Control system and control method for reefer container

Abstract

To provide a control system and control method for a reefer container capable of efficiently utilizing cold energy to standardize system power used in the entire container terminal.SOLUTION: In a control system 20 for a reefer container 10 stored in a container terminal 1 and using system power, a calculation device 22 has a memory device 23 for an excess cooling time band tda and a power reduction time band tbc, each of which lasts for several hours, where during the excess cooling time band tda, temperature control is performed with an excess cooling temperature range set lower than a set temperature range of a frozen cargo 2 as a target temperature, to store cold energy, and during the power reduction time band tbc, with the set temperature range as the target temperature, temperature control is performed to stop the operation of the cooling device 12 by using the cold energy until a predetermined temperature within the set temperature range is reached, or set a cooling level by the operation of the cooling device 12 to a weak cooling state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control system and a control method for a reefer container, and more particularly to a control system and a control method for a reefer container that can more efficiently utilize cold energy to level out the system power used in the entire container terminal. [Background technology]

[0002] Container terminals mainly use grid power supplied by power companies. There is a large difference in the grid power used throughout the container terminal during the day and night, and the difference between day and night can be nearly double. Therefore, if the grid power can be averaged throughout the day and the difference between day and night can be reduced, the maximum value of grid power used will be reduced. As a result, the contracted power for grid power can be reduced, reducing electricity bills. In addition, electricity bills can be reduced by reducing the amount of grid power used during times when the unit price per unit power is high and increasing the amount of grid power used during times when the unit price is low.

[0003] Various methods for peak cutting (reducing the maximum value of grid power used) have been studied and proposed for the purpose of leveling grid power used throughout the container terminal, but no fundamental solution has been achieved. For example, promoting the use of grid power at night when the unit price per unit of power is low, and energy management through efficient use of grid power using demand response have been proposed, but these methods are unlikely to result in significant improvement. Even if an external power source such as a generator or renewable energy source is installed at the container terminal and the power from the external power source is used when the grid power is tight near the maximum value, the cost-effectiveness is poor. Although a power leveling system using thermal storage materials has a certain effect, it requires large-scale capital investment and has little economic advantage.

[0004] Incidentally, container terminals handle many reefer containers that store refrigerated goods and frozen cargo in addition to regular dry containers. The electricity used by each reefer container can account for about 40% to 50% of the electricity used in the entire container terminal. In other words, one way to level out the grid electricity used in the entire container terminal is to devise ways to control the electricity used by each reefer container.

[0005] Patent Document 1 proposes a system for controlling the power supplied to reefer containers transported by container ships, with the aim of leveling out the load on the generators installed on the container ships so that they fall within a target load range. The invention proposed in Patent Document 1 uses surplus energy on the container ship to overcool the reefer containers, converting the surplus energy into thermal energy (cold energy) and storing it, and then uses the stored thermal energy when the load on the generator is high.

[0006] Container terminals use grid power and do not have energy equivalent to the surplus energy of Patent Document 1. Therefore, the invention proposed in Patent Document 1 cannot be simply applied to the grid power used in the entire container terminal. In particular, in container ships, there are few opportunities for a situation in which surplus energy occurs to continue for several hours or for a situation in which the load on the generator is high to continue for several hours. Therefore, the degree of excess cooling in reefer containers is low and the amount of accumulated cold energy is small. Therefore, further development is needed to more efficiently use cold energy in order to level out the grid power used in the entire container terminal. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2022-539835 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a control system and a control method for a reefer container that utilizes cold energy more efficiently to level out the system power used throughout the container terminal. [Means for solving the problem]

[0009] The control system for a reefer container of the present invention which achieves the above-mentioned object is a control system for a reefer container stored in a container terminal and using grid power, wherein the reefer container at least comprises a container for storing frozen cargo and the cooling device for cooling the frozen cargo, and the control system at least comprises a calculation device for controlling the cooling device, and the calculation device has a memory device for an excessive cooling time period and a reduced power time period, each of which lasts for several hours, and during the excessive cooling time period, temperature control is executed with an excessive cooling temperature range that is lower than a set temperature range of the frozen cargo as a target temperature to store cold energy, and during the reduced power time period, temperature control is executed with the set temperature range as a target temperature, and the operation of the cooling device is stopped by utilizing the cold energy until a predetermined temperature within the set temperature range is reached, or the cooling level by the operation of the cooling device is set to a weak cooling state.

[0010] A control method for a reefer container of the present invention is a control method for a reefer container stored in a container terminal and using grid power, characterized in that, as a preparatory step, an excess cooling time period and a power reduction time period are stored in a calculation device, and when controlling the reefer container after completion of the preparatory step, during the excess cooling time period, the calculation device performs temperature control with an excess cooling temperature range that is lower than a set temperature range of the frozen cargo as a target temperature to store cold energy, and during the power reduction time period, the calculation device performs temperature control with the set temperature range as a target temperature by using the cold energy to stop operation of the cooling device until a predetermined temperature within the set temperature range is reached or to set the cooling level by operation of the cooling device to a weak cooling state. Effect of the Invention

[0011] According to the present invention, by storing in advance in a storage device an excessive cooling time period and a power reduction time period, each of which lasts for several hours, a different temperature control is performed in each time period stored in the storage device by a computing device. In the excessive cooling time period, power is actively consumed and stored as cold energy. In the power reduction time period, the stored cold energy is used to reduce the power used in the cooling device. Therefore, by efficiently using cold energy in each time period, the system power used in the entire container terminal can be increased in the excessive cooling time period and reduced in the power reduction time period, so that the system power used in the entire container terminal can be leveled. As a result, the contract power of the system power can be reduced, so that the electricity fee can be reduced. In addition, when a time period with a low unit price per unit power overlaps with an excessive cooling time period and a time period with a low unit price overlaps with a power reduction time period, the electricity fee can be further reduced. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is an illustration illustrating an embodiment of a control system for a reefer container. [Diagram 2] FIG. 11 is a flow diagram illustrating a procedure for normal control of a reefer container. [Diagram 3] FIG. 3 is a graph illustrating a transition of the system power used throughout the container terminal in a situation where normal control is performed according to the procedure of FIG. 2. [Figure 4] FIG. 1 is a flow diagram illustrating steps of an embodiment of a method for controlling a reefer container. [Diagram 5] FIG. 13 is a graph comparing the respective temperature ranges. [Figure 6] 11 is a graph illustrating an example of an excessive cooling time period and a power reduction time period. FIG. [Figure 7] FIG. 4 is an explanatory diagram illustrating an example of input data. [Figure 8]8 is an explanatory diagram illustrating input data different from the input data of FIG. 7; [Figure 9] FIG. 5 is a graph illustrating a transition of the system power used throughout the container terminal in a situation where the procedure illustrated in FIG. 4 is carried out. [Figure 10] FIG. 11 is a graph illustrating a transition of system power used in the entire container terminal in the first modification. [Figure 11] FIG. 11 is an explanatory diagram illustrating a configuration for supplying power to a reefer container in Modification 2. [Figure 12] FIG. 11 is an explanatory diagram illustrating an example of a transition of the system power used in the entire container terminal in the second modification. [Figure 13] FIG. 11 is an explanatory diagram illustrating an example of a transition of the system power used in the entire container terminal in the third modification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a reefer container control system and a control method of the present invention will be described based on the embodiments shown in the drawings.

[0014] 1 controls the cooling device 12 of the reefer container 10 stored in the container terminal 1 to control the temperature inside the container 11. By implementing the embodiment of the control method for the reefer container 10 using the control system 20, the grid power used throughout the container terminal 1 is leveled. The grid power means power supplied from the grid power source 3.

[0015] The outline of the control method implemented by the control system 20 will be described. The arithmetic device 22 has a storage device 23 for the excess cooling time period tda and the power reduction time period tbc, which are exemplified in FIG. 9 described later. During the excess cooling time period tda, the arithmetic device 22 executes temperature control with the target temperature set to an excess cooling temperature range lower than the set temperature range of the frozen cargo 2, and stores cold energy. Also, during the power reduction time period tbc, the arithmetic device 22 executes temperature control with the set temperature range as the target temperature, by using cold energy to stop the operation of the cooling device 12 until a predetermined temperature within the set temperature range is reached, or to make the cooling state by the operation of the cooling device 12 weakly cooled. By setting such an excess cooling time period tda as a time period when the system power used in the entire container terminal 1 is low, and setting the power reduction time end tbc as a time period when the system power used in the entire container terminal 1 is high, the system power used in the entire container terminal 1 is leveled.

[0016] First, the container terminal 1, the reefer container 10, and the control system 20 will be described.

[0017] A known container terminal can be used as the container terminal 1. The container terminal 1 serves as a logistics hub by temporarily storing a large number of containers including reefer containers 10. Many types of cargo handling equipment such as cranes and on-site chassis are operated in the container terminal 1. System power is supplied from a system power source 3 to the reefer containers 10, the respective cargo handling equipment, anchored ships, etc. via a substation facility 4 installed in the container terminal 1.

[0018] Grid power is supplied from a commercial distribution network owned by an electric power company. The electricity fee paid to the electric power company for using grid power includes a basic fee determined by the contracted power and an energy fee according to the amount of power used. The contracted power is determined by the maximum amount of grid power that can be used at the same time. Therefore, if the maximum amount can be reduced (peak cutting), the contracted power can be reduced and the basic fee can be lowered. In addition, the unit price of the energy fee per unit of power may vary depending on the time of day. For example, the nighttime unit price from 10 p.m. to 8 a.m. is cheaper than the daytime unit price from 8 a.m. to 10 p.m. Therefore, the energy fee can be reduced by increasing the grid power during times when the unit price is low and reducing the grid power during times when the unit price is high.

