Patent Publication Number: US-11046508-B2

Title: Refrigerated storage container air passage

Description:
BACKGROUND OF THE DISCLOSURE 
     The subject matter disclosed herein relates to refrigerated storage containers and, more particularly, to refrigerated storage container air passage designs, energy efficient refrigerated storage container operation and energy efficient coordination of refrigerated storage containers on cargo ships. 
     A refrigerated storage container or reefer is an intermodal container (i.e., a shipping container) that is used in intermodal freight transport and may be refrigerated for the transportation of temperature sensitive cargo. An intermodal container is a large standardized shipping container, designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport—from ship to rail to truck—without unloading and reloading their cargo. Intermodal containers are primarily used to store and transport materials and products efficiently and securely in the global containerized intermodal freight transport system, but smaller numbers are in regional use as well. 
     Other than the standard, general purpose containers, many variations of intermodal containers exist for use with different types of cargoes. The most prominent of these are refrigerated containers, such as containers with integrated refrigeration units (a.k.a. reefers) that are used in the transport of temperature sensitive goods. 
     BRIEF DESCRIPTION OF THE DISCLOSURE 
     According to one aspect of the disclosure, a refrigerated storage container is provided and includes a container housing defining an interior in which cargo is storable, a condenser configured to receive air to remove heat from a refrigerant passing through the condenser, a condenser air inlet receptive of the air, a condenser air outlet configured to direct air exhausted from the condenser away from the condenser air inlet and a reefer air outlet configured to direct conditioned air exhausted from the interior toward the condenser air inlet. 
     In accordance with additional or alternative embodiments, the condenser air inlet is configured to be receptive of the conditioned air from the reefer air outlet. 
     In accordance with additional or alternative embodiments, the condenser air inlet, the condenser air outlet and the reefer air outlet each include louvers. 
     In accordance with additional or alternative embodiments, a local or remote controller is disposed to dependently or independently control an angling of each of the louvers. 
     In accordance with additional or alternative embodiments, the louvers are movable relative to a plane of a wall of the container housing. 
     In accordance with additional or alternative embodiments, the condenser air inlet, the condenser air outlet and the reefer air outlet are disposed on an end wall of the container housing. 
     In accordance with additional or alternative embodiments, the condenser air outlet is in a central region of the wall, the condenser air inlet includes first and second condenser air inlets aside the central region and a third condenser air inlet below the central region and the reefer air outlet includes first and second reefer air outlets outside the first and second condenser air inlets and a third reefer air outlet below the third condenser air inlet. 
     In accordance with additional or alternative embodiments, the condenser air outlet includes louvers angled upwardly, the first and second condenser air inlets each include louvers angled outwardly, the third condenser air inlet includes louvers angled downwardly, the first and second reefer air outlets each include louvers angled inwardly and the third reefer air outlet includes louvers angled upwardly. 
     In accordance with additional or alternative embodiments, an attachment is removably attachable to the reefer air outlet and configured to constrain a flow of the conditioned air to remain in a flowpath directed toward the condenser air inlet. 
     According to another aspect of the disclosure, a refrigerated storage container is provided and includes a container housing, a condenser configured to receive air to remove heat from a refrigerant passing through the condenser, a condenser air inlet by which the air is received, a condenser air outlet and a reefer air outlet configured such that air exhausted from the condenser is directed away from the condenser air inlet and conditioned air exhausted from the interior is directed toward the condenser air inlet. 
     In accordance with additional or alternative embodiments, the condenser air inlet, the condenser air outlet and the reefer air outlet each include louvers. 
     In accordance with additional or alternative embodiments, a local or remote controller is disposed to dependently or independently control an angling of each of the louvers. 
     In accordance with additional or alternative embodiments, the louvers are movable relative to a plane of a wall of the container housing. 
     In accordance with additional or alternative embodiments, the condenser air inlet, the condenser air outlet, and the reefer air outlet are disposed on an end wall of the container housing. 
     In accordance with additional or alternative embodiments, the condenser air outlet is in a central region of the wall, the condenser air inlet includes first and second condenser air inlets aside the central region and a third condenser air inlet below the central region and the reefer air outlet includes first and second reefer air outlets outside the first and second condenser air inlets and a third reefer air outlet below the third condenser air inlet. 
     In accordance with additional or alternative embodiments, the condenser air outlet includes louvers angled upwardly, the first and second condenser air inlets each include louvers angled outwardly, the third condenser air inlet includes louvers angled downwardly, the first and second reefer air outlets each include louvers angled inwardly and the third reefer air outlet includes louvers angled upwardly. 
