Note: Descriptions are shown in the official language in which they were submitted.
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CA 02546544 2006-05-10
Fuel Cell Power Pack
TECHNICAL FIELD
The present invention relates generally to fuel cells, and in particular to a
fuel cell
generator and a fuel cell power pack comprising the generator.
BACKGROUND OF THE INVENTION
Fuel cells produce electricity from an electrochemical reaction between a
hydrogen-
containing fuel and oxygen. One type of fuel cell is a proton-exchange-
membrane (PEM)
fuel cell. PEM fuel cells are typically combined into fuel cell stacks to
provide a greater
voltage than can be generated by a single fuel cell. The fuel used by a PEM
fuel cell is
typically a gaseous fuel, and the gaseous fuel is typically hydrogen, but may
be another
hydrogen-containing fuel, such as reformate. In a typical PEM fuel cell, a
chamber of
hydrogen gas is separated from a chamber of oxidant gas by a proton-conductive
membrane that is impermeable to oxidant gases. The membrane is typically
formed of
NAFION polymer manufactured by DuPont or some similar ion-conductive polymer.
NAFION polymer is highly selectively permeable to water when exposed to gases.
A fuel cell stack can be combined with a number of balance of plant components
to
form an electric generator. Such balance of plant components support operation
of the fuel
cell stack, and include components for removing product heat, excess water and
unused
reactant air and hydrogen from the generator, as well as components for
delivering
reactants to the fuel cell stack, and for controlling fuel cell operation. The
fuel cell generator
can be combined with a fuel supply to form a fuel cell power pack.
Fuel cell power packs have been proposed to provide motive energy for
vehicles,
and to provide power for back up and auxiliary power applications. Such power
packs have
also been considered for retrofitting into vehicles originally designed to use
another power
source, such as electric industrial vehicles powered by chemical batteries.
Such industrial
trucks include electric lift trucks, automated guided vehicles and ground
service equipment.
There are a number of challenges in retrofitting a fuel cell power pack into
existing
vehicles, or designing a vehicle from the outset to use a fuel cell power
pack. For example,
such vehicles present a packaging challenge, particularly in retrofit
projects. The batteries
can be removed from the electric vehicle and replaced with the power pack;
however, the
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CA 02546544 2006-05-10
battery compartment in such vehicles limits the dimensions and shape of the
power pack.
Therefore, special consideration must be given to ensure that the power pack
contains a
sufficient supply of fuel and the fuel cell stack produces an output that is
comparable to the
batteries. Also, such battery compartments are typically not designed for the
particular
operating needs of a fuel cell power pack, and challenges include providing
sufficient
oxidant to the fuel cells, providing means for cooling the power pack, and
providing
measures to protect the vehicle and surroundings from the possibility of
explosion caused
by a hydrogen leak.
Known fuel cell generators and fuel cell power packs have not been
particularly
successful in providing comparable performance to batteries in electric
vehicles in a safe
and economical manner. In particular, there are no known fuel cell power packs
that can be
retrofit into a battery compartment of an existing electric vehicle that
provides fuel and
electrical output that result in performance comparable to the replaced
batteries.
SUMMARY OF THE INVENTION
An object of the invention is to provide an apparatus that solves at least
some of the
problems in the prior art. Particular objectives include providing a compact
fuel cell
generator or power pack that is able to supply electrical power in a cost-
effective and
efficient manner.
According to one aspect of the invention, there is provided an electrical
generator
comprising a fuel cell stack and balance of plant components arranged so that
a continuous
air flow path is defined in the generator that extends from an air inlet end
to an air outlet end
of the generator. At least some of the balance of plant components are located
in the air
flow path such that a sufficient air flow can be provided from the air flow
path to supply
reactant air to the fuel cell stack and remove heat generated by the fuel
cells stack and
select balance of plant components. By arranging the balance of plant
components in such
a manner, the generator can produce a particularly high electrical output
relative to its size,
thus making the generator particularly desirable for use in applications where
space is
limited and high output may be desired.
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According to another aspect of the invention, there is provided a fuel cell
power pack
comprising the above generator, a gaseous hydrogen fuel cylinder; and an
enclosure
comprising a volume for receiving the cylinder and an air duct spanning from
an air inlet at
one end of the enclosure to an air outlet at an opposed end of the enclosure.
The generator
is mounted in the duct such that air received by the inlet flows through the
air flow path, and
out of the power pack through the air outlet. By utilizing such a generator
and arranging the
power pack components in such a manner, the power pack can provide a
particularly large
fuel supply and electrical output relative to its size, thus making the power
pack particularly
desirable for use in applications where space is limited, and extended and
high output may
be desired.
