fuel cells within the corresponding fuel cell
cartridge 14.
Interface switches 20 permit a user to control operations of fuel
cell power system 10. For example, one interface switch 20 can be
provided to enable a user to turn on fuel cell power system 10. In
addition, another interface switch 20 can include a load enable switch
which permits a user to selectively apply power from fuel cell power
system 10 to a load 22 coupled with the fuel cell power system 10.
Another interface switch 20 can control a cartridge reset function
described below.
Referring to Fig. 2, some components of fuel cell power
system 10 are shown. The components are internal and external of
housing 12 of fuel cell power system 10. Internally, only three fuel
cell cartridges 14 are shown for purposes of discussion herein. More
fuel cell cartridges 14 are provided in typical configurations.
Fuel cell power system 10 is shown coupled with a remote
device 24. Fuel cell power system 10 is preferably configured to
communicate with remote device 24. An exemplary remote device 24
comprises an off-site control and monitoring station. Fuel cell power
system 10 receives communications from remote device 24 which may
comprise data and commands. Fuel cell power system 10 is also
configured to output data, requests, etc. to remote device 24.
The depicted components include the plural fuel cell cartridges 14
and operator interface 16 discussed above. In addition, fuel cell power
system 10 includes a control system 30. One configuration of control
system 30 is described below in detail. The illustrated control
system 30 is coupled with a power supply sensor 31 associated with a
power supply 32, and charge circuitry 34. Control system 30 is
additionally coupled with fuel cell cartridges 14 and operator
interface 16. Further, control system 30 is coupled with a
communication port 36, switching device 38 and current sensor 40.
Control system 30 is additionally coupled with a bleed solenoid 42
associated with a bleed valve 43.
The depicted fuel cell power system 10 includes a fuel delivery
system 28. Fuel delivery system 28 couples with a fuel supply 23 to
supply fuel to fuel cell cartridges 14. Exemplary fuel comprises
hydrogen gas in the described embodiment. Other fuels may be
possible.
The depicted fuel delivery system 28 includes a main valve 47
and plural auxiliary valves 45 associated with respective fuel cell
cartridges 14. Main valve 47 controls the flow of fuel from fuel
supply 23 into fuel cell power system 10. Auxiliary valves 45 control
the flow of fuel to respective fuel cell cartridges 14. Control
system 30 is coupled with plural auxiliary solenoids 44 of associated
auxiliary valves 45. Control system 30 is further coupled with a main
solenoid 46 of associated main valve 47.
The depicted fuel cell power system 10 includes an air
temperature control assembly 50. The illustrated air temperature
control assembly 50 includes a plenum 51 having associated ports 52
corresponding to fuel cell cartridges 14. Within plenum 51 of air
temperature control assembly 50, a temperature modifying element 53,
fan 54, temperature sensor 55 and fuel sensor 61 are provided.
A controllable air flow device or air passage 56 couples
plenum 51 to exterior ambient air outside of housing 12. Air
passage 56 can permit the intake of air into plenum 51 as well as the
exhaustion of air from plenum 51. Control system 30 is coupled with
control circuitry 51 of modifying element 53, control circuitry 48 and
monitoring circuitry 49 of fan 54, temperature circuitry 68 associated
with temperature sensor 55, control circuitry 57 of air passage 56, and
heater 75 of fuel sensor 61.
A first fuel sensor 58 is provided within housing 12 and outside
of plenum 51 as shown. First fuel sensor 58 is operable to monitor
for the presence of fuel within housing 12. A second fuel sensor 61
is provided within plenum 51 to monitor for the presence of fuel within
plenum 51. Control system 30 is configured to couple with fuel
detection circuitry 64 associated with fuel sensors 58, 61. Fuel
detection circuitry 64 can condition measurements obtained from
sensors 58, 61.
Heaters 74, 75 are coupled with respective fuel sensors 58, 61 to
provide selective heating of fuel sensors 58, 61 responsive to control
from control system 30. Heaters 74, 75 are integral of fuel
sensors 58, 61 in some configurations. An exemplary fuel sensor
configuration with an integral heater has designation TGS 813 available
from Figaro Engineering, Inc. Such heaters are preferably provided in
a predefined temperature range to assure proper operation. Other
configurations of sensors 58, 61 are possible.
An external temperature sensor 59 is provided outside of
housing 12 in one embodiment. Control system 30 is also coupled with
temperature circuitry 67 associated with temperature sensor 59 to
monitor the exterior temperature. Temperature circuitry 67 conditions
signals received from temperature sensor 59.
Control system 30 is configured to at least one of control and
monitor at least one operation of fuel cell power system 10. During
operation, fuel from fuel supply 23 is applied to main valve 47. Main
valve 47 is coupled with auxiliary valves 45 as shown. Responsive to
control from control system 30, main valve 47 and auxiliary valves 45
apply fuel to respective fuel cell cartridges 14. Responsive to the
supply of fuel, and in the presence of oxygen, fuel cell cartridges 14
produce electrical power.
A power bus 60 couples the fuel cell cartridges 14 in series.
Power bus 60 is coupled with external terminals 62, 63 which may be
connected with an external load 22 (shown in Fig. 1). Terminal 62
provides a positive terminal and terminal 63 provides a negative
terminal of fuel cell power system 10.
Air temperature control assembly 50 applies oxygen to the
respective fuel cell cartridges 14 via ports 52. Fuel cell cartridges 14
are individually operable to convert chemical energy into electricity. As
described below, fuel cartridges 14 individually contain plural fuel cells
individually having an anode side and a cathode side. Auxiliary
valves 45 apply fuel to the anode sides of the fuel cells. Plenum 51
directs air within the cathode sides of the fuel cells.
Air temperature control assembly 50 preferably provides circulated
air within a predetermined temperature range. Such circulated air can
be exterior air and/or recirculated air. In the preferred embodiment,
air temperature control assembly 50 provides air within plenum 51
within an approximate temperature range of 25 °Celsius to 80 °Celsius.
Upon start-up conditions of fuel cell power system 10, modifying
element 53 may be controlled via control system 30 using element
control circuitry 41 to either increase or decrease the temperature of
air present within plenum 51. Fan 54 operates to circulate the air
within plenum 51 to respective fuel cell cartridges 14. Fan control
circuitry 48 and fan monitor circuitry 49 are shown coupled with fan
54. Responsive to control from control system 30, fan control circuitry
48 operates to control air flow rates (e.g., speed of rotation) of fan 54.
Fan monitor circuitry 49 operates to monitor the actual air flow rates
induced by fan 54 (e.g., circuitry 49 can comprise a tachometer for
rotational fan configurations).
Control system 30 monitors the temperature of the air within
plenum 51 using temperature sensor 55. During operation, heat is
generated and emitted from fuel cell cartridges 14. Thus, it may be
necessary to decrease the temperature of air within plenum 51 to
provide efficient operation of fuel cell power system 10. Responsive
to control from control system 30, air passage 56 can be utilized to
introduce exterior air into plenum 51 and exhaust air from plenum 51
to ambient.
Control system 30 communicates with control circuitry 57 to
control air passage 56. In one embodiment, air passage 56 includes a
plurality of vanes and control circuitry 57 operates to control the
position of the vanes of air passage 56 to selectively introduce exterior
air into plenum 51. The vanes of air passage 56 can preferably be
provided in a plurality of orientations between an open position and a
closed position to vary the amount of exterior fresh air introduced into
plenum 51 or the amount of air exhausted from plenum 51 responsive
to control from control system 30. Air circulated within plenum 51 can
comprise recirculated and/or fresh ambient air.
Utilizing temperature sensor 59, control system 30 can also
monitor the temperature of ambient air about housing 12. Control
system 30 can utilize such exterior temperature information from
temperature sensor 59 to control the operation of air passage 56.
Temperature sensor 59 is located adjacent air passage 56 in a preferred
embodiment.
As described in further detail below, control system 30 controls
air flow rates of fan 54 using fan control circuitry 48. Fan monitor
circuitry 49 provides air flow rate information to control system 30.
Control system 30 can monitor the total system voltage being delivered
via power bus 60 by summing the individual cell voltages. Control
system 30 can also monitor the electrical load being delivered via power
bus 60 using current sensor 40. With knowledge of the system bus
voltage and load, control system 30 can calculate waste thermal power
and provide a desired cooling air flow.
More specifically, the efficiency of one or more fuel cells may be
determined by dividing the respective fuel cell voltage by 1.23 (a
theoretical maximum voltage of a single fuel cell). An average
efficiency can be determined for all fuel cells 90 of fuel cell power
system 10. The remaining energy (energy not associated to electricity)
as determined from the efficiency calculation is waste thermal power.
The determined waste thermal power may be utilized to provide a
desired cooling air flow. Control system 30 controls the air flow rates
of fan 54 depending upon the waste thermal power in accordance with
one aspect of the described fuel cell power system 10.
During operation of fuel cell cartridges 14, non-fuel diluents such