[0019] The reefer container 10 is a container used for transporting frozen cargo 2 or refrigerated cargo, and any known reefer container may be used. The reefer container 10 includes a container 11, a cooling device 12 (12a, 12b, 12c, 12d), a fan 13, and a control system 20. A power plug 6 electrically connected to a distribution board 5 connected to a substation facility 4 is inserted into the reefer container 10, and system power is supplied from a system power supply 3 via the power plug 6. In the example of FIG. 1, the reefer container 10 includes the control system 20, but as described later, a management system for managing loading and unloading at the container terminal 1 may also be used as the control system 20. A known computer may be used as the management system.

[0020] In the reefer container 10, the temperature inside the container 11 is adjusted to a desired set temperature range by driving the cooling device 12 and the fan 13, respectively. The desired set temperature range can be set arbitrarily within a preset settable temperature range. The settable temperature range differs depending on the specifications of the reefer container 10. For example, for a general reefer container 10, the range is -30°C or more and +30°C or less, and for a special reefer container 10, the range is -90°C or more and +30°C or less.

[0021] Unlike a dry container, the container 11 is filled with a heat insulating material 16 between an outer wall 14 and an inner wall 15. Inside the container 11, a partition wall 17 separates the cargo storage area from the cooling device 12, and a duct 18 is formed on the upper part of the partition wall 17. The floor 19 of the container 11 is raised by a plurality of T-rails arranged at intervals in the front-to-back direction (width direction of the container 11) of FIG. 1. The cooling device 12 has an evaporator 12a arranged inside the container 11, and a compressor 12b, a condenser 12c, and an expander 12d arranged outside the container 11, and cools the air inside the container 11. The fan 13 is arranged inside the container 11 and circulates the air inside the container 11. The thin solid arrows in FIG. 1 indicate the circulation of air inside the container 11. The cooling device 12 and the fan 13 may be linked, but it is preferable to configure them to be driven separately. Specifically, the fan 13 is driven independently of the operation of the cooling device 12, and constantly circulates the air inside the container 11 when the container 11 stores refrigerated cargo 2.

[0022] The control system 20 includes a thermometer 21 and a computing device 22, and the computing device 22 includes a storage device 23. The control system 20 is individually installed in each of the multiple reefer containers 10 stored in the container terminal 1.

[0023] Various known thermometers can be used as the thermometer 21. The thermometer 21 measures the temperature inside the container 11. In the illustrated example, the thermometer 21 measures the temperature of air after heat exchange with the refrigerated cargo 2 stored inside the container 11 and before being introduced into the cooling device 12. The number of thermometers 21 is not limited to one, and a plurality of thermometers 21 may be provided inside the container 11. The thermometer 21 may measure, for example, the temperature of air before and after the cooling device 12, or may measure the temperature of air at the bottom of the container 11 before it passes through the floor 19.

[0024] The arithmetic device 22 is configured with a computer, and various data are input and stored, and these data are used to perform data processing and control the cooling device 12. Various known computers can be used for the arithmetic device 22. The arithmetic device 22 has a calculation processing unit (CPU), a main storage unit (memory), an auxiliary storage unit (e.g., HDD), an input unit (keyboard), and an output unit (display).

[0025] The storage device 23 stores an excessive cooling time period tda and a power reduction time period tbc, which will be described later. For example, an auxiliary storage unit of the arithmetic device 22 can be used as the storage device 23. The storage device 23 is not limited to an auxiliary storage unit, and it is sufficient if it can store the excessive cooling time period tda and the power reduction time period tbc, and for example, a DIP (Dual Inline Package) type switch can also be used.

[0026] The control system 20 controls the reefer container 10 in which refrigerated cargo is stored in the container 11 and the reefer container 10 in which frozen cargo 2 is stored in the container 11, in a procedure shown in Fig. 2, which will be described later. The control system 20 can also control the reefer container 10 in which refrigerated cargo is stored in the container 11, in a procedure shown in Fig. 4, which will be described later, but it is preferable to control the reefer container 10 in which frozen cargo 2 is stored in the container 11 in this procedure. The reason for this will be described below.

[0027] The types of frozen cargo 2 and refrigerated cargo stored in the container 11 include fresh foods, chemical products, pharmaceuticals, etc. An optimal temperature range for storage is set in advance for each type of cargo. This temperature range may have only an upper limit set, or both an upper and lower limit set. Generally, only an upper limit is set in the optimal temperature range for storing frozen cargo 2, and both an upper and lower limit are set in the optimal temperature range for storing refrigerated cargo. The set temperature range set based on this optimal temperature range for storage is input to the computing device 22, and the temperature inside the container 11 is maintained within the input set temperature range.

[0028] The optimum temperature range for storing refrigerated cargo is higher than the optimum temperature range for storing frozen cargo 2. In addition, refrigerated cargo, for which both an upper limit and a lower limit are set as the optimum temperature range for storage, cannot be stored in the container 11 at a temperature lower than the set lower limit because the quality of the refrigerated cargo deteriorates if stored in the container 11 at a temperature lower than the set lower limit. Therefore, in the reefer container 10 in which the refrigerated cargo is stored in the container 11, cold energy cannot be stored by excessive cooling. In addition, the optimum temperature range for storing refrigerated cargo is set more finely depending on the type of refrigerated cargo, and the temperature inside the container 11 needs to be adjusted with higher accuracy. In contrast, the quality of the frozen cargo 2 does not deteriorate unless it exceeds the upper limit of the optimum temperature range for storage, so it can be stored in the container 11 at a temperature lower than the set upper limit. For the above reasons, the control system 20 of the embodiment executes the control illustrated in FIG. 4 described later only for the reefer container 10 in which the frozen cargo 2 is stored in the container 11 among the many reefer containers 10 stored in the container terminal 1.

[0029] When the control system 20 controls the reefer container 10 in which frozen cargo 2 is stored in the container 11, it is advisable to appropriately select the specifications (settable temperature range) of the reefer container. The specifications (settable temperature range) of the reefer container 10 are preferably selected based on the optimum temperature range for storing the frozen cargo 2 to be stored or a set temperature range that is set based on that temperature range, and it is desirable that the lower limit of the settable temperature range of the reefer container 10 is lower than the lower limit of the optimum temperature range for storing the frozen cargo 2. The lower limit of the settable temperature range of the reefer container 10 is, for example, 10° C. or more lower than the lower limit of the set temperature range.

[0030] The optimum temperature range for storing frozen cargo 2 is generally classified as -18°C or below, -35°C or below, and -60°C or below. For example, the temperature range for frozen foods is set to -18°C or below, for ice cream, frozen desserts, and frozen fish with a high oil content to -35°C or below, and for frozen tuna to -60°C or below. In addition, when frozen cargo 2 is pharmaceuticals, both an upper and lower limit are set as the temperature range, and the temperature range for such pharmaceuticals is set to, for example, -90°C or above and -60°C or below.

[0031] For example, if the frozen cargo 2 is frozen food, a reefer container 10 with a settable temperature range with a lower limit of -30°C or less is desirable, and a reefer container 10 with a lower limit of -50°C or less is more desirable. If the frozen cargo 2 is ice cream, frozen desserts, frozen fish with a high oil content, or the like, a reefer container 10 with a settable temperature range with a lower limit of -50°C or less is desirable, and a reefer container 10 with a lower limit of -60°C or less is more desirable. If the frozen cargo 2 is frozen tuna, a reefer container 10 with a settable temperature range with a lower limit of -70°C or less is desirable, and a reefer container 10 with a lower limit of -90°C or less is more desirable. In this way, the lower the lower limit of the settable temperature range of the reefer container 10 is based on the optimum temperature range for storage or the set temperature range, the more desirable it is, and this is advantageous for increasing the degree of overcooling.

[0032] Before describing an embodiment of the control method for the reefer container 10, we will describe general control of the reefer container 10. This general control is called normal control, and refers to control when control of the excessive cooling time period tda and control of the power reduction time period in the control method for the reefer container 10 described later are not being executed.

[0033] FIG. 2 shows an example of a procedure in normal control. This normal control is executed before the shipper stores the frozen cargo 2 in the container 11 outside the container terminal 1, and it is desirable that the temperature inside the container 11 is within the set temperature range at the stage of storing the frozen cargo 2 in the container 11. In the procedure in normal control, first, the set temperature range is input to the calculation device 22 (S110). Next, the thermometer 21 obtains the temperature inside the container 11 (S120), and the calculation device 22 controls the cooling device 12 based on the obtained temperature (S130). The control of the cooling device 12 is repeatedly executed until it is released after the stored frozen cargo 2 is carried out to the outside of the container 11 (S140). The contents of each step (S110 to S140) will be described in detail below.

[0034] In step (S110), a set temperature range based on the optimum temperature range according to the type of frozen cargo 2 stored in the container 11 is input to the calculation device 22. Specifically, the calculation device 22 executes data processing to output an input screen for the set temperature range to the output unit, and the set temperature range is input to the input screen by the input unit. The set temperature range can be set arbitrarily as long as it is within the optimum temperature range for storing frozen cargo 2. The set temperature range can be set to the same range as the optimum temperature range for storage, or can be set to a range that is narrower than the optimum temperature range for storage.

[0035] For example, when the frozen cargo 2 is a frozen food, the set temperature range may be set to a range of -30°C or more and -20°C or less. However, when setting the set temperature range for the frozen cargo 2, it is preferable to set the upper limit of the set temperature range to a temperature equal to or lower than the upper limit of the temperature range optimal for storage, and the lower limit of the set temperature range to a temperature approximately -20°C or more and -10°C or less lower than the set upper limit. The lower the lower limit of the set temperature range, the more power is used by the cooling device 12. Therefore, in order to reduce the power used in normal control, it is preferable to set the lower limit of the set temperature range appropriately. The set temperature range can be set, for example, in units of 0.1°C. Furthermore, when the frozen cargo 2 is stored in the container 11, only the upper limit of the set temperature range may be input. When only the upper limit is input as the set temperature range, for example, a temperature approximately -20°C or more and -10°C or less lower than the upper limit is automatically set as the lower limit. By inputting the set temperature range into the arithmetic device 22, it is possible to determine whether the cargo stored in the container 11 is a refrigerated cargo or a frozen cargo 2. When a temperature below 0° C., more preferably below −10° C., is input as the upper limit of the set temperature range, the cargo stored in the container 11 can be determined as frozen cargo 2.