The balance of plant components in the air flow path can include:
o a fan effective to generate an air flow in the air flow path.
o a compressor fluidly coupled to the fuel cell stack and operable to compress
and
deliver reactant air from the air flow path to the fuel cell stack;
o a radiator thermally coupled to the fuel cell stack and operable to radiate
heat from
the fuel cell stack into the air flow path;
o electrical components located in the air flow path such that heat generated
by the
electrical components are removed by the air flow; the electrical components
can
include at least one component selected from the group consisting of a power
supply, hydrogen circulation pump, coolant circulation pump, double-layer
capacitor
bank, controller, contactor, fuse box, pressure reducer, and gas shut-off
valve;
o a fluid dissipater fluidly coupled to the fuel cell stack and located in the
air flow path
such that fluids in the dissipater is dissipated into the air flow; and
o a hydrogen sensor and a controller communicative with the hydrogen sensor
and
programmed to stop operation of the generator when the hydrogen sensor detects
a
hydrogen concentration that exceeds a selected threshold.
The power pack can also include an air filter located in the air inlet; such
an air filter is
particularly useful to remove any contaminants in air that is to be used by
the power pack.
Also, the generator can include a double-layer capacitor bank having at least
a portion
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CA 02546544 2006-05-10
thereof in the air flow path such that heat generated by the double-layer
capacitor is
removed by the same air flow that cools other balance of plant components.
The fuel cell power pack can be configured to fit within a battery bay of an
electric
vehicle. When so configured, the power pack can have a ballast module having a
mass
selected such that the total mass of the power pack is substantially the same
as the mass of
a battery designed for use in the vehicle and to be stored in the battery bay.
The ballast
module can form part of a support structure for receiving the fuel cylinder
inside the
enclosure; in such case, the support structure along with a portion of the
enclosure defines
the air duct.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures 1(a) and (b) are two perspective views of a fuel cell power pack.
Figures 2(a) and (b) are two perspective views of the power pack shown in
Figures
1(a) and (b) with cover panels removed.
Figure 3(a) and 3(b) are two perspective views of the power pack shown in
Figures
1(a) and (b) with some cover panels and a generator removed.
Figures 4(a) and (b) are two perspective views of a base module of the fuel
cell
power pack.
Figures 5(a) and (b) are two perspective views of a ballast module of the fuel
cell
power pack.
Figures 6(a) and (b) are two perspective views of a fuel module of the fuel
cell power
pack.
Figures 7(a) and (b) are side elevation and end elevation views of the fuel
module.
Figures 7(c) is an exploded perspective view of a fuel storage cylinder and
fuel
supply assembly of the fuel module.
Figure 7(d) is a side elevation view of a fuel regulator of the fuel supply
assembly.
Figures 8(a) to 8(c) are perspective views of a fuel cell generator module of
the fuel
cell power pack.
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CA 02546544 2006-05-10
Figure 8(d) is an exploded view of a fuel cell generator module of the fuel
cell power
pack.
Figure 9(a) is a perspective view of a generator module with all components
removed.
Figure 9(b) is a perspective view of the generator module with certain balance
of
plant components removed.
Figures 10(a) and 10(b) are left and right side elevation views of the
generator
module.
Figure 11 is a plan view of an upper cover panel of the fuel cell power pack.
Figures 12(a) and (b) are plan views of explosion dissipation mechanisms of
the
upper cover panel.
Figures 13(a) and (b) are perspective views of two different embodiments of
the
upper cover panel after dissipating the force of an explosion.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
According to one embodiment of the invention, a fuel cell power pack is
provided that
electrochemically generates electricity from compressed gaseous hydrogen and
oxidant
from air using a fuel cell stack. The fuel cell power pack integrates a
support structure, fuel
cell generator including generator balance of plant components, optional
ballast, and fuel
module into a single unit, and is particularly useful for mobile applications,
such as providing
motive power for electric vehicles. In one particular application, the fuel
cell power pack can
be retrofitted into battery-powered vehicles and can be mounted in the vehicle
where the
vehicle's battery would normally reside. However, it is within the scope of
the invention to
use the power pack in other applications, such as to supply electricity as a
stationary power
generator.
Referring to Figures 1(a) and 1(b), the fuel cell power pack is referenced by
numeral
5 and has an enclosure 6 having a first cover 60, a second cover 61, a first
panel 62, a
second panel 63, a third panel 64, a fourth panel 65, and a bottom section 11.
