TRANSPORT REFRIGERATION SYSTEM AND METHOD FOR OPERATING
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. 61/471,463, filed April 4, 2011, and entitled
TRANSPORT REFRIGERATION SYSTEM AND METHOD FOR OPERATING, which
application is incorporated herein in its entirety by reference.
Background of the Invention
[0002] This invention relates generally to transport refrigeration systems and, more
particularly, to supplying electrical power to all the power demand loads of the transport
refrigeration unit while reducing engine fuel consumption.
[0003] Refrigerated trucks and hailers 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. A transport refrigeration system is mounted to the truck or to the
trailer in operative association with a cargo space defined within the truck or trailer for
maintaining a controlled temperature environment within the cargo space.
[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 with one or more associated condenser fans, an expansion
device, and an evaporator 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 is
drawn from the interior volume of the cargo space 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 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 pulldown mode, a temperature maintenance
mode, or a standstill mode. In the temperature pulldown 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
pulldown 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 pulldown mode, with efficient fuel consumption. Therefore, during the
temperature maintenance mode and standstill mode, the diesel engine is operating at lower
efficiency and with increased fuel consumption.
Summary of the Invention
[0009] It would be desirable to reduce overall fuel consumption in a transport
refrigeration system by reducing the time the engine is operating and/or reducing the size of the
engine. It would also be desirable to have the capability to operate the transport refrigeration unit
with reduced noise generation, particularly during the night when in populated areas.
[0010] A method is provided for operating a refrigeration system having a refrigeration
unit for providing temperature conditioned air to a temperature controlled space, an engine and
an electric generation device. The disclosed method includes the steps of: providing a battery
system having a least one battery unit supplying electric power, and during a high cooling
demand mode, operating the engine to drive the electric generation device for supplying electric
power and simultaneously employing the battery system for supplying electric power to jointly
power the plurality of power demand loads of the refrigerant unit. The disclosed method may
include the further step of, during a low cooling demand mode, operating the engine to drive the
electric generation device to power the plurality of power demand loads of the refrigeration unit
and also charge the battery system. The disclosed method may include the step of, during a low
cooling demand mode, employing the battery system to power the plurality of power demand
loads of the refrigeration unit. The method may include the step of, during a period of shutdown
of the engine, employing the battery system to power the plurality of power demand loads of the
refrigeration unit, which may include the step of selectively powering the refrigeration heat
absorption heat exchanger for selected periods of time and at selected intervals.
[0011] In an embodiment of the disclosed method wherein the refrigeration unit includes
a refrigerant compression device, a refrigerant heat rejection heat exchanger and an associated
fan, a refrigerant heat absorption heat exchanger and an associated fan, and a plurality of power
demand loads including a compression device drive motor, a refrigerant heat rejection heat
exchanger fan motor and a refrigerant heat absorption heat exchanger fan motor, the step of
operating the engine to drive the electric generation device and simultaneously employing the
battery system to power the plurality of power demand loads of the refrigerant unit during a high
cooling demand mode includes the step of simultaneously operating both the engine to drive the
electric generation device and employing the battery system to power the compression device
drive motor. In this embodiment, the method may include the step of employing the battery
system to power the refrigerant heat rejection heat exchanger fan motor and the refrigerant heat
absorption heat exchanger fan motor.
[0012] In an embodiment of the method wherein the refrigeration unit includes a
refrigerant compression device, a refrigerant heat rejection heat exchanger and an associated fan,
a refrigerant heat absorption heat exchanger and an associated fan, and a plurality of power
demand loads including a compression device drive motor, a refrigerant heat rejection heat
exchanger fan motor and a refrigerant heat absorption heat exchanger fan motor, the step of
operating the engine to drive the electric generation device and simultaneously employing the
battery system to power the plurality of power demand loads of the refrigerant unit during a high
cooling demand mode includes the step of operating the engine to drive the electric generation
device to power the compression device drive motor and employing the battery system to power
the refrigerant heat rejection heat exchanger fan motor and the refrigerant heat absorption heat
exchanger fan motor.
