Pondering what has happened, and still occurs, in recent times concerning the climatic crisis for which we have no more excuses, the theme of refrigeration and of refrigerants is a hotter and hotter issue, which I would not hesitate defining “burning”.
Producing cooling energy to satisfy the growing requirements of the commercial and industrial refrigeration, of transports, without neglecting the residential one, which in the last three five-year periods is witnessing a more and more important diffusion of heat pumps, implies increasingly attentive assessment and choice, first of all by manufacturers and by designers and maintenance engineers afterwards, of the most suitable refrigerants to be used.
The last 150 years have seen what we might define an “upside down” in gymnastic terms; starting from “natural” refrigerants (phase 1, ex. CO2 in 1890) we have shifted to the first synthetic refrigerants since 1930 (phase 2), then we have understood that these refrigerants damaged ozone and then we took a further step forward towards still synthetic, but less noxious, refrigerants for the ozone (phase 3) which has gone on with the perfecting of the latter, once the ozone problem has been downsized and the greenhouse effect problem has emerged. Now we are facing a new challenge, because the efforts made until now do not seem to produce the expected results and we enter what we might call “phase 4” with a possible return to natural refrigerants for manifold applications.
The sector is the focus of the umpteenth revolution, the fourth. Unfortunately, the refrigerants that had been studied and chosen just fifteen years ago prove to generate too many problems essentially connected with the climate, owing to their high climate-altering power. Chemistry enables the implementation of new molecules (how many we want!), however few can have all the specifications we expect from a refrigerant. At this stage, we have understood it is necessary to give up some of these characteristics.
The first compromise we are called to accept is the non-flammability, and in my modest opinion it is not a very serious problem, provided that technicians are supported by suitable safety codes and regulations (anyway, properly devised and applied in other sectors such as the heating one), and that the machine technology is developed to allow an optimal use of these fluids.
The second compromise, much more relevant in my modest opinion, is the fact to renounce the universal solution, there is not in fact a refrigerant that is even remotely comparable to the ideal properties for all applications. The commercial refrigeration, for instance, has already addressed natural fluids, highlighting the choice of the carbon dioxide as technical option that seems nowadays irremissible. Concerning other applications, such as for instance the world of the air conditioning and of water refrigerators, either we accept a moderate flammability or we cannot find what we are looking for and we would like. Let us simply think of manufacturers that, just three years ago, stated “we will take hydrocarbons into account in 5 years”, and since the year-start they have presented propane heat pumps in their catalogue.
Therefore, the future seems to suggest a change of technologies, to use these different refrigerants at best. Starting from compressors, field where generally volumetric compressors have been adopted until now, they are developing the technology of centrifugal mini compressors that will be able, assuring high flow rates, to manufacture compact machines with reduced charge of refrigerant fluid, to compensate partially the risk caused by flammability.
Science, then, leads us to carry out this umpteenth course correction that seems to bring us back to origins, accompanied by the technological progress on one hand, and supported by the regulatory evolution on the other hand.