Another refrigerant

Cars built after about 1993 use a gas that is not a CFC. This is called R134a and saves using a name that is about as long as a certain Welsh railway station. There should be a sticker in the engine bay telling you if you have R134a.
There are many other refrigerants many of which are based on inflammable gases but obviously these cannot be used in a moving vehicle (imagine a crash, the front radiator could be at 300 psi full of something like butane and has just had a small hole punctured in it - WW2 flame-throwers could learn a thing or two from this). Both R12 and R134a are not flammable. Although R12 is no longer fitted into new cars those built before about 1993 will still need to be recharged with it say every three years.
A fact not always appreciated is that R12 is so efficient that it needs lower pressures to achieve the same result and thus creates fewer greenhouse gases than R134a.

R134a systems are becoming more and more efficient as developments occur so are becoming smaller, contain less refrigerant, use even less fuel to run and have lower losses. Nevertheless the powers that be are legislating that the use of R134a be phased out in the next few years to be replaced by a refrigerant R744. This refrigerant is actually Carbon Dioxide, CO2. The technology to achieve this is already here, indeed I saw a demonstration vehicle in Frankfurt in September 2004, but it is likely that it is going to be another three or four years before the first production models start arriving in the showrooms. The pressures needed to make this system work efficiently are considerably higher than for R134a, extending into the thousands of pounds per square inch rather just into the hundreds. Inevitably this is creating tehnical problems that need addressing. There are interesting offshoots that are possible from using this refrigerant that are more acceptable than from R134a such as the ability to have the heater going full blast within a few seconds of starting the engine by means of using the AC system as a heat pump. This may not sound too important but already diesel engine technology has advanced so much that there is very little waste heat to utilise in the car's heater system and the manufacturers are having to include a supplimentary heater (like a mini central heating boiler running on diesel) to provide enough heat for the occupants comfort. Petrol engines will surely progress to a similar level of efficiency in time.

New evaluations of the the impact on global warming of R134a and R744 presented in July 2005 showed that the long term results of R744 were in fact considerably inferior to that of R134a but as government dislike changing their minds I suspect that we are going to be stuck with R744 for the future.

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