as cathode-side water and atmospheric constituents can diffuse from the
cathode side of the fuel cell through a membrane electrode assembly
of the fuel cell and accumulate in the anode side of the fuel cell. In
addition, impurities in the fuel supply delivered directly to the anode
side of the fuel cell also accumulate. Without intervention, these
diluents can dilute the fuel sufficiently enough to degrade performance.
Accordingly, the anode side of the individual fuel cells is connected to
a bleed manifold 65. Bleed manifold 65 is additionally coupled with
bleed valve 43.
Control system 30 selectively operates bleed solenoid 42 to
selectively open and close bleed valve 43 permitting exhaustion of
matter such as entrained diluents and perhaps some fuel via a bleed
exhaust 66 within housing 12. Control system 30 can operate to open
and close bleed valve 43 on a periodic basis. The frequency of
openings and closings of bleed valve 43 can be determined by a
number of factors, such as electrical load coupled with terminals 62, 63,
etc. Although not shown, a fuel recovery system may be coupled with
bleed exhaust 66 to retrieve unused fuel for recirculation or other uses.
Following a start-up condition either inputted via interface or
from remote device 24, control system 30 selectively controls switching
device 38 to couple power bus 60 with positive terminal 62. Switching
device 38 can comprise parallel MOSFET switches to selectively couple
power bus 60 with an external load 22.
For example, control system 30 may verify when an appropriate
operational temperature within plenum 51 has been reached utilizing
temperature sensor 55. In addition, control system 30 can verify that
at least one electrical characteristic, such as voltage and/or current, of
respective fuel cell cartridges 14 has been reached before closing
switching device 38 to couple power bus 60 with an associated load 22.
Such provides proper operation of fuel cell power system 10 before
coupling bus 60 with an external load 22.
Power supply 32 includes power supplies having different voltage
potentials in the described embodiment. For example, power supply 32
can provide a 5-volt supply voltage for operating the digital circuitry of
fuel cell power system 10, such as control system 30. Power supply 32
can also provide higher voltage potentials, such as +/- 12 volts for
operation of components such as fan 54 within fuel cell power
system 10.
Further, power supply 32 can include a battery powering
components during start-up procedures. Following start-up procedures,
power supply 32 can be coupled with power bus 60 and internal power
utilized by fuel cell power system 10 can be derived from electrical
power generated from fuel cell cartridges 14. Charge circuitry 34 is
provided to selectively charge batteries of power supply 32 utilizing
power from power bus 60. Control system 30 is configured to monitor
electrical conditions of the batteries and the supplied voltages of power
supply 32 using power supply sensors 31. Control system 30 can
operate charge circuitry 34 to charge batteries of power supply 32
depending upon such monitoring operations.
Control system 30 is also coupled with communication port 36
providing communications to an external device such as a remote
device 24. An exemplary remote device 24 comprises an external
control system or monitoring system off-site from fuel cell power
system 10. Control system 30 can output data including requests,
commands, operational conditions, etc., of fuel cell power system 10
using communication port 36. In addition, control system 30 can
receive data including commands, requests, etc., from remote device 24
using communication port 36.
Referring to Fig. 3, an exemplary fuel cell cartridge 14 is shown.
Further details of fuel cell cartridge 14 are disclosed in detail in U.S.
Patent Application Serial No. 08/979,853 incorporated by reference
above. The depicted fuel cell cartridge 14 includes a fuel distribution
frame 70 and a force application assembly which includes plural cathode
covers 71 which partially occlude respective cavities housing membrane
electrode assemblies (MEA) or membrane electrode diffusion assemblies
(MEDA) within fuel distribution frame 70. The depicted fuel cell
cartridge 14 includes four fuel cells (individually shown as reference
numeral 90 in Fig. 4). Other configurations are possible.
The respective cathode covers 71 individually cooperate or
otherwise mate with each other, and with the fuel distribution frame 70.
Individual apertures 72 which are defined by the cathode cover, define
passageways 73 which permit air from plenum 51 to circulate to the
cathode side of the membrane electrode diffusion assembly contained
within fuel distribution frame 70. The circulation of air through the
fuel cell cartridge 14 is discussed in significant detail in U.S. patent
application Serial No. 08/979,853 incorporated by reference above.
Conductive members 63 extend outwardly from a main body of
individual fuel cells within fuel cell cartridge 14. Conductive
members 63 are designed to extend through respective gaps or openings
which are provided in fuel distribution frame 70. Each conductive
member 63 is received between and thereafter electrically coupled with
pairs of conductive contacts which are mounted on a rear wall of a
subrack described in greater detail below.
Fuel cell cartridge 14 is operable to be serially electrically
coupled with a plurality of other fuel cell cartridges 14 by way of a
subrack which is generally indicated by the numeral 76. Subrack 76
has a main body 77 having top and bottom portions 78, 79,
respectively. The top and bottom portions are joined together by a
rear wall 80. Elongated channels 81 are individually formed in top and
bottom portions 78, 79 and are operable to slidably receive individual
spines 74 which are formed on fuel distribution frame 70.
Subrack 76 is made of a number of mirror image portions 85,
which when joined together, form the main body 77 of subrack 76.
These mirror image portions 85 are fabricated from a moldable
dielectric substrate. Power bus 60 is affixed on rear wall 80 of the
subrack 90. A repeating pattern of eight pairs of conductive
contacts 84 are attached on rear wall 80 and are coupled with power
bus 60. Electrical coupling of fuel cells within fuel cell cartridge 14
with power bus 60 is implemented using contacts 84 in the described
embodiment.
First and second conduits 86, 87 are also attached to rear
wall 80 and are operable to matingly couple in fluid flowing relation
to the fuel distribution frame 70. The respective first and second
conduits 86, 87 extend through rear wall 80 and connect with suitable
external conduits (not shown). First conduit 86 is coupled in fluid
flowing relation with fuel supply 23 (Fig. 1) and with anode sides of
internal fuel cells. Further, second conduit 87 exhausts from the anode
sides of the fuel cells to bleed manifold 65 (Fig. 2).
Individual fuel cell cartridges 14 may be selectively deactivated.
For example, fuel cell cartridges 14 are individually physically removable
from fuel cell power system 10. Removal of one or more fuel cell
cartridges 14 may be desired for maintenance, replacement, etc. of the
fuel cell cartridges 14. The remaining fuel cell cartridges 14 and
internal fuel cells thereof may continue to supply power to an
associated load 22 with one or more of the fuel cell cartridges 14
deactivated.
Individual contacts 84 may be configured to maintain electrical
continuity of bus 60 upon physical removal of a fuel cell cartridge 14
from an associated subrack 76. As shown, individual contacts 84
comprise make before break contacts which individually include plural
conductive members configured to receive an associated contact 69 of
a fuel cell cartridge 14. Individual contacts 69 can comprise a tang or
knife. Upon physical removal of fuel cell cartridge 14 and the
corresponding terminals 69, conductive members of contacts 84 are
mechanically coupled together to maintain a closed circuit within bus 60
intermediate terminals 62, 63. Such maintains a supply of electrical
power to load 22 coupled with terminals 62, 63 during removal of one
or more fuel cell cartridges 14 from fuel cell power system 10.
Referring to Fig. 4, a schematic representation of four fuel
cells 90 of a fuel cell cartridge 14 is shown. Individual fuel cells 90
have plural contacts 84 as described above. Fuel cells 90 are typically
coupled in series using power bus 60. Control system 30 is configured
to monitor at least one electrical characteristic of individual fuel
cells 90 using analysis circuitry 91 in the described embodiment.
More specifically, analysis circuitry 91 includes a voltage sensor
92 which may be provided electrically coupled with contacts 84 as
shown. Such coupling enables voltage sensor 92 to monitor the voltages
of the individual respective fuel cells 90. Fuel cells 90 have been
observed to typically produce a useful voltage of about 0.45 to about
0.7 volts DC under a typical load.
An exemplary configuration of voltage sensor 92 is implemented
as a differential amplifier for monitoring voltages. Voltage sensor 92
is preferably configured to monitor voltage magnitude across individual
fuel cells 90 as well as polarity of individual fuel cells 90.
Analysis circuitry 91 can additionally include plural current
sensors 94, 97. Individual current sensors may be coupled with
contacts 84 of individual fuel cells 90 to monitor current flowing
through respective individual fuel cells 90 in an alternative arrangement
(not shown). Control system 30 is coupled with current sensors 94, 97
and is configured to monitor corresponding respective currents through
fuel cells 90 and outputted to load 22 via bus 60.
Current sensor 94 is coupled intermediate one of fuel cells 90
and a coupling with internal power supply 93. Current sensor 94 is
coupled intermediate the coupling with internal power supply 93 and
external terminal 62 coupled with an associated load.
Following start-up operations, power for internal use within fuel