     In accordance with additional or alternative embodiments, an attachment is removably attachable to the reefer air outlet and configured to constrain a flow of the conditioned air to remain in a flowpath directed toward the condenser air inlet. 
     According to yet another aspect of the disclosure, a ship or yard is provided and includes first and second sets of one or more refrigerated storage containers respectively stackable to define a pathway. Each one of the first and second sets of the one or more refrigerated storage containers includes a container housing having an end wall facing the pathway, a condenser configured to receive air to remove heat from a refrigerant passing through the condenser and a condenser air inlet by which the air is received, a condenser air outlet and a reefer air outlet configured such that air exhausted from the condenser is directed away from the condenser air inlet and conditioned air exhausted from the interior is directed toward the condenser air inlet. 
     In accordance with additional or alternative embodiments, the condenser air inlet, the condenser air outlet and the reefer air outlet each include louvers. 
     In accordance with additional or alternative embodiments, a local or remote controller is disposed to dependently or independently control an angling of each of the louvers. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The subject matter, which is regarded as the disclosure, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a ship in accordance with embodiments; 
         FIG. 2  is a perspective view of stacks of refrigerated storage containers within a ship in accordance with embodiments; 
         FIG. 3  is a schematic diagram illustrating local controllers and a supervisory controller for refrigerated storage containers in accordance with embodiments; 
         FIG. 4  is a schematic diagram illustrating local controllers and two or more supervisory controllers for refrigerated storage containers in accordance with embodiments; 
         FIG. 5  is a cut-away, top-down view of a refrigerated storage container in accordance with embodiments; 
         FIG. 6  is a cut-away, side view of a refrigerated storage container in accordance with embodiments; 
         FIG. 7  is an end view of an end wall of the refrigerated storage container of  FIGS. 5 and 6  in accordance with embodiments; 
         FIG. 8  is a top-down view of movable louvers in accordance with embodiments; 
         FIG. 9  is a top down view of an attachment to an end wall of a refrigerated storage container in accordance with embodiments; 
         FIG. 10  is a graphical illustration of temperature vs. time performance of a refrigerated storage container; 
         FIG. 11  is a flow diagram illustrating a method of executing energy-efficient operations of an air conditioner of a refrigerated storage container; and 
         FIG. 12  is a flow diagram illustrating a method of operating refrigerated storage containers provided on a ship or in a yard. 
     
    
    
     The detailed description explains embodiments of the disclosure, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     As will be described below, containers with refrigeration systems which are generally referred to as reefers, need to dissipate heat through condensers. Air-cooled reefers employ fans to extract ambient air from the reefer&#39;s surroundings, pass the extracted air through condensers and then discharge the resulting heated air back into the ambient air of the surroundings. On a container ship or in a container yard, reefers are stacked in rows separated by a narrow aisle, however, and therefore air exhaust from a condenser may impinge on containers across the aisle. Such impingement can lead to the heating of reefers across the aisle, increased condensing pressure and hence power consumption with elevated air temperatures with condenser air recirculation due to reflection and potential cargo degradation caused by system trip-offs with continuous increasing air temperature into condenser due to recirculated air. 
     As such, air openings are typically designed into reefers in order to alleviate the effects of recirculated heated air (condenser air recirculation due to reflection can also be reduced or avoided by increasing the distance between aisles, but space constraints on a ship or in a yard are frequently stringent). Such air openings can be more effective, however, with the addition of louvers with adjustable parallel blades that can direct air at an angle to reduce direct impingement and hence decrease air reflection. The blades can be set at an angle between 30-60 degrees relative to the horizontal so that air will be exhausted upward with buoyance or so that cool exhaust air from inside the reefer will be directed toward the condenser air inlets. 
     With reference to  FIG. 1 , a transport ship  10  is provided. The transport ship  10  can be configured for any type of transportation mode but for purposes of clarity and brevity will be referred to hereinafter as a transport ship  10 . The transport ship  10  includes a hull  11 , a propeller (not shown) to drive the hull  11  through water, an engine room (not shown) that is disposed within the hull  11  to drive rotations of the propeller and a bridge or command center  14 . The command center  14  is disposed within or on the hull  11  and includes a bridge and operational computers that control various operations of the transport ship  10 . 
