U.S. patent application number 11/649977 was filed with the patent office on 2007-08-30 for hybrid power supply apparatus for battery replacement applications.
This patent application is currently assigned to Cellex Power Products, Inc.. Invention is credited to Adrian J. Corless, Kenneth W. Kratschmar, Carolyn Lawrence, David Leboe, Christopher E.J. Reid.
Application Number | 20070199746 11/649977 |
Document ID | / |
Family ID | 25136908 |
Filed Date | 2007-08-30 |
United States Patent
Application |
20070199746 |
Kind Code |
A1 |
Reid; Christopher E.J. ; et
al. |
August 30, 2007 |
Hybrid power supply apparatus for battery replacement
applications
Abstract
This application relates to a hybrid power supply apparatus
comprising a fuel cell and an energy storage device for use in
off-road electric vehicles, such as lift trucks. The apparatus is a
substitute for conventional lead acid batteries and is sized to fit
within a conventional lift truck battery receptacle tray. The fuel
cell and fuel processor systems are designed to meet the average
load requirements of the vehicle, while the batteries and power
control hardware are capable of responding to very high
instantaneous load demands. The invention has a similar electrical
interface as conventional battery systems and does not require
vehicle modification. The apparatus is air-cooled to ensure that
the hybrid power components operate within a preferred temperature
range and to maintain the external surfaces of the apparatus and
exhaust gases within safe temperature limits. Apart from vehicular
applications, low power hybrid fuel cell products as exemplified by
the present invention may also find application in uninterruptable
power supply systems, recreational power, off-grid power generation
and other analogous applications.
Inventors: |
Reid; Christopher E.J.;
(Vancouver, CA) ; Corless; Adrian J.; (Vancouver,
CA) ; Leboe; David; (Vancouver, CA) ;
Lawrence; Carolyn; (Vancouver, CA) ; Kratschmar;
Kenneth W.; (Victoria, CA) |
Correspondence
Address: |
L. Grant Foster;HOLLAND & HART LLP
P.O. Box 11583
Salt Lake City
UT
84147-0583
US
|
Assignee: |
Cellex Power Products, Inc.
Richmond
CA
|
Family ID: |
25136908 |
Appl. No.: |
11/649977 |
Filed: |
January 5, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10684622 |
Oct 14, 2003 |
7207405 |
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11649977 |
Jan 5, 2007 |
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09785878 |
Feb 16, 2001 |
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10684622 |
Oct 14, 2003 |
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Current U.S.
Class: |
180/65.31 ;
429/440; 429/442; 429/513; 429/515; 903/908 |
Current CPC
Class: |
B66F 9/07595 20130101;
Y02E 60/10 20130101; H01M 8/04768 20130101; H01M 10/625 20150401;
H01M 10/66 20150401; Y02P 90/60 20151101; H01M 8/00 20130101; H01M
16/006 20130101; H01M 8/04701 20130101; B60K 1/04 20130101; B60L
53/80 20190201; H01M 8/04014 20130101; B60K 2001/005 20130101; B60L
50/40 20190201; B60L 50/72 20190201; B66F 9/07572 20130101; H01M
8/2475 20130101; Y02T 90/12 20130101; B60L 58/40 20190201; H01M
8/0491 20130101; H01M 10/6563 20150401; B60L 2200/42 20130101; H01M
8/04567 20130101; H01M 8/0612 20130101; B60L 58/33 20190201; Y02T
10/70 20130101; Y02T 10/7072 20130101; Y02T 90/40 20130101; B60K
2001/0455 20130101; H01M 8/04373 20130101; B60L 58/34 20190201;
B60Y 2200/15 20130101; H01M 50/20 20210101; Y02E 60/50 20130101;
H01M 8/04417 20130101; H01M 8/04597 20130101; B60L 50/66 20190201;
Y02T 90/14 20130101; H01M 10/613 20150401; H01M 10/6565
20150401 |
Class at
Publication: |
180/065.3 ;
429/012; 429/034; 903/908 |
International
Class: |
B60L 11/18 20060101
B60L011/18; H01M 8/22 20060101 H01M008/22 |
Claims
1. A hybrid power supply apparatus interchangeable with a
conventional battery removably positionable within a battery
receptacle tray of an electric vehicle, the battery having a power
output connectable to the drive system of the vehicle, said hybrid
power apparatus comprising: (a) a fuel cell; (b) an energy storage
device chargeable by said fuel cell; (c) a housing enclosing said
fuel cell and said energy storage device, wherein said housing is
sized to fit within said battery receptacle tray; and (d) a power
output electrically connectable to said storage device and
extending externally of said housing for electrically coupling said
apparatus to said drive system of said vehicle when said housing is
positioned within said battery receptacle tray.
2. The apparatus of claim 1, further comprising a coolant system
for flowing gas through said housing, said coolant system
comprising: (a) a gas inlet for drawing gas into said housing; (b)
at least one blower positioned within said housing for moving gas
through said housing in predetermined flow paths to regulate the
temperature of said apparatus; and (c) a gas outlet for expelling
exhaust gas from said housing.
3. The apparatus of claim 2, wherein said housing comprises a user
interface surface which is exposed when said housing is placed
within said vehicle receptacle tray, wherein said gas inlet and gas
outlet are located on said user interface surface.
4. The apparatus of claim 3, wherein the temperature of said
exhaust gas does not exceed 50.degree. C. when said coolant system
is in operation.
5. The apparatus of claim 3, wherein said coolant system maintains
said user interface surface at a temperature not exceeding
50.degree. C. when said apparatus is in operation.
6. The apparatus of claim 2, wherein said energy storage device is
located within said housing proximate said gas inlet.
7. The apparatus of claim 1, further comprising a fuel processor
positioned within said housing for converting a source of fuel to
hydrogen-enriched gas for delivery to said fuel cell.
8. The apparatus of claim 7, further comprising a fuel storage
chamber located within said housing, wherein said storage chamber
is in fluid communication with said fuel processor.
