SEMI-ELECTRIC MOBILE REFRIGERATED SYSTEM
Cross-Reference to Related Application
[0001] Reference is made to and this application claims priority from and the benefit of
U.S. Provisional Application Serial No. 61/471,470, filed April 4, 2011, and entitled SEMIELECTRIC
MOBILE REFRIGERATED SYSTEM, which application is incorporated herein in
its entirety by reference.
Background of the Invention
[0002] This invention relates generally to mobile refrigerated systems for transport of
perishable cargo and, more particularly, to a power supply system for a semi-electric transport
refrigeration system and method for operating a semi-electric transport refrigeration system.
[0003] Refrigerated trucks and trailers are commonly used to transport perishable cargo,
such as, for example, produce, meat, poultry, fish, dairy products, cut flowers, and other fresh or
frozen perishable products stored in a refrigerated cargo space, commonly referred to as the
cargo box, within the truck or trailer. A transport refrigeration system is mounted to the truck or
the trailer for maintaining a controlled temperature environment within the cargo space within
the truck or trailer.
[0004] Conventionally, transport refrigeration systems used in connection with
refrigerated trucks and refrigerated trailers include a transport refrigeration unit having a
refrigerant compressor, a condenser coil with one or more associated condenser fans, an
expansion device, and an evaporator coil with one or more associated evaporator fans, which are
connected via appropriate refrigerant lines in a closed refrigerant flow circuit. Air or an air/gas
mixture or other gas is drawn from the interior volume of the trailer by means of the evaporator
fan(s) associated with the evaporator, passed through the airside of the evaporator in heat
exchange relationship with refrigerant whereby the refrigerant absorbs heat from the air, thereby
cooling the air. The cooled air is then supplied back to the cargo space.
[0005] On commercially available transport refrigeration systems used in connection
with refrigerated trucks and refrigerated trailers, the compressor, and typically other components
of the transport refrigeration unit, must be powered during transit by a prime mover. In the case
of refrigerated trailers, the prime mover typically comprises a Diesel engine carried on and
considered part of the transport refrigeration system. In mechanically driven transport
refrigeration systems the compressor is mechanically driven by the Diesel engine, either through
a direct mechanical coupling or a belt drive, and other components, such as the condenser and
evaporator fans are belt driven.
[0006] An all electric transport refrigeration system for refrigerated trailer application is
also commercially available through Carrier Corporation headquartered in Farmington,
Connecticut, USA. In the all electric transport refrigeration system, a prime mover, most
commonly a Diesel engine, carried on and considered part of the transport refrigeration system,
drives an AC synchronous generator that generates AC power. The generated AC power is used
to power an electric compressor motor for driving the refrigerant compressor of the transport
refrigeration unit and also powering electric AC fan motors for driving the condenser and
evaporator motors and electric heaters associated with the evaporator. For example, U.S. Pat. No.
6,223,546 discloses an all electric transport refrigeration system.
[0007] In conventional practice, a transport refrigeration unit installed on a refrigerated
truck or trailer operates in one of a temperature pull down mode, a temperature maintenance
mode, or a standstill mode. In the temperature pull down mode, the refrigerant compressor, the
condenser fan(s) and the evaporator fan(s) are operating with the refrigerant compressor
generally operating at full capacity to lower the temperature within the cargo space as rapidly as
possible to a desired set point temperature appropriate for the particular cargo stowed in the
cargo space. In the temperature maintenance mode, the refrigerant compressor, the condenser
fan(s) and the evaporator fan(s) are still operating, but the refrigerant compressor is operating at
a significantly lower capacity so as to maintain the temperature in the cargo space within a
specified range of the desired set point temperature and avoid over cooling. In the temperature
maintenance mode, heaters associated with the evaporator may also be activated as necessary to
warm the air passed through the evaporators by the evaporator fan(s) to prevent over cooling. In
the standstill mode, the refrigerant compressor and the condenser and evaporator fans are off.
[0008] Diesel engines used as prime movers on transport refrigeration systems generally
have two operating speeds, that is a high RPM speed, such as 2200 RPM, and a low RPM speed,
such as 1400 RPM. In operation, the Diesel engine is operated at high speed during temperature
pull down and at low speed during the temperature maintenance mode. During standstill, the
Diesel engine is typically idling at low speed. The Diesel engine is generally designed to meet
the power needs of the transport refrigeration system during operation at maximum capacity,
such as during the temperature pull down mode, with efficient fuel consumption.
