Propane could be the answer to sustainable air conditioning

According to a new study, using propane as a refrigerant could reduce the effects on global temperature increase from space cooling.

Heatwaves have been on the rise globally. This has led to an increase in the usage of air conditioners, which unfavourably impact the environment due to their high energy consumption and use of halogenated refrigerants with high global warming potential. As the heatwaves are likely to increase in severity and frequency in the future, it is important to look for sustainable refrigerant alternatives. 

Most of the current split ACs use HCFC-22 and HFC-410 as refrigerants, both of which are characterized by a very high global warming potential score, up to 2,256. This means that they trap up to 2,256 times more heat than carbon dioxide over 100 years. Alternatives such as HFC-32 have been considered but with a score of 771, it still poses a threat to the environment. 

A study led by IIASA researcher Pallav Purohit in collaboration with researchers from the United Nations Environment Programme and Dr Chris Smith from the University of Leeds, showed that by switching to propane, a low (<1) global warming potential refrigerant for space cooling, we could avoid a 0.09°C increase in global temperature by the end of the century. This would result in a significant contribution towards keeping the global temperature rise below 1.5 °C.

Dr Smith said: “As the climate warms we are going to use more air conditioning, so we should ensure that gases used as refrigerants don’t contribute further to climate change.

By using propane in new air conditioning units in place of the highly potent fluorinated gases that we currently use, we can avoid nearly a tenth of a degree of warming by the end of the century if air conditioner use expands as predicted.

He continued: Using propane doesn’t alleviate the demand for fossil fuels, which at the moment provides the majority of global propane supply, so sourcing sustainable feedstocks is also critically important.”

The researchers arrived at their findings by using the IIASA Greenhouse Gas – Air Pollution Interactions and Synergies (GAINS) model to compare the baseline halogenated refrigerant emission scenarios by switching to HFC-32 or propane. Dr Smith’s climate assessment found that while the use of HFC-32 lessened the global temperature to 0.03°C by the end of the century, propane lessened it to 0.09°C, proving to be a better choice of refrigerant in terms of sustainability.

This study signifies the urgent need for policy changes as well. ACs with propane as refrigerants are already available in the Indian and Chinese markets. However, their adoption has not been successful at a large scale due to national restrictions, with standards and codes limiting the use of refrigerants with higher flammability, although their performance is similar to HFC-32 and better than HFC-22 and HFC-410.

To achieve the EU's ambitious 2050 climate neutrality targets, early and aggressive action is needed. In the short term, converting new air-conditioning systems to more environmentally-friendly refrigerants can reduce their climate impact significantly, underlining the urgency of updating standards for policymakers.

Pallav Purohit, lead author, IIASA

Further Information

The study is titled “The key role of propane in a sustainable cooling sector” and is published in Proceedings of the National Academy of Sciences (PNAS). It’s available to read here

Image by Dewi Karuniasih on Unplash.