The
enclosure 6 serves to house power pack components, protect these components
from the
outside environment, control the flow of air into and out of the power pack 5,
and provide
protection from explosion or fire within the enclosure 6. The first cover 60
includes an
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CA 02546544 2006-05-10
access port 51, a cable pass-through 57 and a lifting device fastening point
85. The second
cover 61 includes a lifting device fastening point 85. The two lifting device
fastening points
85 are provided to allow a lifting device such as a hoist (not shown) to
attach to the top
surface of the fuel cell power pack 5 and move the fuel cell power pack. The
access port 51
is provided to allow service access to intemal components. The cable pass-
through 57 is
provided to allow a power output cable (not shown) to pass from the interior
to the exterior of
the fuel cell power pack 5. The access port 51 and the cable pass-through 57
can be air-
sealed for operation. The third panel 64 includes an enclosure air inlet 58 to
allow air from
the environment to enter the interior of the fuel cell power pack 5. The
fourth panel 65
includes an enclosure air outlet 55, a fueling access cutout 50, and a fuel
regulator access
port 56. The enclosure air outlet 55 is provided to allow air from the
interior of the fuel cell
power pack 5 to reach the environment. The enclosure air outlet 55 includes a
grill 55a. The
fueling access cutout 50 is provided to allow access to fueling connections.
Although multiple covers are shown in this embodiment, a single cover can be
substituted in place of the first cover 60, the second cover 61 and the third
panel 64 within
the scope of the invention. A single cover can be substituted in place of the
first cover 60,
the second cover 61, the first panel 62, the second panel 63, the third panel
64 and the
fourth panel 65 within the scope of the invention.
Referring to Figures 2(a) and 2(b), the fuel cell power pack 5 is shown with
the
covers and panels removed in order to illustrate intemal components of the
power pack.
These internal components comprise a base module 10, a fuel module 20, a
ballast module
30, and a generator module 40.
Referring to Figures 3(a) and 3(b), the enclosure 6 in cooperation with the
base
module 10, fuel module 20 and ballast module 30 define an air duct 2 inside
the enclosure
that extends from the enclosure air inlet 58 at a first end of the enclosure
to the enclosure air
outlet 55 at the opposing end of the enclosure. The generator module 40 is
mounted in this
air duct 2, and is designed such that air flowing through the air duct
provides reactant air to
fuel cells in the generator module 40, cooling air to a radiator 108 and to
certain balance of
plant components, removes leaked hydrogen inside the generator module 40, and
removes
water from the fuel cell stack through a fluid dissipater 104. An air inlet
particulate filter 59 in
the enclosure air inlet 58 removes particulates from the air as it enters the
enclosure 6 to
prevent the incursion of particulates into the interior of the enclosure. A
cooling circuit fan
106 pulls air into the air duct 2 and pushes the air out of the air duct.
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CA 02546544 2006-05-10
Referring to Figures 4(a) and 4(b), the base module 10 provides structural
support
for the power pack components, and base ballast. The base module 10 includes
the bottom
section 11 of the fuel cell power pack 5 and a top section 12. An inside
surface of the top
section 12 has a concave shape that conforms to the shape of the fuel module
20. Ballast
positioning guides 14 extend vertically from corners of the base module 10 to
allow accurate
positioning of the ballast module 30. Base-to-generator fasteners 19 allow the
generator
module 40 to be attached to the base module 10.
Referring to Figures 5(a) and 5(b), the ballast module 30 mounts over the base
module 10 and the fuel module 20 to provide additional ballast. Such ballast
is often
required when the power pack 5 is being retrofitted into a vehicle (not shown)
that was
designed to be powered by other means, e.g. by batteries. In such cases, the
weight and
center of gravity of the power pack 5 and the original power plant sans
ballast will likely
differ, and the weight of the ballast can be adjusted to compensate
accordingly. Where the
vehicle is designed from the outset to use the power pack 5, there may be no
need for
ballast, and in such case, the ballast module 30 can be hollow to render it
essentially
weightless or omitted altogether, and the base module 10 can be hollow to
render it
essentially weightless.
The fuel cell power pack 5 is particularly useful for application in electric
industrial
trucks such as lift trucks, automated guided vehicles and ground service
equipment.
Conventional lift trucks that are used within enclosed environments are
typically electrically
powered by batteries and driven by electric motors. Such lift trucks suffer
from the limited
range and long recharge periods characteristic of the batteries, and are thus
ideal
candidates for retrofitting with the power pack 5. As is well documented in
the art, fuel cell
electrical generators provide significant advantages over batteries as a
source of power for
electric vehicles, such as substantially increased range and faster refueling
periods. When
the power pack 5 is intended for use in lift trucks, the weight and centre of
gravity of the
base module 10 and ballast module can be selected to match the battery
originally designed
for the lift truck.