     With reference to  FIG. 2 , the hull  11  is formed to define an interior  110  in which reefers or refrigerated storage containers  20  are stowed (the terms “reefer” and “refrigerated storage container” will hereinafter be used interchangeably). The refrigerated storage containers  20  may be provided in at least first and second stacks  201  and  202  that are separated by an aisle  203 . The aisle  203  is generally wide enough for a person to walk between the first and second stacks  201  and  202  and is provided at the ambient temperature of the interior  110 . Each of the first and second stacks  201  and  202  may have one or more refrigerated storage containers  20  stacked top-to-bottom. 
     For the purposes of the present description, each refrigerated storage container  20  may have a substantially uniform structure and configuration. That is, each refrigerated storage container  20  may be provided as a substantially rectangular body  21  that is formed to define an interior  22  in which cargo is stored. The body  21  includes a bottom, sidewalls and a top that are provided to enclose the interior  22  and the sidewalls include an endwall  23  that faces the aisle  203 . Each refrigerated storage container  20  may further include a condenser  24  of an air conditioning unit which is disposed within the interior  22  to condition the air in the interior  22  and sensors  25  (e.g., cargo space temperature sensors) to sense various operational parameters of the refrigerated storage container  20 . 
     Various operations of the refrigerated storage containers  20  are controllable by one or more local controllers  30  and one or more supervisory controllers  40 . The one or more local controllers  30  and the one or more supervisory controllers  40  may be stand-alone components or components of the above-mentioned operational computers. 
     In accordance with embodiments and, as shown in  FIGS. 3 and 4 , each local controller  30  may be associated and coupled with a corresponding one of the refrigerated storage containers  20 . In some cases, a single distributed supervisory controller  40  may be associated and coupled with each of the local controllers  30  or multiple local controllers  30  and their corresponding refrigerated storage containers  20  (see  FIG. 3 ) whereas, in other cases, two or more supervisory controllers  40  may be associated and coupled with respective groups of local controllers  30  and each of their corresponding refrigerated storage containers  20 . In any case, each local controller  30  controls various operations of its corresponding refrigerated storage container  20  while the readings generated by the sensors  25  are provided to either or both of the supervisory controller  40  and the local controller  30  such that the controls exerted by the local controller  30  can be optimized via local and/or remote feedback control. 
     With reference to  FIGS. 5-7 , the condenser  24  is disposed within the interior  22  and at an end of the refrigerated storage container  20  near the end wall  23  and is configured to remove heat from a refrigerant passing through the condenser  24 . The end wall  23  is formed to support the operations of the condenser  24 . That is, first, second and third condenser air inlets  240   1-3 , a condenser air outlet  241  and first, second and third reefer air outlets  242   1-3  are supportively disposed on the end wall  23 . The first, second and third condenser air inlets  240   1-3  are receptive of the air to remove heat from a refrigerant passing through the condenser  24  and thus should be receptive of relatively cool air for encouraging optimal, efficient operation of the condenser  24 . The condenser air outlet  241  is configured to direct the relatively high temperature air exhausted from the condenser  24  away from the first, second and third condenser air inlets  240   1-3  such that the relatively high temperature air is not received or ingested by the first, second and third condenser air inlets  240   1-3 . The first, second and third reefer air outlets  242   1-3  are configured to direct the conditioned air and relatively low temperature air that is exhausted from the interior  22  toward the first, second and third condenser air inlets  240   1-3 . This relatively low temperature air then mixes with ambient air provided within the region in and around the aisle  203  before being received or ingested by the first, second and third condenser air inlets  240   1-3 . 
     In accordance with embodiments, the condenser air outlet  241  may be located in a central, somewhat upper region of the end wall  23 . In such cases, the first and second condenser air inlets  240   1  and  240   2  may be located proximate to opposite sides of the condenser air outlet  241  with the third condenser air inlet  240   3  located just below the condenser air outlet  241 . The condenser air outlet  241  may therefore be configured to direct the relatively high temperature air in an upward direction so as to avoid generating flows of air toward and over the first, second and third condenser air inlets  240   1-3 . In addition, the first and second reefer air outlets  242   1  and  242   2  may be located proximate to and outside of the first and second condenser air inlets  240   1  and  240   2 , respectively, with the third reefer air outlet  242   3  located just below the third condenser air inlet  240   3 . 