[0013] The high cooling demand mode may comprise a temperature pulldown mode
wherein the refrigeration unit is operated to reduce a temperature within the temperature
controlled space to a set-point temperature. The low cooling demand mode comprises a
temperature control mode wherein the transport refrigeration unit is operated to maintain a
temperature within the temperature controlled space within a specified range of a set-point
temperature. The temperature controlled space comprises the perishable cargo hold of a truck,
trailer, intermodal container or other transport container.
[0014] In an aspect, a transport refrigeration system is provided having a refrigeration
unit for providing temperature conditioned air to a cargo storage space of a truck, trailer,
intermodal container or other transport container, the refrigeration unit having a refrigerant
compression device, a refrigerant heat rejection heat exchanger and an associated fan, a
refrigerant heat absorption heat exchanger and an associated fan, and a plurality of power
demand loads including a compression device drive motor, a refrigerant heat rejection heat
exchanger fan drive motor and a refrigerant heat absorption heat exchanger fan drive motor, the
transport refrigeration system having an electric generating device and an engine for driving the
electric generating device. The transport refrigeration system further includes a controller
operatively associated with the refrigeration unit, the controller operative to selectively operate
the refrigeration unit in a high cooling demand mode during which the controller operates the
engine to drive the electric generation device for supplying electric power and simultaneously
employs the battery system to supply electric power to jointly power the plurality of power
demand loads of the refrigerant unit.
[0015] In an embodiment, the controller is further operative to selectively operate the
refrigeration unit in a low cooling demand mode and during operation in the low cooling demand
mode operating the engine to drive the electric generation device to power the plurality of power
demand loads of the refrigeration unit and also charge the battery system. In an embodiment, the
controller is further operative to selectively operate the refrigeration unit in a low cooling
demand mode and during operation in the low cooling demand mode employing the battery
system to power the plurality of power demand loads of the refrigeration unit. In an embodiment,
the controller is further operative to selectively shutdown the engine and the refrigerant
compression device and to selectively employ the battery system to power the refrigerant heat
absorption heat exchanger fan. In an embodiment, the controller employs the battery system to
selectively power the refrigeration heat absorption heat exchanger fan for selected periods of
time and at selected intervals. In an embodiment, the controller may simultaneously operate the
engine to drive the electric generation device and employ the battery system to jointly power the
compression device motor. In an embodiment, the controller may operate the engine to drive the
electric generation device to power the compression device drive motor and simultaneously
employ the battery system to power the refrigerant heat rejection heat exchanger fan motor and
the refrigerant heat absorption heat exchanger fan motor.
Brief Description of the Drawings
[0016] For a further understanding of the disclosure, reference will be made to the
following detailed description which is to be read in connection with the accompanying drawing,
where:
[0017] FIG. 1 is a schematic illustration of an exemplary transport refrigeration system in
accordance with the disclosure; and
[0018] FIG. 2 is a schematic illustration of an embodiment of the power supply control
system associated with the refrigeration system of FIG. 1.
Detailed Description of the Invention
[0019] The exemplary transport refrigeration system 20 depicted in FIG. 1 includes a
refrigeration unit 22, an electric generating device 24, a prime mover 26 for driving the electric
generating device 24, a battery system 28, 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 wherein a perishable product is stored
during transport and to maintain the product storage temperature within a specified temperature
range. The refrigerated cargo space may be the cargo box of a trailer, a truck, a seaboard
shipping container 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] The refrigerant compression device 32 may comprise a single-stage or multiplestage
compressor such as, for example, a reciprocating compressor or a scroll compressor. The
compression device 32 has a compression mechanism (not shown) driven by an electric motor
50. In an embodiment, the motor 50 may be disposed internally within the compressor with a
drive shaft interconnected with a shaft of the compression mechanism, all sealed within a
common housing of the compression device 32.
[0024] 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 truck or trailer, 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.
[0025] The refrigeration unit 22 has a plurality power demand loads, including, but not
limited to, the compression device drive motor 50, the drive motor 42 for the fan 40 associated
with the refrigerant heat rejection heat exchanger 34, and the drive motor 46 for the fan 44
associated with the refrigerant heat absorption heat exchanger 38. In the depicted embodiment,
the electric resistance heater 48 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.