9. The apparatus of claim 8, further comprising a fuel inlet on
said housing in fluid communication with said fuel storage
chamber.
10. The apparatus of claim 9, wherein said housing comprises a user
interface surface which is exposed when said housing is placed
within said vehicle receptacle tray, wherein said fuel inlet is
located on said user interface surface.
11. The apparatus of claim 8, wherein said fuel chamber is
thermally isolated from the remainder of said housing.
12. The apparatus of claim 1, further comprising a fuel storage
chamber located within said housing, wherein said storage chamber
is in fluid communication with said fuel cell.
13. The apparatus of claim 8, wherein said fuel storage chamber
stores menthanol fuel.
14. The apparatus of claim 8, wherein said fuel storage chamber
stores propane fuel.
15. The apparatus of claim 1, further comprising a controller
positioned within said housing for regulating operation of said
fuel cell depending upon the state of charge of said energy storage
device.
16. The apparatus of claim 1, wherein said energy storage device
comprises at least one battery.
17. The apparatus of claim 1, wherein said energy storage device
comprises at least one capacitor.
18. The apparatus of claim 1, further comprising a DC/DC power
converter positioned within said housing for converting DC current
generated by said fuel cell to a voltage suitable for charging said
energy storage device.
19. The apparatus of claim 1, further comprising a load compensator
positioned within said housing for increasing the weight of said
apparatus to a weight approximating the weight of said conventional
battery.
20. The apparatus of claim 1, further comprising a first vibration
dampener positioned within said housing for absorbing vibration
when said vehicle is in operation.
21. The apparatus of claim 20, comprising a second vibration
dampener which surrounds at least part of said housing when said
housing is positioned within said battery receptacle tray.
22. The apparatus of claim 1, wherein said housing is sized to fit
within a pallet truck battery receptacle tray having the following
dimensions: 31'' L.times.13'' W.times.32'' H.
23. The apparatus of claim 1, wherein said housing is sized to fit
within a narrow aisle lift truck battery receptacle tray having the
following dimensions: 38'' L.times.20'' W.times.31'' H.
24. The apparatus of claim 1, wherein said housing is sized to fit
within a sit-down lift truck battery receptacle tray having the
following dimensions: 38'' L.times.32'' W.times.22'' H.
25. A method of converting an electric vehicle having a high peak
power to average power ratio to hybrid power, the vehicle having a
conventional battery removably positionable within a battery
receptacle tray of the vehicle and electrically connectable to a
drive system of the vehicle, said method comprising; (a) providing
a hybrid power supply apparatus as defined in claim 1; (b) removing
said conventional battery from said battery receptacle tray; (c)
positioning said housing of said hybrid power apparatus within said
battery receptacle tray; and (d) electrically connecting said power
output of said hybrid power apparatus to said drive system of said
vehicle.
26. A stand-alone hybrid power supply apparatus comprising: (a) a
fuel cell; (b) an energy storage device chargeable by said fuel
cell; (c) a housing enclosing said fuel cell and said energy
storage device within a self-contained space; and (d) a power
output on an external surface of said housing for electrically
connecting said apparatus to a load, wherein said output is the
sole interface between said apparatus and said load.
27. The apparatus of claim 26, wherein said housing has a size not
exceeding 38'' L.times.32'' W.times.31'' H.
28. A hybrid power apparatus for use in a battery-operated vehicle
provided with an electrical receptacle and a battery receptacle
tray, the hybrid power apparatus comprising; (a) a hybrid fuel cell
subsystem including a fuel reformer, fuel cell, DC power converter,
microcontroller and energy storage device; (b) a housing containing
said hybrid fuel cell subsystem and having dimensions less than
said battery receptacle tray such that said housing is movable
within said tray; (c) an external DC interface attached to said
housing and electrically connected to said hybrid fuel cell
subsystem and including a plug interface suitable to mate to said
vehicle electrical receptacle; and (d) gas inlet and outlet
interfaces mounted on at least one uncovered surface of said
housing when said housing is placed within said tray, wherein said
interfaces are connected to said hybrid fuel cell subsystem and
include circulation fans and valves connected to and controlled by
said microcontroller of said hybrid fuel cell subsystem.
Description
TECHNICAL FIELD
[0001] This application relates to a hybrid power supply apparatus
comprising a fuel cell and an energy storage device suitable for
use in electric off-road vehicles, such as lift trucks and ground
support equipment. The invention is a substitute for conventional
lead acid batteries and is sized to fit within a standard electric
vehicle battery receptacle tray. Other low power product
applications are also described.
BACKGROUND
[0002] Off-road electric vehicles, such as lift trucks, sweepers
and scrubbers and ground support equipment, are used in a variety
of commercial and recreational applications. By way of example,
electric lift trucks comprising pallet forks are commonly used in
retailing, wholesaling and manufacturing operations for lifting and
moving materials inside warehouses and the like. Since lift trucks
are often operated indoors, the use of internal combustion engines
is precluded. In most cases lift trucks are battery powered to
avoid potentially harmful emissions. Each battery is mounted within
an enclosure comprising a battery receptacle tray or cavity
typically located near the rear of the vehicle (although the
location varies depending upon the vehicle model). The batteries
typically include handles or lifting grips and the receptacle tray
may include rollers to facilitate battery movement, for example
during recharging operations. When in use, the battery output is
electrically connected to the vehicle drive system with a DC
interface plug.
[0003] Various types of lead acid battery systems are available for
use in lift trucks and other similar electric vehicles. Flooded
battery systems provide approximately 6-8 hours of operation and
require frequent watering to maintain the chemistries in their
cells as they are charged and discharged. Batteries requiring less
frequent watering, such as "Water-less".TM. battery systems
manufactured by Hawker Powersource, are also available and provide
similar performance to flooded batteries. Recently "maintenance
free" battery systems have been introduced which do not require any
watering, but require more expensive chargers. Maintenance-free
systems have a lower energy storage capacity per cubic foot and
therefore provide fewer hours of operation than flooded or reduced
water batteries of the same size.