[0036] In step (S120), the thermometer 21 acquires the temperature inside the container 11. It is assumed that the fan 13 starts to operate at the stage when the set temperature range is input in step (S110).

[0037] In step (S130), the arithmetic device 22 controls the cooling device 12 based on the temperature acquired by the thermometer 21. Specifically, the arithmetic device 22 executes control by the cooling device 12 to maintain the temperature acquired by the thermometer 21 within a set temperature range. This control is temperature control in which the controlled object is the temperature acquired by the thermometer 21 and the target temperature is the set temperature range. In the temperature control, any one of on-off control, feedback control (proportional control, PID control), and feedforward control, or a combination thereof, is executed using various parameters such as the difference between the temperature acquired by the thermometer 21 and the set temperature range, and the temperature rise rate based on a plurality of temperatures acquired consecutively by the thermometer 21.

[0038] In step (S140), the above steps (S120, S130) are repeated until the normal control is released. The normal control may be released via the input unit of the computing device 22, or by cutting off the power supply to the reefer container 10.

[0039] The normal control described above is mainly executed while the reefer container 10 is being transported outside the container terminal 1 by a ship, an external chassis, or the like. Furthermore, the above-mentioned steps (S120, S130) are repeated until the normal control is released, but when temperature control is being executed during the excessive cooling time period tda and the reduced power time period tbc described below, it is desirable not to execute the normal control during the gap time period between the respective time periods. Specifically, when the excessive cooling time period tda and the reduced power time period tbc are stored in the storage device 23, the calculation device 22 executes a data procedure to stop the execution of the normal control, and when the temperature control for each time period is released, the calculation device 22 releases the stop of the execution of the normal control and re-executes it.

[0040] Fig. 3 shows the change in the grid power used throughout the container terminal 1 over one day, as determined when all reefer containers 10 stored in the container terminal 1 are controlled by the normal control described above. The change in grid power can be expressed as the power used [kW] or the hourly power usage rate [%]. The power usage rate means the proportion of power used, with 100% representing a situation where grid power is used to the maximum, and 0% representing a situation where no grid power is used at all.

[0041] In FIG. 3, the horizontal axis is time [h], and the vertical axis is power usage rate [%]. The thick solid line in FIG. 3 represents the transition of the grid power. Specifically, in FIG. 3, the power usage rate exceeds 60% after time a, exceeds 85% after time b, falls below 85% after time c, and falls below 60% after time d. Therefore, in a situation where each reefer container 10 stored in the container terminal 1 is controlled by normal control, it can be seen that the power usage rate is high in the time period from time b to time c, and is low in the time period from time d to time a on the next day. In FIG. 3, the transition of the power usage rate for one day is shown as the transition of the grid power, but, for example, the transition of the power usage rate for one week may be obtained, and a representative value (average value, median value, mode value, etc.) for each hour may be calculated, and the transition of the average power usage rate may be grasped using each calculated representative value. Instead of the graph shown in FIG. 3, a graph may be used in which the vertical axis is power usage [kW] and the power usage per unit time is shown as a bar graph.

[0042] Next, a procedure of an embodiment of a control method for the reefer container 10 illustrated in Fig. 4 will be described. This control method is performed by using the control system 20.

[0043] In one example of the procedure in Fig. 4, in a preparation stage S200 prior to controlling the reefer container 10 stored in the container terminal 1, an excess cooling time period tda and a power reduction time period tbc are set in advance (S210, S220), and the set excess cooling time period tda and power reduction time period tbc are stored in the storage device 23 of the calculation device 22 (S230). When controlling the reefer container 10 stored in the container terminal 1 after completion of the preparation stage S200, the calculation device 22 executes different temperature controls for each time period (S240 to S280). The contents of each step (S210 to S280) will be described in detail below.

[0044] In step (S210), in a situation where all reefer containers 10 stored in the container terminal 1 are controlled by the normal control described above (hereinafter, normal control situation), the change in the system power used throughout the container terminal 1 within a predetermined period is grasped. The predetermined period can be set to any period including at least one day (24 hours), but it is preferable to set it to multiple days (for example, one week or one month). By using multiple days as the predetermined period, the change in the average system power in the container terminal 1 can be grasped. The system power used throughout the container terminal 1 is the total of the system power used by all reefer containers 10 stored in the container terminal 1, as well as all loading and unloading equipment, various facilities such as lighting devices, and ships at anchor that are operated in the container terminal 1.

[0045] The change in the grid power may be grasped through the electric power company that provides the grid power, or may be grasped using data acquired by a power meter installed in the grid power source 3 or the substation equipment 4. In addition, the operator and manager of the container terminal 1 accumulates data that allows the operator to grasp the change in the grid power used in the container terminal 1 under normal control conditions. The data accumulated by these operators includes laboratory data such as measured values ​​during the actual operation of the container terminal 1, results of multiple experiments and tests in research and development, and computer simulation results. The accumulated data can be used to grasp the change in the grid power. The change in the grid power varies depending on the season. Therefore, by acquiring the change in the grid power for each season (for example, summer, winter, and other seasons), it becomes possible to control the reefer container 10 differently depending on the season.

[0046] In step (S220), an excessive cooling time period tda and a power reduction time period tbc, each of which continues for several hours, are set based on the grasped transition of the grid power. The term "several hours" can be arbitrarily determined, preferably between 4 hours and 20 hours, more preferably between 7 hours and 17 hours, and even more preferably between 10 hours and 14 hours. Each time period may be determined manually or by data processing using a computer (including the arithmetic unit 22). A desired value or range can be used as an index for setting each time period based on the transition of the grid power. However, there are cases where each time period cannot be set using an inappropriate index. Details of the setting index will be described later. Each time period is paired, and the power reduction time period tbc is set as a time period after the excessive cooling time period tda.

[0047] The excessive cooling time period tda is a time period lasting several hours in which the system power used in the entire container terminal 1 under normal control conditions is generally below the index. The index for the excessive cooling time period tda is, for example, a power usage rate of 70% or less. During the excessive cooling time period tda, temperature control is executed with the target temperature set to the excessive cooling temperature range, which is lower than the set temperature range of the frozen cargo 2, and cold energy is stored. The reduced power time period tbc is a time period lasting several hours in which the system power used in the entire container terminal 1 under normal control conditions is generally higher than the index. The index for the reduced power time period tbc is, for example, a power usage rate of 70% or more. During the reduced power time period tbc, temperature control is executed to stop the operation of the cooling device 12 until the temperature reaches a predetermined temperature within the set temperature range by using the stored cold energy, or to set the cooling state by the operation of the cooling device 12 to a weak cooling state, with the set temperature range as the target temperature. Details of the temperature control in each time period will be described later.

[0048] The excess cooling temperature range is a temperature range that is lower than the set temperature range of the frozen cargo 2. Lower than the set temperature range means that the upper limit of the excess cooling temperature range is lower than the lower limit of the set temperature range. The excess cooling temperature range can be set arbitrarily within a temperature range that is lower than the set temperature range of the frozen cargo 2, but may also be automatically set by the calculation device 22 based on the amount of cold energy stored in the excess cooling time zone tda and the amount of cold energy consumed in the power reduction time zone tbc.

[0049] In FIG. 3 described above, if grid power is consumed more actively during time periods when the power usage rate is 60% or less and grid power consumed during time periods when the power usage rate exceeds 60%, the trend in grid power can be leveled out to approximate a power usage rate of 60%. Therefore, a power usage rate of 60% is used as the setting index. In this case, the excessive cooling time period tda is the time period from time d to time a the next day when the grid power has a power usage rate of 60% or less for several consecutive hours. In addition, the power reduction time period tbc is the time period after the excessive cooling time period tda, and is the time period from time a to time d when the grid power has a power usage rate exceeding 60% for several consecutive hours.

[0050] In addition, in FIG. 3 described above, if grid power is consumed more actively in the time period when the power usage rate is 60% or less and grid power consumed in the time period when the power usage rate exceeds 85%, the transition of grid power can be leveled out to approximate the range of power usage rate of 60% to 85%. Therefore, a range of power usage rate of 60% or more and 85% or less is used as a setting index. In this case, the excessive cooling time period tda is the time period from time d to time a the next day when the grid power has a power usage rate of 60% or less for several consecutive hours. Moreover, the power reduction time period tbc is the time period after the excessive cooling time period tda, and is the time period from time b to time c when the grid power has a power usage rate exceeding 85% for several consecutive hours.

[0051] It should be noted that the start and end times of each of the set time periods can be shifted forward or backward as long as it can roughly determine the time periods when the grid power is relatively low or high, and it is not necessary to set them precisely to the time when the grid power falls below the index or exceeds the index. The shift can be done by, for example, about 2 hours or less.