Summary of the Invention
[0009] A mobile refrigerated system for transport of perishable cargo includes a
refrigeration unit having a compressor and a plurality of refrigeration unit electric loads, and a
power supply system for powering the compressor and the plurality of electric loads.
[0010] In an aspect, the power supply system includes an engine coupled to the
compressor for direct drive powering the compressor, and a generator arranged to be direct
driven by the engine for generating electric power, the generator and the compressor are
mounted to a common drive shaft driven by the engine. The generator may be integrated with the
compressor. The power supply system may further include an alternator arranged to be belt
driven by the engine for generating electric power. The refrigeration unit may be operatively
associated with a refrigerated cargo box, such as a truck, trailer or intermodal container, for
controlling a temperature with the cargo box.
[0011] The power supply system may further include a power distribution system
arranged to receive electric power generated by the generator and by the alternator and
configured to selectively distribute electric power to the plurality of refrigeration unit electric
loads. The generator generates alternating current power and the alternator generates direct
current power and the power distribution system is configured to distribute alternating current
power to at least one of the plurality of refrigeration unit electric loads and to distribute direct
current power to at least one of the plurality of refrigeration unit electric loads. The power supply
system may further include a high voltage battery pack for storing electric power and providing a
second source of direct current power. A high voltage battery pack charger electrically coupled
to the generator may be provided and configured to charge the high voltage battery pack.
[0012] A method is provided for operating a transport refrigeration system having a
refrigeration unit having a compressor, a condenser fan and an evaporator fan. In an aspect the
method includes the steps of: providing an engine and coupling the engine to the compressor for
directly driving the compressor; providing a generator and coupling the generator to the engine
for directly driving the generator for generating alternating current power; providing alternating
current motors for driving the condenser fan and the evaporator fan; and powering the alternating
current motors with alternating current generated by the generator. The method may further
include the step of integrating the generator into the compressor.
[0013] In another aspect the method includes the steps of: providing an engine and
coupling the engine to the compressor for directly driving the compressor; providing a generator
and coupling the generator to the engine for directly driving the generator for generating
alternating current power; providing a high voltage battery pack for storing and supplying direct
current power; providing direct current motors for driving the condenser fan and the evaporator
fan; and during a temperature pull down mode, operating the engine to drive the compressor,
switching off the generator and powering the direct current motors with direct current supplied
by the high voltage battery pack. The method may include the further steps of during a
temperature control mode: switching on the generator; operating the engine to drive the
compressor and the generator; converting alternating current power generated by the generator to
direct current power; and powering the direct current motors with the converted power.
[0014] The method may include the further steps of during a standstill mode: shutting
down the engine; and operating the evaporator fan at selected intervals for selected time periods
using direct current power supplied by the high voltage battery pack. The method may include
the further steps of: providing a low voltage battery pack; and during a standstill mode, shutting
down the engine and operating the evaporator fan at selected intervals for selected time periods
using direct current power supplied by the low voltage battery pack. The method may include the
further step of charging the high voltage battery pack using alternating power generated by the
generator.
Brief Description of the Drawings
[0015] For a further understanding of the disclosure, reference will be made to the
following detailed description of the disclosure which is to be read in connection with the
accompanying drawing, where:
[0016] FIG. 1 is a schematic representation of a transport refrigeration system having a
refrigeration unit and an associated power supply system as disclosed herein;
[0017] FIG. 2 is a perspective view of an embodiment of an assembly of a compressor
with an integrated generator mounted to an engine in a direct drive relationship;
[0018] FIG. 3 is a schematic representation of an exemplary embodiment of a power
supply system as disclosed herein;
[0019] FIG. 4 is a schematic representation of another exemplary embodiment of a power
supply system as disclosed herein;
[0020] FIG. 5 is a schematic representation of still another exemplary embodiment of a
power supply system as disclosed herein; and
[0021] FIG. 6 is a schematic representation of an alternate embodiment of the power
supply system illustrated in FIG. 5.