[0026] The transport refrigeration system 20 disclosed herein includes two onboard
power supplies, namely an electric generating device 24 driven by prime mover 26 and also a
high voltage battery system 28. As will be discussed further herein, all of the afore-mentioned
plurality of power load demands of the transport refrigeration unit 22 may be powered
exclusively by electric power from onboard sources. Optionally, the transport refrigeration
system 20 may be provided with a connection 52 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.
[0027] The prime mover 26, which comprises an on-board fossil-fuel engine, most
commonly a Diesel engine, drives the electric generating device 24 that generates electrical
power. The drive shaft of the engine drives the shaft of the electric generating device. In an
electrically powered embodiment of the transport refrigeration unit 10, the electric generating
device 42 may comprise a single on- board, engine driven AC generator configured to generate
alternating current (AC) power including at least one AC voltage at one or more frequencies. In
an embodiment, the electric generating device 42 may, for example, be a permanent magnet AC
generator or a synchronous AC generator. In another embodiment, the electric generating device
42 may comprise a single on-board, engine driven DC generator configured to generate direct
current (DC) power at at least one voltage. As each of the fan motors 42, 46 and the compression
device drive motor 50 may be an AC motor or a DC motor, it is to be understood that various
power converters, such as AC to DC rectifiers, DC to AC inverters, AC to AC voltage/frequency
converters, and DC to DC voltage converters, may be employed in connection with the electric
generating device 42 as appropriate.
[0028] In addition to the power sources provided by the standby power grid connection
52 and by the electric generating device 42 driven by the engine 26, a further power source is
made available by providing a high voltage battery system 28 made up of a single battery unit
58 or a plurality of battery units 58 appropriately connected together. Referring now to FIG. 2
in particular, the controller 30 is configured to select which power source or power sources to
employ to power the refrigeration unit 22 in any particular cooling demand mode of the
refrigeration unit 22. The standby power grid connection 52 is only employed when the truck or
trailer is parked at a truck stop or warehouse or other facility for an extended period of time. In
such case, the power grid connection 52 is mated with a grid power source to supply grid power
to the refrigeration unit 22, thereby permitting the controller 30 to shut down the Diesel engine
26 to save fuel and to not tap into the battery system 28 so as to also converse battery power.
[0029] However, when the refrigerant unit 22 is operated in other than the aforedescribed
standby mode, the controller 30 must selectively choose to employ one or both of the
engine 26 to drive the electric generating device 24 and the battery system 28 to supply power
to meet the plurality of power demand loads of the refrigeration unit 22. In accord with the
method disclosed herein for operating the refrigeration unit 22, during a high cooling demand
mode, the controller 30 operates the engine 26 to drive the electric generation device 24 for
supplying electric power and simultaneously employs the battery system 28 for supplying
electric power to jointly power the plurality of power demand loads of the refrigerant unit 22. In
a further aspect of the method disclosed herein, during a low cooling demand mode, the
controller 30 operates the engine 26 to drive the electric generation device 24 to power the
plurality of power demand loads of the refrigeration unit 22 and also charge the battery system
22. The disclosed method may also include the step of, during a low cooling demand mode,
employing the battery system 28 to power the plurality of power demand loads of the
refrigeration unit 22.
[0030] The high cooling demand mode may comprise a temperature pulldown mode
wherein the refrigeration unit is operated to reduce a temperature within the temperature
controlled space to a set-point temperature. The low cooling demand mode comprises a
temperature control mode wherein the refrigeration unit is operated to maintain a temperature
within the temperature controlled space within a specified range of a set-point temperature.