     Each one of the first, second and third condenser air inlets  240   1-3  includes CAI louvers  501 ,  502  and  503 , the condenser air outlet  241  includes CAO louvers  51  and each one of the first, second and third reefer air outlets  242   1-3  includes RAO louvers  521 ,  522  and  523 . The CAI louvers  501 ,  502  and  503 , the CAO louvers  51  and the RAO louvers  521 ,  522  and  523  may all be independently or dependently controlled by the local controllers  30  and/or the supervisory controllers  40 . Such independent or dependent controls generally relates to angling of respective louver blades and in some cases to positioning of the angled louver blades relative to the end wall  23 . 
     In accordance with embodiments and, as shown in  FIG. 7 , the blades of the CAI louvers  501  and  502  are oriented substantially vertically and in parallel with each other. During operational modes of the refrigerated storage container  20 , the blades of the CAI louvers  501  and  502  may be angled outwardly (at approximately 30-60 degrees, for example) toward the first and second reefer air outlets  242   1  and  242   2 , respectively. Similarly, the blades of the CAI louver  503  are oriented substantially horizontally and in parallel with each other. During operational modes of the refrigerated storage container  20 , the blades of the CAI louver  503  may be angled downwardly (at approximately 30-60 degrees, for example) toward the third reefer air outlet  242   3 . The blades of the RAO louvers  521  and  522  are oriented substantially vertically and in parallel with each other. During operational modes of the refrigerated storage container  20 , the blades of the RAO louvers  521  and  522  may be angled inwardly (at approximately 30-60 degrees, for example) toward the first and second condenser air inlets  240   1  and  240   2 , respectively. Similarly, the blades of the RAO louver  523  are oriented substantially horizontally and in parallel with each other. During operational modes of the refrigerated storage container  20 , the blades of the RAO louver  523  may be angled upwardly (at approximately 60 degrees, for example) toward the third condenser air inlet  2403 . The blades of the CAO louver  51  are oriented substantially horizontally and in parallel with each other. During operational modes of the refrigerated storage container  20 , the blades of the CAO louvers  51  may be angled upwardly (at approximately 60 degrees, for example) away from the first, second and third condenser air inlets  240   1 ,  240   2  and  240   3 . 
     With reference to  FIG. 8 , at least the blades of the RAO louvers  521 ,  522  and  523  may be independently or dependently movable by the local controllers  30  and/or the supervisory controllers  40  relative to a plane of the end wall  23 . That is, as shown in  FIG. 8 , during operational modes of the refrigerated storage container  20 , at least the blades of the RAO louvers  521 ,  522  and  523  may be extended such that they protrude from the plane of the end wall  23  and thereby increase flows of air exhausted from the interior  22  into the first, second and third condenser air inlets  240   1-3 . 
     With reference to  FIG. 9 , at least the first, second and third reefer air outlets  242   1-3  may be provided with an attachment  60 . The attachment  60  is removably attachable to the end wall  23  by, for example, press-fitting or other similar attachment methods (i.e., by an operator walking down the aisle  203 ), and is shaped to direct air exhausted from the interior  22  toward the condenser air inlets  240   1-3 . The attachment  60  has an open end that terminates short of the first, second and third condenser air inlets  240   1-3  so as to avoid interfering with flows of ambient air into the condenser  24  and to encourage air exiting the attachment  60  to be entrained to flow into the condenser  24  by other flows of ambient air. 
     In accordance with further embodiments, to the extent any of the blades of the RAO louvers  521 ,  522  or  523  protrude from the plane of the end wall  23  or to the extent that an attachment  60  is removably attached to the first, second and third reefer air outlets  242   1-3 , it is to be understood that the length of the protrusion or the width of the attachment  60  is substantially less than the width of the aisle  203 . For example, if the aisle  203  is about 2 meters wide, the length of the protrusion or the width of the attachment  60  is on the order of only a few centimeters. 
     The above-described louvers will help reduce recirculation of heated air and direct impingement of heated air into and onto refrigerated storage containers  20  and will thereby improve energy efficiency and operation of the refrigerated storage containers  20 . For refrigerated storage containers  20  with ventilation or air modification capabilities, cold air that is discharged from interiors  22  can be utilized to lower condenser air temperatures and therefore reduce energy consumption of the refrigeration system and improve operation to maintain cargo quality. 
     In accordance with another aspect and, with reference back to  FIGS. 2-4 , when refrigerated storage containers  20  are stacked close to each other within an interior  110 , some of the exhaust hot air from one refrigerated storage container  20  may enter the condensers of nearby refrigerated storage containers  20  even if the above-described louvers are provided. Such re-ingestion of hot air can lead to elevated air temperatures entering condensers  24  and result in increased condensing pressure of refrigerant as well as increased power usage to maintain refrigerant flow in the vapor compression system. Re-ingestion can also lead to cooling systems being tripped off when refrigerant condensing pressures exceed control limits with a potential result of degraded cargo quality. 