[0004] All conventional battery systems designed for low power
vehicular applications suffer from serious shortcomings. A primary
limitation is that conventional batteries must be recharged at
frequent intervals, usually at least every 6-8 hours. Accordingly,
battery charging stations must be provided at the worksite. The
establishment of a battery charging infrastructure is costly and
occupies valuable warehouse space. Moreover, the vehicles cannot be
continuously operated (i.e. in sequential shifts) without routinely
swapping discharged and charged batteries. This frequent daily
removal of discharged batteries and substitution of fully charged
batteries is labor-intensive and potentially dangerous
(conventional battery enclosure systems for Class A lift trucks
weigh up to 900 pounds). In order to be effective, such battery
swapping also requires multiple batteries per vehicle which
increases operating costs.
[0005] Conventional batteries must also be serviced at frequent
intervals for cleaning and watering. The presence of battery acid
poses employee safety risks and the potential to damage
equipment.
[0006] Further, conventional battery systems are incapable of
operating at optimum efficiency in many industrial applications. As
shown in the Table 1 below, lift trucks typically have a pattern of
power usage or "duty cycle" which is characterized by loads which
fluctuate substantially during the course of a work shift. For
example, although the average load across an entire seven hour work
shift is less than 1 kW, power requirements on the order of 8-10 kW
for short durations are required at irregular intervals to meet
operational demands. The state of charge of the battery must always
be high enough to ensure that the battery is capable of responding
to high current requests by the lift truck (even though the average
power requirement is relatively low). This decreases the effective
charge life of the battery, requiring recharging at more frequent
intervals and resulting in operating downtimes.
[0007] The use of fuel cell power systems in industrial vehicles as
an alternative to battery power is well known in the prior art.
Fuel cell systems offer many important benefits including extended
operating tunes, low emissions and the flexibility to utilize
readily available fuels, such as methanol and propane (LPG).
Further, the need for a battery charging infrastructure as
described above is avoided, including the need for multiple
batteries.
[0008] Notwithstanding these advantages, previous attempts by
original equipment manufacturers (OEMs) to integrate fuel cell
power systems employing conventional fuels into industrial trucks
at a reasonable cost have been largely unsuccessful. It is not
feasible to adapt existing trucks to fuel cell power without making
extensive truck-level modifications. Each OEM brand truck requires
a unique integration approach which is often difficult and
expensive to implement, especially for existing fleets of vehicles.
Moreover, if the fuel cell system fails, the truck must be taken
out of service.
[0009] The fact that duty cycles for lift trucks and other similar
vehicles are characterized by very high peak to average load ratios
poses particular operational challenges. Many fuel cell systems
employ reformers which convert conventional fuels into
hydrogen-enriched gas which the fuel cell system transforms into
electricity. However, this reforming process is relatively slow
which limits the load following capabilities of the fuel cell.
Also, in order to maximize the useful life of fuel cell components,
it is preferable to operate the fuel cell at near steady state
conditions rather than adopting a load following approach.
[0010] Some hybrid power supply systems are known in the prior art
for use in applications subject to sudden load fluctuations. U.S.
Pat. No. 4,883,724, Yamamoto, issued Nov. 28, 1989 relates to a
control unit for a fuel cell generating system which varies the
output of the fuel cell depending upon the state of charge of the
battery. In particular, a DC/DC converter is connected between the
output of the fuel cell and the battery and is responsive to a
control signal produced by a controller. The purpose of the
Yamamoto invention is to ensure the storage battery is charged for
recovery within the shortest possible time to reach a target
remaining charge capacity under charging conditions that do not
cause deterioration of performance of the battery. When the charged
quantity of the battery is recovered to the target value, the
controller lowers the output of the fuel cell to its normal
operating state. In the case of no external load, such as during
extended periods of interruption in the operation of the lift
truck, the fuel cell is controlled to stop after the storage
battery is charged.
[0011] The primary limitation of the Yamamoto control system is
that control algorithm is designed for prolonging the useful life
of the storage battery rather than the fuel cell. By varying the
fuel cell output to charge the storage battery for recovery within
the shortest possible time, the long-term performance of the fuel
cell is compromised. Moreover, Yamamoto does not disclose a hybrid
fuel cell system which is configured to fit within a small
geometric space.
[0012] The need has accordingly arisen for a hybrid architecture
specifically adapted for lift trucks and other low power
applications which integrates fuel cell technology with
conventional battery systems. In the present invention the fuel
cell and fuel processor systems are sized to meet the average load
requirements of the vehicle, while the batteries and power control
hardware are capable of responding to very high instantaneous load
demands. The invention may be substituted for conventional
batteries to improve performance without retrofitting existing
fleets of vehicles. As described further below, the applicant's
invention fits into conventional lift truck battery receptacle
trays and has a similar electrical interface as conventional
battery systems. Apart from vehicular applications, low power
hybrid fuel cell products as exemplified by the present invention
may also find application in uninterruptable power supply systems,
recreational power, off-grid power generation and other analogous
applications.
SUMMARY OF INVENTION
[0013] Conventional traction batteries are removably positionable
within a battery receptacle tray of an electric vehicle and include
a power output connectable to the vehicle drive system. In
accordance with the invention, a hybrid power supply apparatus is
provided which is interchangeable with such conventional batteries.
The apparatus includes a fuel cell; an energy storage device
chargeable by the fuel cell; a housing enclosing the fuel cell and
the energy storage device, the housing being sized to fit within
the battery receptacle tray; and a power output electrically
connectable to the storage device and extending externally of the
housing for electrically coupling the apparatus to the drive system
of the vehicle when the housing is positioned within the battery
receptacle tray.
