How do refrigerated shipping containers work?

Question

I understand the refrigeration part but how are they powered and how long can they operate for? How cold can they keep things?

Answer 1

There are two types:

1. Integral Unit (Integral Reefer Container, Integrated Unit):

This type of refrigerated container has an integral refrigeration unit for controlling the temperature inside the container. The refrigeration unit is arranged in such a way that the external dimensions of the container meet ISO standards and thus fit into the container ship cell guides, for example. The presence of an integral refrigeration unit entails a loss of internal volume and payload.

When being transported by ship, integral units have to be connected to the on-board power supply system. The number of refrigerated containers which may be connected depends on the capacity of the ship's power supply system. If the aforesaid capacity is too low for the refrigerated containers to be transported, "power packs" may be used, which are equipped with relatively large diesel generators and satisfy ISO requirements with regard to the dimensions of a 20' container. When at the terminal, the containers are connected to the terminal's power supply system. For transport by road and rail, most integral unit refrigeration units are operated by a generator set (genset). This may either be a component of the refrigeration unit or connected to the refrigeration unit.

2. Porthole containers:

This type of container is often referred to not as a refrigerated container but as an insulated container, as it has no integral refrigeration unit. The lack of a refrigeration unit allows such containers to have a larger internal volume and payload than integral units. On board, the inside of the container is supplied with cold air via the ship's central cooling plant. The air flows through the container in the same way as in integral units. Cold air is blown in at the bottom and the "warm" air is removed at the top.

Answer 2

Most containers for ship transit are powered electrically however some have dual power from 440 mains or from a small IC engine.
The most common method is to plug them into the 440 v ships mains system while on board. Ships buily for refrigerated containers are referred to as reefers, They are also connected into the ships control monitoring system and temperatures are logged accordingly. Most carriers get penalised if the container temperatures are not maintained within limits.

Answer 3

They are engine driven small refrigeration plants that run off their own tank of gasoline or diesel fuel. They can either keep insulated containers at a refrigerator temperature (33-40F) or at freezing temperature (-10 to 32F). Run time depends on tank size and ambient temperature. They should go for a few days in general.