     Scheduling reefer operations to avoid re-ingestion of hot air typically relies on local feedback control where the refrigeration unit including the condenser  24  of each refrigerated storage container  20  is cycled on and off based primarily on the cargo temperature requirements of each particular refrigerated storage container  20  and without any information on the operation of adjacent refrigerated storage containers  20  and their exhaust air flow distributions. A decentralized control algorithm is provided, however, with low sensing and communication requirements in which each local controller  30  determines when to turn its corresponding refrigerated storage container  20  on and off within a given time window in order to minimize waste heat ingestion from neighboring refrigerated storage containers  20 . 
     Using the control algorithm, ambient air temperature and condenser inlet air temperature are measured and the difference between them (ΔT) is utilized as a pseudo-data element for potential exhaust air ingestion. The algorithm further includes on-off control logic that minimizes interactions between adjacent refrigerated storage containers  20  and enables higher system operation efficiency by running the refrigerated storage containers when ΔT is sufficiently small. The time window for the on-off decision making depends on cargo space temperature performance information and allowable temperature variability (Thigh, Tlow) around given set-point (Tsp). 
     In greater detail and, with reference to  FIG. 10 , each refrigerated storage container  20  includes its local controller  30  and the local controller  30  is configured to cycle the corresponding condenser  24  of its air conditioner on an off within a time window based on waste heat ingestion from the neighboring refrigerated storage containers  20 . The time window is predefined in accordance with temperatures within the interior  22  and allowable temperature variability around a set-point Tsp. This allowable temperature variability gives rise to high and low temperature limits (T high  and T low ) as well as high and low temperature near-limits (T h1  and T l1 ). 
     The local controller  30  derives a value of the waste heat ingestion from a difference between periodically measured ambient and condenser inlet air temperatures and is configured to limit a number of cycles within the time window, implement an override command to force the air conditioner to cycle in an event a temperature within the interior reaches a limit and potentially override a cycling command issued by a supervisory controller (generally, if a supervisory controller is present, it is to be understood that a default condition could be that the supervisory controller would have priority to override local level decisions except in critical situations or for safety reasons). 
     Thus, for the example of  FIG. 10 , as a temperature of the interior  22  of a given refrigerated storage container  20  increases beyond high temperature near-limit T h1 , which is passed at time t 1 , until the high temperature limit T high  is reached at time t 2 , the local controller  30  will determine if the difference between the ambient air temperature and the condenser inlet air temperature is less than a predefined threshold. If so, the local controller  30  will cycle the condenser  24  and the air conditioning unit to turn on and, if not, the local controller  30  will maintain the condenser  24  and the air conditioning unit in the off state until time t 2  when the high temperature limit (T high ) is reached, and must then turn on the air conditioning unit and the condenser  24 . Conversely, as the temperature of the interior  22  decreases beyond low temperature near-limit TR, which is passed at time t 3 , until the low temperature limit T low  is reached at time t 4 , the local controller  30  will determine if the difference between the ambient air temperature and the condenser inlet air temperature exceeds a predefined threshold. If so, the local controller  30  will cycle the condenser  24  and the air conditioning unit to turn off and, if not, the local controller  30  will maintain the condenser  24  and the air conditioning unit in the on state until time t 4 . 
     With reference to  FIG. 11 , a method of executing energy-efficient operations of an air conditioner of each of the refrigerated storage containers  20  is provided. The method includes establishing a time window for operating the air conditioner in accordance with temperatures within an interior of a container housing and allowable temperature variability around a set-point (block  1101 ), periodically measuring ambient and condenser inlet air temperatures within the time window and calculating a difference between the ambient and condenser inlet air temperatures (block  1102 ) and cycling the air conditioner within the time window in an event a local controller determines that temperatures within the interior exceed the allowable temperature near limits variability and the difference exceeds a predefined threshold (block  1103 ). 
     The autonomous reefer schedule logic based on the quality of air at the unit&#39;s condenser inlet, in addition to the cargo space temperature, minimizes potential waste heat ingestion and thereby reduces energy usage for refrigeration. The decentralized control logic only requires one additional sensor for condenser inlet temperature, rendering the solution practical with low implementation cost. The control logic can be easily integrated with the individual unit legacy controller or implemented as a stand-alone local controller for each reefer. 