[0031] After the temperature within the controlled space has been pulled down and has
been stabilized at the desired set point temperature selected for the perishable product stowed
within the temperature controlled space, the controller 30 may selectively shut the engine 26
down to save fuel and reduce the emission of combustion products into the atmosphere. During
the period of shutdown of the engine 26, the controller 30 may selectively employ the battery
system alone to power the plurality of power demand loads of the refrigeration unit 22. For
example, during the period of engine shutdown, the air within the temperature controlled space
is not being circulated. As a consequence, the potential exits for formation of "hot spots", that is
localized regions within the cargo box wherein the local temperature has risen above the set
point temperature. In an aspect of the method disclosed herein, to prevent the formation of
localized hot spots within the temperature controlled space, the controller 30 may selectively
power the refrigeration heat absorption heat exchanger fan(s) 46 for selected periods of time
and at selected intervals for drawing air from the temperature controlled space, passing the air
through the airside passage of the refrigerant heat absorption heat exchanger 44 and supplying
the air back to the temperature controlled space thereby causing circulation of air within the
temperature controlled space. Although the air is not cooled when traversing the refrigerant
heat absorption heat exchanger 44 (the compression device 32 not being in operation), the
resultant circulation currents within the temperature controlled space will promote sufficient
mixing to reduce, if not eliminate, the formation and severity of "hot spots" within the
temperature controlled space.
[0032] In an embodiment of the disclosed method, the controller 30 carries out the step
of operating the engine 26 to drive the electric generation device 24 and simultaneously
employing the battery system 28 to power the plurality of power demand loads of the
refrigeration unit 22 during a high cooling demand mode by simultaneously operating both the
engine 26 driving the electric generation device 24 and employing the battery system 28 to
power the compression device drive motor. The controller 30 may also employ the battery
system 28 to power the refrigerant heat rejection heat exchanger fan motor 42 and the
refrigerant heat absorption heat exchanger fan motor 46. In an embodiment of the method, the
controller 30 carries out the step of operating the engine 26 to drive the electric generation
device 24 and simultaneously employing the battery system 28 to together power the plurality
of power demand loads of the refrigerant unit 22 during a high cooling demand mode by
operating the engine 26 to drive the electric generation device 24 to power the compression
device drive motor 50 and employing the battery system 28 to power the refrigerant heat
rejection heat exchanger fan motor 42 and the refrigerant heat absorption heat exchanger fan
motor 46. During operation of the refrigeration unit 22 at a low cooling demand, the method
may include the step of selectively operating the engine 26 to drive the electric generation
device 24 to power the plurality of power demand loads of the refrigeration unit 22 and also
charge the battery system 28.
[0033] In the transport refrigeration system 22 as disclosed herein, the controller 30, in
addition to controlling operation of the refrigeration unit 30 in response to cooling demand, is
configured, that is operative, to selectively choose which power source or sources to employ in
supplying electrical power to meet the plurality of power demand loads of the refrigerant unit
22 and also to select which power source or source will power which components, that is which
power demand loads, of the refrigeration unit 22. In a high cooling demand mode during, the
controller 30 simultaneously operates the engine 26 to drive the electric generation device 24
for supplying electric power and also employs the battery system 28 to supply electric power to
jointly power the plurality of power demand loads of the refrigerant unit 22. In a low cooling
demand mode, the controller 30 selectively operates the engine 26 to drive the electric
generation device 24 to power the plurality of power demand loads of the refrigeration unit 22
and also charge the battery system 28.
[0034] Therefore, unlike in conventional systems wherein the engine 26 must be sized
to on its own meet the entire collective plurality of power load demands of the refrigeration unit
22 during operation at maximum cooling demand, in a refrigeration system 20 equipped with a
high voltage battery system 28 dedicated to supplying power to the refrigeration unit 22 and
operated in accordance with the method disclosed herein, the engine 26 can be used less,
thereby saving fuel and reducing emissions to the atmosphere by using less fuel, or the engine
26 can be downsized to a smaller size engine, thereby saving weight and also leading to less
fuel consumption. For example, the engine 26 can be downsized to meet the entire collective
plurality of power load demands of the refrigeration unit 22 during operation at a cooling
capacity significantly below the maximum cooling demand and to simultaneously provide
power to charge the battery system 28.