cell power system 10 (e.g., power provided to the circuitry of control
system 30) is provided from fuel cell cartridges 14. Internal power
supply 93 extracts current from bus 60 as shown to provide internal
power to fuel cell power system 10.
Accordingly, current sensor 94 provides information regarding
current flow through serially coupled fuel cell cartridges 14. Current
sensor 97 provides information regarding current flow to a load coupled
with terminal 62 (i.e., load 22 shown in Fig. 1).
Plural switching devices 96 are also provided which correspond to
respective fuel cells 90. Switching devices 96 can be individually
provided intermediate contacts 84 of respective fuel cells 90 as
illustrated. In the depicted configuration, switching devices 96 can
comprise MOSFET devices. Gate electrodes of switching devices 96 are
coupled with control system 30.
Control system 30 is operable to selectively shunt electrodes 84
using switching devices 96 corresponding to a desired one or more of
fuel cells 90 to electrically bypass or deactivate such fuel cells 90. For
example, if control system 30 observes that an electrical characteristic
(e.g., voltage) of a fuel cell 90 as sensed via sensors 92, 94 is below
a desired range, control system 30 can instruct a respective switching
device 96 to turn on and shunt the respective fuel cell 90. In
addition, individual fuel cells 90 can be selectively shunted using
respective switching devices 96 to enhance the performance of fuel
cells 90.
In one configuration, fuel cells 90 can be shunted according to
a duty cycle. The duty cycle may be adjusted by control system 30
depending upon operation of fuel cell cartridges 14 and fuel cell power
system 10. Fuel cells 90 can be shunted by sequential order as
determined by control system 30. Shunting is also helpful during start-
up operations to generate heat within housing 12 to bring fuel power
system 10 up to operating temperature in an expedient manner.
Alternatively, individual fuel cells 90 may be shunted for extended
periods of time if control system 30 observes such fuel cells are
operating below desired ranges (e.g., low voltage conditions, reverse
polarity conditions). Shunting operations are discussed in co-pending
U.S. Patent Application Serial No. 09/108,667, entitled Improved Fuel
Cell and Method for Controlling Same", filed on July 1, 1998, naming
William A. Fuglevand, Peter D. Devries, Greg A. Lloyd, David R. Lott,
and John P. Scartozzi as inventors, assigned to the assignee hereof,
having attorney docket number WA23-005, and incorporated herein by
reference.
Referring to Fig. 5, one configuration of control system 30 is
illustrated. In the depicted arrangement, control system 30 includes a
distributed control system including a plurality of controllers 100-120.
Individual controllers 100-120 comprise programmable microcontrollers in
the described embodiment. Exemplary microcontrollers have trade
designation MC68HC705P6A available from Motorola, Inc. In the
described embodiment, controllers 100-120 individually comprise a
controller configured to execute instructions provided within executable
code. In an alternative configuration, the steps described with reference
to Figs. 16-28 below are implemented within hardware.
Individual controllers can include random access memory (RAM),
read only memory (ROM), analog-to-digital (A/D) converters, serial
input/output port (SIOP) communications, timers, digital input/
output (I/O), timer interrupts and external interrupts. Individual
controllers 102-120 have internal digital processing circuitry configured
to execute a set of software or firmware instructions. Such instructions
can be stored within the internal read only memory of the respective
controllers 100-120. Other configurations of control system 30 are
possible.
Among other functions, master controller 100 functions as a
communication router to implement communications intermediate master
controller 100 and individual slave controllers 102-120. In the described
embodiment, communications are implemented in a limited full-duplex
mode. Other communication protocols may be utilized.
Master controller 100 outputs messages to slave
controllers 102-120. Outputted messages are seen by all slave
controllers 102-120. Individual slaves 102-120 identified by the outgoing
message process the corresponding message. Thereafter, receiving slave
controllers 102-120 can output a message to master controller 100. In
addition, master controller 100 can sequentially poll slave
controllers 102-120 to determine whether such slave controllers 102-120
have communications for master controller 100. Master controller 100
can also supply clock information to slave controllers 102-120 to
establish a common timing reference within control system 30.
Individual slave controllers 102-120 perform specific tasks in
control system 30 including a plurality of distributed controllers.
Individual slave controllers 102-120 can monitor specified functions of
fuel cell power system 10 and report to master controller 100. Further,
master controller 100 can direct operations of individual slave
controllers 102-120.
Referring to Fig. 6, cartridge analysis slave controller 102 is
coupled with master controller 100 and associated circuitry. In
particular, cartridge analysis slave controller 102 is coupled with analysis
circuitry 91 which is in turn coupled with fuel cells 90 and power
bus 60 as previously described. Utilizing voltage sensor 92 and current
sensor 94 of analysis circuitry 91, cartridge analysis slave controller 102
can monitor electrical characteristics such as the voltage of individual
fuel cells 90 as well as the current through fuel cells 90. Further,
cartridge analysis slave controller 102 can monitor current flowing
through power bus 60 to load 22 using current sensor 97 of analysis
circuitry 91. As described below, cartridge analysis slave controller 102
can communicate such electrical characteristics to master controller 100.
Referring to Fig. 7, auxiliary valve slave controller 104 is shown
coupled with master controller 100 and auxiliary solenoids 44 and bleed
solenoid 42. In turn, auxiliary solenoids 44 are coupled with auxiliary
valves 45 and bleed solenoid 42 is coupled with bleed valve 43 as
discussed above. Responsive to control communications from master
controller 100, auxiliary valve slave controller 104 is configured to
operate auxiliary solenoids 44 and bleed solenoid 42 to control auxiliary
valves 45 and bleed valve 43, respectively.
Referring to Fig. 8, fan slave controller 106 is coupled with fan
control circuitry 48 and fan monitor circuitry 49. As described above,
fan control circuitry 48 and fan monitor circuitry 49 are individually
coupled with fan 54. Upon receiving instruction from master
controller 100, fan slave controller 106 is operable to control operation
of fan 54 using fan control circuitry 48. For example, fan slave
controller 106 controls on/off operational modes of fan 54 and the air
flow rate of fan 54. Using fan monitor circuitry 49, fan slave
controller 106 can monitor operation of fan 54. Fan slave
controller 106 can output fan status information (e.g., RPM for a
rotational fan) to master controller 100.
Referring to Fig. 9, interface slave controller 108 is coupled with
master controller 100 and operator interface 16. Master controller 100
supplies operational status information from other slave controllers to
interface slave controller 108. Thereafter, interface slave controller 108
can control operator interface 16 to convey such status information to
an operator. Exemplary indications can include a light emitting
diode (LED) array, bar graph display, audio warning buzzer, etc.
Referring to Fig. 10, external port slave controller 110 is coupled
with communication port 36 and memory 37 as well as master
controller 100. As described previously, communication port 36 is
additionally coupled with a remote device 24. Communication port 36
and memory 37 operate to provide bi-directional communications
intermediate external port slave controller 110 and remote device 24.
Although memory 37 is shown external of external port slave
controller 110, in some configurations such memory 37 can be
implemented as internal circuitry of external port slave controller 110.
Memory 37 operates to buffer data passing to remote device 24
or data received from remote device 24 within external port slave
controller 110. External port slave controller 110 operates to forward
received communications to master controller 100 according to timing
of master controller 100. External port slave controller 110 operates
to output messages from master controller 100 to remote device 24
using communication port 36 according to an agreed-upon communication
protocol intermediate external port slave controller 110 and remote
device 24.
Referring to Fig. 11, system slave controller 112 is coupled with
master controller 100 as well as main solenoid 46, charge circuitry 34,
power supply sensors 31, current sensor 40 and element control
circuitry 41. Responsive to control from master controller 100, system
slave controller 112 is configured to control the operation of main
valve 47 using main solenoid 46. Further, responsive to control from
master controller 100, system slave controller 112 can selectively charge
a battery 35 of power supply 30 using charge circuitry 34.
Slave controller 112 can implement the charging of battery 35
responsive to information from power supply sensors 31. Power supply
sensors 31 provide electrical characteristic information of battery 35 and
internal power sources 39 to system slave controller 112. Internal
power sources 39 of power supply 32 include the 5 Volt DC source
and +/- 12 Volt DC source previously described.
Using current sensor 40, system slave controller 112 can monitor
current flowing through power bus 60. Such provides load information
and output power of fuel cell power system 10 to system slave
controller 112. Thereafter, system slave controller 112 can provide such
current and load information to master controller 100.