     In accordance with still further aspects, overall electrical energy consumption related to operations of the refrigerated storage containers  20  is controlled through coordination of multiple refrigerated storage containers  20  and the local controllers  30  by the supervisory controller  40 . The supervisory controller  40  (e.g., the reefer coordinator) receives condenser inlet temperate measurements and operational parameters from the local controllers  30  and uses the data to learn or identify (online) correlations between the total electric power consumption of each of the refrigerated storage containers  20  and their respective operations and thus determines an optimal on-off control strategy that satisfies cargo space temperature requirements and minimizes power consumption and short cycling. 
     As shown in  FIG. 3 , operational data transmitted to an input unit  401  of the supervisory coordinator  40  is transmitted at sampling instants and includes individual unit on/off mode information, cargo space controlled temperature information, desired set-point information, allowable temperature variability information, electrical power draw information and ambient air temperature information. Output of the supervisory controller  40  and on/off commands are generated by processing unit  402  and may be sent from an output unit  403  to the various local controllers  30 . The supervisory controller  40  architecture could be distributed or centralized. That is, as noted above, in the distributed framework, a supervisory coordinator  40  is assigned to a cluster of refrigerated storage containers  20  and the predictive model is localized to a given neighborhood whereas, in a centralized strategy, a single supervisory coordinator monitors and schedules all the on-board refrigerated storage containers  20 . 
     With reference to  FIG. 12 , a method of operating refrigerated storage containers  20  provided on a ship or in a yard is provided. The method includes receiving first data (i.e., condenser air inlet temperate measurements and operational parameters, such as on/off mode information, desired set point information, allowable temperature variability information and ambient temperature information) from local controllers of the refrigerated storage containers (block  1201 ), receiving second data (i.e., cargo space controlled temperature information, and electrical power draw information) from sensors of the refrigerated storage containers (block  1202 ), identifying a correlation between the electric power consumption of the refrigerated storage containers and operations of the refrigerated storage containers from the first and second data (block  1203 ) and determining an optimal on-off control strategy for each refrigerated storage container based on the correlation that satisfies cargo space temperature requirements and minimizes power consumption and short cycling (block  1204 ). 
     In accordance with embodiments, the determining may be further based on at least one or more of a learned time constant of one or more of the refrigerated storage containers, a time constant associated with an interaction of a group of the refrigerated storage containers and knowledge of expected environmental conditions. That is, if over time one of the refrigerated storage containers  20  (or a group of refrigerated storage containers  20 ) is/are found to respond more quickly to controls executed by its/their local controller  30  while another refrigerated storage container  20  responds slowly, the supervisory controller  40  can derive a learned time constant for each refrigerated storage container  20 . This learned time constant can thereafter be updated periodically and used in concert with knowledge of future or expected environmental conditions (e.g., weather, on-board and off-board temperatures, transport time, etc.) to modulate the determining of the on-off control strategy. 
     The method further includes issuing control commands based on the optimal on-off control strategy for each refrigerated storage container to the local controllers (block  1205 ). These control commands can be overridden in some cases by the local controllers  30  if they are in conflict with control algorithms resident in the local controllers  30  individually. For example, if the control algorithm of the embodiments of  FIGS. 10 and 11  dictate that a local controller  30  should cycle a condenser  24  on at time t 2  when the T high  limit of  FIG. 10  is reached but the control algorithm of the supervisory controller  40  dictates the opposite, the local controller  30  will override the commands of the supervisory controller  40 . 
     When additional data related to, for example, diesel generator(s) and fuel efficiencies are available, the supervisory controller  40  may also optimize generator fuel consumption while guaranteeing cargo reliability based on a holistic view of on-board electrical systems. Such energy aware scheduling systems may achieve fuel savings by reducing generator(s) operation at inefficient part-load conditions, generator (and reefer) cycling rates and hot air re-ingestion. 
     The supervisory controller  40  serves to minimize total electrical energy usage while maintaining cargo space temperatures within acceptable ranges by coordination of multiple refrigerated storage containers  20  to prevent unwanted waste heat re-ingestion. Also, the solution guarantees dynamic optimal performance by learning system behaviors online and adapting to operational and ambient changes. 
     While the disclosure is provided in detail in connection with only a limited number of embodiments, it should be readily understood that the disclosure is not limited to such disclosed embodiments. Rather, the disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the disclosure. Additionally, while various embodiments of the disclosure have been described, it is to be understood that the exemplary embodiment(s) may include only some of the described exemplary aspects. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.