Changes to Refrigerant Gases

Overview
There has been quite a bit of discussion recently around refrigeration gasses. The move is to phase out the high GWP (Global warming potential) refrigeration gasses and replace with low GWP gasses.
Under the New Zealand Emissions trading scheme, refrigeration gasses with a high GWP will be phased out and replaced with low GWP gasses. Gasses with a GWP of <150 are considered to be “Low GWP”.
Under this scheme the cost of high GWP gasses such as R407c and R134a will increase due to government levies.
There has been talk that this will make the current systems using the old gasses obsolete and will require a complete system replacement.
Our Energie Solar Block systems have been using R407c. This was originally introduced to replace R22, which was classed as ozone depleting.
R407c is non-ozone depleting, non-toxic and non-flammable, but has a GWP of 1774, which is considered too high.
Our Energie systems also use R134a. R134a is still used in many systems in New Zealand, including refrigeration, hot water heat pumps, and automotive air conditioning. R134a has a GWP of 1430 and hence will also be phased out.
The low GWP replacement gasses are often flammable, such as R290 (propane), or R600 (butane), or toxic, such as R717 (ammonia).
Interestingly, R744 (CO2) has a GWP of 1 and thus classed as a low GWP, but outside the refrigeration industry it is considered a major contributor to climate change.
As a comparison, the refrigerant R32, which is commonly used in heat pumps, has a GWP of 675, and is classed as A2L, slightly flammable.
For reference, the A2L flammability class states “they are unlikely to ignite from a spark or naked flame”. The L means they have a low burning velocity, so in the event of ignition the flame will burn slowly and self-extinguish. However, they do require additional equipment such as a flameproof compressor, and specific handling equipment and practices. In large systems they may require additional safety measures such as leak detection.
The process still seems to be under discussion, but my understanding is that the draft plan is to move to refrigerants with a GWP less than 750 as soon as possible, then move to refrigerants with a GWP less than 150 by the year 2032. This may create problems with existing systems due to the suitability and/or flammability of the replacement gasses.
Replacement for R407c
The current replacement for the R407c refrigerant is R454c.
This has very similar characteristics to R407c, is non-ozone depleting, non-toxic and has a GWP of 148 and thus classed as a low GWP gas and acceptable for the future.
It is however, classed as slightly flammable (A2L). Because of this flammability class, it would probably require a compressor change. This is quite straight forward and can be easily done.
The solar panels, and pipework etc would not need to be modified in any way.
Because the refrigerant charge is normally around 5-6kg, under EN 378, the system would not require a leak detection system, although this may depend on the individual situation.
Replacement for R134a
The current replacement for the R134a gas is R513a.
R513a has a GWP of 573, which is lower than that of R32 (GWP of 675). It is classed as non-toxic and non-flammable.
R513a is a direct drop-in replacement for R134a and there are no changes required to the system, solar panels, or pipework.
We have a number of systems currently running on R513a with no problems reported.
Longer term, the replacement for R134a and R513a is currently looking like R512a, R134yf or R1234ze.
R512a is directly compatible with R134a, non-toxic, but classed as A2L, mildly flammable. It has a GWP of 185 so just misses out on the <150 low GWP limit.
R1234yf and R1234ze are low GWP gasses. However, they are classed as low toxicity and mildly flammable (A2L) and have different characteristics. The lubrication oils used with R134a are not compatible with R1234yf, so this would require a compressor and oil change.
In my opinion, as R134a is so common, and the refrigeration industry is fast moving and will adapt to demand. I am confident that there will be another better alternative by the time it is required.