Detailed Description of the Invention
[0022] A mobile refrigerated system for transport of perishable cargo comprises a
transport refrigeration system 20. In the exemplary embodiment depicted in FIG. 1, the transport
refrigeration system 20 includes a refrigeration unit 22, a power supply system including an
electric generator 24 and an engine 26, and a controller 30. The refrigeration unit 22 functions,
under the control of the controller 30, to establish and regulate a desired product storage
temperature within a refrigerated cargo space of the mobile refrigerated system wherein a
perishable product is stored during transport and to maintain the product storage temperature
within a specified temperature range. The mobile refrigerated system may be a trailer, a truck, or
an intermodal container wherein perishable cargo, such as, for example, produce, meat, poultry,
fish, dairy products, cut flowers, and other fresh or frozen perishable products, is stowed for
transport in the refrigerated cargo space, commonly referred to as the cargo box, of the truck,
trailer or intermodal container.
[0023] The transport refrigeration unit 22 includes a refrigerant compression device 32, a
refrigerant heat rejection heat exchanger 34, an expansion device 36, and a refrigerant heat
absorption heat exchanger 38 connected in refrigerant flow communication in a closed loop
refrigerant circuit and arranged in a conventional refrigeration cycle. The refrigeration unit 22
also includes one or more fans 40 associated with the refrigerant heat rejection heat exchanger 34
and driven by fan motor(s) 42 and one or more fans 44 associated with the refrigerant heat
absorption heat exchanger 38 and driven by fan motor(s) 46. The refrigeration unit 22 may also
include an electric resistance heater 48 associated with the refrigerant heat absorption heat
exchanger 38. It is to be understood that other components (not shown) may be incorporated into
the refrigerant circuit as desired, including for example, but not limited to, a suction modulation
valve, a receiver, a filter/dryer, an economizer circuit.
[0024] The refrigerant heat rejection heat exchanger 34 may, for example, comprise one
or more refrigerant conveying coiled tubes or one or more tube banks formed of a plurality of
refrigerant conveying tubes extending between respective inlet and outlet manifolds. The fan(s)
40 are operative to pass air, typically ambient air, across the tubes of the refrigerant heat
rejection heat exchanger 34 to cool refrigerant vapor passing through the tubes. The refrigerant
heat rejection heat exchanger 34 may operate either as a refrigerant condenser, such as if the
refrigeration unit 22 is operating in a subcritical refrigerant cycle or as a refrigerant gas cooler,
such as if the refrigeration unit 22 is operating in a transcritical cycle.
[0025] The refrigerant heat absorption heat exchanger 38 may, for example, also
comprise one or more refrigerant conveying coiled tubes or one or more tube banks formed of a
plurality of refrigerant conveying tubes extending between respective inlet and outlet manifolds.
The fan(s) 44 are operative to pass air drawn from the temperature controlled cargo box across
the tubes of the refrigerant heat absorption heat exchanger 38 to heat and evaporate refrigerant
liquid passing through the tubes and cool the air. The air cooled in traversing the refrigerant heat
rejection heat exchanger 38 is supplied back to the temperature controlled cargo box. It is to be
understood that the term "air" when used herein with reference to the atmosphere within the
cargo box includes mixtures of air with other gases, such as for example, but not limited to,
nitrogen or carbon dioxide, sometimes introduced into a refrigerated cargo box for transport of
perishable produce.
[0026] The refrigeration system 20 also includes a controller 30 configured for
controlling operation of the refrigeration system 20 including, but not limited to, operation of
various components of the refrigerant unit 22, to provide and maintain a desired thermal
environment within the cargo box of the mobile refrigerated system, that is within the
temperature controlled space in which a perishable product is stowed. The controller 30 may be
an electronic controller including a microprocessor and an associated memory bank. The
controller 30 controls operation of various components of the refrigerant unit 22, such as the
refrigerant compression device 32 and its associated drive motor 50, the fan motors 42, 46 and
the electric heater 48. The controller 30 may also be also to selectively operate the engine 26,
typically through an electronic engine controller (not shown) operatively associated with the
engine 26.
[0027] The refrigerant compression device 32, which may comprise a single- stage or
multiple-stage compressor, such as, for example, a reciprocating compressor, is directly driven
by the engine 26, which comprises an on-board fossil- fuel engine, most commonly a Diesel
engine. The compression device 32 has a compression mechanism (not shown) directly coupled
to a drive shaft 25 of the engine 26. For example, the compression mechanism of the
compression device 32 may be mechanically mounted to the engine drive shaft 25 or mounted to
a shaft mechanically coupled in a direct drive relationship to the engine drive shaft 25.
