The perfect refrigerant is non-ozone depleting, has a global warming potential [GWP] of zero, is non-flammable, has a short atmospheric lifetime with benign residual elements upon breakdown, and is non-corrosive and non-toxic.
Unfortunately, the immutable laws of chemical engineering dictate that the perfect refrigerant does not – and, indeed, cannot – exist.
It is possible for refrigerants to possess some of the qualities listed above, but not all of them at the same time. That means the best refrigerant for a particular application will inevitably be a compromise; in other words, there is an inescapable trade-off between properties of practicality and performance.
The first refrigerants
Water and air were the first refrigerants considered for use in mechanical refrigeration systems, and the first artificial refrigeration machine was developed by Scottish physician and professor William Cullen in the mid-1700s.
Later, in the 19th century, refrigerants such as methyl chloride, ammonia, propane, and sulphur dioxide were key components in the first air conditioners and refrigerators, and refrigerants have developed in leaps and bounds since then.
More recently, the focus has shifted from the flammability and toxicity of refrigerant gases to reducing their potentially devastating impact on the environment.
Indeed, fluorinated gases (F-gases) used as refrigerants represent a clear and present danger to the environment. Although the modern incarnations of these substances don’t damage the atmospheric ozone layer, they are nonetheless powerful greenhouse gases, with a global warming impact up to 23,000 times greater than carbon dioxide (CO2).
F Gas regulations
Emissions of F-gases in Europe almost doubled between 1990 and 2014. However, thanks to EU legislation on fluorinated gases – namely, the F-gas Regulation – F-gas emissions have been falling steadily since 2015.
The first F-gas Regulation was adopted in 2006 and succeeded in stabilising EU F-gas emissions. However, on 1 January 2015 it was replaced by Regulation (EU) 517/2014. Among other things, this newer regulation was designed to cut the EU’s F-gas emissions by two-thirds by 2030 compared with 2014 levels by reducing the use of high-GWP hydrofluorocarbon (HFC) refrigerants, some by bans and others by pressure on the CO2 equivalence of refrigerants in use.
But the story is more complex than these bare facts suggest. The high-GWP HFC refrigerants (such as R134a, R407C and R410A) that the F-gas Regulation is designed to reduce are not the only refrigerants available for air conditioning systems.
Among refrigerant gases, the mainstream low GWP alternatives to HFCs are hydrofluoro-olefins (HFOs) or blends which use them. HFOs are organic compounds that still use hydrogen, fluorine, and carbon, like traditional F-gases, but their chemical structure is such that they are unstable: this is a blessing and a curse – it means these gases are flammable (albeit mildly so), but it also means they break down more quickly than traditional F-gases, which is what makes HFO GWPs so low.
Complicating the picture further, there are also so-called ‘natural’ refrigerants such as ammonia, hydrocarbons like propane and isobutane, and (ironically, given it is the original global warming super-villain) CO2.
Ammonia’s GWP is 0, but it is incompatible with copper piping and wiring, is poisonous in high concentrations, and can be flammable; CO2 has a GWP of 1 (it is the base for the GWP metric), but it demands high working pressures; propane’s GWP is 3, but it is highly flammable.
These GWP numbers compare with the lowest of the “low GWP” HFCs that we see growing in use in HVAC applications – R32 – which has a GWP of 675.
Choosing the right refrigerant
If you are starting fresh on a new HVAC project, it is important to remember that the refrigerant used in an air conditioning system must be fundamentally suited to the equipment it cools and heats. So, to determine the right solution for the job, you must focus on the application – what specifically is the system being used to do?
The challenge is not only choosing the right cooling and heating system, but also making the right refrigerant choice to ensure safety and to have a positive effect on operational efficiency, which reduces operating costs.
The refrigerant used must also be reliable and meet legislation relevant to the application, and – most importantly – it should be readily available for the life of the plant and reasonably priced.
This is where an expert HVAC systems supplier like Klima-Therm can help. We have the expertise, experience and product range to support you as you navigate the minefield of available options, to ensure that you select the right system for the job.
Contact us to find out how we can help you choose the right systems for your heating and/or cooling application.