Although there are no bans on the on the use of HFCs in new refrigerated transport systems, the 2014 F-Gas Regulation, particularly the HFC phase-down, are resulting in the selection of lower GWP refrigerants, particularly the replacement of R-404A, compatible with the technical safety requirements for transport refrigeration systems. In addition to leak prevention, possible mandatory leak checks, and record keeping, the service ban from 1st January 2020 on the use of refrigerants with a GWP above 2,500 for transport refrigeration systems with a charge size of 40 tonnes CO2e or more is prohibited. This would affect R-404A for charge sizes greater than 10.2 kg, but in practice most refrigerated trucks and trailers, vans and containers will be unaffected as they have smaller charges. Even so R-404A use should be avoided where practicable.
Technical requirements for transport refrigeration systems are very complex. They have to operate over a wide range of weather conditions, carry different cargos at different temperatures, sometimes with two different compartments at different temperatures. They have to be very robust and reliable to withstand vibrations and shocks and must meet ship and road safety requirements. HFC refrigerants have been the refrigerant of choice for the majority of refrigerated containers, refrigerated vans, trucks or trailer-mounted refrigerated systems and refrigerated railcars.
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Flammability risks are a main concern, along with energy efficiency and reliability, for transport applications and affect current and future refrigerant choices. Non-flammable HFCs continue to be widely used and lower GWP non-flammable alternatives such as HFC/HFO blends are being used or developed as replacements in some applications. R-744 (CO2) has inferior energy performance at medium to high ambient temperatures when compared to the non-flammable fluorocarbons used for transport refrigeration. Flammability mitigation still represents a major challenge, but research continues for the use of mildly flammable A2L refrigerants, such as HFO-1234yf, HFO-1234ze(E) and HFC-32.
Refrigerated containers that are designed for use with R-134a are being offered as compatible with R-513A for future conversion or are available with non-flammable HFC/HFO refrigerant R-513A. This refrigerant has a GWP of 631 compared to 1430 for R-134a. The HFC/HFO blend R-452A is the preferred refrigerant choice, replacing R-404A, in Europe for truck and trailer refrigeration units. Non-flammable R-452A has a good match of properties and discharge temperature to R404A and has a GWP of 2140 (compared to 3922 for R-404A) and is suitable as an alternative to R-404A for refrigerated containers.
Diesel free solutions are being used more widely with electric compressors and for small refrigerated vans all electric vehicles to provide zero emissions for the ‘last kms’ of cold food delivery particularly in urban areas. Hermetic electric refrigeration systems using non-flammable R-134a can be factory assembled and pre-tested to ensure containment.
Transporting healthcare products by air demands a rigorous logistical approach and ensures rapid delivery under tightly controlled temperatures conditions. Typically, active air freight containers use non-flammable R-134a in a battery-powered vapour compression cycle, with fully redundant electric heating and compressor cooling systems and an insulated container shell. The cooling capacity and the refrigerant charge are low.
The main non-flammable fluorocarbon refrigerants used or being considered for transport refrigeration are shown in the table. This shows the currently used HFCs and lower GWP replacements that are already being used or in the process of being implemented for these applications.
2018 AFCE Final Report Energy Efficient State of the Art of Available Low-GWP Refrigerants and Systems. This report can be downloaded from the AFCE (Alliance Froid Climatisation Environnement) website at http://www.afce.asso.fr/wp-content/uploads/2018/10/Final-rapport-energy-efficiency-GWP-2018.pdf
2018 Assessment Report of the Refrigeration, Air-conditioning and Heat Pumps Technical Options Committee available from the ozone secretariat website https://ozone.unep.org/science/assessment/teap