[0028] The engine 26 also drives the electric generator 24 for generating alternating
current (AC) electrical power. The electric generator 24 may, for example, comprise a
synchronous AC generator or a permanent magnet AC generator. The electric generator 24 may
be integrated with the compression device 32 into a unit mounted to and directly driven by the
engine 26. For example, referring now to FIG. 2, the compression device 32 may comprise an
open drive reciprocating compressor having a compression mechanism mounted on the drive
draft of the engine 26 and the electric generator 24 may be mounted on a distal end of the engine
drive shaft outboard of the compression mechanism of the compression device 32, but integrated
within the housing of the compression device 32. In this manner, both the compression
mechanism of the compression device 32 and the electric generator 24 are housed as a single unit
and commonly direct driven by the engine 26.
[0029] The refrigeration unit 22 has a plurality power demand loads, including, but not
limited to, the drive motor(s) 42 for the fan(s) 40 associated with the refrigerant heat rejection
heat exchanger 34 and the drive motor(s) 46 for the fan(s) 44 associated with the refrigerant heat
absorption heat exchanger 38. In the depicted embodiment, an electric resistance heater 48 is
provided that also constitutes a power demand load. The electric resistance heater may be
selectively operated by the controller 30 whenever a control temperature within the temperature
controlled cargo box drops below a preset lower temperature limit, which may occur in a cold
ambient environment. In such an event the controller 30 would activate the electric resistance
heater 48 to heat air circulated over the electric resistance heater by the fan(s) 44 associated with
the refrigerant heat absorption heat exchanger.
[0030] The plurality of power demand loads may be alternating current loads (AC loads)
and/or direct current loads (DC loads). For example, in an embodiment of the transport
refrigerant unit 22, both fan motors 42, 46 may be alternating current (AC) motors. In another
embodiment of the transport refrigeration unit, both fan motors 42, 46 may be direct current
(DC) motors. In another embodiment, one of the fan motors 42, 46 may be an AC motor and the
other a DC motor. Therefore, the power supply system disclosed herein may further include a
direct current (DC) alternator 50 belt driven off the engine 26 as illustrated schematically in FIG.
1. It is to be understood that "belt driven" as used herein includes not only belt drives, but also
chain drives, band drives and the like.
[0031] When the engine 26 is operating, the AC generator 24, being directly driven by
the engine 26, generates alternating current power (AC power) that may be used to power AC
loads of the refrigerant unit 22 and the DC alternator 50, being belt driven by the engine 26,
generates direct current power (DC power) that may be used to power DC loads. To provide a
source of power when the engine 26 is not operating, such during a period when the control
temperature within the refrigerated cargo space is stable and within the specified product
temperature range and the compression device 32 is not in operation, a period commonly
referred to a standstill, temperature conditions, the power supply system may include a battery
pack 28.
[0032] Various exemplary embodiments of the power supply system associated with the
transport refrigeration system 20 are depicted schematically in FIGs. 3-6. In the embodiments
depicted in FIGs. 3 and 4, the battery pack 28 comprises a low voltage battery pack. In the
embodiments depicted in FIGs. 5 and 6, the battery pack 28 includes both a low voltage battery
pack 28HV and also includes a high voltage battery pack 28LV. The low voltage battery pack
28LV may be used to power electronic equipment, such as the system controller 30 and other
control system components, as well as lighting associated with the transport refrigeration system.
The high voltage battery pack 28HV may be used for storing direct current (DC) power and for
providing a second source of direct current (DC) power to supplement the direct current power
produced by the alternator 50 for powering one or more of the refrigerant unit power loads. A
high voltage battery pack charger 70 may be provided and electrically coupled to the electric
generator 24 and configured to charge the high voltage battery pack 28HV. However, as will be
discussed further hereinafter, a low voltage battery pack may also be used, particularly if no high
voltage battery pack is included, during standstill periods to selectively power one or more
refrigeration unit power loads. Optionally, the power supply system may include a connection
(not shown) adapted to connect to an electric power grid for supplying grid electric power to the
transport refrigeration unit 22 during periods when the truck, trailer or container is parked, for
example at an overnight truck stop or at a warehouse.
