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ORNL research informs landmark decision on heat-trapping refrigerants

A global agreement to phase down the use of potent greenhouse gas refrigerants and replace them with climate-friendly alternatives leaned on multiple ORNL studies.

In a landmark decision, climate leaders from more than 190 countries agreed to amend the Montreal Protocol to discontinue producing and consuming high-global warming hydrofluorocarbons, or HFCs. HFCs used in today’s air conditioners and refrigerators were first introduced as a way to combat depletion of the ozone layer. Researchers now know that although HFCs are friendly to the ozone layer, they contribute to global warming.

A series of DOE-funded reports co-authored by ORNL and Navigant Consulting investigated the performance of HFC alternatives such as hydrofluoroolefin mixtures and hydrocarbons. The researchers’ latest study evaluated the energy efficiency and cooling capacity of nine low-global warming potential options in roof top and small residential air conditioners in simulated temperature and climate conditions similar to the Middle East and parts of Asia and North Africa.

“It was thought that the soaring temperatures of 100-130 degrees Fahrenheit can degrade air-conditioner performance when using the alternative refrigerants,” ORNL’s Omar Abdelaziz said. “Our research demonstrated that similar or better energy efficiency and cooling capacity could be achieved with other low-global warming potential refrigerants compared to the baseline HFC refrigerants.”

Abdelaziz, who leads ORNL’s High-Ambient-Temperature Evaluation Program for Low Global Warming Potential Refrigerants, presented results of “The Future of Air Conditioning for Buildings” to Montreal Protocol representatives during a workshop in Vienna. The State Department, White House and DOE referenced the report’s key findings that influenced the protocol’s amendment.

Phasing down HFCs could avoid up to 0.5 degrees Celsius of global warming by the end of the century, contributing to the Paris Agreement goal to limit global temperature rise to well below 2 degrees Celsius.

The ORNL reports evaluated multiple refrigerant alternatives for rooftop air conditioners and for mini-split, or ductless, air conditioners.