[0014] Preferably the apparatus further includes a coolant system
for flowing gas through the housing. The coolant system may include
a gas inlet for drawing gas into the housing; at least one blower
positioned within the housing for moving gas through the housing in
predetermined flow paths to regulate the temperature of the
apparatus; and a gas outlet for expelling exhaust gas from the
housing. In a particular embodiment of the invention, the housing
includes a user interface surface which is exposed when the housing
is placed within the vehicle receptacle tray. Both the gas inlet
and gas outlet are located on the user interface surface. The
coolant system is configured so that the temperature of the exhaust
gas and the user interface surface does not exceed 50.degree. C.
when the coolant system is in operation.
[0015] The apparatus further preferably includes a fuel processor
positioned within the housing for converting a source of fuel to
hydrogen-enriched gas for delivery to the fuel cell. In one
preferred embodiment of the invention, the fuel processor is a
reformer for converting conventional fuels, such as methanol and
propane, to hydrogen gas. The apparatus may include a fuel storage
chamber located within the housing which is in fluid communication
with the fuel processor. A fuel inlet may be provided on the
housing, such as on the user interface surface, for supplying fuel
to the fuel storage chamber. In one embodiment, the fuel storage
chamber is thermally isolated from the remainder of the
housing.
[0016] The apparatus also preferably includes a DC/DC power
converter positioned within the housing for converting the DC
current generated by the fuel cell to a voltage suitable for
delivery to the energy storage device, which may consist of a
battery or capacitor, or to an external load. A controller may also
be mounted within the housing for regulating operation of the fuel
cell and power converter depending upon the state of charge of the
energy storage device.
[0017] The apparatus is designed to closely simulate the weight
characteristics of a conventional traction battery to ensure proper
balancing of the electric vehicle. To this end, one or more load
compensators may be positioned within the housing for increasing
the weight of the apparatus to a weight approximating the weight of
a conventional battery. Since fuel cell systems are more sensitive
to vibration and shock than conventional batteries, vibration
dampeners may be positioned within or surrounding a portion of the
housing for absorbing vibration when the housing is within the
battery receptacle tray and the vehicle is in operation. Preferably
the apparatus is sized to fit within receptacle trays of standard
dimensions for pallet truck, narrow aisle lift trucks, sit-down
lift trucks and the like.
[0018] A method of converting an electric vehicle having a high
peak power to average power ratio from electric power to hybrid
power is also described. The method includes the steps of providing
a hybrid power supply apparatus as described above; removing a
conventional battery from the battery receptacle tray; positioning
the housing of the hybrid power supply apparatus within the battery
receptacle tray; and electrically connecting the power output of
the hybrid power supply apparatus to the drive system of the
vehicle.
[0019] The invention may also be employed in non-vehicular
applications where a hybrid power supply is required for use in a
relatively small, self-contained space. In the applicant's
invention, the power output located on the apparatus housing is
preferably the only interface between the apparatus and the
load.
[0020] As should be apparent from the foregoing, it is an object of
the invention to provide a high energy density hybrid power supply
system that is optimized for operation within an enclosure space
similar to traditional removable battery systems, with identical
electrical DC output, and having extended operational time between
refueling stops.
[0021] A further object of the invention is to provide precise
thermal regulation of the power supply components and safe and
ergonomic external interfaces for ease of operator use.
[0022] Still another object is to replicate the traditional battery
physical characteristics, such as weight and enclosure size, so
that the battery replacement procedure is transparent and safe for
the vehicle operator. A related object is to reduce system
vibrations to increase performance of the hybrid system.
[0023] Another object is to provide a specialized chamber within
the apparatus housing for temperature-controlled fuel storage.
[0024] A further object is to allow for fuel tank resizing to
effectively increase or decrease the range of the vehicle.
BRIEF DESCRIPTION OF DRAWINGS
[0025] In drawings which illustrate embodiments of the invention
but which should not be construed as restricting the spirit or
scope of the invention in any way,
[0026] FIG. 1(a) is a rear isometric view of an electric lift truck
showing a conventional prior art battery in its installed
configuration.
[0027] FIG. 1(b) is an enlarged isometric view of the conventional
battery of FIG. 1(a).
[0028] FIG. 2 is a rear isometric view of the truck of FIG. 1
fitted with the applicant's hybrid power supply apparatus.
[0029] FIG. 3 is an isometric view showing the general layout of
the applicant's hybrid power supply apparatus.
[0030] FIG. 4 is an isometric view of an alternative embodiment of
the apparatus of FIG. 3 including weight counterbalancing and
vibration damping features.
[0031] FIG. 5 is an isometric view showing the general layout of an
alternative embodiment of applicant's hybrid power generating
apparatus including an internally sealed temperature controlled
fuel storage chamber.
[0032] FIG. 6 is a schematic diagram showing the hybrid fuel
cell/battery architecture and charging characteristics of the
applicant's system.
[0033] FIG. 7 is an isometric view of one particular embodiment of
the applicant's hybrid power supply apparatus using liquid fuel and
showing side panels of the apparatus housing in an open position to
expose internal components.
[0034] FIG. 8 is a side elevational view of the embodiment of FIG.
7 with a side panel removed and showing exemplary air flow paths in
dotted outline.
[0035] FIG. 9 is an end isometric view of the embodiment of FIG. 7
showing the user interface which is exposed in use.
[0036] FIG. 10 is a further isometric view of the embodiment of
FIG. 7 showing the side panels of the housing in a open position to
expose internal components.
[0037] FIG. 11 is an isometric view of an alternative embodiment of
the invention suitable for using compressed gas fuel.
[0038] FIG. 12 is a schematic drawing of one possible arrangement
for air cooling of the applicant's hybrid power supply
apparatus.
[0039] FIG. 13 is an isometric view of a further alternative
embodiment of the invention similar to the embodiment of FIG. 7 but
configured as a Genset.
