Typically a reefer will have an integral refrigeration unit that will rely on external power from electrical power points (reefer points) at a land-based site, a container ship or on a quay.
Generally, air cooling systems are used that remove heat generated by the reefers.
Water cooling systems are also used. This system can be used if the reefer is stored below deck on a vessel without adequate ventilation to remove the heat generated.
Another refrigeration system is sometimes used when the journey time is short or during a period when there is a total loss refrigeration.
This involves the use of frozen carbon dioxide ice or sometimes liquid nitrogen for cooling.
The cryogenically frozen gas slowly evaporates and cools the container and is vented from it.
Full-size intermodal containers equipped with cryogenic systems can maintain their temperature for the 30 days needed for sea transport.
Recent years have seen various new technologies released by shipping container manufacturers to better address the cooling requirements of specific cargo.
There has been a particular focus on controlled atmosphere (CA) technology.
This active oxygen removal system delays the ripening, ageing and decay of perishables to preserve their quality, taste and value during long-distance transportation.
Many innovations in areas such as energy efficiency are occurring as the result of increased regulation.
HFC refrigerants in particular have been identified as a major contributor to global warming.
Movement towards more environmentally sustainable refrigerants is rapidly gaining pace within the container reefer industry.
In 2015, European Union’s F-Gas regulation set out a timetable to cut the amount of CO2 contributing to global warming by 2030 by half.
Bans have also been proposed by the US Environmental Protection Agency’s Significant New Alternatives Policy.
Produce reefers carry and challenges presented
Fruit and meat have historically been the main cargo of refrigerated ships.
Bananas represent the single most important reefer cargo.
Cargoes of shrimp, asparagus, caviar and blood are considered among the most expensive refrigerated items.
Other cargo includes dairy products, flowers and pharmaceuticals.
Because the characteristics of reefer cargo vary from commodity to commodity, factors such as temperature control, air exchange, humidity levels and proper packing and stuffing become extremely important.
For example, cargoes such as meat have to be kept chilled between 0 degrees and minus 2 degrees, or frozen at minus 18 degrees or colder.
Other cargoes such as fresh fruit have to be kept at temperatures ranging from minus 3 degrees celsius to 16 degrees celsius to ensure they arrive in the best possible condition.
Specific goods also present challenges for transportation
For example, some products such as tomatoes and potatoes require changes in temperature throughout the voyage.
Containers now use pre-programmed multi-temperature systems.
Other products, such as fruits and vegetables, require a reduced level of humidity.
Many containers can regulate humidity between 55% and 95%.
Normal carrier lines: taking away trade
Reefer containers are rapidly gaining market share and are competing with reefer ships for trade.
Traditional systems built around reefer ships involve food sitting on pallets in a refrigerated hold; delivered to a cold storage facility on arrival.
At the beginning of 2000 there were over 20 companies worldwide who were specialised in transport with reefers. Now there are only eight.
A key reason behind this change is that diversified carriers that have the capacity to hold reefer containers offer a faster return on investment as well as the fact that they give carriers greater security in an unstable market.
Every dollar a carrier puts into a bulk carrier is made back in two years on average.
However, for reefers, it can often take 20 years to earn it back.