The ballast module 30 includes ballast-to-base fasteners 31, positioning holes
33, a
lower section 32, and generator fastening points 39. An inside surface of the
lower section
32 has a concave shape that conforms to the shape of the fuel module 20. The
ballast
module 30 is accurately aligned to the base module 10 by placing the ballast
module 30
such that the positioning holes 33 fit over the ballast module positioning
guides 14 and allow
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CA 02546544 2006-05-10
the ballast module 30 to be lowered until its bottom surface contacts the
upper surface of
the base module 10. The ballast-to-base fasteners 31 fasten to the upper end
of the
positioning guides 14 to secure the ballast module 30 to the base module 10.
The base module 10 and the ballast module 30 are preferably cast from gray
iron.
Such material is inexpensive and dense, and thus is useful for providing
reduced
manufacturing costs and providing ballast. However, other materials and
manufacturing
techniques can be substituted within the scope of the invention as will be
apparent to one
skilled in the art.
Referring to Figures 6(a) and 6(b), the fuel module 20 includes a fuel storage
cylinder 21 that stores compressed hydrogen gas ("fuel"), mounting components
for
mounting the fuel module 20 to the base module 10, and a fuel supply assembly
80 for
transferring fuel from the fuel storage cylinder 21 to the generator module
40. A suitable
such fuel storage cylinder 21 can be a Type 4 pressure vessel rated to 700 bar
manufactured by Lincoln Composites. The fuel storage cylinder 21 is generally
cylindrical
with semi-spherical ends; as mentioned above, the ballast module 30 and base
module 10
are shaped to conform to the shape of the fuel storage cylinder 21 with air
spaces
therebetween. These air spaces allow the fuel storage cylinder 21 to expand in
response to
increases in fuel pressure. An end plug 28 is mounted to one end of the fuel
storage cylinder
21 and the fuel supply assembly 80 is mounted to the other end of the fuel
storage cylinder
21; the fuel storage cylinder has a fuel port (not shown) at this end which is
fluidly coupled to
the fuel supply assembly 80.
An end plug mounting bracket 29 is attached to the end plug 28 and serves to
fasten
the fuel module 20 to the base module 10. The lower end of the end plug
mounting bracket
29 is attached to the base module 10, while the upper end is free to flex. The
upper end of
the bracket 29 is shaped to loosely contain the end plug 28 such that the fuel
module 20 can
be easily rotated for the purpose of installation. The flexibility of this
bracket 29 also allows
the fuel storage cylinder 21 to expand and contract axially, according to
changes in fuel
pressure. The end plug 28 can contain a temperature transducer (not shown) for
sensing
the internal temperature of the fuel storage cylinder 21 and transmitting the
temperature
value electronically by way of a signal wire (not shown) to the controller
(not shown) of the
generator module 40. Alternatively, the temperature transducer can be coupled
to the fuel
supply assembly 80.
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CA 02546544 2006-05-10
The power pack 5 is designed to maximize the size of the fuel storage cylinder
21
within the confines of the enclosure 6; the dimensions of the enclosure are
dictated by the
application and are particularly limited when the fuel cell power pack 5 is
retrofitted into a
space originally designed for a battery. Design considerations to maximize
fuel storage
cylinder size include minimizing the size of the base and ballast modules 10,
30 and
minimizing the air spaces between the fuel storage cylinder 21 and these
modules 10, 30.
Also, the length of the fuel supply assembly 80 is minimized to maximize the
length of the
fuel storage cylinder 21. In this description, "length" refers to the
dimension parallel to the
fuel storage cylinder axis, and "width" and height" and "lateral" refer to
dimensions
perpendicular to the fuel storage cylinder axis.
Referring to Figures 7(a) to 7(c), the fuel supply assembly 80 serves to
fluidly couple
the fuel storage cylinder 21 to the generator module 40, regulate the pressure
and flow rate
of the fuel supply, provide means for refueling the fuel storage cylinder 21,
and provide
means for detecting leaked fuel and flames. In this connection, the fuel
supply assembly 80
comprises a fuel regulator 82 fluidly coupled to the fuel port (not shown) in
the fuel storage
cylinder 21, a check valve 83 fluidly coupled to the fuel regulator 82, a fuel
filling line 81
fluidly coupled at one end to the check valve 83 and at another end to a
refueling port 52.
The refueling port 52 has a connector for coupling to an extemal fuel source
(not shown) to
refuel the fuel storage cylinder 21. The fuel regulator 82 also has a fuel
outlet 23 that is
fluidly coupled to a solenoid-operated valve 86 and a fuel transfer conduit
93. The solenoid-
operated valve 86 opens and closes in response to signals from the system
controller (not
shown) by way of a signal wire (not shown). The fuel transfer conduit 93 is
coupled to the
generator module 40 and thus defines a fuel pathway from the fuel storage
cylinder 21 to
the fuel cells in the generator module 40.