System slave controller 112 is also coupled with element control
circuitry 41 utilized to control modifying element 53. Such is utilized
to control the temperature within plenum 51. Modifying element 53
can be controlled to provide circulated air within plenum 51 within a
desired operational temperature range. Modifying element 53 is
advantageously utilized in some start-up situations to bring the
temperature within plenum 51 within the operational range in an
expedient manner.
Referring to Fig. 12, sensor slave controller 114 is coupled with
master controller 100, heaters 74, 75, fuel detection circuitry 64 and
temperature circuitry 67. Fuel detection circuitry 64 is associated with
plural fuel sensors 58, 61 provided within housing 12 and plenum 51,
respectively. Temperature circuitry 67 is coupled with temperature
sensor 59 located outside of housing 12. Sensor slave 114 can control
heaters 74, 75 to selectively bring fuel sensors 58, 61 within an
appropriate temperature range for operation.
Fuel detection circuitry 64 receives data from fuel sensors 58, 61
and can condition such information for application to sensor slave
controller 114. If fuel is detected using fuel sensors 58, 61, fuel
detection circuitry 64 can process such information and provide such
data to sensor slave controller 114. Such information can indicate the
concentration of fuel detected within housing 12 or plenum 51 using
fuel sensors 58, 61, respectively. Sensor slave controller 114 can in
turn provide such information to master controller 100.
Temperature sensor 59 provides information regarding the
temperature of the surroundings of fuel cell power system 10.
Temperature circuitry 67 receives outputted signals from temperature
sensor 59 and can condition such signals for application to sensor slave
controller 114 monitoring the external temperature. Sensor slave
controller 114 can provide external temperature information to master
controller 100.
Referring to Fig. 13, air temperature slave controller 116 is
coupled with master controller 100 and temperature circuitry 68 and
passage control circuitry 57. Temperature circuitry 68 is associated with
temperature sensor 55 provided within plenum 51. Passage control
circuitry 57 operates to control air passage 56. For example, passage
control circuitry 57 can control the position of vanes of air passage 56
in an exemplary embodiment.
Temperature sensor 55 is positioned within plenum 51 to monitor
the temperature of circulated air within plenum 51. Temperature
circuitry 68 receives the sensor information from temperature sensor 55
and conditions the information for application to air temperature slave
controller 116. Thereafter, air temperature slave controller 116 may
operate to output the temperature information to master controller 100.
During operation of fuel cell power system 10, air temperature
slave controller 116 operates to control the flow of air into housing 12
using air passage 56 as well as the exhaustion of air within plenum 51
to the exterior of housing 12. Air temperature slave controller 116
controls air passage 56 using passage control circuitry 57 to maintain
the temperature of circulated air within plenum 51 within the desired
operational temperature range. Further, modifying element 63 of
Fig. 11 can be controlled as previously discussed to raise or lower the
temperature of the circulated air. Such control of air passage 56 by
air temperature slave controller 116 can be responsive to information
from temperature sensor 55 and external temperature sensor 59.
Further, efficiency information regarding fuel cells 90 can be calculated
by air temperature slave controller 116 to determine waste thermal
power. Air passage 56 may be controlled responsive to the calculated
waste thermal power.
Referring to Fig. 14, shunt slave controller 118 is coupled with
master controller 100 and switch control circuitry 95. Plural switching
devices 96 are coupled with switch control circuitry 95. As described
above, switching devices 96 are provided to implement selective shunting
of respective fuel cells 90 of fuel cell cartridges 14. Master
controller 100 can be configured to output shunt information to shunt
slave controller 118 for selectively shunting using switching devices 96.
Alternatively, shunt slave controller 118 can execute internally stored
code to provide controlled selective shunting of switching devices 96.
Such shunting operations of fuel cells 90 can be utilized to
provide increased power, to expedite start-up procedures, to shunt a
faulty fuel cell cartridge 14, and to monitor for fuel leaks in exemplary
embodiments. Switch control circuitry 95 is provided to provide
conditioning of control signals intermediate shunt slave controller 118
and switching devices 96.
Referring to Fig. 15, switch slave controller 120 is coupled with
master controller 100 and switch control circuitry 33 and switch
conditioning circuitry 19. Switch control circuitry 33 is coupled with
switching device 38 provided in series with power bus 60. Responsive
to master controller 100, switch slave controller 120 can instruct switch
controller circuitry 33 to control switching device 38. Switching
device 38 provides selective coupling of power bus 60 to an external
load 22. Such can be utilized to assure proper operation of fuel cell
power system 10 prior to coupling power bus 60 with load 22.
Switch slave controller 120 can also monitor the status of
operator interface switches 20 which may be set by an operator of fuel
cell power system 10. Exemplary switches include power on/off of fuel
cell power system 10, enable load, cartridge reset, etc. Switch
conditioning circuitry 19 can filter signals provided from switches 20 and
provide corresponding information regarding switch position to switch
slave controller 120. Thereafter, switch slave controller 120 can output
the switch status information to master controller 100.
Referring to Figs. 16-16A, a flow chart illustrating exemplary
operations of master controller 100 of control system 30 is shown.
Initially, master controller 100 performs a communications check at
step S10. Communication checks may be implemented on a periodic
interrupt basis to verify communications of master controller 100 and
slave controllers 102-120.
At step S12, master controller 100 determines whether a
communication error was discovered. If such an error is present,
master controller 100 issues a shut down command to slave
controllers 102-120 at step S14. Respective slave controllers 102-120
implement shut down operations to bring fuel cell power system 10 into
a shut down condition. Interface slave controller 108 can indicate the
shut down status using operator interface 16. Further, master
controller 100 can instruct external port slave controller 110 to notify
remote device 24 of the shut down condition.
Alternatively, if no communication error is present in step S12,
master controller 100 instructs system slave controller 112 to open main
valve 47 at step S16. In addition, master controller 100 instructs fan
slave controller 106 to start fan 54 at step S16. At step S18, master
controller 100 instructs auxiliary valve slave controller 104 to open
auxiliary valves 45 using auxiliary solenoids 44. Next, master
controller 100 issues a command to auxiliary valve slave controller 104
to open bleed valve 43 using bleed solenoid 42 at step S20.
Thereafter, master controller 100 may execute a start-up subroutine as
set forth in Fig. 17 at step S22. Following successful execution of the
start-up subroutine, master controller 100 outputs a load enable "ready"
signal to switch slave controller 120 at step S24. Switch slave
controller 120 controls, using switch control circuitry 33, switching
device 38 to couple power bus 60 with an external load.
At step S26 of Fig. 16A, master controller 100 extracts data from
slave controllers 102-120. More specifically, master controller 100 can
receive information from cartridge analysis slave controller 102, auxiliary
valve slave controller 104, fan slave controller 106, external port slave
controller 110, system slave controller 112, sensor slave controller 114,
air temperature slave controller 116 and switch slave controller 120.
Next, master controller 100 proceeds to step S28 where it is
determined if a cartridge reset request has been issued. An operator
can implement a cartridge reset condition using switches 20. If a
cartridge reset is indicated, master controller 100 proceeds to step S30
and issues an on-line command to change the status of all off-line fuel
cell cartridges 14 to being on-line. Thereafter, master controller 100
initiates a bleed cycle utilizing auxiliary valve slave controller 104 at
step S32. During the bleed cycle, fuel may be applied to individual
fuel cell cartridges 14 and the bleed valve 43 can be opened to allow
exhaust operations using bleed manifold 65 and bleed exhaust 66.
If no cartridge reset request is indicated at step S28, or after the
bleed cycle is initiated at step S32, master controller 100 proceeds to
step S34 to determine whether a communication error is present. If
a communication error is present, master controller 100 issues a shut
down command at step S36.
If no communication error is present at step S34, master
controller 100 proceeds to step S38 to execute an error subroutine as
described in Figs. 18-18A below. At step S40, master controller 100
calculates operating parameters utilizing the data obtained at step S26.
Based upon the calculated operating parameters (e.g., setting of fan 54,
modifying element 53, etc.), master controller 100 sends the. system
settings at step S42 to the appropriate slave controllers 102-120.
Referring to Fig. 17, a start-up subroutine executable by master
controller 100 is described. Initially, data from sensor slave
controller 114 is analyzed to determine whether the temperature within
plenum 51 is less than 15 °Celsius. If yes, master controller 100 turns
on modifying element 53 utilizing system slave controller 112 at
step S52. Alternatively, master controller 100 instructs systems slave
