Refrigerants in vehicles
Refrigerants are a key element of modern car air conditioning systems. In the air conditioning system, it ensures that heat is dissipated from the passenger compartment by using cooled fresh air. Its refrigerating capacity and the pressure in the air conditioning system determine the cooling performance. However, improper filling or refilling with unsuitable substances can lead to safety risks and increased global warming potential.
Global warming potential (GWP)
Refrigerants are an important element in refrigerators or air conditioning systems, for example. In addition to the heat transfer characteristic, other factors are crucial when selecting the refrigerant. The GWP (global warming potential) is particularly important here. This value indicates the contribution to the greenhouse effect over a selected period of time, usually 100 years (GWP100) in relation to CO2. CO2 has a GWP of 1 here. The lower the GWP, the better. This applies above all to natural refrigerants, while synthetic refrigerants usually have a high GWP value.
Example calculation:
The refrigerant R-134a has a GWP of 1430 over 100 years; 800 g of refrigerant is used in an air conditioning system.
CO2 equivalent = GWP × R-134a filling quantity
CO2 equivalent = 1430 × 800 g
CO2 equivalent = 1.144 t
The use of 800 g refrigerant therefore corresponds to CO2 emissions of 1.144 t over 100 years if it enters the environment.
The lower the GWP, the better. This applies above all to natural refrigerants, while synthetic refrigerants usually have a high GWP value.
Refrigerant groups
In layman’s terms refrigerants can be distinguished into natural and synthetic refrigerants. Natural refrigerants are also the oldest group of refrigerants and are currently gaining in importance, e.g. ammonia (R-717), carbon dioxide (R-744), water (R-718) or other hydrocarbons such as butane (R-600) or propane (R-290).
But why are these refrigerants from the infancy of cooling being used again?
Halogenated and partially halogenated hydrocarbons need to be mentioned here: CFCs (chlorofluorocarbons), PFCs (perfluorocarbons), HCFCs (hydrochlorofluorocarbons) and HFCs (hydrofluorocarbons).
Alongside many advantages, these halogenated and partially halogenated hydrocarbons have two crucial disadvantages:
- an enormous greenhouse effect that helps drive global warming,
- and damage to the ozone layer.
The production and use of CFCs was therefore discontinued in line with the Montreal Protocol of 1987 – and the use of other refrigerants was restricted.
Refrigerant R-1234yf
R-1234yf, 2,3,3,3-Tetrafluoropropene, is a refrigerant that is used in many modern vehicle air conditioning systems today. In particular, the refrigerant became established in the market after R-134a was prohibited for newly registered passenger cars in the European Union from 2017.
The biggest advantage of R-1234yf is the GWP (global warming potential) of under 1, where the standard value is CO2 with a GWP of 1. Some refrigerants have a GWP of over 10,000.
This means that R-1234yf is very environmentally friendly and does not deplete the ozone layer.
R-1234yf is not uncontroversial, though, as it is flammable and breaks down into hydrogen fluoride, among other things, which reacts with water to form the extremely toxic and corrosive hydrofluoric acid. Even small quantities of this are dangerous. In liquid form, R-1234yf can lead to severe frostbite if it comes into contact with the skin.
It is particularly important to note that R-1234yf is a PFAS (per- and polyfluoroalkyl substance). A forever chemical that, once it reaches the environment, remains there forever and is not broken down.
In the atmosphere, R-1234yf mainly breaks down into trifluoroacetic acid, also a forever chemical (PFAS). Trifluoroacetic acid is extremely water-soluble and passes into the water through rainfall – leading to increased values being demonstrated in water in recent years.
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