The fuel regulator 82 and port 52 are fastened to an assembly mount 89, which
in
turn is fastened to the base module 10. The assembly mount 89 is also provided
with a
mounting hole for mounting a grounding connection 53, a hydrogen sensor 90,
and a flame
sensor 91. The refueling port 52 is compliant with the Society of Automatic
Engineers J2600
standard for transfer of high pressure hydrogen gas. The grounding connection
53 is
provided to allow a ground cable (not shown) to be interconnected between the
external fuel
source equipment (not shown) and the fuel cell power pack 5. A fuel regulator
access port
56 is provided in the mount 89 to allow service access to the fuel regulator
82. The
hydrogen sensor 90 is provided to sense the presence of leaked fuel within the
fuel cell
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CA 02546544 2006-05-10
power pack 5 and to send a corresponding signal to a system controller (not
shown) by way
of a signal wire (not shown). The flame sensor 91 is provided to sense the
presence of
flames within the fuel cell power pack 5, and send a corresponding signal to
the system
controller (not shown) by way of a signal wire (not shown).
The fuel regulator 82 includes a built-in excess flow fuse (not shown), and a
manually activated shutoff valve (not shown) as are well known for fuel
regulators. Also
coupled to the fuel regulator 82 are a pressure transducer 84 and a pressure
transducer
signal wire 96, a fuel bleed valve 97, and a pressure relief device 87. The
pressure
transducer 84 is provided to sense the pressure of the fuel in the fuel
storage cylinder 21
and to send a corresponding signal to the system controller (not shown) by way
of the
pressure transducer signal wire 96. The fuel bleed valve 92 is provided to
allow manual
venting of fuel from the fuel storage cylinder 21. The pressure relief device
87 is provided to
allow fuel to escape from the fuel storage cylinder 21 in the event of an over-
pressure
condition, as required by law.
In order to reduce the length of the fuel supply assembly 80 (thereby
increasing the
available length for the fuel storage cylinder 21) the mount 89 is designed to
extend
perpendicularly from the fuel storage cylinder axis, which allows the fuel
supply assembly
components to be mounted in a lateral direction from the fuel storage cylinder
axis. Also, the
fuel regulator 82, which is typically a bulky component, is designed
especially to minimize its
length. As can be seen in Figure 7(d), the fuel regulator 82 has a fuel
storage cylinder
connector 94 and a main body 95. The fuel storage cylinder connector 94
extends axially
and into the fuel storage cylinder 21, and the main body 95 is provided with
laterally-
mounted ports for coupling to the fuel filling line 83 and the fuel transfer
conduit 93. These
ports are laterally-mounted so that the fuel filling line 83 and fuel transfer
conduit 93 extend
laterally from the fuel storage cylinder axis, thereby minimizing the length
of the fuel supply
assembly 80. A suitable such fuel regulator 82 can be a fuel regulator
manufactured by
Tescom Corporation.
Referring now to Figures 8(a) to 8(d), the generator module 40 includes a
generator
frame 41, which is attached to the base module 10 by way of generator-to-
ballast fasteners
42, and is attached to the ballast module 30 by way of the base-to-generator
fasteners 19.
The generator module 40 includes a fuel cell stack 100 that electrochemically
reacts
gaseous hydrogen fuel supplied by the fuel storage cylinder 21 and oxygen from
ambient air
to produce electricity. By-products of the reaction include water and heat.
The fuel cell stack
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CA 02546544 2006-05-10
100 comprises a stack of a proton exchange membrane (PEM) type fuel cells; a
suitable
such fuel cell stack is the Mark 9 stack manufactured by Ballard Power
Systems. However, it
is within the scope of the invention for the power pack to use other types and
makes of fuel
cells.
The generator module 40 also includes balance of plant components for
controlling
and humidifying the supply of air and fuel to the fuel cell stack 100,
controlling and
conditioning the supply of electricity generated by the fuel cell stack,
cooling the fuel cell
stack, and removing excess water, unreacted fuel and air and contaminants from
the fuel
cell stack. Such balance of plant components include a fluid management
apparatus 102, a
fluid dissipater 104, a cooling circuit fan 106, a radiator 108, a coolant
tank 110, an air
compressor 112, an energy storage array 114, a power supply 116, a system
controller 120,
a subsystem controller 121, a coolant bypass valve 111, an air compressor
filter 11 2b, an air
compressor motor controller 112d, a fuel circulation pump 118, a coolant
circulation pump
119, a de-ionizing filter 122, a contactor 123, a fuse box 124, a fuel
pressure reducer 125,
and a fuel shutoff valve 126. A plurality of air flow holes 113 in the air
compressor's
mounting plate provide air flow paths through the plate.