[0052] The excess cooling time period tda and the power reduction time period tbc can also be set based on the operation status of the container terminal 1, such as the size of the container terminal 1, the loading and unloading status, and the number of reefer containers 10 stored. By understanding the operation status of the container terminal 1, a person skilled in the art can set the excess cooling time period tda and the power reduction time period tbc by referring to experience gained in the operation process of the container terminal 1, various publicly known documents, the accumulation of a large number of experimental and test data, and the accumulation of computer simulation results. In the above-mentioned steps (S210, S220), the excess cooling time period tda and the power reduction time period tbc may be set using such knowledge of a person skilled in the art. For example, when it is determined that the container terminal 1 uses more grid power during the daytime period than during the nighttime period using the knowledge of a person skilled in the art, the daytime period is set to the power reduction time period tbc, and the nighttime period is set to the excess cooling time period tda. The nighttime period is, for example, from 10 p.m. to 8 a.m., and the daytime period is, for example, from 8 a.m. to 10 p.m.

[0053] The set excess cooling time period tda and power reduction time period tbc may be used as common time periods for multiple reefer containers 10 stored in the same container terminal 1, or at least some of them may be different time periods. The transition of the grid power in the normal control state varies depending on the weather and the loading and unloading situation at the container terminal 1, but the time periods when the grid power used is high or low are generally the same time periods even if the weather and the loading and unloading situation at the container terminal 1 change. In other words, the excess cooling time period tda and power reduction time period tbc once set can be used without change unless the equipment and scale of the container terminal 1 are significantly changed. Therefore, if it is the same container terminal 1, after the excess cooling time period tda and power reduction time period tbc are set, the above-mentioned steps (S210, S220) can be omitted. In addition, the above-mentioned steps (S210, S220) can also be performed by a management system installed in the container terminal 1.

[0054] In step (S230), the set excessive cooling time zone tda and power reduction time zone tbc are stored in the storage device 23 of the calculation device 22. When storing each time zone in the storage device 23, the start time and end time of each time zone may be input, or a threshold value capable of distinguishing each time zone may be input and each time may be determined based on the threshold value. Also, both the start time and end time of each time zone and the threshold value may be input. In this manner, the storage of each time zone in the storage device 23 can be appropriately selected. Specifically, the calculation device 22 executes data processing to output an input screen for each time and threshold value to the output unit, and either or both of the time and threshold value are input to the input screen by the input unit. When the calculation device 22 is communicably connected to the management system, the input to the calculation device 22 can also be performed by the management system. This step (S230) is performed, for example, at the timing when the reefer container 10 is stored in the container terminal 1, or at the timing when the reefer container 10 is stored in a predetermined storage position in the container terminal 1 and the power plug 6 is inserted.

[0055] The thresholds are set to values ​​that enable each time zone to be distinguished based on the grid power in a situation where temperature control has been performed for each of the excessive cooling time zone tda and the reduced power time zone tbc, in other words, in a situation where the procedure shown in Fig. 4 has been performed and the grid power used throughout the container terminal 1 has been leveled (hereinafter, referred to as time zone control situation). The number of thresholds is not limited to one, and there may be multiple thresholds for the excessive cooling time zone tda and the reduced power time zone tbc. Details of the thresholds will be described later.

[0056] The above steps (S210 to S230) are performed as the preparation stage S200 before controlling the reefer container 10 actually stored in the container terminal 1. As described above, steps (S210, S220) can be omitted once they have been performed, so for a new reefer container 10 that has entered the container terminal 1, the preparation stage S200 is completed by simply performing step (S230). Once the preparation stage S200 is completed, the process proceeds to the next step (S240).

[0057] In step (S240), the arithmetic device 22 executes data processing to determine whether or not it is an excessive cooling time period tda. Similarly, in step (S250), the arithmetic device 22 executes data processing to determine whether or not it is a reduced power time period tbc. If it is an excessive cooling time period tda, the process proceeds to step (S260), and if it is a reduced power time period tbc, the process proceeds to step (S270).

[0058] In step (S260), the arithmetic device 22 executes temperature control with the target temperature set to an excess cooling temperature range that is lower than the installation temperature range of the frozen cargo 2. In this temperature control, since the excess cooling temperature range is used as the target temperature, the power consumed by the cooling device 12 becomes greater than the power consumed by the cooling device 12 in normal control. In other words, in the excess cooling time zone tda, the frozen cargo 2 becomes overcooled to the excess cooling temperature range by consuming more power, and cold energy is stored in the frozen cargo 2.

[0059] More specifically, the target temperature in the temperature control during the excess cooling time period tda is different from that in the normal control described above. In normal control, the target temperature is the set temperature range of the frozen cargo 2, whereas in temperature control during the excess cooling time period tda, the target temperature is the excess cooling temperature range which is lower than the set temperature range. In the temperature control during the excess cooling time period tda, on-off control, feedback control (proportional control, PID control), feedforward control or a combination of several controls is executed using various parameters such as the difference between the temperature acquired by the thermometer 21 and the excess cooling temperature range, and the temperature drop rate at multiple temperatures acquired consecutively by the thermometer 21.

[0060] Temperature control during the excess cooling time period tda may be performed as long as the target temperature is within the excess cooling temperature range, but the higher the degree of excess cooling, the more power is consumed and the lower the power reduction effect. Therefore, in this temperature control, it is preferable to set an excess target temperature as the target temperature based on the total amount of cold energy stored during the excess cooling time period tda, and it is more preferable to set a temperature 1°C to 5°C lower than the excess cooling target temperature. If the target temperature for temperature control during the excess cooling time period tda is set 6°C or more lower than the excess cooling target temperature, much of the cold energy stored due to excess cooling will be wasted, resulting in higher electricity bills.

[0061] The amount of cold energy stored in the excess cooling time period tda is preferably equal to or somewhat greater than the amount of cold energy consumed in the reduced power time period tbc. Since stopping the operation of the cooling device 12 during the reduced power time period tbc is effective for reducing power consumption, the latter amount may be assumed to be a situation in which the operation of the cooling device 12 is stopped. The excess cooling target temperature is set based on the estimated amount of cold energy, estimating the amount of cold energy consumed during the reduced power time period tbc, on the condition that the operation of the cooling device 12 is stopped during the reduced power time period tbc. For example, assuming a situation in which the temperature of the frozen cargo 2 reaches a predetermined temperature in the set temperature range at the end time c of the reduced power time period tbc, the temperature of the frozen cargo 2 at the start time b of the reduced power time period tbc is estimated, and the estimated temperature is used as the excess cooling target temperature. However, if the estimated temperature is outside the excess cooling temperature range (a temperature lower than the lower limit of the excess cooling temperature range), the lower limit of the excess cooling temperature range is used as the excess cooling target temperature. The lower limit of the excessive cooling temperature range is the lowest temperature in the settable temperature range defined in the specifications of the reefer container 10, and is defined as, for example, -30°C, -60°C, -90°C, etc.

[0062] Making the amount of cold energy in each time period roughly equal is advantageous for using cold energy without waste. Also, in the excess cooling time period tda, if the temperature of the frozen cargo 2 reaches the set excess cooling target temperature, it is advisable to stop the excess cooling by the cooling device 12 and execute temperature control by the cooling device 12 to maintain the excess cooling target temperature. Since the power consumed by the temperature control to maintain the excess cooling target temperature is lower than the power consumed by the excess cooling by the cooling device 12, it is also advantageous for suppressing wasteful power consumption.

[0063] In the temperature control in the excess cooling time zone tda, it is sufficient that the frozen cargo 2 is overcooled to the target temperature at the end time a of the excess cooling time zone tda, and it is not necessary that the frozen cargo 2 is overcooled to the target temperature at a time halfway through the excess cooling time zone tda. Therefore, in the temperature control in the excess cooling time zone tda, the cooling degree by driving the cooling device 12 may be adjusted so that the time between the start time d and the end time a is spent until the temperature acquired by the thermometer 21 falls to the target temperature. For example, when the above-mentioned excess cooling target temperature is used as the target temperature, the frozen cargo 2 is overcooled to the excess cooling target temperature at the end time a of the excess cooling time zone tda. In this way, by controlling the cooling device 12 so that the frozen cargo 2 is overcooled to the target temperature throughout the excess cooling time zone tda, an excessive increase in the power consumed by the cooling device 12 in the excess cooling time zone tda can be suppressed. When the start time and end time of each time zone are input in the above-mentioned step (S230), the calculation device 22 adjusts the cooling degree of the cooling device 12 based on the current time and the start time and end time of each time zone. When a threshold value is input, the calculation device 22 performs data processing to predict the start time and end time of each time period based on the acquired trend in the overall system power of the container terminal 1 and the threshold value, and adjusts the cooling level of the cooling device 12 based on the predicted start time and end time.

[0064] In step (S270), the arithmetic device 22 executes temperature control using the cold energy to stop driving the cooling device 12 until a predetermined temperature within the set temperature range is reached as a target temperature, or to make the cooling state by driving the cooling device 12 weakly cooled. In the reduced power time period tbc, if the frozen cargo 2 is overcooled to the overcooling temperature range, the overcooled frozen cargo 2 functions as a refrigerant. Therefore, in the temperature control using the set temperature range of the frozen cargo 2 in the reduced power time period tbc, the cooling state by driving the cooling device 12 can be reduced. In this way, in the reduced power time period tbc, the cold energy stored in the overcooling time period tda is used, so the power consumed by the cooling device 12 is less than the power consumed by the cooling device 12 in normal control.

[0065] In detail, the temperature control in the power reduction time period tbc is similar to the normal control described above, in that the target temperature is set to the set temperature range of the frozen cargo 2, but the cold energy stored by overcooling is used. In the power reduction time period tbc, the temperature control is performed to stop the operation of the cooling device 12 or to set the cooling state by driving the cooling device 12 to a weak cooling state, with the range up to a predetermined temperature within the set temperature range being regarded as the range in which cold energy can be used, and after the predetermined temperature within the set temperature range is reached, the temperature control is performed similar to the normal control. The predetermined temperature within the set temperature range can be set to, for example, a temperature 2°C to 10°C lower than the upper limit of the set temperature range. In this way, by regarding the range up to a predetermined temperature 2°C to 10°C lower than the upper limit of the set temperature range as the range in which cold energy can be used, it is advantageous to more effectively utilize the cold energy stored by overcooling.