DESCRIPTION OF INVENTION
[0040] A conventional industrial or "traction" battery 10 for a
forklift truck 20 is shown in FIGS. 1(a) and 1(b). Battery 10
includes a box-shaped housing 12 having opposed end faces 14, side
faces 15 and top and bottom faces 16. As shown in FIG. 1(a), truck
20 typically includes a main body 22 mounted on wheels 24 and
having a fork lift mechanism 26 attached. The main body 22 has a
cavity or battery receptacle tray 28 which is sized and shaped to
removably receive one battery 10. In the example shown, tray 28 is
rectangular in shape and is located in the center of the main
vehicle body 22. However, the location and dimensions of tray 28
will vary depending on the specific truck manufacturer, model and
application. By way of example, pallet trucks have maximum
allowable battery tray dimensions of 31'' L.times.13'' W.times.32''
H (the height is variable depending upon the battery capacity).
Narrow aisle lift trucks vary to a greater extent, but a typical
battery tray 28, for a 36 volt DC model, is 38'' L.times.20''
W.times.31'' H. A sit-down fork lift truck also has several
variations, but a typical battery tray 28, for a 36 or 48 volt DC
model, is 38'' L.times.32'' W.times.22'' H.
[0041] Battery 10 is enclosed to a greater or lesser extent
depending on the location of battery tray 28 in truck 20. In the
example shown in FIG. 1(a), end faces 14 and a top face 16 are
exposed. In other common configurations only one end face 14 of
housing 12 is exposed, the remainder being enclosed by the main
truck body 22. Since battery 10 is extremely heavy (approximately
900 pounds in some applications), the battery charging station
and/or vehicle 20 may include a transport system (not shown)
consisting of rollers and guides for ease of sliding the battery 10
in and out of tray 28. The lift truck 20 or other vehicle may also
include standard mechanical retainers (not shown) to lock the
battery 10 in place within tray 28 for safety during operation.
[0042] The structure of conventional traction battery 10 is shown
in greater detail in FIG. 1(b). Battery housing 12 is typically
constructed from steel and includes a pair of lifting handles 17
mounted on opposed end faces 14. A DC cable and plug interface 18
extends from housing 12 and is connected to the electrical drive
system (not shown) of truck 20. Plug interface 18 is standard for
most electric vehicles. A plurality of battery cells 19 are mounted
within battery housing 12 as shown and are electrically connected
to the DC output plug interface 18. Battery 10 is typically of the
lead acid type. When battery 10 requires recharging, it is usually
manually rolled off truck 20 to a recharging station (not shown), a
charged replacement battery 10 is rolled into tray 28, and the DC
output plug 18 of the replacement battery 10 is connected to the
electrical drive system of truck 20. Depending upon the
application, conventional batteries 10 have operating times as low
as 4-5 hours and therefore require frequent recharging. As
discussed above, the frequent daily removal of discharged batteries
and substitution of fully charged batteries is labor-intensive and
requires a costly inventory of spare batteries. Of course, battery
charging stations and associated instrumentation must also be
provided.
[0043] The hybrid power supply apparatus 30 of the present
invention is illustrated in its installed configuration on a truck
20 in FIG. 2. As discussed further below, apparatus 30 is "hybrid"
in character since it includes both a fuel cell to generate
electrical power and an energy storage means, such a storage
battery, which is connectable to a load. Apparatus 30 has been
engineered so that it is transparently interchangeable with a
conventional battery 10 in a "plug and play" manner without
requiring any modification to truck 20. More particularly,
apparatus 30 has substantially the same shape, dimensions, weight
and electrical interface as a battery 10 of FIGS. 1(a) and (b).
This enables apparatus 30 to be easily inserted into or removed
from an existing battery tray 28 and used in the same manner as a
conventional battery 10. However, apparatus 30 has performance
characteristics, including an effective operating time, which are
far superior to a conventional battery 10. By way of example,
prototype apparatuses 30 tested by the inventors have provided an
order of magnitude greater operating time before requiring
refueling/recharging (i.e. up to 50 hours compared to 4-8 hours for
conventional batteries 10).
[0044] While hybrid fuel cell/battery power systems are of course
well known in the prior art, the integration of such a system
within a small geometric space (i.e. an enclosure capable of
fitting within the dimensions of a standard battery tray 28) poses
multiple design challenges. As described in detail below, the
various fuel cell hybrid components must be efficiently arranged
within a small enclosure while maintaining weight characteristics
and a DC interface similar or identical to conventional battery
systems 10. Further, the placement of air inlets and outlets is
important to avoid adding heat to truck 20 and for optimum internal
thermal management. Accessibility of fuel inlets is similarly
important to ensure ease of refueling by operators.
[0045] Further, trucks 20 are designed for holding traction
batteries 10 which are very robust and insensitive to many
environmental conditions. Fuel cell hybrid systems, by contrast,
are much more sensitive to temperature, vibration, shock, debris,
moisture and the like and hence the applicant's invention has been
engineered to address such environmental factors, as discussed
further below.
[0046] The general layout of the applicant's hybrid power supply
apparatus 30 is illustrated in FIG. 3. Apparatus 30 includes an
external housing 32 which encloses a hybrid power subsystem
generally designated 34. The various component parts and features
of subsystem 34 are described in detail below. Housing 32 further
includes an exposed end panel 36 which is accessible when apparatus
30 is in use (i.e. corresponding to the exposed end face 14 of a
conventional battery 10). Subsystem 34 is preferably air-cooled. In
the illustrated embodiment, an air inlet 38 and an exhaust outlet
40 are located on housing panel 36. As discussed further below,
hybrid apparatus 30 is configured to ensure that the temperature of
housing 32, and the exhaust expelled from outlet 40, is kept within
safe limits to avoid operator injury. As shown in FIG. 4, air inlet
38 and outlet 40 may optionally be covered by a conventional grill
or deflector shield 78 to filter debris and ensure the exhaust gas
stream is ergonomically located for operator comfort.