The generator frame 41 includes a top rack 44, a bottom rack 45 and a frame
end
46. The fuel cell stack 100 and fluid management apparatus 102 are coupled to
each other
and are together mounted to the top surface of the top rack 44. The fuel
circulation pump
118, system controller 120, air compressor motor controller 112d, fuel
pressure reducer 125,
fuel shutoff valve 126, de-ionizing filter 122 are mounted to the bottom
surface of the top
rack 44. The air compressor 112, air compressor filter 112b, air compressor
filter inlet 112c,
power supply 116, subsystem controller 121 are mounted to the top surface of
the bottom
rack 45. The energy storage array 114 is mounted to the bottom surface of the
bottom rack
45. The coolant tank 110 and radiator 108 are mounted to the frame end 46. The
cooling
circuit fan 106, fluid dissipater 104 and coolant bypass valve 111 are mounted
to the
radiator 108.
The space between the bottom surface of the top rack 44 and the top surface of
the
bottom rack 45 is not filled by the components mounted to the bottom surface
of the top rack
44 and to the top surface of the bottom rack 45 and their interconnecting
pipes, tubes,
cables and wires, such that an air flow path 3 through the generator module 40
is
maintained. In other words, the balance of plant components are positioned to
allow
sufficient air flow through the generator module 40 for supplying reactant air
to fuel cells in
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CA 02546544 2006-05-10
the generator module 40, cooling air to the radiator and the balance of plant
components,
removal of leaked hydrogen inside the generator module 40, and removal of
water from the
fuel cell stack. Figures 9(a) and 9(b) illustrates a plurality of air flow sub-
paths through the
generator as denoted by dashed arrows.
Referring now to Figures 10(a) and 10(b), the generator module 40 is shown to
have
a plurality of air flow sub-paths around and past the balance of plant
components, as
denoted by dashed arrows. The air flow is coolest at the enclosure air inlet
58, and
increases in temperature as it flows past warmer components. The air flow
provides the
most cooling where it is coolest.
The air compressor 112 is provided to compress air for a reactant air circuit
of the
fuel cell stack 100, as is typical for PEM-type fuel cell power systems. The
air compressor
112 generates large amounts of heat when operating, and can overheat and fail
from
overheating, unless provided with cooling. The positioning of the air
compressor 112 near
the enclosure air inlet 58 locates the compressor within the coolest part of
the air flow path
3, such that the air flow can maintain the compressor below its maximum
operating
temperature. The positioning of the air compressor filter 112b and the air
compressor filter
inlet 112c is for convenience, and does not reflect a need for cooling. A
suitable such air
compressor can be a scroll-type air compressor manufactured by Air Squared
under the
model number P32H58W2.
The power supply 116 is provided to convert the output voltage of the fuel
cell stack
100 to at least one standard voltage suitable for electric equipment, as is
typical of fuel cell
power systems. The power supply 116 of the current invention includes a first
DC voltage
regulator, a second voltage regulator and a third voltage regulator. The power
supply
generates heat when operating, and can overheat and fail from overheating,
unless
provided with cooling. The positioning of the power supply 116 within the air
flow path 3,
allows the air flow to maintain the power supply 116 below its maximum
operating
temperature. In the preferred embodiment of the invention, the first DC
voltage regulator
additionally includes a coolant circuit of the liquid cooling system of the
fuel cell stack to
provide additional cooling.
The fuel circulation pump 118 is provided to circulate hydrogen in a fuel
circuit of the
fuel cell stack 100, and the coolant circulation pump 119 is provided to
circulate coolant in a
coolant circuit of the fuel cell stack 100, as is typical for PEM-type fuel
cell power systems.
The fuel circulation pump 118 and the coolant circulation pump 119 generate
heat when
12
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CA 02546544 2006-05-10
operating, and can overheat and fail from overheating, unless provided with
cooling. The
positioning of the pumps 118, 119 within the air flow path 3 allows the air
flow to maintain
the compressor below its maximum operating temperature.
The energy storage array 114 is provided to store energy generated by the fuel
cell
stack 100, as is typical for hybrid fuel cell power systems. In the preferred
embodiment of
the invention, the energy storage array 114 is a bank of double-layer
capacitors. The
preferred double-layer capacitor is sold by Maxwell Technologies under the
brand name
Boostcap and the part number BCAP2600-E270-T05; however, another capacitor
could be
substituted without detracting from the invention. The energy storage array
114 generates
heat when operating, and can overheat and fail from overheating, unless
provided with
cooling. The positioning of the energy storage array 114 within the air flow
path 3 allows the
air flow to maintain the energy storage array 114 below its maximum operating
temperature.