controller 112 to turn off modifying element 53 if appropriate at
step S54.
Thereafter, master controller 100 proceeds to step S56 and
instructs shunt slave controller 118 to set a shunting duty cycle to
maximum. At step S58, master controller 100 again retrieves the
temperature within plenum 51 from air temperature slave controller 116.
At step S58, master controller 100 determines whether the temperature
within plenum 51 is less than 30 °Celsius. If so, master controller
loops at step S58 until the temperature within plenum 51 is equal to
or greater 30 °Celsius. Next, at step S60, master controller 100 can
calculate a new duty cycle for application to shunt slave controllers 118.
Thereafter, master controller 100 returns to the main set of instructions
described in Fig.s 16-16A.
Referring to Figs. 18-18A, a flow chart illustrating exemplary error
operations of master controller 100 is illustrated. Initially, at step S62,
master controller 100 determines whether fan operation is proper.
Master controller 100 observes data from fan slave controller 106 and
outputs a fan error message to interface slave controller 108 at
step S64 if fan operation is not proper. Thereafter, a shut down
command is issued at step S66 to initiate a shut down procedure of
fuel cell power system 10.
At step S68, it is determined whether internal power supplies are
operating properly. More specifically, master controller 100 interfaces
with system slave controller 112 to determine whether values monitored
by power supply sensors 31 are within range. If not, master
controller 100 sends a power supply error message to interface slave
controller 108 at step S70. Thereafter, master controller 100 issues a
shut down command at step S72.
At step S74, master controller 100 determines whether auxiliary
valve operation is proper. Such is determined by data received from
auxiliary valve slave controller 104 regarding the status of auxiliary
valves 45. This can be additionally performed by monitoring the
voltage of a deactivated fuel cell 90. A zero voltage should result if
auxiliary valve operation is proper. Master controller 100 outputs an
auxiliary valve error message at step S76 to interface slave controller
108 if operation is not proper. Such error message can thereafter be
displayed using operator interface 16. At step S78, master
controller 100 issues a shut down command.
Alternatively, master controller 100 proceeds to step S80 and
determines whether a major fuel leak is present. Such is determined
by monitoring data received from sensor slave controller 114 responsive
to the monitoring of fuel sensors 58, 61. If a major fuel leak is
detected, master controller 100 sends a major fuel leak error message
to interface slave controller 108 at step S82. Thereafter, a shut down
command is issued at step S84.
If no major fuel leak is determined, master controller 100
proceeds to step S86 to determine whether a minor fuel leak is
present. In one configuration, a major fuel leak may be defined as
=5000 ppm and a minor fuel leak may be defined as 1000-4999 ppm.
In some applications, the ranges may be varied for increased or
decreased sensitivity to fuel.
If a minor fuel leak is determined at step S86, master
controller 100 proceeds to step S88 to try to determine if one of fuel
cell cartridges 14 is faulty and the source of the fuel leak.
Accordingly, a first fuel cell cartridge 14 is deactivated at step S88.
Next, master controller 100 attempts to determine whether the fuel leak
is gone. Deactivation of the fuel cell cartridge 14 ceases the supply
of fuel to the fuel cell cartridge 14 using the appropriate auxiliary
valve 45. If it is determined that the fuel leak is gone, an error
message is sent at step S92 to interface slave controller 108 for
conveyance to operator interface 16.
If the fuel leak remains as determined at step S90, master
controller 100 proceeds to step S94 to reactivate the previously
deactivated fuel cell cartridge 14 and deactivate a subsequent fuel cell
cartridge 14. At step S96, master controller 100 determines whether
an index has led past the last fuel cell cartridge 14. If not, master
controller 100 returns to steps S90-S94 to continue with the minor leak
analysis. Alternatively, master controller 100 proceeds to step S98 and
ignores the minor leak for a specified period of time. Once the
specified period of time has elapsed, and the fuel leak is still present,
master controller 100 can issue a shut down command which will cease
the supply of fuel from fuel supply 23 into housing 12 using main
valve 47.
At step S100, master controller 100 determines whether there is
a failed fuel cell cartridge 14. If so, master controller 100 shuts off
the supply fuel to the failed fuel cell cartridge 14 using the appropriate
auxiliary valve 45 at step S102. In addition, a full-time shunt command
for the failed fuel cell cartridge 14 is applied to shunt slave
controller 118 at step S104. At step S106, master controller 100 sends
an error message to interface slave controller 108 for conveyance using
operator interface 16.
At step S108, master controller 100 determines whether enough
fuel cell cartridges 14 are currently on-line. In one exemplary
arrangement, master controller 100 determines whether less than eight
fuel cell cartridges 14 are on-line. If not enough cartridges are on-line,
master controller 100 sends an error command at step S110 to interface
slave controller 108. Such error message can be conveyed to an
operator using operator interface 16. Next, at step S112, master
controller 100 issues a shut down command for fuel cell power
system 10. If enough fuel cell cartridges 14 are on-line at step S108,
master controller 100 proceeds to the main set of instructions defined
in the flow chart of Figs. 16-16A.
Referring to Figs. 19-19B, a flow chart illustrating exemplary
operations of cartridge analysis slave controller 102 is shown. Initially,
at step S120, slave controller 102 indexes to a first fuel cell 90 within
fuel cell power system 10. A transient counter described below is
cleared at step S121. Slave controller 102 obtains a voltage reading
of the indexed fuel cell 90 at step S122. At step S124, slave
controller 102 determines whether the polarity of the indexed fuel
cell 90 is proper. If not, slave controller 102 proceeds to step S126
and sets the indicated fuel cell voltage to zero. Thereafter, the voltage
for the currently indexed fuel cell 90 is posted to a fuel cell array at
step S134.
Alternatively, if the polarity of the indexed fuel cell 90 is proper
at step S124, slave controller 102 determines whether the voltage is
proper at step S128. If not, slave controller 102 increments a ride-
through transient counter at step S130. Thereafter, slave controller 102
determines whether the transient counter is at a maximum value at
step S132. If not, slave controller 102 returns to step S122. If the
transient counter has reached a maximum value, slave controller 102
proceeds to step S134 to post the voltage to the fuel cell array.
At step S136, slave controller 102 determines whether all of the
fuel cells 90 have been indexed. If not, slave controller 102 indexes
to a next fuel cell 90 at step S138 and thereafter returns to step S122.
If all fuel cells 90 have been analyzed using analysis circuitry 91, slave
controller 102 proceeds to step S140 to arrange the fuel cell readings
into readings for respective fuel cell cartridges 14.
Next, slave controller 102 proceeds to step S141 to index to a
first of fuel cell cartridges 14. Slave controller 102 then proceeds to
step S142 to determine whether any of the fuel cell cartridges 14 were
previously provided in a down or off-line condition. If so, slave
controller 102 proceeds to step S160 to determine whether the last fuel
cell cartridge 14 has been indexed. Otherwise, slave controller 102
proceeds to step S144 to determine whether a voltage of any of the
fuel cells of a currently indexed fuel cell cartridge 14 have an
unacceptable voltage condition (e.g., low voltage). If so, slave
controller 102 increments a low voltage counter at step S146. Next,
slave controller 102 proceeds to step S148 to determine whether the
low voltage counter is at a maximum value. The maximum value is
selected to provide the unacceptable fuel cell with a chance to recover
and provide an acceptable voltage during a subsequent pass through the
flow chart. If the low voltage counter is at maximum, slave controller
102 proceeds to step S150 to set the currently indexed fuel cell
cartridge 14 status as deactivated (e.g., down or off-line). Slave
controller 102 instructs master controller 100 to shut off fuel to the
currently indexed fuel cell cartridge 14 at step S152. Master controller
100 thereafter instructs auxiliary valve slave controller 104 to shut off
fuel to the respective fuel cell cartridge 14. At step S154, master
controller 100 additionally outputs a command to shunt slave controller
118 to shunt the appropriate fuel cell cartridge 14. Also, master
controller 100 can output the message to interface slave controller 108
to convey the status of the currently indexed fuel cell cartridge 14
using operator interface 16.
If the currently indexed fuel cell cartridge 14 has a proper
voltage as determined at step S144, slave controller 102 proceeds to
step S145 to clear the low voltage counter. Slave controller 102
associates the fuel cells with respective low voltage counter values. The
low voltage counter for a given fuel cell previously determined to be
unacceptable during the current pass through the flow chart is cleared
at step S145 if the voltage is deemed acceptable at step S144.
Slave controller 102 proceeds to step S156 to post high and low
voltages of the fuel cells of the currently indexed fuel cell cartridge 14
to memory. At step S158, slave controller 102 outputs the high and
low voltage information of the fuel cells of the fuel cell cartridge 14
to master controller 100. Master controller 100 processes the high and
low voltages for the fuel cell cartridge 14 and can instruct interface
