Snail mail. Rolodexes. Boomboxes. We’ve given up the familiarity of the past for the promise of the future. But is the same happening in the chiller industry? Is the push for lower global warming potential (GWP) refrigerants changing the industry as we know it? In some ways, yes. But, in the United States in particular, the change may be more gradual than it appears at first glance.
As the industry has moved away from chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) – with their ozone-damaging chlorine molecules – something has had to take their place. Since then, the three major players have been hydrofluorocarbons (HFCs), natural refrigerants, and hydrofluoroolefins (HFOs). Each comes with its own unique set of pros and cons.
So what’s next? With three contenders in the ring, is there a clear-cut winner? Let’s take a look.
The commercial chiller and cooling game changed as soon as scientific evidence linked certain refrigerants to environmental detriments. Since then, both commercial chiller manufacturers and the companies that rely on them have had to consider not just the efficiency and cost of a refrigerant, but also its ozone depletion and global warming potential. In addition, different refrigerants can need different lubricating oils, which are important for long operation.
The change wasn’t just pushed by a general sense of wanting to protect the environment, either. The Montreal Protocol, which went into effect in 1987, mandated the phaseout of CFCs by 1996. As HCFCs were also linked to environmental degradation, the Montreal Protocol was amended to include their gradual phaseout, too.
Until that point, a wide range of industries relied heavily on CFCs and HCFCs as primary refrigerants in all chilling and cooling operations. The rapid phaseout of CFCs and more gradual phaseout of HCFCs created an urgent need for a refrigerant that could deliver on three fronts. It needed to be efficient, it needed to be safe for the environment, and it needed to be safe for use in a wide range of facilities and processes.
Does such a magic elixir exist? We talked to refrigerant subject matter experts to find out.
HFCs: A Step in the Right Direction
As the commercial chiller and cooling industry moved away from both CFCs and HCFCs because of their ozone-depletion factors, they searched for a replacement – and found it in HFCs. With no chlorine and zero Ozone Depletion Potential (ODP), HFCs seemed like the ideal solution to the industry’s need and the hole in our ozone layer.
That said, ozone depletion isn’t the only environmental concern. Gases, when released to atmosphere, have the potential to create an insulating effect that contributes to global warming. To measure this environmental impact, refrigerants are labeled with a global warming potential (GWP). And while HFCs don’t deplete the ozone, their GWPs are not negligible.
Take R-134a as an example. This HFC is widely used in a variety of applications. Brian Smith, Director of Global Marketing, Global Chiller Products, Building Technologies and Solutions at Johnson Controls said, “I’d estimate that the vast majority of the North American centrifugal chiller market is using R-134a.”
Johnson Controls currently uses R-134a in their 10- to 300-ton water-cooled chillers using screw compressors, 300+ ton water-cooled chillers using centrifugal compressors (they also use R-1233zd, a low-pressure HFO for this application), and 100- to 500-ton air-cooled chillers using screw and scroll compressors. Meanwhile, they’re using R-410A, another HFC, for their low-pressure (under 100 ton) scroll compressors.
With widespread usage and an ozone depletion potential of zero, R-134a seems to be an ideal refrigerant. But, upon closer examination, one discovers that it has a GWP of 1,430. And as governments (particularly in Europe), companies, and individuals feel heightened urgency to minimize environmental impact, there is some need to move away from R-134a. The U.S. Significant New Alternatives Policy (SNAP) regulated that R-134a is “unacceptable in new [chiller] equipment, except as otherwise allowed under a narrowed use limit, as of January 1, 2024.” For more about the policy, visit https://www.epa.gov/snap/substitutes-centrifugal-chillers.
SNAP was challenged and ultimately overruled on a federal level, but that hasn’t stopped the changes it put into motion. As Mark Menzer, Director of Public Affairs at Danfoss, pointed out at a breakfast Danfoss hosted at AHR, California has adopted SNAP regardless of the federal ruling.
“California is leading the way, but other states like New York, Maryland, and Connecticut have already announced their intention to start phasedown programs as well,” Menzer explains. “And the U.S. Climate Alliance, a group of like-minded state governors who banded together after the president announced the U.S. pullout from the Paris climate agreement, is also expected to make additional program announcements this year. Together, these states represent more than 40% of the US population and GDP.”