The radiator 108 is provided as part of the cooling circuit of the generator
module 40
to radiate heat from the coolant to the environment. The radiator 108 is
located near the
enclosure air outlet 55 such that radiated heat is readily conveyed to the
environment. A
suitable such radiator can be a radiator manufactured by Modine under the part
number
NPD2146D3.
The cooling circuit fan 106 is provided to generate an air flow path 3 through
the air
flow path. The cooling circuit fan 106 is positioned near and upstream of the
radiator 108 to
push air through the radiator in effecting heat transfer from the radiator to
the cooling air
stream, and in pushing the heated air through the enclosure air outlet 55 to
the environment.
The positioning of the cooling circuit fan 106 near the enclosure air outlet
55 also allows the
fan to pull air from the environment through the enclosure air inlet 58 and
the generator
module 40. In the preferred operation method of the power system, the cooling
circuit fan
106 is running whenever the power system is running, and the fan speed is
controlled
according to the temperature of coolant at the radiator 108. A suitable such
cooling circuit
fan can be a fan assembly manufactured by Tripac under the part number 14-
LZ310BH2A.
The fluid dissipater 104 is provided to evaporate water from the fuel cell
stack 100,
and to dilute and disperse unreacted fuel from the fuel cells. The positioning
of the fluid
dissipater 104 near and downstream of the radiator 108 locates the fluid
dissipater 104
within the warmest part of the air flow path 3, such that the air flow can
heat and ventilate
the fluid dissipater to speed the evaporation of fuel cell water within the
fluid dissipater, and
speed the dilution and dispersal of unreacted fuel cell fuel within the fluid
dissipater. The
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CA 02546544 2006-05-10
positioning of the fuel cell stack 100 and the fluid management apparatus 102
at the top of
the generator module 40 allows water from those components to flow under
gravity to the
fluid dissipater 104, and coolant to flow under gravity to the radiator 108
and the coolant
tank 110.
The hydrogen sensor 90a is provided to sense leaked hydrogen from hydrogen
containing components within the enclosure 6. The positioning of the hydrogen
sensor 90a
near the cooling circuit fan 106 locates the hydrogen sensor 90a where the fan
draws most
of the gases from within the enclosure 6. The hydrogen sensor 90a and the
hydrogen
sensor 90 are communicative with the system controller 120 to provide hydrogen
detection
information to the system controller. When starting the power system, a
hydrogen reading
above a predetermined value prevents start up through controller logic in
order to avoid
providing an ignition source to a potentially dangerous mixture of hydrogen in
air. When the
power system is running, a hydrogen reading above a predetermined value causes
the
power system to shut down through controller logic in order to isolate the
fuel source and to
avoid providing an ignition source to a potentially dangerous mixture of
hydrogen in air. The
hydrogen sensors 90a, 90 and their signals do not affect the speed or
operational state of
the cooling circuit fan 106.
The system controller 120, air compressor motor controller 112d, subsystem
controller 121, contactor 123, fuse box 124, fuel pressure reducer 125, and
fuel shutoff
valve 126 generate heat when operating. The positioning of these components
within the air
flow path 3 allows the air flow to maintain the components below their maximum
operating
temperature. A suitable such system controller can be a controller
manufactured by Amp
under the part number F5SB-1 4A624-AA.
The packaging of the fuel cell stack 100, the fluid management apparatus 102,
the
fluid dissipater 104, the balance of plant components, and connecting pipes,
tubes, cables
and wires within the generator module 40 allows easy installation, removal and
replacement
of the generator module.
The fuel cell power pack 5 is designed so that the generator module 40 can
operate
to generate electricity with or without the enclosure panels in place.
Operating without the
enclosure panels is useful for commissioning, testing and troubleshooting
purposes.
However it is preferable that the panels be in place, as such panels help
regulate the air flow
through the generator module 40 as well as protect users from the dangers of
fire or
explosion.
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CA 02546544 2006-05-10
The ignition of fuel mixed with air within the enclosure 6 may cause an
explosion and
a sudden rise in the pressure of the gases within the enclosure. Referring to
Figure 11, the
second cover 61 is provided with an explosion dissipating mechanism 140 for
dissipating the
effects of an explosion. The dissipating mechanism 140 consists of multiple
explosion
dissipating structures 150 on one edge of the second cover 61, and multiple
retaining hinges
149 on the opposite edge of the cover 61. As shown in Figure 12(a), the
explosion
dissipating structure comprises a cover fastener 157 and a plurality of
cutouts and cuts,
namely: a first cut 151, a second cut 152, a third cut 153, a first group of
cutouts 154, and a
second group of cutouts 155. The cuts and cutouts can be produced by laser,
water jet or
plasma cutting. The cover fastener 157 is provided to secure the cover 61 to
the fuel cell
power pack structure below. The cuts 151, 152 are parallel to each other and
extend
through the cover 61. The third cut 153 is perpendicular to and contiguous
with the second
cut 152 and extends from the second cut 152 to the cover's edge 156. The
cutouts 154, 155
are rectangular openings in the cover 61, and the first group of cutouts 154
is located
between the first cut 151 and the second cut 152, and the second group of
cutouts 155 is
located between the first cut 151 and the edge 156.