slave controller 108 to display or otherwise convey the voltages to an
operator using operator interface 16.
At step S160, slave controller 102 determines whether the last
fuel cell cartridge 14 has been indexed. If not, slave controller 102
indexes to a next fuel cell cartridge 14 at step S162 and thereafter
returns to step S142. If the last fuel cell cartridge 14 has been
indexed at step S160, slave controller 102 proceeds to step S164 to
determine whether too many fuel cell cartridges 14 are down (e.g., less
than seven fuel cell cartridges 14 are down or off-line). If so, slave
controller 102 sends an appropriate message to master controller 100
at step S166.
At step S168, slave controller 102 monitors for the reception of
messages from master controller 100. If a message is received, slave
controller 102 processes the incoming message at step S170. At
step S172, slave controller 102 can transmit fuel cell data and any
messages. Thereafter, slave controller 102 returns to step S120 to
index the first fuel cell 90 to repeat the analysis.
Referring to Figs. 20-20A, a flow chart illustrating exemplary
operations of auxiliary valve slave controller 104 is shown. Initially,
slave controller 104 performs a communication check at step S180 to
assure proper communications with master controller 100. At step S182,
slave controller 104 listens for a start-up signal from master
controller 100. At step S184, it is determined whether the appropriate
start-up signal has been received. Once the start-up signal is received,
slave controller 104 instructs auxiliary solenoids 44 to open respective
auxiliary valves 45 at step S186. At step S188, slave controller 104
commences to perform a bleed procedure wherein slave controller 104
instructs bleed solenoid 42 to open bleed valve 43 for a defined length
of time.
At step S190, slave controller 104 reads data and messages from
master controller 100. Slave controller 104 determines whether the
master is off-line at step S192. If so, slave controller 104 closes
auxiliary valves 45 at step S194. Otherwise, slave controller 104
proceeds to step S196 to determine whether a shut down request has
been issued by master controller 100. If so, slave controller 104
proceeds to step S194. Otherwise, slave controller 104 proceeds to
step S198 to determine whether a change in status of any fuel cell
cartridges 14 has been made. If so, slave controller 104 controls
respective auxiliary valves 45 at step S200 to either supply fuel if the
corresponding fuel cell cartridge 14 is on-line, or cease supply of fuel
if the fuel cell cartridge 14 has been taken off-line.
At step S202, slave controller 104 monitors to determine whether
it is time for a bleed cycle. Slave controller 104 can be configured to
periodically implement a bleed cycle using bleed solenoid 42 and bleed
valve 43 according to a bleed timer. If it is time for a bleed cycle,
slave controller 104 proceeds to step S204 to reset the bleed timer and
thereafter commence a bleed procedure at step S206. As shown, slave
controller 104 cycles back to step S190 to read any new data from
master controller 100.
Referring to Figs. 21-21A, a flow chart illustrating exemplary
operations of fan slave controller 106 is illustrated. Slave
controller 106 initially proceeds to step S210 and performs a
communications check to verify proper communications with master
controller 100. At step S212, slave controller 106 listens for an
appropriate fan start-up signal from master controller 100.
Once the appropriate start-up signal is received as determined at
step S214, slave controller 106 proceeds to step S216 to start operation
of fan 54 at a maximum air flow setting. Thereafter, slave
controller 106 reads fan status information from fan monitoring
circuitry 49 at step S218. At step S220, slave controller 106 determines
whether fan 54 is operating properly. If not, slave controller 106 issues
a shut down request to master controller 100 at step S222.
Otherwise, slave controller 106 receives any updated fan setting
from master controller 100 at step S224. At step S226, slave
controller 106 can output appropriate signals to fan control circuitry 48
to adjust the operation of fan 54. At step S228, slave controller 106
determines whether a shut down command has been issued by master
controller 100. If not, slave controller 106 returns to step S218 to
read the status of fan 54. Otherwise, slave controller 106 proceeds to
step S230 to shut off fan 54.
Referring to Fig. 22, a flow chart illustrating exemplary operations
of interface slave controller 108 is shown. Initially, slave controller 108
proceeds to step S240 to perform a communications check with master
controller 100. Thereafter, slave controller 108 outputs appropriate
message information to operator interface 16 for conveyance to an
operator. In the described embodiment, operator interface 16 displays
the message information received from master controller 100.
Slave controller 108 listens for updates to operator interface 16
at step S244. At step S246, it is determined whether master
controller 100 is off-line. If so, slave controller 108 sends an error
message to operator interface 16 to indicate master controller 100 is
off-line. Otherwise, slave controller 108 proceeds to step S250 to
determine whether there was a change in the status of operator
interface 16. If not, slave controller 108 proceeds to step S244 and
listens for updates for operator interface 16. If a change in interface
status is indicated at step S250, slave controller 108 proceeds to
step S252 to update operator interface 16.
Referring to Fig. 23, a flow chart illustrating exemplary operations
of external port slave controller 110 is illustrated. Initially, slave
controller 110 performs a communications check with master
controller 100 at step S260. Thereafter, slave controller 100 reads any
input communication from remote device 24 and communication port 36.
At step S264, slave controller 110 sends any received communications
to master controller 100. At step S266, slave controller 110 receives
any communications from master controller 100. Slave controller 110
proceeds to forward any communications to communication port 36 and
remote device 24 at step S268.
Referring to Figs. 24-24A, a flow chart illustrating exemplary
operations of system slave controller 112 is shown. Initially, at
step S270, slave controller 112 performs a communications check with
master controller 100. Next, slave controller 112 can read status
information from power supply sensors 31 and current sensor 40 at
step S272. At step S274, it is determined by slave controller 112
whether the inputted status values are within appropriate ranges. If
not, slave controller 112 can generate an error message at step S276
for application to master controller 100.
Otherwise, slave controller 112 proceeds to step S278 and listens
for a main valve open command from master controller 100. At
step S280, it is determined whether the open valve command was
received. Once the open valve command is received, slave
controller 112 proceeds to step S282 to activate main valve 47 using
main solenoid 46. At step S284, slave controller 112 listens for a shut
down command from master controller 100.
Proceeding to step S286, slave controller 112 determines whether
the master controller 100 is off-line. If so, slave controller 112
proceeds to step S296 to shut off power supply 32 and main valve 47
using main solenoid 46. If master controller 100 is on-line, slave
controller 112 proceeds to step S288 to again read status values from
power supply sensors 31 and current sensor 40. Slave controller 112
can control charge circuitry 34 to charge battery 35, if necessary, at
step S290 responsive to the values read at step S288.
At step S292, slave controller 112 determines whether the values
are within the appropriate ranges. If not, slave controller 112 proceeds
to step S294 to generate an error message for application to master
controller 100. Otherwise, at step S296, slave controller 112 monitors
for the presence of a shut down command or request from master
controller 100. If no shut down command is issued, slave
controller 112 returns to step S284. If a shut down request or
command is received at step S296, slave controller 112 proceeds to
step S296 to shut off main valve 47 using main solenoid 46 as well as
turn off power supply 32.
Referring to Fig. 25, a flow chart illustrating exemplary operations
of sensor slave controller 114 is shown. Initially, at step S300, slave
controller 114 performs a communication check with master
controller 100. At step S302, slave controller 114 controls
heaters 74, 75, if necessary, to bring associated fuel sensors 58, 61
within proper operating temperature ranges. Thereafter, slave
controller 114 is configured to read information from fuel detection
circuitry 64 and corresponding fuel sensors 58, 61.
Responsive to reading the fuel sensor values, slave controller 114
determines at step S306 whether a major leak was detected. If so,
slave controller 114 forwards an appropriate major leak message to
master controller 100 at step S308. At step S310, the fuel sensor
values are analyzed to determine whether a minor leak was detected.
If so, slave controller 114 sends an appropriate minor leak message to
master controller 100 at step S312.
At step S314, slave controller 114 reads external temperature
information from temperature circuitry 67 and associated temperature
sensor 59. At step S316, slave controller 114 sends external
temperature values to master controller 100.
Referring to Fig. 26, a flow chart illustrating exemplary operations
of air temperature slave controller 116 is shown. Initially, slave
controller 116 performs a communication check with master
controller 100 at step S320. Thereafter, slave controller 116 reads
temperature values from temperature circuitry 68 and associated
temperature sensor 55 located within air plenum 51. At step S324,
slave controller 116 reads a temperature set point as calculated from
master controller 100.