[0066] The weak cooling state means a state in which the cooling device 12 is driven with less power than the power consumed by the cooling device 12 under normal control. Specifically, the weak cooling state is a state in which cold energy is available and the cooling effect caused by the operation of the cooling device 12 is such that the temperature inside the container 11 is maintained or the temperature rise is slowed down. The normal control is a state in which cold energy is unavailable and the cooling effect caused by the operation of the cooling device 12 is such that the temperature inside the container 11 is maintained or the temperature is reduced. Therefore, by setting the cooling effect caused by the operation of the cooling device 12 to the weak cooling state, the power consumed by the cooling device 12 can be reduced compared to normal control. The power consumed in the weak cooling state differs depending on the specifications of the reefer container 10, but is less than the power consumed by the cooling device 12 to maintain the set temperature range under normal control.

[0067] The temperature control during the power reduction time period tbc is preferably a control to stop the operation of the cooling device 12 throughout the power reduction time period tbc, but it may be possible to switch between a control to stop the operation of the cooling device 12 and a control to make the cooling state by driving the cooling device 12 weak cooling according to the situation. As the situation, the temperature situation inside the container 11 or the accumulation situation of cold energy can be used.

[0068] The degree of overcooling of each reefer container 10 during the overcooling time period tda differs depending on the type of frozen cargo 2 stored in each container 11 and the specifications of the reefer container 10. Similarly, the degree of release of cold energy stored by overcooling of each reefer container 10 during the power reduction time period tbc also differs, and the time required to completely release the cold energy also differs. That is, the amount of cold energy available in each reefer container 10 differs. Due to such a difference in the amount of cold energy, in some reefer containers 10, the control to stop the operation of the cooling device 12 may shorten the time during which cold energy can be used, resulting in a low effect of reducing power. Therefore, in the temperature control during the power reduction time period tbc, the degree of cooling by the operation of the cooling device 12 may be adjusted so that the time between the start time b and the end time c is spent until the temperature acquired by the thermometer 21 rises to the target temperature (a predetermined temperature in the set temperature range).

[0069] Specifically, it is preferable to switch between a control to stop the operation of the cooling device 12 and a control to set the cooling state by driving the cooling device 12 to a weak cooling state according to the temperature acquired by the thermometer 21. The switching temperature can be set arbitrarily, but for example, in the excessive cooling temperature range, the operation of the cooling device 12 is stopped, and outside the excessive cooling temperature range, the cooling state by driving the cooling device 12 is set to a weak cooling state. Also, it is preferable to switch between a control to stop the operation of the cooling device 12 and a control to set the cooling state by driving the cooling device 12 to a weak cooling state according to the amount of cold energy. For example, in a reefer container 10 in which frozen food has been excessively cooled to -90°C, the amount of cold energy is large, so the operation of the cooling device 12 is stopped. In a reefer container 10 in which frozen tuna has been excessively cooled to -90°C, the amount of cold energy is small compared to -60°C, which is the upper limit of the set temperature range for frozen tuna, so the cooling state by driving the cooling device 12 is set to a weak cooling state. By switching between the various temperature controls according to the situation, the cold energy stored in each reefer container 10 can be fully released at the end time c of the power reduction time period tbc, making it possible to utilize the cold energy without waste, and also increasing the effect of reducing the power consumed by the cooling device 12.

[0070] Furthermore, the temperature control during the power reduction time period tbc may be switched between control to stop driving the cooling device 12 and control to make the cooling state by driving the cooling device 12 weak cooling by power adjustment based on the system power used throughout the container terminal 1. The power adjustment is control to adjust the system power used throughout the container terminal 1 to less than the target power. To execute the power adjustment, specifically, each of the arithmetic devices 22 must be in a state in which they can communicate with each other, and the system power used throughout the container terminal 1 must be obtained in real time. Each of the arithmetic devices 22 may be in a state in which they can communicate with each other via a management system.

[0071] The target power can be set arbitrarily, but it is preferable to set it based on the ratio of power to be reduced relative to the contracted power. For example, in FIG. 2 described above, if it is desired to reduce the grid power by 15%, the target power is set to 85% of the contracted power. In the power adjustment, when it is predicted that the grid power used in the entire container terminal 1 will exceed the target power, the temperature control of each reefer container 10 during the power reduction time slot tbc is switched from a control that causes the cooling state by driving the cooling device 12 to be in a weak cooling state to a control that stops the driving of the cooling device 12. Note that, in the power adjustment, when the grid power used in the entire container terminal 1 is significantly lower than the target power, it is also possible to switch the temperature control of the power reduction time slot tbc from a control that stops the driving of the cooling device 12 to a control that causes the cooling state by driving the cooling device 12 to be in a weak cooling state, by considering that there is a surplus of grid power available for each reefer container 10. In the power adjustment, each computing device 22 may adjust the operation of each cooling device 12 so that the system power used in the entire container terminal 1 is less than the target power and the stored cold energy is consumed near the end time c of the reduced power time period tbc. In this way, by performing the power adjustment in the reduced power time period tbc, it is possible to suppress the system power used in the entire container terminal 1 to less than the target power.

[0072] In step (S280), when the respective controls based on the excessive cooling time zone tda and the power reduction time zone tbc are released, normal control is resumed, and the above steps (S240 to S270) are repeated until the respective controls based on the respective time zones are released. Release of the respective controls based on the respective time zones may be performed by the input unit of the computing device 22 or by the management system. This step (S230) is performed, for example, when the reefer container 10 is unloaded from the container terminal 1, when the power plug 6 is unplugged when the reefer container 10 is loaded from a predetermined storage position in the container terminal 1, or the like.

[0073] FIG. 5 shows an example of each temperature range when the frozen cargo 2 stored in the container 11 is frozen food. The settable temperature range of the reefer container 10 shown by the open bars in FIG. 5 is a range of -90°C to +30°C, the optimum temperature range for storing the frozen cargo 2 shown by the bars with diagonal lines extending from the upper right to the lower left is a range of -18°C or less, the set temperature range shown by the bars with diagonal lines extending from the upper left to the lower right is a range of -29°C to -18°C or less, and the overcooling temperature range shown by the bars with diagonal lines crossing each other is a range of -90°C to -30°C or less. The upper limit of the overcooling temperature range is preferably -20°C to -10°C lower than the upper limit of the set temperature range, and more preferably lower than the lower limit of the set temperature range. Moreover, the lower limit of the overcooling temperature range is preferably the lower limit of the settable temperature range. For example, if the settable temperature range of the reefer container 10 is -90°C or more and +30°C or less, the set temperature range of the frozen cargo 2 may be set to an appropriate temperature range of -29°C or more and -10°C or less, and the excessive cooling temperature range may be set to an appropriate temperature range of -90°C or more and -30°C or less. Alternatively, the set temperature range may be set to an appropriate temperature range of -59°C or more and -30°C or less, and the excessive cooling temperature range may be set to an appropriate temperature range of -90°C or more and -60°C or less. Furthermore, the set temperature range may be set to a temperature range of -70°C or more and -60°C or less, and the excessive cooling temperature range may be set to a temperature range of -90°C or more and -80°C or less.

[0074] The excessive cooling time period tda and the power reduction time period tbc illustrated in Fig. 6 are set using the transition of the system power under normal control conditions (the same transition as in Fig. 3 described above) and a desired range as an index. The desired range is, for example, a power usage rate of 60% or more and 85% or less. The excessive cooling time period tda indicated by the double-headed arrow of the dashed line in Fig. 6 is a time period from time d to time a of the next day, which continues for several consecutive hours after the power usage rate falls to 60% or less. The power reduction time period tbc indicated by the double-headed arrow of the dashed line in Fig. 6 is a time period that follows the excessive cooling time period tda, and is a time period from time b to time c, which continues for several consecutive hours after the power usage rate exceeds 85%.

[0075] In this container terminal 1, more grid power is used during the daytime hours and less grid power is used during the nighttime hours, so it is advisable to set the lower limit of the set index range based on the maximum value of grid power used during the nighttime hours and the upper limit of the range based on the minimum value of grid power used during the daytime hours. For example, the set index has a lower limit of a power usage rate of 50% to 70% and an upper limit of a power usage rate of 70% to 90%.

[0076] If a range is used as an index, there are gap time periods from time a to time b and from time c to time d. In such gap time periods, it is preferable to execute temperature control in adjacent time periods. In the gap time period, the selection of whether to execute temperature control in the excess cooling time period tda or the power reduction time period tbc can be arbitrarily set, but it is preferable to execute temperature control in the time period immediately before the gap time period. For example, in the gap time period from time a to time b, the temperature control of the immediately preceding excess cooling time period tda is executed, and in the gap time period from time c to time d, the temperature control of the immediately preceding power reduction time period tbc is executed. However, in the gap time period, the temperature control of the immediately preceding time period is executed, but the temperature control of the immediately preceding time period is merely continued. For example, in the case where the immediately preceding time period is the excess cooling time period tda, if the frozen cargo 2 is in a state of being overcooled to a target temperature within the excess cooling temperature range at the end time a of the excess cooling time period tda, temperature control to maintain the target temperature is executed in the gap time period. In addition, if the immediately preceding time period is a reduced power time period tbc, if the stored cold energy has been released at the end time c of the reduced power time period tbc, temperature control similar to normal control is performed during the gap time period.

[0077] The setting indexes can be arbitrarily selected with the constraint that each time period can be set, but there are cases where the appropriate excessive cooling time period tda and power reduction time period tbc cannot be set simply by satisfying that constraint. Therefore, it is desirable to select each index using another constraint that restricts the length, start time, and end time of each time period, and to select an index that satisfies that other constraint.

