8.1.2   Actual power consumption
The actual power consumption of an integral refrigerated container will depend on its operating status. Here, a particularly important role is played by the internal temperature of the container which determines the required evaporation temperature of the refrigerant. Generally the higher the internal temperature, the higher the electrical power consumption and the higher the refrigeration capacity that is available. Table 11 shows the refrigeration capacities and power consumption for some of the ThermoKing refrigeration units.
Click on the table to enlarge.
Table 11: Manufacturer specifications regarding the refrigeration capacity and the power consumption of a Thermo King Smart Reefer with different compressor types and refrigerants.

All values given in table 11 are maximum values for full refrigeration capacity and an external temperature of 37.8°C. This occurs, for example, when cooling the cargo. One should also bear in mind the fact that the permitted ambient temperature for a refrigerated container is usually 50°C which may result in increased power consumption.
Usually, once the cargo has been cooled, the average power consumption falls. In low-temperature mode (below -10°C) the refrigeration unit is run in on/off mode, whereas in chilled mode (above -10°C) the output of the refrigeration circuit is regulated constantly (e.g. using the suction modulation valve as shown in figure 14). With a 40' container and an ambient temperature of 45°C, average power consumption values of approximately 4.2 kW can be expected for low-temperature operation (-21°C) and 7 - 8 kW for transporting bananas (+16°C).
For a very broad average value for all container types, ambient conditions and cargo types, the value 3.6 kW/TEU can be used. A 20' container tends to be closer to 4 kW and a 40' container tends towards 7 kW. As a result of new developments and the associated improvements in the efficiency of the containers, this value is dropping.

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