At step S326, slave controller 116 sets recirculation using air
passage 56 and fan 54 to maintain a set point temperature. Slave
controller 116 outputs the air temperature of plenum 51 as determined
by temperature sensor 55 to master controller 100 at step S328.
Referring to Fig. 27, a flow chart illustrating exemplary operations
of shunt slave controller 118 is shown. Initially, at step S330, slave
controller 118 performs a communication check with master
controller 100. At step S332, slave controller 118 reads data from
master controller 100.
At step S334, it is determined whether there was a change in
status of the fuel cell cartridges 14. If so, slave controller 118
proceeds to step S336 to determine whether there is a change of any
of the fuel cell cartridges 14 to an off-line condition. If not, the
appropriate switching device 96 for the respective fuel cell cartridge 14
is latched to an off position at step S338. Alternatively, slave
controller 118 proceeds to step S340 to latch the appropriate switching
device 96 for the respective fuel cell cartridge 14 in an on position.
Following processing of steps S338 or S340, or alternatively if
there is no change in status of fuel cell cartridges 14 as determined at
step S334, slave controller 118 proceeds to step S342 to cyclically shunt
fuel cells 90 within fuel cell cartridges 14 as described in detail in U.S.
Patent Application Serial No. 09/108,667 incorporated by reference
above.
Referring to Fig. 28, a flow chart illustrating exemplary operations
of switch slave controller 120 is shown. Slave controller 120 performs
a communication check with master controller 100 at step S350.
Thereafter, slave controller 120 reads switch status information from
switches 20 and switch conditioning circuitry 19 at step S352. At
step S354, slave controller 120 reads load enable status information
from master controller 100.
Slave controller 120 determines whether a power off request was
received from master controller 100 at step S356. If yes, slave
controller 120 proceeds to step S358 to send a shut dov/n message to
master controller 100. Otherwise, slave controller 120 proceeds to
step S360. Slave controller 120 determines whether a load enable
request was provided from switches 20. If so, slave controller 120
proceeds to step S362 to determine whether master controller 100 has
indicated fuel cell power system 10 is ready to provide power as
determined in step S354. If so, slave controller 120 proceeds to
step S364 to enable switching device 38.
At step S366, slave controller 120 determines whether the master
controller 100 is in an off-line condition. If so, slave controller 120
disables switching device 38 at step S368. Otherwise, slave
controller 120 proceeds to step S370 to determine whether a cartridge
reset has been indicated from switches 20. If so, slave controller 120
proceeds to send a cartridge reset message to master controller 100 at
step S372. Slave controller 120 then returns to step S352 to read
switch status from switch conditioning circuitry 19 and associated
switches 20 at step S352.
In compliance with the statute, the invention has been described
in language more or less specific as to structural and methodical
features. It is to be understood, however, that the invention is not
limited to the specific features shown and described, since the means
herein disclosed comprise preferred forms of putting the invention into
effect. The invention is, therefore, claimed in any of its forms or
modifications within the proper scope of the appended claims
appropriately interpreted in accordance with the doctrine of
equivalents.
1. A fuel cell power system, comprising:
a housing defining a cavity;
a plurality of terminals borne by the housing and electrically coupled with a load
which has a voltage demand;
a plurality of fuel cells received in the cavity of the housing and electrically
coupled to the plurality of terminals, and wherein the plurality of fuel cells convert
chemical energy into electricity which is supplied to the terminals to meet, at least in part,
the electrical current demand of the load, and wherein the fuel cells are configured to be
individually selectively deactivated, and can be physically removed, by hand, from the
housing while the remaining ones of the fuel cells continue to operate and supply
electricity to the terminals; and
a digital control system which is electrically coupled with the plurality of fuel
cells and is configured to control and monitor an operation of the plurality of fuel cells
and the fuel cell power system.
2. A fuel cell power system as claimed in claim 1, and wherein the digital control
system comprises:
a plurality of distributed controllers, and wherein at least some of the distributed
controllers are in a master/slave relationship.
3. A fuel cell power system as claimed in claim 1, and wherein the digital control
system is configured to electrically bypass individual fuel cells.
4. A fuel cell power system as claimed in claim 1, and comprising :
a plurality of switching devices borne by the housing and individually electrically
coupled with the respective fuel cells, and controlled by the digital control system, and
wherein the switching devices are each configured to shunt one of the fuel cells when
activated by the digital control system.
5. A fuel cell power system as claimed in claim 4, and wherein the digital control
system monitors an electrical characteristic of at least one of the fuel cells, and
selectively controls at least one of switching devices responsive to such monitoring.
6. A fuel cell power system as claimed in claim 1, and comprising :
a temperature sensor borne by the housing and positioned in the cavity, and which
is further electrically coupled in temperature signal transmitting relation with the digital
control system; and
an air temperature control assembly which is operably coupled to the digital
control system, and wherein the digital control system causes the temperature control
assembly to selectively increase or decrease the air temperature in the cavity of the
housing based, at least in part, upon the air temperature sensed by the temperature sensor.
7. A fuel cell power system as claimed in claim 6, and wherein the air temperature
control device comprises a fan which is borne by the housing and which is operably coupled
with and controlled by the digital control system and which is further configured to direct a
flow of air to the respective plurality of fuel cells.
8. A fuel cell power system as claimed in claim 1, and comprising :
a source of fuel which is coupled in fluid flowing relation relative to the plurality
of fuel cells; and
a fuel valve which is controllably coupled with the digital control system and
which selectively meters the source of fuel to the respective fuel cells.
9. A fuel cell power system as claimed in claim 8, and comprising :
a fuel sensor borne by the housing and positioned in the cavity, and wherein the
fuel sensor is coupled in signal transmitting relation relative to the digital control system,
and wherein the digital control system upon sensing the presence of the fuel within the
cavity of the housing, by way of the fuel sensor, implements a shut down operation for
the fuel cell power system.
10. A fuel cell power system as claimed in claim 1, and comprising :
a bleed valve borne by the housing and coupled in fluid flowing relation relative
to at least one of the fuel cells, and wherein the bleed valve is operably coupled with and
controlled by the digital control system, and wherein the bleed valve selectively purges
matter from the at least one fuel cell.
11. A fuel cell power system as claimed in claim 1, and comprising :
a sensor for monitoring the electrical current supplied to the load and the voltage
of at least one of the fuel cells, and wherein the sensor is coupled in signal transmitting
relation relative to the digital control system, and wherein the digital control system
selectively electrically couples and decouples individual fuel cells to the plurality of
terminals based, at least in part, upon the signal received from the sensor.
12. A fuel cell power system as claimed in claim 1, and comprising :
a battery which is electrically coupled with the digital control system, and which
is operable to supply electrical current to energize the digital control system; and
charge circuitry controllably coupled with digital control system and electrically
coupled with the plurality of terminals, and wherein the digital control system monitors
the electrical charge condition of the battery and causes the charge circuitry to selectively
deliver electricity generated by the respective fuel cells to the battery to maintain the
electrical charge of the battery.
13. A fuel cell power system as claimed in claim 1, and comprising :
a communications port electrically coupled with the digital control system and
further coupled in signal transmitting and receiving relation relative to a remote device,
and wherein the digital control system communicates with the remote device by way of
the communications port.
14. A fuel cell power system, substantially as herein described, particularly
with reference to and as illustrated In the accompanying drawings
Fuel cell power systems (10) and methods of controlling a fuel cell power
system are provided. According to one aspect, a fuel cell power system includes
a plurality of fuel cells (14) electrically coupled with plural terminals and
individually configured to convert chemical energy into electricity; and a digital
control system (30) configured to at least one of control and monitor an operation
of the fuel cells. Another aspect provides a method of controlling a fuel cell
power system including providing a plurality of fuel cells individually configured to
convert chemical energy into electricity ; electrically coupling the plurality of fuel
cells ; providing first and second terminals coupled with the fuel cells and
coupling a digital control system with the fuel cells to at least one of monitor and
control an operation of the fuel cells.