[0033] Referring to FIGS. 3-6, in particular, the power supply system may further
include a power distribution system 60 arranged to receive AC power generated by the generator
24, to receive DC power generated by the alternator 50, and to receive DC power drawn from the
battery pack 28. The power distribution system 60 is configured to selectively distribute electric
power to the plurality of refrigeration unit electric loads, including at least the fan motors 42, 46.
The power distribution system 60 may include both an AC power distribution bus 62 and a DC
power distribution bus 64. The power supply system may further include various power
converters, such as AC to DC converters 66 to convert alternating current power distributed
through the AC distribution bus 62 into direct current power, and DC to AC inverters 68 to
convert direct current power distributed through the DC distribution bus 64 into alternating
current power. The power supply system may also include other power modifiers such as, but not
limited to, AC to AC voltage/frequency converters, and DC to DC voltage converters, as
appropriate.
[0034] The controller 30 may selectively distribute electric power through the power
distribution system 60 to each of the refrigeration unit power loads in the form of AC power
through the AC distribution bus 62 and DC power through the DC distribution bus 64. For
example, in the FIG. 3 embodiment, the fan motors 42, 46 are both AC motor. Alternating
current power is supplied to power distribution system 60 from the electric generator 24 and
direct current power is supplied to the power distribution system 60 from both the DC alternator
50 and the low voltage battery pack 28LV. The power supply system is configured to provide
alternating current power to a plurality of refrigeration unit AC power loads 72, including the AC
fan motors 42, 46. In this embodiment, the plurality of refrigerant unit AC power loads 72 may
be electrically connected directly to the AC power bus 62 and also connected through a DC to
AC power converter 74 to the DC power bus 64 of the power distribution system 60.
[0035] In the embodiment depicted in FIG. 4, the fan motor(s) 42 is a high voltage AC
fan motor(s) and the fan motor(s) 46 is a high voltage DC fan motor(s). Again, alternating
current power is supplied to power distribution system 60 from the electric generator 24 and
direct current power is supplied to the power distribution system 60 form both the DC alternator
50 and the low voltage battery pack 28. However, the power supply system is configured to not
only deliver AC power through the AC distribution bus 62 to a plurality of refrigeration unit AC
power loads 72, including the AC fan motor(s) 42, but also deliver DC power through the DC
distribution bus 64 to a plurality of refrigeration unit DC power loads 76, including the DC fan
motor(s) 46. In this embodiment, the refrigeration unit AC power loads 72 may be electrically
connected directly to the AC distribution bus 62 and the refrigeration unit DC power loads 76
may be electrically connected directly to the DC distribution bus 64. Additionally, a DC to DC
converter may be included in the circuit between the DC fan motor(s) 46 and the DC power
distribution bus 64 for boosting the voltage of the DC power as necessary.
[0036] In the embodiments depicted in FIGS. 5 and 6, the fan motor(s) 42 and the fan
motor(s) 46 are high voltage DC fan motors. Again, alternating current power is supplied to
power distribution system 60 from the electric generator 24. Direct power is supplied to the
power distribution system 60 from both the DC alternator 50 and the high voltage battery pack
28HV. The power supply system is configured to deliver direct current power to a plurality of
refrigeration unit DC power loads 76, including the high voltage DC fan motors 42, 46. In this
embodiment, the plurality of refrigeration unit DC power loads may be electrically connected
directly to the DC power distribution bus 64 and may also be electrically connected through an
AC to DC converter 80 to the AC power distribution bus 62.
[0037] In the embodiment of the power supply system depicted in FIG. 5, the electric
generator 24 is directly coupled to the shaft of the engine 26 to be directly driven by the engine
26. The embodiment of the power supply system depicted in FIG. 6 is identical to the
embodiment of the power supply system depicted in FIG. 5 with the exception that the electric
generator 24 is belt driven, that is coupled to the drive shaft of the engine 26 through a belt drive
arrangement. In either dive arrangement, the electric generator 24 is coupled to the engine 26 for
driving the electric generator 24 for generating alternating current (AC) power. Although the
electric generator 24 in the embodiments of the power supply system depicted in FIGs. 3 and 4 is
directly driven by the engine 26, it is to be understood that the electric generator 24 could
alternatively be belt driven through a belt drive arrangement such as illustrated schematically in
FIG. 6. As noted previously with respect to the alternator 50, "belt driven" includes not only belt
drives, but also chain drives, band drives and the like.