[0047] A fuel inlet 42 is also provided on housing panel 36 for
delivering fuel from a fuel source to hybrid power subsystem 34. In
the illustrated embodiment, fuel inlet 42 is connectable to a fuel
storage chamber 50 located within housing 32. In use, fuel is
delivered from storage chamber 50 to subsystem 34 to generate
electrical power which is delivered to a power output 44
connectable to a load, such as the drive system of a lift truck
20.
[0048] The housing 32 of FIGS. 2-5 is box-shaped to fit within the
space constraints of a conventional battery tray 28. However, as
will be apparent to a person skilled in the art, housing 32 could
be any geometric shape provided that it is safely compatible with
tray 28 and is ergonomically connectable to the vehicle electric
drive system. For example, the electrical interfaces of power
output 44 could be exposed at different locations to ergonomically
mate with the electrical sub-system of the particular vehicle (or
other load device) in question.
[0049] As mentioned above, the weight characteristics of
applicant's apparatus 30 preferably simulate a conventional battery
10 to avoid the need for vehicle modification. Hybrid power
subsystem 34 is much lighter than standard lead acid batteries.
Accordingly, for apparatus 30 to have a mass similar to existing
batteries 10, mass must be added. Such added mass is essential as
the counterbalance of many vehicles 20 is designed for the heavy
lead acid battery mass. As shown generally in FIG. 3, apparatus 30
may include a weight counterbalance 46 located within housing 32.
As will be understood to a person skilled in the art, weights could
alternatively be selectively added at various different void
locations within housing 32 to optimize counterbalance requirements
based on the mass distribution of the hybrid power subsystem 34 and
fuel storage configurations. Housing 32 may also include a handle
37 for ease of transport (FIG. 4).
[0050] As mentioned above, hybrid power subsystem 34 is more
sensitive to vibration and shock than conventional batteries 10.
Accordingly, apparatus 30 also preferably includes vibration
damping material 48 located within housing 32. As shown in FIG. 4,
damping material 48 may be located, for example, immediately
underneath hybrid power subsystem 34 and underneath fuel storage
chamber 50 in a lower portion of housing 32. Closed cell foam or
elastomeric materials such as sorbothane are examples of suitable
damping materials. Another possible embodiment includes damping
material specifically tuned to reduce coupling of specific vehicle
vibrations and specific resonant frequencies of apparatus 30 and
enclosed subsystems. A further damping embodiment may incorporate
shock absorbing mechanical connectors, as known in the art for use
in vehicles, for internal mounting isolation of the hybrid power
subsystem 34. In yet another embodiment an external damping layer
may be provided positionable within receptacle tray 28 for
supporting or attachment to housing 32. Preferably such an external
damping layer should be constructed from a material that it is
suitably rugged to withstand insertion and removal friction (for
example, damping materials having a high sheer strength).
[0051] Hybrid power subsystem 34 may utilize various different
types of liquid, compressed gas and hydride fuels. Suitable fuels
include pure or enriched hydrogen gas, metal hydride, methanol,
natural gas and propane (LPG). FIG. 5 illustrates the general
layout of one embodiment of the invention wherein the fuel storage
chamber 50 is thermally isolated from the remainder of housing 32
by a baffle 52. In this embodiment, chamber 50 would be suitable
for holding a fuel source which should be maintained at a
particular temperature and pressure for optimum performance (for
example, LPG stored within a secured container 54).
[0052] FIG. 6 illustrates schematically the architecture of the
hybrid power subsystem 34 of apparatus 30 in further detail.
Subsystem 34 includes a fuel cell 60 which delivers raw DC current
to a DC/DC converter 62. An energy storage device 64 is connected
to the DC/DC converter 62 for storing at least part of the
conditioned DC current outputted by converter 62. Energy storage
device 64 may comprise, for example, a battery, a capacitor, or a
combination thereof. Energy storage device 64 is electrically
coupled to a DC bus 66 for delivering electrical energy to a load
67, such as the drive system of a lift truck 20.
[0053] As explained above, hybrid power subsystem 34 may employ
various types of fuels. In preferred embodiments subsystem 34 uses
readily available fuels such as methanol and propane (LPG). In such
cases, subsystem 34 includes a fuel processor, such as a reformer
68, for converting raw fuel to substantially pure hydrogen or
hydrogen-enriched gas suitable for use by fuel cell 60. Reformer 68
is coupled to fuel storage chamber 50 with suitable fuel lines. A
fuel pump 69 may be provided for delivering fuel from chamber 50 to
reformer 68.
[0054] A computer controller 70 which receives input from various
sensors, such as voltage and current sensors 72, controls charging
of storage device 64 by fuel cell 60. As discussed further below,
subsystem 34 also includes fan blowers 74 for circulating air
through flow paths within housing 32 to maintain the temperature of
each component of apparatus 30 within a preferred temperature range
and to dilute exhaust gases prior to expulsion from housing 32. The
operation of blowers 74 may also be regulated by controller 70.
[0055] As explained above, sudden load fluctuations are
common-place in lift trucks 20 and similar vehicles. Due to the
slow response time of reformer 68, a fuel cell system alone cannot
respond quickly to rapid changes in load and hence a hybrid system
as exemplified by the applicant's invention is desirable for such
applications. Hybrid power subsystem 34 is configured to maintain
storage device 64 in a state of high residual capacity to cope with
load surges. This enables "on demand" power to be supplied by
storage device 64 while the power output of fuel cell 60 can be
varied independently to replenish energy to storage device 64, or
deliver power jointly to the load on an opportunistic basis.
Moreover, the hybridization of subsystem 34 allows for the fuel
cell 60 and reformer 68 components to be sized to meet only the
average power requirements of the application (rather than the peak
power requirements). In the case of the duty cycle of an electric
lift truck 20, with characteristic peak power to average power
ratios of approximately 10:1, this results in a significant
reduction in the quantity of the higher priced fuel cell components
of the system.