Documents:

in-pct-2001-974-kol-granted-abstract.pdf

in-pct-2001-974-kol-granted-assignment.pdf

in-pct-2001-974-kol-granted-claims.pdf

in-pct-2001-974-kol-granted-correspondence.pdf

in-pct-2001-974-kol-granted-description (complete).pdf

in-pct-2001-974-kol-granted-drawings.pdf

in-pct-2001-974-kol-granted-examination report.pdf

in-pct-2001-974-kol-granted-form 1.pdf

in-pct-2001-974-kol-granted-form 18.pdf

in-pct-2001-974-kol-granted-form 2.pdf

in-pct-2001-974-kol-granted-form 3.pdf

in-pct-2001-974-kol-granted-form 5.pdf

in-pct-2001-974-kol-granted-gpa.pdf

in-pct-2001-974-kol-granted-reply to examination report.pdf

in-pct-2001-974-kol-granted-specification.pdf

in-pct-2001-974-kol-granted-translated copy of priority document.pdf


« Previous Patent
Next Patent »
Patent Number 225664
Indian Patent Application Number IN/PCT/2001/974/KOL
PG Journal Number 47/2008
Publication Date 21-Nov-2008
Grant Date 19-Nov-2008
Date of Filing 19-Sep-2001
Name of Patentee AVISTA LABORATORIES INC.
Applicant Address 15913 E. EUCLID, SPOKANE, WASHINGTON
Inventors:
# Inventor's Name Inventor's Address
1 FUGLEVAND WILLIAM A 8025 E WOODVIEW DRIVE, SPOKANE, WASHINGTON 99212
2 BAYYUK SHIBILHANNA I 2703 E 38TH AVENUE, SPOKANE, WASHINGTON 99223
3 LLYOD GREG A 12822 E, 23RD AVENUE, SPOKANE, WASHINGTON 99216
4 DEVRIES PETER D NORTH 125, CROSBY STREET, TEKON, WASHINGTON 99033
5 LOTT DAVID R N 2215 WASHINGTON, SPOKANE, WASHINGTON 99205
6 SCARTOZZI JOHN P 13721 E 25TH AVENUE, SPOKANE, WASHINGTON 99216
PCT International Classification Number H01M 8/04
PCT International Application Number PCT/US2000/13911
PCT International Filing date 2000-05-18
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 09/322,666 1999-05-20 U.S.A.