[0078] Another constraint, for example, is to limit the time between the start time d and the end time a of the excess cooling time zone tda based on the cooling state of the frozen cargo 2 during the excess cooling time zone tda. Specifically, the time is preferably a time that allows each frozen cargo 2 stored in the reefer container 10 to be overcooled to the excess cooling temperature range, and more preferably a time that allows each frozen cargo 2 stored in the reefer container 10 to be overcooled to the excess cooling target temperature. This time differs depending on the set temperature range of the frozen cargo 2, the settable temperature range of the reefer container 10, and the power reduction time zone tbc.

[0079] Another constraint condition is, for example, to limit the time between the start time b and the end time c of the power reduction time period tbc based on the relationship between the cold energy stored by overcooling and the time when the system power used in the entire container terminal 1 reaches a maximum value. In the power reduction time period tbc, the system power used in the cooling device 12 is reduced by utilizing the cold energy stored by overcooling in the overcooling time period tda. Therefore, by making the cold energy available at the time when the system power used in the entire container terminal 1 reaches a maximum value, the maximum value can be effectively reduced. Therefore, this time is preferably a time when the cold energy stored by overcooling can be utilized at the time when the system power used in the entire container terminal 1 reaches a maximum value, and more preferably a time during several hours including at least one hour before and after that time when the cold energy stored by overcooling can be utilized. This time period differs depending on the set temperature range of the frozen cargo 2 and the set temperature range of the reefer container 10.

[0080] As another constraint, for example, the excess cooling time period tda and the power reduction time period tbc are set as a pair of time periods, and the power reduction time period tbc is limited to a time period after the excess cooling time period tda. Depending on the transition of the system power used throughout the container terminal 1, there may be multiple peaks and valleys in the transition, and the transition may fluctuate beyond the index. In such a case, if the start time and end time of each are not set appropriately, it may not be possible to store cold energy during the excess cooling time period tda and use cold energy during the power reduction time period tbc. In other words, as long as the condition that cold energy is stored during the excess cooling time period tda and cold energy is used during the power reduction time period tbc to level the entire system power of the container terminal 1 is satisfied, the excess cooling time period tda and the power reduction time period tbc may be set as a pair of time periods, and one or more paired time periods may exist within one day (24 hours). In FIG. 6, there is one paired time period. Depending on the transition of the system power used throughout the container terminal 1, there may be two or more paired time periods. Also, depending on the operation status of the container terminal 1, the grid power during the nighttime hours may be higher than the grid power during the daytime hours. In either case, the overall grid power of the container terminal 1 can be leveled out by storing cold energy during the excess cooling time period tda and using the cold energy during the power reduction time period tbc.

[0081] Another constraint condition, for example, is to limit the gap time period between a pair of excess cooling time period tda and power reduction time period tbc to a short time period. A short time period is, for example, less than three hours. The shorter the gap time period, the more continuous the excess cooling time period tda and power reduction time period tbc are, which is advantageous for more effective use of cold energy. Note that when there are multiple pairs of time periods, the total of the gap time periods between each pair of time periods may exceed the short time period.

[0082] The other constraint conditions are not limited to the above. For example, each time period may be limited based on the unit price of the unit amount of power in the grid power source 3. Specifically, a threshold value of the unit price per unit amount of power of the grid power may be set, and the excessive cooling time period tda may be a time period in which the unit price per unit amount of power of the grid power is equal to or lower than the threshold value, and the power reduction time period tbc may be a time period in which the unit price per unit amount of power of the grid power exceeds a predetermined threshold value. The excessive cooling time period tda may be set to a time period with a low unit price, and the power reduction time period tbc may be set to a time period with a high unit price. For example, if the unit price during the nighttime from 10 p.m. to 8 a.m. is lower than the unit price during the daytime from 8 p.m. to 10 p.m., the nighttime unit price may be used as the threshold value of the unit price per unit amount of power.

[0083] The input data D1 illustrated in Fig. 7 is data input to the calculation device 22 in the above-mentioned step (S230). The input of the input data D1 means that the excess cooling time period tda and the reduced power time period tbc are stored in the storage device 23. The input data D1 has a start time d and an end time a of the excess cooling time period tda, and a start time b and an end time c of the reduced power time period tbc. When the input data D1 is used as an input to the calculation device 22 for each time period, the calculation device 22 has a function of acquiring the time. By using the input data D1, it is possible to switch the temperature control in each of the excess cooling time period tda and the reduced power time period tbc by time.

[0084] The input data D2 illustrated in Fig. 8 is data input to the calculation device 22 in the above-mentioned step (S230). The input of the input data D2 means that the excess cooling time zone tda and the reduced power time zone tbc are stored in the storage device 23. The input data D2 has a threshold value that can determine the start time and end time of each of the excess cooling time zone tda and the excess cooling time zone tbc based on the transition of the system power in a time zone control situation (a situation in which the reefer container 10 is controlled according to the procedure in Fig. 4 described above). The threshold value uses the system power used throughout the container terminal 1 predicted at each of the start time and end time of the excess cooling time zone tda and the start time and end time of the reduced power time zone tbc. A computer simulation can also be used for the prediction.

[0085] In the illustrated example, the threshold of the excessive cooling time period tda is a power usage rate of 60%, and the threshold of the reduced power time period tbc is a power usage rate of 75%. When the input data D2 is used, the control system 20 has a power meter (not shown) installed in the system power source 3 or the substation equipment 4. The arithmetic device 22 executes data processing to compare the power (power amount, power usage rate) acquired by the power meter with each threshold input as the input data D2 and to determine each time period. Specifically, the time when the power usage rate acquired by the power meter becomes equal to or lower than the threshold of the excessive cooling time period tda is regarded as the start time d of the excessive cooling time period tda, and the time when the power usage rate exceeds the threshold is regarded as the end time a of the excessive cooling time period tda. Similarly, the time when the acquired power usage rate exceeds the threshold of the reduced power time period tbc is regarded as the start time b of the reduced power time period tbc, and the time when the acquired power usage rate becomes equal to or lower than the threshold is regarded as the end time c of the reduced power time period tbc. By using the input data D2, each time period can be determined according to fluctuations in electricity usage at the container terminal 1 due to weather and loading conditions.

[0086] However, if the system power used in the entire container terminal 1 suddenly changes, each time period will start and end at an unintended timing if only the input data D2 is used. For example, if the system power used in the entire container terminal 1 suddenly increases in the middle of the period between the start time d and the end time a of the excessive cooling time period tda, and the power usage rate exceeds the threshold of the excessive cooling time period tda, the excessive cooling time period tda will end in the middle of the period. Therefore, by determining the priority order using both the input data D1 and D2 and further setting the time periods to several consecutive hours from the start time, it is possible to avoid the start and end of each time period due to a sudden change. Here, the several consecutive hours can be arbitrarily determined between preferably 4 hours or more and 20 hours or less, more preferably 7 hours or more and 17 hours or less, and even more preferably 10 hours or more and 14 hours or less.

[0087] Alternatively, the arithmetic device 22 executes data processing to set a judgment time zone including a start time and an end time of each time zone based on the input data D1. The judgment time zone is a time zone including about one hour before and after each input time. The arithmetic device 22 executes data processing to determine each time zone using the set judgment time zone and each threshold value. For example, the start of the excessive cooling time zone tda is determined when the system power used throughout the container terminal 1 becomes equal to or lower than the threshold value of the excessive cooling time zone tda during the judgment time zone from one hour before to one hour after the input start time d. In this way, by using both the input data D1 and D2, the arithmetic device 22 can appropriately determine each time zone.

[0088] The input data D1 and D2 can be changed as appropriate during the operation of the container terminal 1. In particular, when the input data D2 is used, it is advisable to change it in accordance with the change in the system power actually used throughout the container terminal 1. In addition, when the input data D1 is used, it is advisable to appropriately shift the start time and end time of each time period indicated by the input data D1 based on the change in the system power. For example, if the rate at which the system power consumed throughout the container terminal 1 increases is fast, the start time of the power reduction time period tbc can be made earlier than the start time of the input data D1, and if the rate of increase is slow, the start time of the power reduction time period tbc can be made later than the start time of the input data D1. The amount of time that can be shifted is, for example, about two hours or less.

[0089] FIG. 9 shows an example of the transition of the grid power in a situation where each reefer container 10 stored in the container terminal 1 is controlled according to the procedure shown in FIG. 4 described above (time zone control situation). The thick solid line in FIG. 9 shows the transition of the grid power in the time zone control situation. In the illustrated example, a range of power usage rate of 60% or more and 85% or less is used as a setting index, and the threshold of the excessive cooling time zone tda is set to a power usage rate of 60%, and the threshold of the power reduction time zone tbc is set to a power usage rate of 75% as input data D2. In addition, in the temperature control of the excessive cooling time zone tda, a temperature higher than the lower limit of the excessive cooling temperature range is used as the target temperature. The dashed line in FIG. 9 shows the transition of the grid power in a normal control situation (the same transition as in FIG. 3 described above).

[0090] In the time period from time b to time c, the power usage rate indicated by the thick solid line is lower than the power usage rate indicated by the dashed line, and is lower than the power usage rate of 85%. In addition, in the time period from time d to time a on the next day, the power usage rate indicated by the thick solid line is higher than the power usage rate indicated by the dashed line, and is approaching the power usage rate of 60%. In other words, it can be seen that the system power used throughout the container terminal 1 throughout one day (24 hours) is approximately leveled out to a power usage rate range of 60% to 85%. In addition, in the gap time period from time a to time b and the gap time period from time c to time d, temperature control is performed in the time period immediately before each gap time period. The total amount of system power used throughout the container terminal 1 in the time period control status throughout the day is approximately the same as the total amount of system power used throughout the container terminal 1 in the normal control status.

