Refrigerated container

A refrigerated container or reefer is an intermodal container (shipping container) used in intermodal freight transport that is capable of refrigeration for the transportation of temperature-sensitive, perishable cargo. These containers are a critical component of the cold chain, the supply chain that preserves goods like fruits, vegetables, meat, and pharmaceuticals at a specific low temperature.^[1]

A Maersk Line reefer container on a semi-trailer truck

Containers loaded on a container ship with the refrigeration units visible

Interior of a refrigerated container

Reefer containers of Maersk Line and Hamburg Süd

Reefer sockets used to power reefer containers

While a reefer has an integral refrigeration unit, it relies on external power from electrical power points (“reefer points”) at a land-based site, a container ship, or on a quay. When being transported over the road on a trailer or over a rail wagon, it can be powered from a diesel-powered generator ("gen set") that attaches to the container during road journeys. Refrigerated containers are capable of maintaining a constant internal temperature ranging from −65 °C (−85 °F) up to 40 °C (104 °F).

The market for cold chain tracking solutions is growing rapidly, driven by the increasing global demand for fresh food and temperature-sensitive pharmaceuticals.^[2] The number of active tracking devices for refrigerated containers is projected to grow significantly, highlighting the increasing importance of this technology for ensuring food safety and product integrity.^[3] The impact on society of reefer containers is vast, allowing consumers all over the world to enjoy fresh produce at any time of year.

Remote monitoring and control

Modern refrigerated containers are often equipped with a telematic control unit and a GPS tracking unit that enables remote monitoring of the container's parameters as part of a fleet telematics system. This integration is part of the fleet digitalization of the logistics industry, making the container an element of a larger Vehicle tracking system. The system allows a fleet management operator to track the container's location and monitor internal parameters such as temperature, humidity, and door status.^[4]

This continuous stream of telemetry provides a complete track and trace record of the container's temperature throughout its journey, which helps ensure the integrity of the cold chain. If the temperature deviates from the set point, the system can send an automatic alert to the operator, allowing for immediate intervention.^[5] These systems also allow for remote control, enabling an operator to change the temperature settings or turn the refrigeration unit on or off from a central software platform.^[6][7]

Cryogenic cooling

Another refrigeration system sometimes used where the journey time is short is total loss refrigeration, in which frozen carbon dioxide ice (or sometimes liquid nitrogen) is used for cooling.^[8] The cryogenically frozen gas slowly evaporates, and thus cools the container and is vented from it. The container is cooled for as long as there is frozen gas available in the system. These have been used in railcars for many years, providing up to 17 days temperature regulation.^[9] Whilst refrigerated containers are not common for air transport, total loss dry ice systems are usually used.^[8] These containers have a chamber which is loaded with solid carbon dioxide and the temperature is regulated by a thermostatically controlled electric fan, and the air freight versions are intended to maintain temperature for up to around 100 hours.^[10]

Full-size intermodal containers equipped with these "cryogenic" systems can maintain their temperature for the 30 days needed for sea transport.^[9] Since they do not require an external power supply, cryogenically refrigerated containers can be stored anywhere on any vessel that can accommodate "dry" (un-refrigerated) ocean freight containers.

Redundant refrigeration

A container fitted with two refrigeration units and a single diesel generator

Valuable, temperature-sensitive, or hazardous cargo often require the utmost in system reliability. This type of reliability can only be achieved through the installation of a redundant refrigeration system.

A redundant refrigeration system consists of integrated primary and back-up refrigeration units. If the primary unit malfunctions, the secondary unit automatically starts. To provide reliable power to the refrigeration units, these containers are often fitted with one or more diesel generator sets.

Containers fitted with these systems may be required for transporting certain dangerous goods in order to comply with the International Maritime Organization’s regulations.

See also

• Cold chain
• Reefer ship
• Refrigerator car
• Refrigerator truck
• Thermal insulation
• Reefer container housing units