[0038] A method is disclosed for operating a transport refrigeration system 20 having a
refrigeration unit 22 having a compressor 32, a condenser/gas cooler fan 40 and an evaporator
fan 44. Referring to the embodiment of the power supply system depicted in FIG. 3, the
disclosed method in this embodiment includes the steps of: providing an engine 26 and coupling
the engine 26 to the compressor 32 for directly driving the compressor 32; providing a generator
24 and coupling the generator 24 to the engine 26 for driving the generator 24 for generating
alternating current power; providing alternating current motors 42,46 for driving the
condenser/gas cooler fan 40 and the evaporator fan 44; and powering the alternating current
motors with alternating current generated by the generator. The method may further include the
step of integrating the generator 24 into the compressor 32, for example as depicted in FIG. 2.
[0039] Referring to the embodiments of the power supply system depicted in FIGS. 5
and 6, the disclosed method in this embodiment includes the steps of: providing an engine 26 and
coupling the engine 26 to the compressor 32 for directly driving the compressor 32; providing a
generator 24 and coupling the generator 24 to the engine 26 for driving the generator 24 for
generating alternating current power; providing a high voltage battery pack 28HV for storing and
supplying direct current power; providing direct current motors 42, 46 for driving the
condenser/gas cooler fan and the evaporator fan; and during a temperature pull down mode,
operating the engine 26 to drive the compressor 32, switching off the generator 24 and powering
the direct current motors 42, 46 with direct current supplied by the high voltage battery pack
28HV.
[0040] The disclosed method may also include the further steps of during a temperature
control mode: switching on the generator 24; operating the engine 26 to drive the compressor 32
and the generator 24; converting alternating current power generated by the generator 24 to
direct current power; and powering the direct current motors 42, 46 with the converted power.
The method may include the further step of charging the high voltage battery pack 28HV using
alternating power generated by the generator 24
[0041] The disclosed method may include the further steps of during a standstill mode:
shutting down the engine 26; and operating the evaporator fan 44 at selected intervals for
selected time periods using direct current power supplied by the high voltage battery pack 28HV.
The disclosed method may include the further steps of: providing a low voltage battery pack; and
during a standstill mode, shutting down the engine 26 and operating the evaporator fan 44 at
selected intervals for selected time periods using direct current power supplied by the low
voltage battery pack. In this mode, the method may include the further step of boosting the
voltage of the direct current supplied by the low voltage battery pack as necessary to power the
evaporator fan 44 during periods of operation during the standstill mode.
[0042] Providing DC fan motors for driving the fans 40, 44 and providing a high voltage
battery pack 28HV and operating the transport refrigeration system 22 during peak load demand
with the engine 26 coupled to the compressor for directly driving the compressor 32, while
switching off the generator 24 and powering the fan motors 42, 46 with direct current power
drawn from the high voltage battery pack 28HV permits downsizing of the engine 26. For
example, providing a 3 kilowatt high voltage battery pack for powering the fan motors 42, 46
associated with the condenser/gas cooler fan(s) 40 and evaporator fan(s) 44, respectively, during
peak load demand, e.g. during operation of the refrigeration unit in a temperature pull down
mode, permits the engine to be downsized from a typical 16 kilowatt output engine to a smaller
13 kilowatt output engine. Use of a smaller output engine results in lower weight and lower fuel
consumption. Despite the downsizing of the engine 26, the engine 26 will still have ample excess
output capacity during lower load demand modes, e.g. during operation of the refrigeration unit
in the temperature control mode, to recharge the high voltage battery pack 28HV using power
provided through the generator 24 driven by the engine 26.
[0043] The terminology used herein is for the purpose of description, not limitation.
Specific structural and functional details disclosed herein are not to be interpreted as limiting, but
merely as basis for teaching one skilled in the art to employ the present invention. Those skilled
in the art will also recognize the equivalents that may be substituted for elements described with
reference to the exemplary embodiments disclosed herein without departing from the scope of
the present invention.
[0044] While the present invention has been particularly shown and described with
reference to the exemplary embodiments as illustrated in the drawing, it will be recognized by
those skilled in the art that various modifications may be made without departing from the spirit
and scope of the invention. Therefore, it is intended that the present disclosure not be limited to
the particular embodiment(s) disclosed as, but that the disclosure will include all embodiments
falling within the scope of the appended claims.