[0091] As described above, according to this embodiment, the excessive cooling time period tda and the power reduction time period tbc, each of which lasts for several hours, are stored in the storage device 23 in advance, and the arithmetic device 22 performs different temperature control in each time period stored in the storage device 23. In the excessive cooling time period tda, power is actively consumed and stored as cold energy. In the power reduction time period tbc, the stored cold energy is utilized to reduce the power used by the cooling device 12. Therefore, by efficiently utilizing cold energy in each time period, the system power used throughout the container terminal 1 can be increased in the excessive cooling time period tda, and the system power used throughout the container terminal 1 can be reduced in the power reduction time period tbc. As a result, the system power used throughout the container terminal 1 can be leveled.

[0092] As a result of leveling out the grid power used throughout the container terminal 1, the contract power of the grid power source 3 can be lowered, making it possible to reduce the basic electricity charge. For example, in FIG. 9 described above, since the maximum value of the power usage rate has fallen to less than 85%, the contract power of the grid power source 3 can be reduced to a power usage rate equivalent to 85%. To reduce the contract power, it is advisable to appropriately set the setting index and input data according to the desired contract power.

[0093] Furthermore, according to this embodiment, the time period when the unit price per unit power is high overlaps with the power reduction time period tbc, and the time period when the unit price is low overlaps with the excess cooling time period tda, so that the power charge can be reduced. For example, if the nighttime unit price from 10 pm to 8 am is lower than the daytime unit price from 8 pm to 10 pm, the power reduction time period tbc in FIG. 9 described above overlaps mostly with the daytime unit price band, and the excess cooling time period tda also overlaps mostly with the nighttime unit price band. Therefore, in addition to the basic charge, the power charge can also be reduced, and the electricity charge at the container terminal 1 can be significantly reduced. In this way, the excess cooling time period tda may be limited to the time period when the power unit price is low.

[0094] Thus, according to this embodiment, by switching the control of the reefer container 10 according to time period, the system power used throughout the container terminal 1 can be leveled out and electricity charges can be reduced. Because the control is switched according to time period, it is possible to sufficiently overcool the multiple frozen cargoes 2 stored in the container 11, and the cold energy stored in each of the overcooled frozen cargoes 2 can be utilized without being wasted. This also contributes greatly to the decarbonization of the container terminal 1.

[0095] In this embodiment, a simple method is used in which the set excessive cooling time zone tda and power reduction time zone tbc are stored in the storage device 23 of the calculation device 22, and the calculation device 22 controls the cooling device 12 based on each of the stored time zones. Therefore, since the existing container terminal 1 and reefer containers 10 can be utilized, the system power used throughout the container terminal 1 can be leveled with minimal capital investment.

[0096] Next, a first modified example of the reefer container control system and control method will be described. The first modified example is an embodiment in which an excessive cooling time period tda and a power reduction time period tbc are set using a power usage rate of 85% as a setting index, and a power usage rate of 80% which is a common threshold value for each time period is used as input data D2.

[0097] The excessive cooling time zone tda and the power reduction time zone tbc in Modification 1 illustrated in Fig. 10 have different indices for setting the time zones from those shown in Fig. 9 described above. The thick solid line in Fig. 10 represents the transition of the grid power in Modification 1. The dashed line in Fig. 10 represents the transition of the grid power in a normal control situation (the same transition as in Fig. 3 described above). The thick dashed dotted line in Fig. 10 represents the transition of the grid power shown in Fig. 9 described above.

[0098] When a desired value (for example, a power usage rate of 85%) is used as a setting index, it is advisable to set an appropriate value based on the maximum value of the system power used in the entire container terminal 1. Since reducing the maximum value of the system power (peak cutting) is effective for leveling out the system power, when a desired value is used as an index, the maximum value of the system power can be reduced more effectively by using the maximum value as a reference. By using a desired value as a setting index, the start time d of the excessive cooling time period tda and the end time c of the power reduction time period tbc become the same time, and the end time a of the excessive cooling time period tda and the start time b of the power reduction time period tbc become the same time. Therefore, the excessive cooling time period tda and the power reduction time period tbc are continuously switched because there is no gap time period between each time period. In other words, from the viewpoint of efficiency of cold energy, cold energy can be used more efficiently by using a value as a setting index rather than a range. However, when the transition of the system power used in the entire container terminal 1 fluctuates in a complex manner, it may be possible to appropriately set each time period by using a range as a predetermined index rather than a value. The setting index in the first modification is, for example, a value within the range of 60% to 90%.

[0099] 10 is more even throughout the day than the change in grid power indicated by the dashed line. Therefore, in the first modification, the grid power used throughout the entire container terminal 1 can also be equalized.

[0100] Next, a second variation of the reefer container control system and control method will be described. In the second variation, an excessive cooling time period tda and a power reduction time period tbc are set using a power usage rate of 85% as a setting index, as in the first variation, and in addition, a power usage rate of 80% is used as a common threshold value for each time period as input data D2, and an external power source is used.

[0101] In the modified example 2 illustrated in Fig. 11, an external power source 7 is added to the configuration in Fig. 1 described above. In the modified example 2, power is supplied from the external power source 7 to the distribution board 5, and power is supplied from both the system power source 3 and the external power source 7 to the reefer container 10 through the power plug 6.

[0102] The external power source 7 may be configured as a generator that uses fossil fuels, hydrogen fuel, etc., but is preferably configured as a renewable energy power source that uses renewable energy. The renewable energy power source supplies only power obtained by utilizing renewable energy such as sunlight, solar heat, wind power, geothermal power, hydroelectric power, and biomass. Note that there are also cases where a portion of the power of the system power source 3 is obtained by utilizing renewable energy. The external power source 7 is installed in the container terminal 1 and is connected to a distribution board 5 that distributes power to the reefer containers 10 via a rectifier (inverter) 8. This makes it possible to supply power from the external power source 7 to the reefer containers 10.

[0103] The external power source 7 of the container terminal 1 is, for example, solar power generation or wind power generation, but these renewable energies are unstable in power generation and fluctuate in output, so that they may not be able to supply power stably like the grid power source 3. Normally, a storage battery is used to utilize renewable energy, and the power obtained from the renewable energy is stored in the storage battery and discharged as necessary to meet the power demand. However, since storage batteries are expensive, there is a risk that profitability will deteriorate. Therefore, in the second modification, it is preferable that the power of the external power source 7 is directly supplied to the reefer container 10 without being stored. In the second modification, instead of installing a storage battery, the temperature control of each of the excessive cooling time period tda and the power reduction time period tbc is made different from that of the first modification according to the timing when power can be supplied from the external power source 7.

[0104] In the temperature control during the excessive cooling time period tda in the modified example 2 in a situation where power can be supplied from the external power source 7, both the system power and the power of the external power source 7 are used to drive the cooling device 12. In addition, in the temperature control during the reduced power time period tbc in the modified example 2 in a situation where power can be supplied from the external power source 7, the cooling device 12 is driven using the power of the external power source 7, and the cooling state is set to a weak cooling state. That is, the reefer container 10 is excessively cooled by the power of the external power source 7 in the excessive cooling time period tda, and the reefer container 10 is cooled in a weak cooling state in the reduced power time period tbc, thereby substituting for a storage battery. This makes it possible to reduce the cost required for the storage battery, and the deterioration of profitability can be suppressed by using the external power source 7. Note that the temperature control during each time period in the modified example 2 in a situation where power cannot be supplied from the external power source 7 is the same as that in the modified example 1.

[0105] It is desirable to set the output of the external power source 7 based on the power consumed when executing temperature control during the power reduction time period tbc for each reefer container stored in the container terminal 1. Specifically, the output of the external power source 7 is set to be equal to or slightly higher than that power, for example, within a range of 100% to 120% of that power. Setting the output of the external power source 7 in this manner is advantageous in suppressing excessive investment in the use of renewable energy.

[0106] In the second modification, the grid power consumed by the entire container terminal 1 differs between a situation where power can be supplied from the external power source 7 and a situation where power cannot be supplied. When power is generated from renewable energy during the power reduction time period tbc, the reefer container 10 can be cooled only by the power obtained from the renewable energy. That is, in a situation where power can be supplied from the external power source 7 during the power reduction time period tbc, the grid power consumed by the reefer container 10 is substantially zero. Also, when power is generated from renewable energy during the excess cooling time period tda, the power obtained from the renewable energy can be supplied to the reefer container 10 together with the grid power to store cold energy by excess cooling. That is, in a situation where power can be supplied from the external power source 7 during the excess cooling time period tda, the grid power consumed by the reefer container 10 is reduced. Thus, in the second modification, the grid power consumed in a situation where power cannot be supplied from the external power source 7 is about the same as in the first modification, but the grid power consumed in a situation where power can be supplied is less than that in the first modification.

[0107] FIG. 12 shows the transition of the grid power excluding the power of the external power source 7 in each situation. The thick solid line in FIG. 12 shows the transition of the grid power in the second modification. Here, the external power source 7 can supply power in the excessive cooling time period tda, and the external power source 7 cannot supply power in the reduced power time period tbc. The dashed line in FIG. 12 shows the transition of the grid power in the normal control situation (the same transition as in FIG. 3 described above). The thick dashed line in FIG. 12 shows the transition of the grid power in the first modification (the same transition as in FIG. 10 described above). The transition of the grid power shown by the thick solid line is more even throughout the day than the transition of the grid power shown by the dashed line. Moreover, the transition of the grid power shown by the thick solid line shows that the grid power used is less by the amount of the power of the external power source 7 used in the excessive cooling time period tda, and is approximately equivalent to the grid power under normal control (dashed line).

