The scale and potential impact of the ORNL effort is vast: Consider how many air conditioners and refrigeration systems you encounter regularly, especially during trips to the supermarket, where invisible refrigerant lines cool everything from produce to frozen pizzas.
Those supermarket lines — and compressors and pipes — leak an estimated 25 percent of their coolant into the atmosphere every year, according to Brian Fricke, a group leader for building equipment research at ORNL who specializes in retail cooling.
The coolant known as R404A, commonly used in supermarket systems, can be 4,000 times more potent as a greenhouse gas than carbon dioxide (the “global warming potential” of certain gases has a baseline of 1, which represents carbon dioxide), Fricke said.
The use of that coolant, aside from reclamation purposes, was banned beginning in 2020 in the European Union. In the U.S., the coolant is set for phaseout by 2030.
Supermarket cooling infrastructure is just one source of the pollutant.
“Think about air conditioners, heat pumps, refrigerant charge … if you sum all those millions of units up, residential, commercial, industrial sector,” the climate-change effects are vast.
“What we’re trying to do is develop energy-efficient and low-emission equipment,” he said, and the Building Equipment Research Group focus ranges from water heaters to heat pumps and refrigeration.
He spoke to Hellbender Press in a Zoom interview about his group’s work, but first wanted to provide a history lesson about the toxic and somewhat haphazard and dangerous development of refrigerants beginning in the late 1800s.
“There were some fairly nasty chemicals, that were used as refrigerants, like methyl chloride, like sulfur dioxide, and and maybe some more familiar ones, like ammonia and carbon dioxide,” he said.
(More irony: carbon dioxide, the climate change poster child, is a quality coolant that is the subject of increasing research and use).
The cooling process was stabilized somewhat over the decades to the point that refrigerators became a more common feature of homes and businesses, but coolants still had widespread toxicity and flammability issues.
In the 1930s, an engineer with General Motors’ Frigid Air division introduced a new refrigerant that harnessed CFC for its cooling properties. It was ultimately marketed under what became a familiar trade name: Freon. An old tale still survives of the engineer, Thomas Midgley Jr., inhaling Freon to prove its safety to interested clients.
The problem was, and it wasn’t noticed until decades later, chlorine damaged high-level ozone, one of Earth’s shields against solar damage that makes the planet hospitable to life.
In a further cycle of irony and alphabet soup, the HFC that replaced the CFC (the chlorine molecule was replaced with a hydrogen molecule) were extremely potent greenhouse gases.
Those gases, most notoriously carbon dioxide, “are gases that will absorb radiation from the sun and then reemit that typically in the infrared area,” Fricke said.
“If we have a lot of types of those gases in the atmosphere absorbing and then reemitting the radiation at a different wavelength … then we’ll experience heating of the planet.
“What we’re trying to do is develop energy-efficient and low-emission equipment,” he said, and the group’s focus ranges from water heaters to heat pumps and refrigeration.
In terms of refrigeration systems, the group’s focus is on ensuring the coolant stays contained and that minimal amounts are needed in the first place.
One efficient coolant suggests that “what once was old is new again,” Fricke said in reference to the revival of carbon dioxide as a refrigerant. Its GWP is 1, as mentioned above, which means it’s a relatively benign greenhouse gas compared to refrigerants such as R404A .
Fricke said some new supermarkets in the Atlanta area now use a CO2-powered refrigerant system, which can also be used in tandem with ammonia to improve cooling efficiency,
Gases such as butane and ammonia and even a new class of molecule (hydrofluoroolefins) offer more benign refrigerant alternatives for the future, and Fricke’s team is pursuing all possibilities, including how to safely deliver and contain the emerging new coolant classes.
“There are issues with these new refrigerants?” he said, such as toxicity and flammability. A main concern is “how can we design equipment that can safely use these refrigerants?”
And in the case of carbon dioxide for use as a commercial-level coolant, it must be delivered via high pressure through an especially “robust” pipe system.
“Throughout the whole history of refrigeration, we’ve been looking for silver bullets, but there is no silver bullet. There are always tradeoffs, in terms of performance, flammability, toxicity and now we can add impact to the environment to that, as well.”
This story has been corrected: Ammonia is not a hydrocarbon.