Rooftop of a commercial building with heating, ventilation, air conditioning and refrigeration units.

Buildings in the U.S. consume 38.5 quads of energy annually, of which nearly half is used for heating, ventilation, air conditioning and refrigeration (HVAC&R). Traditional HVAC&R systems rely on a process called vapor compression to cool and heat our buildings, using a compressor to circulate liquid refrigerants, typically hydrofluorocarbons (HFC). HFCs are hundreds to thousands of times more potent than carbon dioxide and can last for centuries when released into the atmosphere. Phasing down HFCs could avoid up to 0.5°C of global warming by the end of the century; however, their use in air conditioning and refrigeration is growing rapidly around the globe – energy consumption may grow over 450% by 2050.

In October 2016, the global community committed to the Kigali Agreement, an amendment to the Montreal Protocol that will avoid rampant growth of HFC emissions and phase out their usage over time, replacing them with climate-friendly, energy-efficient alternatives. U.S. Secretary of Energy Ernest Moniz said the Kigali Agreement, in coordination with the Paris Agreement on climate change, will “send signals to industry and innovators that countries are committed to developing and deploying a new generation of energy-efficient and low-carbon solutions to meet the goals our nations have declared before the world, and encourage even greater ambition in the future.”

The Department of Energy’s Building Technologies Office (BTO) is working to develop the next generation of HVAC&R technologies to revolutionize the industry by utilizing low- to zero-global warming potential (GWP) technologies. BTO has a comprehensive strategy that seeks to bring low-global warming potential refrigerants to market, improve the performance and costs of existing technologies, and develop next-generation technologies that push the U.S. toward a zero-GWP refrigerant future.

In the last year leading up to the Kigali Agreement, BTO worked with Oak Ridge National Laboratory (ORNL) to conduct performance testing of several near- or already-commercially available low-global warming potential alternative refrigerants in rooftop air conditioners and mini-split air conditioners in hot and very climates (up to 131 °F, 55°C). These models were tested due to their prevalence in residential and commercial buildings in the developing world. The research at ORNL shows quite clearly that both R-22 and R-410A – two of today’s most common refrigerants – have several viable replacements, including ones that will give equivalent performance even under extreme ambient temperatures. Because alternatives were tested without making any major equipment changes, researchers believe that their actual performance can be even better when used in air conditioners that are optimized for their unique properties. Both studies provided evidence to the international community that viable replacements for HFC refrigerants can be used across building types and climate zones – including some of the most punishing ones – without significantly impacting unit energy efficiency or cooling capacity, a key issue for many developing nations in negotiations leading up to the agreement.

The performance testing was just a part of BTO’s comprehensive strategy and low-GWP roadmap, through which BTO has supported climate-friendly advances in supermarket refrigeration and the commercialization of alternative refrigerants. Additionally, BTO is working to develop next-generation HVAC&R technologies, such as the first home water heater that uses zero-GWP refrigerants and a magnetocaloric air conditioner that uses zero-GWP refrigerants.