Using propane in air conditioners could prevent 0.1°C of warming

Using propane as a refrigerant in air conditioners could avoid around 0.1°C of global warming by the end of the century. It would be a significant reduction considering that, to achieve the Paris Agreement’s target of limiting warming to 1.5°C above pre-industrial levels, the planet must not warm more than about 0.3°C.

In 1987, most countries committed to ditching the ozone-depleting gases used in cooling appliances for others called hydrofluorocarbons (HFCs). HFCs don’t harm the ozone, but are potent greenhouse gases, some with an impact on global warming thousands of times greater than CO2, tonne for tonne.

More than a hundred countries have since committed to replacing HFC refrigerants to reduce emissions from the cooling sector, which is responsible for around 7 per cent of global greenhouse gas emissions. That figure could double by 2030 if emissions continue as they are now, says Toby Peters at the University of Birmingham, UK.

Pallav Purohit at the International Institute for Applied Systems Analysis in Austria and his colleagues considered the effect of replacing HFCs with propane in the most common air conditioners, called split ACs. A tonne of propane has a smaller warming effect than the same amount of CO2, says Purohit.

The researchers used climate and economic models to compare three scenarios. In one scenario, potent HFCs continues to be used. In the second, the most widely used HFC is replaced with an HFC that results in less warming, but is still hundreds of times more potent than CO2. In the third, propane is used as a refrigerant in all split ACs.

They found switching to propane would avoid between 0.06°C and 0.12°C of warming by 2100, assuming a future in which CO2 emissions continue around current levels to 2050 then begin to fall. Switching to the less potent HFC avoided 0.03°C of warming.

Alex Hillbrand at the Natural Resources Defense Council, a US environmental advocacy organisation, says 0.1°C in avoided warming would be a “huge deal”. It equates to nearly half of what the global HFC phasedown is aiming to achieve by reducing HFC use 80 per cent by 2047. But widespread adoption of propane would be challenging, especially for countries like India and China where demand for cooling is growing rapidly, he says.

Manufacturers have mostly met phase-down commitments so far by switching to less potent HFCs because they are more familiar, says Hillbrand. Propane air conditioners are available in Europe and Asia, but make up a small portion of the current market. Elsewhere they are prohibited because propane is flammable.

3.7 billion air conditioners are expected to be operating in 2050. Peters says it would be good if more of them used propane. But with 80 per cent of cooling-related emissions coming from generating the electricity used to power cooling appliances, more energy-efficient cooling and clean sources of power are also needed. Other climate-friendly refrigerants such as ammonia could also be better suited for different places and applications.

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