[0108] As described above, in Modification 2, the amount of grid power used can be reduced by using the power of the external power source 7 for the reefer container 10. In particular, using a renewable energy power source as the external power source 7 greatly contributes to decarbonization.

[0109] In the second modification, the external power source 7 is connected to the distribution board 5 via the rectifier 8, but any configuration is acceptable as long as the power of the external power source 7 can be directly supplied to the reefer container 10 without being stored, and for example, the external power source 7 may be directly connected between the system power source 3 and the substation equipment 4. Since the power obtained from renewable energy is smaller than the system power, it is absorbed into the system power. Even if the power obtained from renewable energy is absorbed into the system power, the stability of the system power is not lost. Therefore, with this connection method, it is not necessary to use the rectifier 8, and it is possible to reduce the cost required for the rectifier 8.

[0110] Next, a third variation of the reefer container control system and control method will be described. The third variation is an embodiment in which an excessive cooling time zone tda and a reduced power time zone tbc are set using a power usage rate of 70% as a setting index, a power usage rate of 65% is used as a common threshold value for each time zone as input data D2, the target temperature for the excessive cooling time zone tda is set to the lower limit of the excessive cooling temperature range, and power in temperature control for the reduced power time zone tbc is adjusted so that the power usage rate is less than 70% during the reduced power time zone tbc.

[0111] In the third modification, power is supplied to the reefer container 10 in a configuration similar to that of the second modification. The third modification differs in that a power usage rate of 70% lower than a power usage rate of 85% is used as a setting index, and a power usage rate of 65% is used as a threshold value for the input data D2. The third modification also differs in that the target temperature in the excessive cooling time zone tda is set to the lower limit of the excessive cooling temperature range, and that power adjustment is performed using a power usage rate of 70% as the target power in the power reduction time zone tbc.

[0112] More specifically, in the third modification, a power usage rate of 70% is used as a setting index, so that the power reduction time period tbc continues for a longer period. The longer the power reduction time period tbc, the more cold energy needs to be stored in the excess cooling time period tda. Therefore, in the temperature control of the excess cooling time period tda in the third modification, the lower limit of the excess cooling temperature range is used as the target temperature, and both the grid power and the power of the external power source 7 are used to drive the cooling device 12. Also, in the temperature control of the power reduction time period tbc in the third modification, power adjustment is performed with a power usage rate of 70% as the target power, and the power of the external power source 7 is used when driving the cooling device 12.

[0113] Fig. 13 shows the transition of system power excluding the power of external power source 7 in each situation. The thick solid line in Fig. 13 shows the transition of system power in Modification 3. The dashed line in Fig. 13 shows the transition of system power in a normal control situation (the transition in Fig. 3 described above). The thick dashed dotted line in Fig. 13 shows the transition of system power in Fig. 9 described above. The thick dashed dotted line in Fig. 13 shows the transition of system power in Modification 2.

[0114] In the excessive cooling time period tda of the third modification, the target temperature is set to the lower limit of the excessive cooling temperature range, so the power consumed by the cooling device 12 is large, and the system power shown by the thick solid line in Fig. 13 is greater than the system power shown by the dashed line and the thick dashed-dotted line. Also, in the power reduction time period tbc of the third modification, the system power shown by the thick solid line in Fig. 13 is less than the system power in other situations. This is because the cooling device 12 is driven using the power of the external power source 7 while making maximum use of the frozen cargo 2 that has been excessively cooled to the lower limit of the excessive cooling temperature range as a refrigerant.

[0115] As described above, in Modification 3, it is possible to further equalize the grid power used. In Fig. 13 described above, since the maximum value of the power usage rate is reduced to less than 70%, it is possible to reduce the contract capacity of the grid power source 3 to a level equivalent to a power usage rate of 70%. Furthermore, it is possible to significantly reduce the grid power used during times when the unit price per unit of power is high (daytime), so it is also possible to significantly lower the power usage fee.

[0116] The control system 20 may control a plurality of reefer containers 10. In the above-described embodiment and modified examples 1, 2, and 3, the control system 20 is provided for each reefer container 10 individually, but a control device that performs normal control may be provided instead of each arithmetic device 22, and temperature control may be performed in each of the time periods of the overcooling temperature zone tda and the power reduction time period tbc by one arithmetic device 22 connected to each of the control devices. That is, the reefer container 10 is provided with a thermometer 21 and a control device, and normal control is performed by the control device, and the control system 20 is provided with one arithmetic device 22, and the arithmetic device 22 controls the cooling device 12 based on the overcooling time period tda and the power reduction time period tbc via each of the control devices. Note that each thermometer 21 is indirectly connected to one arithmetic device 22 via each of the control devices, and the temperature acquired by the thermometer 21 by the arithmetic device 22 is used for temperature control, so that it can be regarded as a device constituting the control system 20. A management system can be used for such a arithmetic device 22. This is advantageous when performing power adjustment in the power reduction time period tbc. In addition, the connection between each control device and one computing device 22 may be made using wireless communication, or a communication line may be implemented in the power plug 6 so that a direct connection is made when the power plug 6 is inserted into the reefer container 10.

[0117] Although an embodiment of the present invention has been described above, the reefer container control system and control method of the present invention are not limited to the specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0118] 1. Container Terminal 2 Frozen cargo 3 grid power supply 4. Substation equipment 5 Distribution board 6 Power plug 7 External power supply 8 rectifier 10 Reefer Container 11 Container 12 Cooling device 13 Fan 20. Control System 21 Thermometer 22 Arithmetic unit tda Excessive cooling time period tbc Power reduction time period

Claims

1. In the control system of reefer containers stored in container terminals and using grid power, The reefer container has at least a container for storing frozen cargo and a cooling device for cooling the frozen cargo, The control system includes at least a computing device that controls the cooling device, the computing device has a storage device for storing excessive cooling time periods and power reduction time periods each lasting several hours; During the excessive cooling time period, temperature control is performed with a target temperature being an excessive cooling temperature range that is lower than the set temperature range of the frozen cargo, and cold energy is stored; During the power reduction time period, the reefer container control system performs temperature control by using the cold energy to stop operation of the cooling device until a predetermined temperature within the set temperature range is reached, or by setting the cooling level of the cooling device to a weak cooling state, with the set temperature range as a target temperature.

2. 2. The reefer container control system of claim 1, wherein the lower limit of the excess cooling temperature range is a lower limit of a settable temperature range for the reefer container.

3. 2. The reefer container control system according to claim 1, wherein the predetermined temperature within the set temperature range is a temperature that is 2° C. or more and 10° C. or less lower than an upper limit of the set temperature range.

4. 2. The reefer container control system according to claim 1, wherein a target temperature of the temperature control during the excessive cooling time period is set to an excessive cooling target temperature within the excessive cooling temperature range, and the excessive cooling target temperature is a temperature that does not exceed a predetermined temperature within the set temperature range when temperature control is executed to stop driving of the cooling device throughout the entire power reduction time period following the excessive cooling time period.

5. 2. The reefer container control system according to claim 1, wherein the excessive cooling time period is a time period of several consecutive hours after grid power used in the entire container terminal becomes equal to or lower than a predetermined threshold, and the power reduction time period is a time period of several consecutive hours after grid power used in the entire container terminal exceeds a predetermined threshold.

6. 2. The reefer container control system according to claim 1, wherein the excessive cooling time period is a time period during which a unit price per unit power of the grid power is equal to or lower than a threshold, and the power reduction time period is a time period during which the unit price per unit power of the grid power exceeds a predetermined threshold.

7. 2. The reefer container control system of claim 1, wherein power from an external power source is used during the excessive cooling period.

8. The reefer container control system according to claim 1 , wherein power from an external power source is used during the power reduction time period.

9. 9. The reefer container control system according to claim 7 or 8, wherein the electric power of the external power supply is electric power of renewable energy, and the renewable energy is sunlight, solar heat, wind power, wave power, geothermal power, or biomass.

10. The reefer container control system according to claim 7 or 8, wherein power from the external power source is directly supplied to the reefer container without being stored.

11. 9. The reefer container control system according to claim 7 or 8, wherein an output of the external power source is based on power consumed when temperature control is performed by driving the cooling device during the power reduction time period for each of the reefer containers stored in the container terminal.

12. The reefer container control system according to claim 2 or 3, wherein the set temperature range of the frozen cargo is set within a range of -29°C or more and -10°C or less, and the excessive cooling temperature range is set within a range of -90°C or more and -30°C or less.

13. The reefer container control system according to claim 2 or 3, wherein the set temperature range of the frozen cargo is set within a range of -59°C or more and -30°C or less, and the excessive cooling temperature range is set within a range of -90°C or more and -60°C or less.

14. The reefer container control system according to claim 2 or 3, wherein the set temperature range of the frozen cargo is set to -70°C or more and -60°C or less, and the excessive cooling temperature range is set to -90°C or more and -80°C or less.

15. A method for controlling a reefer container stored in a container terminal and using grid power, comprising: In a preparation stage, the excessive cooling time period and the power reduction time period are stored in a computing device, When controlling the reefer container after the preparation stage is completed, the arithmetic device performs temperature control during the excess cooling time period, with the target temperature being an excess cooling temperature range that is lower than the set temperature range of the frozen cargo, to store cold energy; A reefer container control method, comprising: performing temperature control by the computing device during the power reduction time period, with the set temperature range as a target temperature, and stopping operation of the cooling device until a predetermined temperature within the set temperature range is reached by using the cold energy, or setting the cooling level by operation of the cooling device to a weak cooling state.

16. 16. The reefer container control method according to claim 15, wherein in the preparation stage, a change in grid power used in the entire container terminal within a predetermined period is grasped, the excess cooling time zone and the power reduction time zone are set based on the grasped change, and the set excess cooling time zone and the power reduction time zone are stored in the arithmetic device.

Images