1896 marked a milestone in climate science as the year that Nobel-prize winning Swedish physical chemist Svante Arrhenius predicted in a seminal paper that changes in atmospheric carbon dioxide levels could alter the planet’s surface temperature through the greenhouse effect.

This radical departure from traditional notions about climate dynamics revolutionised our thinking on the subtleties of global warming.

Four decades later, in 1938, English steam engineer and inventor Guy Callendar confirmed that rising carbon dioxide levels in Earth’s atmosphere are connected to global warming.

What is ‘Global Warming Potential (GWP)’?

Global warming potential (GWP) is a metric that was developed to allow comparisons of the global warming impact of different gases over different time periods, typically 20, 100 and even 500 years. The higher a gas’s GWP, the greater its propensity for harm to the environment.

The 20-year GWP is based on the energy absorbed by a gas over 20 years, the 100-year GWP is based on the energy absorbed over 100 years, and so on. The 20-year GWP prioritises gases with shorter lifetimes. The most common measurement to quantify greenhouse gas emissions is GWP100 (looking at the GWP of gases over the duration of a century).

The US Environmental Protection Agency describes GWP as “a measure of how much energy the emissions of 1 ton of a gas will absorb over a given period of time, relative to the emissions of 1 ton of carbon dioxide (CO2)” – CO2 has a GWP of 1.

Refrigerants and GWP

Refrigerant gases used in cooling and refrigeration systems vary enormously in GWP. The refrigerant with the highest global warming potential at 14,800 is the potent greenhouse gas Trifluoromethane (R23). At the other end of the scale, the natural refrigerant ammonia (R717) has a GWP of 0. Synthetic refrigerants with the lowest GWP include hydro-fluoro-olefins (HFOs) such as R1234ze and R1234yf which have a GWP of less than 1.

The revelation that high GWP refrigerants – in particular, F gases – are bad for the environment has led to growing regulatory pressure to eliminate them.

F-Gas Regulations 2024

Legislation in the EU and UK revolves around the F-gas Regulation. In April 2022, the European Commission provided the European Parliament and the Council of the European Union with its proposal. The new F-gas Regulation (EU) 2024/573 was adopted on 7 February 2024, and started to apply on 11 March 2024.

This builds on the former F-gas Regulation which, according to the European Commission “was already successful in reducing emissions. Nevertheless, to meet the EU’s 2030 objective and reach climate neutrality by 2050, we aim to phase out the use of F-gases in the EU”.

The central challenge is that the use of any refrigerant involves compromise.

There is, for example, a trade-off between GWP and the degree of flammability or toxicity. Lower GWP refrigerants tend to exhibit higher flammability (as in the case of hydrocarbons) or are more poisonous (as is the case with ammonia).

The perfect refrigerant would be non-ozone depleting with a GWP of zero. It would also be non-flammable, have a short atmospheric lifetime, and be non-corrosive and non-toxic.

Unfortunately, the unalterable 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 a trade-off between practicality and performance.

Low GWP F-Gases

The European FluoroCarbons Technical Committee (EFCTC) says: “As lower GWP fluorocarbon refrigerants are increasingly used in the EU, the average GWP for all HFCs, HFOs, and HCFOs placed on the EU market decreases.

“The reducing F-gas HFC cap, the increasing adoption of lower GWP HFCs, HFC/HFO blends, and ultra-low GWP HFO/HCFOs has resulted in a 36% reduction in average GWP from about 2062 in 2014 to 1319 in 2018 for total reported supply to the EU market.”

In 2018, HFOs and HCFOs accounted for about 20% of the reported total sales in metric tonnes of all HFCs, HFOs and HCFOs, according to the EFCTC.

It adds: “The switch to lower GWP HFCs is also occurring, HFC-32 is an increasing share of the total HFCs/HFOs supplied with a marked increase for 2018 in both metric tonnes and percentage share.”

By 2030 the HFC cap is expected to decrease to 21% of the 2015 cap. The EFCTC again: “To meet market demand, the average GWP will continue to fall in order to maintain the required metric tonnes for use as refrigerants and for other applications.

“The increasing adoption of lower GWP HFC/HFO blends will support this transition, with non-flammable and low GWP mildly flammable refrigerants being available.”

For more information about our Low GWP heat pumps, click here.