In a rare display of bipartisan climate action, the Senate ratified the Kigali Amendment last week. The U.S. joins 137 other nations in the global effort to curb the use of hydrofluorocarbons, or HFCs. Now the race is on to replace them for climate tech startups and traditional HVAC and refrigeration companies alike.
Most HFCs have a global warming potential (GWP) more than 1,000 times that of carbon dioxide — though some are as much as 14,800 times more potent — which makes reducing them a high priority to protect the climate. The treaty mandates that the U.S. and other industrialized nations decrease their use of HFCs to roughly 15% of 2012 levels by 2036.
As HFCs begin to fade from use and the world turns to other chemicals to stay cool on a rapidly warming planet, it’s incumbent on refrigeration tech companies to not repeat past mistakes.
The 1987 Montreal Protocol phased out the use of chlorofluorocarbons once it became clear that they were creating an immense hole in the ozone layer. It was the first treaty in United Nations history to receive universal ratification, and it is often viewed as a template for international climate action. However, the cooling industry largely replaced the offending CFCs with HFCs, which have helped fix the ozone hole but worsened the climate crisis.
“Now, as HFCs are phased out, we need to learn from the past that it’s not enough to ban the problem — we also need to pave the way for a better alternative,” said Vincent Romanin, the CEO of the window heat pump company Gradient, which currently relies on the low-GWP HFC called R32 (a mouthful), but is considering using natural alternatives going forward. Gradient’s units are available for pre-order but have not yet hit the market.
Manufactured hydrofluoroolefins (HFOs) are among the most popular alternative refrigerants available, though they come with concerns about their environmental impact because they break down into another chemical that is increasingly building up in water systems. The exact impact of that chemical is unknown, and more research is needed as to its long-term effects on human environmental health. Romanin expressed particular concern about the environmental and human health consequences of trifluoroacetic acid, saying it “is toxic to marine life, can be hazardous to human health, and can’t be removed using traditional desalination techniques.”
However, HFOs have taken a hold anyway, not only because they are very good at what they do, but also in part because they are patentable in a way that natural refrigerants like ammonia or isobutane are not.
Finding a substance that both sates the growing need for cooling and avoids potential climate or environmental degradation is no small task, though. The ideal refrigerant, according to air-conditioning startup Blue Frontier CEO and co-founder Daniel Betts, would manage to check a number of boxes at once. Among them are being nontoxic, nonflammable, and non-ozone-depleting, as well as possessing a low GWP, the right thermodynamic and flow characteristics, and, crucially, no smells. That’s a long checklist, and ticking all the boxes will require both investment and time.
In the absence of a one-size-fits-all refrigerant, however, the industry will have to take a case-by-case approach to using natural options. Iain Campbell, a senior fellow in RMI’s carbon-free buildings division, said that substances with different strengths “have to be matched to the profile of the application.” For instance, leaks are common in automotive cooling, so “low GWP and low toxicity are [the] most critical attributes to consider.”
And in the meantime, startups in the HVAC space are each taking their own approaches to solving the coolant puzzle. On Gradient’s website, for instance, the company says it is considering moving toward refrigerant-grade propane (R290) in its heat pumps, as the “very efficient and environmentally friendly solution” is gaining popularity internationally.
However, industry standards have prevented its adoption in the U.S., and so Gradient remains in a holding pattern. Those standards are actually already being reviewed and updated, but Romanin said it is a complicated process involving a slew of industry and building code organizations, so while a change is expected, it could be years before R290 and other similar options get the green light for use in the U.S.
Meanwhile, Blue Frontier’s unit, which is still under development, “uses a salt solution to generate air conditioning, with only a small amount of refrigerant used to regulate the concentration of this salt solution,” according to Betts.
Other technologies like solid-state cooling, which uses thermoelectric technology and a mix of water and carbon dioxide, could help keep things chilled without any refrigerants at all. The use case is especially compelling for transporting vaccines or groceries, though it would require a more thorough rework of how cooling has always been done. Tony Atti, CEO of the cooling company Phononic, said the technology could eventually have “several advantages over traditional mechanical methods of refrigeration.”
While the path to sustainable cooling might be a winding one, Campbell said it’s one we’re well prepared to travel.
“The bottom line is that today there is a refrigerant with a GWP below 150 … for every application,” he said, though only roughly 10% of the coolants on the market fit that bill. “We do not need to wait for the discovery of an ‘ultimate’ coolant in order to make the transition to dramatically more sustainable coolants.”