We Claim:
1. A mobile refrigerated system for transport of perishable cargo, the mobile
refrigerated system comprising:
a refrigeration unit having a compressor and a plurality of refrigeration unit electric
loads; and
a power supply system including an engine coupled to the compressor for direct drive
powering the compressor, and a generator arranged to be driven by the engine for generating
electric power.
2. The system as recited in claim 1, the generator and the compressor being mounted
to a common drive shaft driven by the engine.
3. The system as recited in claim 2 wherein the generator is integrated with the
compressor.
4. The system as recited in claim 1 wherein the generator is belt driven by the
engine.
5. The system as recited in claim 1 wherein the power supply system further
comprises an alternator arranged to be belt driven by the engine for generating electric power.
6. The system as recited in claim 5 wherein the power supply system further
comprises a power distribution system arranged to receive electric power generated by the
generator and by the alternator and configured to selectively distribute electric power to the
plurality of refrigeration unit electric loads.
7. The system as recited in claim 6 wherein the generator generates alternating
current power and the alternator generates direct current power and the power distribution
system is configured to distribute alternating current power to at least one of the plurality of
refrigeration unit electric loads and to distribute direct current power to at least one of the
plurality of refrigeration unit electric loads.
8. The system as recited in claim 7 wherein the power supply system further
comprises a high voltage battery pack for storing electric power and providing a second source
of direct current power.
9. The system as recited in claim 8 further comprising a high voltage battery pack
charger electrically coupled to the generator and configured to charge the high voltage battery
pack.
10. The system as recited in claim 6 wherein the plurality of refrigeration unit loads
includes at least one high voltage alternating current fan motor powered by alternating current
generated by the generator.
11. The system as recited in claim 6 wherein the plurality of refrigeration unit loads
includes at least one high voltage direct current fan motor powered by at least one of direct
current generated by the alternator, direct current from the high voltage battery pack, and direct
current derived from converting alternating current generated by the generator.
12. The system as recited in claim 1 wherein the refrigeration unit is operatively
associated with a cargo box of one of a truck, a trailer and an intermodal container for controlling
a temperature within the cargo box.
13. A method for operating a transport refrigeration system having a refrigeration unit
having a compressor, a condenser fan and an evaporator fan, the method comprising the steps of:
providing an engine and coupling the engine to the compressor for directly driving the
compressor;
providing a generator and coupling the generator to the engine for driving the generator
for generating alternating current power;
providing alternating current motors for driving the condenser fan and the evaporator fan;
and
powering the alternating current motors with alternating current generated by the
generator.
14. The method as recited in claim 13 wherein the step of coupling the generator to
the engine comprises coupling the generator to the engine for directly driving the generator for
generating alternating current power.
15. The method as recited in claim 14 further comprising the step of integrating the
generator into the compressor.
16. A method for operating a transport refrigeration system having a refrigeration unit
having a compressor, a condenser fan and an evaporator fan, the method comprising the steps of:
providing an engine and coupling the engine to the compressor for driving the
compressor;
providing a generator and coupling the generator to the engine for directly driving the
generator for generating alternating current power;
providing a high voltage battery pack for storing and supplying direct current power;
providing direct current motors for driving the condenser fan and the evaporator
fan;
during a temperature pull down mode, operating the engine to drive the compressor,
switching off the generator and powering the direct current motors with direct current supplied
by the high voltage battery pack.
17. The method as recited in claim 16 further comprising the steps of during a
temperature control mode:
switching on the generator;
operating the engine to drive the compressor and the generator;
converting alternating current power generated by the generator to direct current power;
and
powering the direct current motors with the converted power.
18. The method as recited in claim 17 further comprising the step of charging the
high voltage battery pack using alternating power generated by the generator.
19. The method as recited in claim 16 further comprising the steps of during a
standstill mode:
shutting down the engine; and
operating the evaporator fan at selected intervals for selected time periods using direct
current power supplied by the high voltage battery pack.
20. The method as recited in claim 16 further comprising the steps of:
providing a low voltage battery pack; and
during a standstill mode, shutting down the engine; and
operating the evaporator fan at selected intervals for selected time periods using direct
current power supplied by the low voltage battery pack.