[0035] In an embodiment, the controller 30 may be configured, that is operative, to in a
low cooling demand mode, and during operation in the low cooling demand mode to shut down
the engine 26 and employ only the battery system 28 to power the plurality of power demand
loads of the refrigeration unit 22. In this embodiment, the battery system 28 must be sized to
provide the required power for meeting the entire plurality of power load demands of the
refrigeration unit in the low cooling mode demand, including the fans 42, 46 and the
compression device drive motor 50, for a desired time period.
[0036] In an embodiment, the controller 30 may be configured to operate the engine 26
to drive the electric generation device 24 to power the compression device drive motor 50 and
simultaneously employ the battery system 28 to power the refrigerant heat rejection heat
exchanger fan motor 42 and the refrigerant heat absorption heat exchanger fan motor 46, and
optionally, if an electric heater is installed, to power the electric heater 48. In this embodiment,
the battery system 28 would need to be sized to provide the required power for the power load
demands imposed by the fan motors 42, 46 during operation of the refrigeration unit 22 at
maximum cooling demand.
[0037] As discussed previously, the standby power grid connection 52 may be employed
as a power source when the truck or trailer is parked at a truck stop or warehouse or other facility
for an extended period of time. In such case, the power grid connection 52 is mated with a grid
power source to supply grid power to the refrigeration unit 22, thereby permitting the controller
30 to shut down the Diesel engine 26 to save fuel and to not tap into the battery system 28 so as
to also converse battery power. Additionally, a battery charger 62 may be added to the
refrigeration system in operational association with the battery pack 28 and the standby power
grid connection 52. With the battery charger 62 installed, when the refrigeration system is
connected to the grid power source through the standby power grid connection 52, the controller
30 may selectively switch on the battery charger 62 and supply electrical power from the power
grid to charge the battery pack 28. The controller 30 may do so whether or not power from the
supply power grid is simultaneously also being supplied through the standby power grid
connection 52 to more one or more of the plurality of power demand loads of the refrigeration
unit 22.
[0038] 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.
[0039] 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 method for operating a refrigeration system having a refrigeration unit for
providing temperature conditioned air to a temperature controlled space, an engine and an
electric generation device, the method comprising the steps of:
providing a battery system having a least one battery unit supplying electric power; and
during a high cooling demand mode, operating the engine to drive the electric
generation device for supplying electric power and simultaneously employing the battery
system for supplying electric power to jointly power the plurality of power demand loads
of the refrigerant unit.
2. The method as set forth in claim 1 further comprising the step of: during a low
cooling demand mode, operating the engine to drive the electric generation device to power the
plurality of power demand loads of the refrigeration unit and also charge the battery system.
3. The method as set forth in claim 1 further comprising the step of: during a low
cooling demand mode, employing the battery system to power the plurality of power demand
loads of the refrigeration unit.
4. The method as set forth in claim 1 further comprising the step of during a period
of shutdown of the engine, employing the battery system to power the plurality of power demand
loads of the refrigeration unit.
5. The method as set forth in claim 4 wherein the step of employing the battery
system to power the plurality of power demand loads of the refrigeration unit during the period
of engine shutdown comprises the step of selectively powering the refrigeration heat absorption
heat exchanger fan for selected periods of time and at selected intervals.
6. The method as set forth in claim 1 further comprising the steps of:
providing a battery charger in operational association with the battery system; and
during a period of shutdown of the engine, selectively employing an external power
source for powering the battery charger to charge the battery system.
7. The method as set forth in claim 6 further comprising the steps of:
providing a standby power grid connection for through connecting to a supply power
grid; and
during a period of shutdown of the engine, selectively powering the battery charger to
charge the battery system with power supplied from the supply power grid through the standby
power grid connection.
8. The method as set forth in claim 1 wherein the refrigeration unit includes a
refrigerant compression device, a refrigerant heat rejection heat exchanger and an associated fan,
a refrigerant heat absorption heat exchanger and an associated fan, and a plurality of power
demand loads including a compression device drive motor, a refrigerant heat rejection heat
exchanger fan drive motor and a refrigerant heat absorption heat exchanger fan drive motor, and
the step of operating the engine to drive the electric generation device and simultaneously
employing the battery system to power the plurality of power demand loads of the refrigerant
unit during a high cooling demand mode comprises the step of simultaneously operating both the
engine to drive the electric generation device and employing the battery system to power the
compression device drive motor.