[0056] In use, hybrid power subsystem 34 is preferably configured
so that sensors 72 continuously monitor the state of charge and/or
the voltage of storage device 64. When hybrid power apparatus 30 is
subjected to a load, the state of charge of storage device 64
decreases as detected by sensors 72. In one embodiment of the
invention, this information is processed by controller 70 which
returns a feedback signal to fuel cell 60 resulting in an increase
in the fuel cell output charge current. In a preferred embodiment
of the invention fuel cell 60 is not operated in a load-following
mode. Rather, changes in the fuel cell charge current are minimized
so that fuel cell 60 operates under near steady state conditions
for the bulk of its charging time to prolong its useful service
life. This may be achieved by programming controller 70 to step up
or step down the fuel cell output charge only at discrete intervals
depending upon the state of charge of storage device 64.
[0057] One representative embodiment of the applicant's hybrid
power apparatus 30 utilizing methanol fuel is illustrated in FIGS.
7-10. In this embodiment, hybrid power apparatus 30 is illustrated
with a top panel of housing 32 removed for clarity. Housing 32 also
includes an end panel 80 located opposite the end panel 36 having
the user interfaces and a pair of side panels 82 and 84 which are
pivotable between open and closed positions (in FIGS. 7 and 10 side
panels 82, 84 are shown in the open position to expose the various
components arranged within housing 32).
[0058] In the embodiment of FIGS. 7-10, fuel chamber 50 for storing
methanol fuel is located in a bottom compartment of apparatus 30.
Fuel inlet 42 is located on exposed end panel 36 for supplying fuel
to fuel chamber 50. Storage device 64, such as a conventional
battery, is positioned above fuel chamber 50 proximate air inlet 38
(as shown best in FIG. 10). DC/DC power converter 62 is positioned
adjacent storage device 64 in a central portion of housing 32. Fuel
cell 60 is positioned in an upper portion of housing 32 above
storage device 64. Controller 70 is located adjacent fuel cell 60
at a location above DC/DC power converter 62. As shown best in FIG.
10, power output 44 is coupled to DC bus 66 which is operatively
coupled to controller 70. A user control panel 85 is provided on
end panel 36 above fuel inlet 42 for monitoring and controlling
operation of apparatus 30. For example, panel 85 may include a
start/stop control button and a fuel level indicator.
[0059] The portion of housing 32 proximate end panel 80 is occupied
principally by reformer 68 which is connected by fuel line(s) to
the underlying fuel storage chamber 50 (FIG. 7). Reformer 68 may be
housed within a shroud (not shown) to help dissipate radiant heat
from reformer 68.
[0060] FIG. 11 illustrates another possible embodiment of the
applicant's hybrid power supply apparatus 30 employing a compressed
gas fuel (e.g. LPG) rather than liquid fuel. This embodiment of the
invention is generally similar in layout to the embodiment of FIGS.
7-10, except that fuel storage chamber 50 is located in an upper
region of housing 32 and is thermally and hermetically isolated
from the remainder of housing 32 by means of wall 90. This enables
the temperature and pressure conditions of chamber 50 to be
modulated independently of the remainder of housing 32 to suit the
requirements of the fuel source. Chamber 50 is sized to receive a
compressed gas tank 92 which may be either refillable or
replaceable depending upon the choice of fuel. An access door
having a self-sealing hinge (not shown) may be provided for gaining
access to chamber 50 to enable easy removal and replacement or
examination of tank 92. Alternatively, in the case of refillable
tanks 92, a fuel inlet port (not shown) in fluid communication with
tank 92 may be provided. As will be apparent to a person skilled in
the art, the size of fuel tank 92 could easily be varied to
effectively increase or decrease the range of vehicle 20.
[0061] Sealed chamber 50 preferably includes a thermal sensor (not
shown) and heating unit (not shown) connected to controller 70. The
chamber temperature can thus be monitored and corrected for
maintenance of a minimum temperature suitable for optimum operation
of hybrid power subsystem 34. The use of a sealed fuel storage
chamber 50 also results in better regulation of fuel pressure and
superior operation of apparatus 30 in refrigerated environments.
Further, a sealed chamber 50 has the additional benefit of
maintaining the cleanliness of hybrid power subsystem 34 which is
located in a separate portion of housing 32 and is not exposed to
the environment when the chamber access door is opened for
refueling etc.
[0062] In the embodiment of FIG. 11 fuel cell 60 is positioned
immediately adjacent reformer 68 in a lower portion of housing 32
and controller 70 is positioned above energy storage device 64
proximate housing surface 36. Notwithstanding the different
internal configuration, the embodiment of 11 functions in a manner
similar to the embodiment of FIGS. 7-10 described above. Other
equivalent configurations could envisioned by a person skilled in
the art without departing from the invention.
[0063] As mentioned above, apparatus 30 is preferably air-cooled
and includes blowers 74 for directing air flow within housing 32
(FIGS. 6 and 11). The various components of apparatus 30 are
geometrically ordered relative to air flow paths based on
temperature limits and sensitivity. Preferably the coolant air is
reused as much as possible to minimize total air flow. Since
apparatus 30 is designed for low power applications, it is
important to minimize flow impedances and electrical parasitic
loads associated with the cooling system.
[0064] Optimum thermal regulation of hybrid power apparatus 30 is
important for several reasons. Fuel cell systems, particularly
those with associated fuel processors, generate significant waste
heat. In many cases hybrid power systems are operated outdoors or
in applications having a fixed outdoor exhaust (e.g. automobiles or
home power systems). However, lift trucks 20 and the like, which
are often operated indoors, are constrained to emit low temperature
exhaust only. More particularly, it is important that the external
surfaces of hybrid power apparatus 30, such as the exposed end
panel 36 of housing 32, be maintained at a low temperature to avoid
operator injury. Further, it is equally important that a
significant amount of heat not be transferred from apparatus 30 to
the body 22 of truck 20 (i.e. all excess heat should preferably be
transferred to the environment rather than placing additional
thermal loads on associated equipment, such as truck 20). Optimum
thermal regulation also enables hybrid power apparatus 30 to be
used in a wide range of ambient temperatures typically serviced by
trucks 20, including sub-freezing refrigerated environments as
would be encountered in freezer lockers and the like.
