Reefer Container
At the end of the 1960’s, the reefer container was introduced. During that time, the ships were equipped with central refrigeration units supplying cold (conditioned) air directly to so-called “porthole” containers. Each refrigeration unit was able to provide refrigeration to up to 48 boxes simultaneously through a piping system. The ventilated containers were connected to the ducts through two lockable portholes in the front of the box, one at the bottom for blowing the air in and one on the top to suck the air out. On land, they were supplied with cold air by a cooling system similar to the one onboard.
“Porthole” containers have now largely, if not wholly, been replaced by the “integral” reefer container where each is equipped with its own, separate cooling unit and equipment controlling the inside atmosphere. Onboard a ship, the reefers are plugged into the onboard power supply system. On the terminal or when carried inland they are connected to reefer plug points or provided with a clip-on generator set.
Goods that are transported in a reefer require a constant temperature. A common categorization of storage temperatures is provided by the table below.
| Type | Temperature range | Typical commodities | Comment |
|---|---|---|---|
| Frozen | -20°C and below | Meat, fish, butter | Completely frozen |
| Partial-frozen | -10°C to -3°C | Meat | Partially frozen |
| Chilled | -3°C to +5°C | Fruit, vegetables, chilled meat | Lowest temperature above freezing |
| Light-chilled | +5°C to +25°C | Fruit, vegetables | Temperature to reduce deterioration |
Typical goods transported in reefer containers are vegetables, fruit, meat, dairy goods, fishery products, flowers or pharmaceuticals. Refrigerated cargo can be classified as food or non-food items and as chilled or frozen items. Some chilled cargoes are live and respiring, with chemical reactions and processes taking place within the product and a continual output of gases and heat. Due to temperature sensitivity of chilled cargo, the generated heat needs to be removed outside the cargo space quicker than it is released to prevent heat build-up and a temperature rise. Gaseous products of the chemical reactions must also be removed to avoid damage and deterioration in the quality of the product.
Reefer containers exist in various types and sizes; nowadays the 40 ft high-cube container is the preferred one, with an internal capacity of up to 2,470 cubic feet. One of the major focuses of the highly technical refrigerated container machinery industry is that of energy efficiency. Given that the electrical power for the machinery units comes from the ship or a diesel genset, and looking at the prices of fuel nowadays, any small gain in energy efficiency may now lead to substantial savings. Improvements can be made in terms of IT programs, e.g. reefer monitoring systems (RMS) that monitor and regulate the (re)action of the machinery to and temperature within the reefer. One example is QUEST (Quality and Energy efficiency in Storage and Transport), an energy saving mode (program). Claims are that when fitted with QUEST, compressors use as little as half the energy compared with others that are not. A further means to improve energy efficiency of the reefer container is the use of regenerative energy. The installation of a shading roof above the reefer stacking area might be a good solution because it keeps sun radiation away and, if equipped with photovoltaic panels, produces regenerative energy.
References
Dynamar B.V. 2012, Dynamar (2012) Reefer Analysis – Market Structure, Conventional, Containers, eds. Waals, F & Visser, D, Alkmaar, The Netherlands.
Maheshwar, C 2008, ‘Container Refrigeration’, Witherby Seamanship Int., Livingston, United Kingdom.