9. The method as set forth in claim 8 further comprising the step of employing the
battery system to power the refrigerant heat rejection heat exchanger fan motor and the
refrigerant heat absorption heat exchanger fan motor.
10. The method as set forth in claim 1 wherein the refrigeration unit includes a
refrigerant compression device, a refrigerant heat rejection heat exchanger and an associated fan,
a refrigerant heat absorption heat exchanger and an associated fan, and a plurality of power
demand loads including a compression device drive motor, a refrigerant heat rejection heat
exchanger fan drive motor and a refrigerant heat absorption heat exchanger fan drive motor, and
the step of operating the engine to drive the electric generation device and simultaneously
employing the battery system to power the plurality of power demand loads of the refrigerant
unit during a high cooling demand mode comprises the step of operating the engine to drive the
electric generation device to power the compression device drive motor and employing the
battery system to power the refrigerant heat rejection heat exchanger fan motor and the
refrigerant heat absorption heat exchanger fan motor.
11. The method as set forth in claim 1 wherein the high cooling demand mode
comprises a temperature pulldown mode wherein the refrigeration unit is operated to reduce a
temperature within the temperature controlled space to a set- point temperature.
12. The method as set forth in claim 1 wherein the low cooling demand mode
comprises a temperature control mode wherein the transport refrigeration unit is operated to
maintain a temperature within the temperature controlled space within a specified range of a setpoint
temperature.
13. The method as recited in claim 1 wherein the temperature controlled space
comprises the perishable cargo hold of a truck, trailer, intermodal container or other transport
container.
14. A transport refrigeration system having a refrigeration unit for providing
temperature conditioned air to a cargo storage space of a truck, trailer, intermodal container or
other transport container, the refrigeration unit having a refrigerant compression device, a
refrigerant heat rejection heat exchanger and an associated fan, a refrigerant heat absorption heat
exchanger and an associated fan, and a plurality of power demand loads including a compression
device drive motor, a refrigerant heat rejection heat exchanger fan drive motor and a refrigerant
heat absorption heat exchanger fan drive motor, the transport refrigeration system having an
electric generating device and an engine for driving the electric generating device, the transport
refrigeration system further comprising:
a controller operatively associated with the refrigeration unit, the controller operative to
selectively operate the refrigeration unit in a high cooling demand mode, and during operation in
the high cooling demand mode operating the engine to drive the electric generation device for
supplying electric power and simultaneously employing the battery system to supply electric
power to jointly power the plurality of power demand loads of the refrigerant unit.
15. The transport refrigeration system as set forth in claim 14 wherein the controller
is further operative to selectively operate the refrigeration unit in a low cooling demand mode,
and during operation in the low cooling demand mode operating the engine to drive the electric
generation device to power the plurality of power demand loads of the refrigeration unit and also
charge the battery system.
16. The transport refrigeration system as set forth in claim 14 wherein the controller
is further operative to selectively operate the refrigeration unit in a low cooling demand mode,
and during operation in the low cooling demand mode employing the battery system to power
the plurality of power demand loads of the refrigeration unit.
17. The transport refrigeration system as set forth in claim 14 wherein the controller
is further operative to selectively shutdown the engine and the refrigerant compression device
and selectively employ the battery system to power the refrigerant heat absorption heat
exchanger fan motor.
18. The transport refrigeration system as set forth in claim 14 wherein the controller
employs the battery system to selectively power the refrigeration heat absorption heat exchanger
fan motor for selected periods of time and at selected intervals.
19. The transport refrigeration system as set forth in claim 14 wherein the controller
is further operative to simultaneously operate the engine to drive the electric generation device
and employ the battery system to jointly power the compression device motor.
20. The transport refrigeration system as set forth in claim 14 wherein the controller
is further operative to operate the engine to drive the electric generation device to power the
compression device drive motor and simultaneously employ the battery system to power the
refrigerant heat rejection heat exchanger fan motor and the refrigerant heat absorption heat
exchanger fan motor.