Referring to Figure 12(b), the portions of the cover 61 that surround and
interpose
the first group of cutouts 154 form largely parallel lands 160, 161, 162, 163
between the first
cut 152 and the second cut 153, and the portions that surround and interpose
the second
group of cutouts 155 form largely parallel lands 164, 165, 166, 167 between
the second cut
153 and the edge 156. This alternation between cuts or cutouts and lands
results in the
lands being flexible in comparison with the main portion of the cover 61, and
the narrow
edges of the cutouts together form lines of weakness 171, 172 in the first
group of cutouts
154 and lines of weakness 173, 174 in the second group of cutouts 155 that
allow the
explosion dissipating mechanism 150 to deflect predictably under force. The
length of the
cutouts 154, 155 determines the length of the portions of the explosion
dissipating
mechanism 140 that can deflect under force, and thereby limits the height to
which the cover
61 can be raised under such force.
The optimum dimensions of the cuts, cutouts and lands, strength of the cover
fastener 157, number of hinges 149, strength of the hinges 149 and hinge
fasteners (not
shown), and number of explosion dissipating mechanisms 150 in the. explosion
dissipating
structure 140 are determined through calculation of the explosive force that
may occur
within the fuel cell power pack 5. The lands are designed to not break upon
internal power
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CA 02546544 2006-05-10
pack fuel explosion, thereby preventing the cover 61 from detaching from the
fuel cell power
pack 5. The lands allow bending in two planes to control tension and shear
force on
fasteners. The lands bend to reduce force on the fastener due to internal
pressure on the
cover.
Figure 13(a) shows the fuel cell power pack 5 with the explosion dissipation
mechanisms 150 deflected and the cover 61 raised after an internal explosion.
Figure 13(b)
shows an alterative embodiment of the cover 61 which covers the entire top of
the power
pack 5.
Assembly of the fuel module 20 includes firstly assembling the fuel supply
assembly
80; and secondly attaching the fuel supply assembly 80 and the end plug 28 to
the fuel
storage cylinder 21. Assembly of the fuel module 20 to the base module 10
includes firstly
attaching the end plug mounting bracket 29 to the base module 10; secondly
positioning the
fuel module 20 within the top section 12 of the base module 10 such that the
end plug 28 is
located within the end plug mounting bracket 29; thirdly rotating the fuel
module 20 such that
the assembly mount 89 fits into a mating shape of the base module 10; and
fourthly
attaching the fuel module 20 to the base module 10 by securing the assembly
mount 89 to
the base module 10 by fastening the assembly-to-base fasteners 92.
Assembly of the ballast module 30 to the base module 10 includes firstly
fitting the
positioning holes 33 of the ballast module 30 over the ballast positioning
guide 14, secondly
lowering the ballast module 30 to contact the base module 10; thirdly securing
the ballast
module 30 to the base module 10 by ballast-to-base fasteners 31
The generator module 40 may be assembled at any time, irrespective of the
assembly of the other modules 10, 20, 30. Assembly of the generator module 40
includes
fastening the fuel cell stack 100 and the balance of plant components to the
generator frame
41.
Assembly of the fuel cell power pack 5 includes firstly assembling the fuel
module 20
and attaching it to the base module 10 as described above; secondly,
positioning and
attaching the ballast module 30 to the base module 10 as described above;
thirdly placing
the generator module 40 on the base module 10 and attaching the generator
frame 41 to the
base module 10 and the ballast module 30; fourthly, coupling the fuel outlet
23 of the fuel
module 20 to the fuel inlet (not shown) of the generator module 40; fifthly,
coupling the
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CA 02546544 2006-05-10
transducer signal wire 96, and all other signal wires (not shown) to the
system controller
120.
The attachment of the covers and panels, and passing the power output cable
(not
shown) from the interior of the power pack through the cable pass-through 57,
together with
suitable air sealing of the cable pass-through, completes the assembly of the
fuel cell power
pack 5.
It is to be understood that even though various embodiments and advantages of
the
present invention have been set forth in the foregoing description, the above
disclosure is
illustrative only, and changes may be made in detail, and yet remain within
the broad
principles of the invention. Therefore, the present invention is to be limited
only by the
claims appended to the patent.
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