[0065] One particular arrangement for thermal management of
apparatus 30 is illustrated generally in FIG. 7 and schematically
in FIG. 12. A heat transfer gas, such as air, is circulated through
apparatus 30 to maintain the various components of hybrid power
subsystem 34 within their optimum temperature ranges. The air is
preferably moved through different flow paths between air inlet 38
and outlet 40. As shown in FIG. 12, a plurality of junctions 120
and adjustable valves 122 are preferably provided for strategically
dividing and merging the air streams. In a normal operational mode
(i.e. at normal ambient temperatures) the incoming air passing
through inlet 38 is divided into three separate substreams 100, 102
and 104 at junctions 120. A first substream 100 is initially passed
over storage device 64 and DC/DC power converter 62. Both of the
above components are sensitive to temperature fluctuations and
should be maintained at relatively cool operating temperatures for
best performance. In the case of low ambient temperatures, at least
some of the inlet air may be pre-heated with heated exhaust air as
discussed further below to protect storage device 64 and converter
62 from excessively cold temperatures.
[0066] After passing over converter 62, the first substream 100 is
diverted through a shroud surrounding reformer 68 to accept waste
heat generated by the reforming process. Reformers 68 typically
operate at very high temperatures (i.e. on the order of 600.degree.
C.). A first portion 100(a) of substream 100 is then diverted to
fuel cell 60 to maintain fuel cell 60 at a desirable operating
temperature (i.e. within the range of approximately 60-80.degree.
C.). A second portion 100(b) of substream 100 bypasses fuel cell 60
and is used to dilute the exhaust stream as described further
below.
[0067] As illustrated in FIG. 12, the second and third substreams
102, 104 of the inlet air may be circulated directly to reformer 68
and fuel cell 60 respectively. Second substream 102 is exhausted
from reformer 68 at a high temperature and is merged with substream
104 at a junction 120 located downstream from reformer 68.
Substream 104 delivers oxident air to fuel cell 60 and contains
water when expelled from fuel cell 60. The hot air present in
substream 102 evaporates the water content of substream 104 and
maintains the merged exhaust airstream in a vapor state suitable
for expulsion to the environment.
[0068] As shown in FIG. 12, a heat exchanger 124 is preferably
provided to cool the hydrogen gas generated by reformer 68 to
ambient or near-ambient temperature and to pre-heat the methanol
fuel before the fuel is pumped to reformer 68.
[0069] In the normal operational mode of the applicant's air
cooling system, first portion 100(a) and second portion 100(b) of
substream 100 are combined with the exhaust stream (resulting from
nixing of substreams 102 and 104) at locations downstream from
reformer 68. Portion 100(b), which is relatively cooler than
portion 100(a) since it has not passed through fuel cell 60,
reduces the temperature of the exhaust stream to a safe temperature
(e.g. below 50.degree. C.) before it is discharged through outlet
40. Substreams 100(a) and 100(b) also serve to dilute the carbon
monoxide content present in the exhaust stream prior to its
expulsion to the environment.
[0070] In an alternative operating mode suitable for low
temperature operation, the first substream 100 is not divided into
first and second portions 100(a) and 100(b) (i.e. all of substream
100 passes through fuel cell 60). In this embodiment, substream 100
may be subdivided downstream from fuel cell 60 at an adjustable
valve 122. A portion of substream 100 may be recycled to pre-heat
the incoming air drawn through outlet 38. In this case the inlet
air may be divided into a further substream 106 for merging with
the reformer exhaust (FIG. 12). An important feature of this
arrangement is that the recycled portion of the heated air does not
contain any reformer exhaust gases.
[0071] The exemplary air flow patterns described above are
preferably under the control of microprocessor controller 70 which
receives input from various temperature and air flow sensors (not
shown). In one embodiment of the invention, controller 70 may be
programmed to periodically reverse the direction of air flow. This
enables the periodic expulsion of built-up debris from the interior
of housing 32 through air inlet 38. As indicated above, air inlet
38 and outlet 40 may also include conventional grills or deflector
shields 78 (FIG. 4) to filter debris and ensure the exhaust gas
stream is ergonomically located for operator comfort.
[0072] As will be apparent to a person skilled in the art, other
equivalent means for flowing cooling gas streams through housing 32
may be envisaged for the purposes of: [0073] (1) Maintaining
exhaust streams and operator interfaces at safe temperatures and
preventing transfer of thermal loads to other equipment. [0074] (2)
Maintaining various components of the hybrid power subsystem within
a preferred temperature range for optimum performance and
longevity. [0075] (3) Controlling the thermal status of different
component parts precisely and independently. [0076] (4) Enabling
operation of electric vehicles at a wide range of ambient
temperatures [0077] (5) Dilution of exhaust gas constituents, such
as carbon monoxide [0078] (6) Purging of waste materials [0079] (7)
Minimizing parasitic electrical loads associated with the cooling
system for improved performance.
[0080] FIG. 13 illustrates a further alternative embodiment of the
invention similar to the embodiment of FIGS. 7-10, but configured
as a portable genset. In this embodiment, a standard AC electrical
power outlet 126 is provided rather than DC power output 44.
[0081] As should be apparent to a person skilled in the art, hybrid
power supply apparatus 30 is suitable for non-vehicular low power
applications where the size of the power supply is limited by size
or geometric constraints. For example, apparatus 30 may be used for
on/off grid power generation, recreational power use,
uninterruptable power supply and conventional battery replacement
applications.
[0082] As will be apparent to those skilled in the art in the light
of the foregoing disclosure, many alterations and modifications are
possible in the practice of this invention without departing from
the spirit or scope thereof. Accordingly, the scope of the
invention is to be construed in accordance with the substance
defined by the following claims.
* * * * *