What’s more, the proposed bipartisan AIM Act would return control of refrigerant regulation to the EPA, most likely putting SNAP back in place.Between the shift in United States regulation and the global market’s move away from HFCs, it’s become clear that another solution is needed. For more about the AIM Act, visit https://www.congress.gov/bill/115th-congress/senate-bill/2448/text.
Fortunately, more and more alternatives are coming to the market all the time. Smith points out there are lower-GDP R-134a alternates that minimize both efficiency losses and the need for retrofits. Smith, even as he sees a long road ahead for R-134a, said Johnson Controls sees R-454B, an R-410A low-GWP alternative, as a frontrunner for use in its scroll compressors in the future.
HFOs: An Ideal Solution – Sometimes
In the hunt for an alternative to high-GWP HFCs, the industry has found good news. Chris Tanaka, Portfolio Leader at Trane, said, “In nearly every case where refrigeration compressors are being used, there is a refrigerant available that can accomplish zero or very near zero GWP.” Trane, specifically, has been exploring the increasing use of HFOs.
Danfoss anticipates change, and they say they’re not alone. “When we look at centrifugal chillers and low-density refrigerants, there have already been major transitions,” Jeff Staub, Director of Application Engineering at Danfoss, said.
In low-pressure applications, HFOs like R-513A and R-1233zd can be an ideal replacement for HCFCs. In medium-pressure applications, Danfoss is moving from R-134a to R-513A, another HFO. “We expect the use of R-134a to continue for the next three to five years or so, but we’re seeing the transition to R-513A,” Staub said.
Similarly, Carrier has made their water-cooled centrifugal AquaEdge and air-cooled rotary screw AquaForce 30XV chillers compatible with R-513A or R-134a. They are also offering a new centrifugal chiller called the 19DV that’s compatible with the ultra-low GWP refrigerant R-1233zd(E). The AquaForce serves applications from 140 to 325 tons and can operate in ambient temperatures from -20 oF to 125 oF. As Greg Alcorn, Vice President and General Manager at Carrier Commercial HVAC, reported at AHR 2019, “Air cooled has come a long way.”
Many of the HFOs in use today have an impressive GWP of less than 2 and, as a drop-in solution, can keep efficiency losses in most applications down to a few percent. But that isn’t true of every application. As pressure increases, the efficiency losses with HFOs can climb to upwards of 25%. When commercial chillers require a higher pressure compressor, HFOs cease to be the clear-cut winner in the category of best refrigerant replacement.
With their efficiency losses in higher pressure applications, HFOs aren’t seen as the be-all and end-all when discussing the future of refrigerants. In the ongoing hunt for a low-GWP, high-efficiency refrigerant, some companies have begun exploring natural solutions, including propane and CO2.
In fact, GWP itself is measured against CO2. The EPA explains, “[GWP] is a measure of how much energy the emissions of 1 ton of a gas will absorb over a given period of time, relative to the emissions of 1 ton of carbon dioxide (CO2).” With this natural refrigerant as our benchmark for ideal environmental friendliness, it’s no surprise that commercial chiller manufacturers are exploring CO2 and other natural refrigerants.
What’s more, other industries have driven the move to CO2. The supermarket industry, in particular, has adopted CO2 in its high-pressure food refrigeration applications. In fact, over 15,000 CO2 refrigeration applications have been installed in Europe, where regulation is driving a faster move to low-GWP refrigerants and away from previously used HFCs like R-404A. This doesn’t guarantee CO2 will have widespread adoption in industrial applications, but it’s a trend worth watching.
While natural refrigerants like CO2 are environmentally ideal and can perform in high-pressure chiller and cooling applications, natural refrigerants bring a different concern with them. As Smith points out, “In the high-pressure range, all the potential replacements are flammable.” Added to that is the issue of toxicity. So while natural refrigerants could be a path forward, they require the companies that use them to think about the safety of their facilities and, potentially, to make changes to ensure that any leaks don’t create significant hazards.
The Efficiency/GWP Interchange
Clearly, the problem of finding a perfect refrigerant is complex. On top of environmental concerns, chiller manufacturers have to consider facility safety, compatibility with existing plant equipment, and efficiency preservation. The last, in particular, is doubly important as we consider the environmental ramifications of these new refrigerants.
“If you do anything with your refrigerant to reduce efficiency, you’re increasing the carbon footprint significantly,” Smith said. Even if a refrigerant has a lower GWP, if it reduces the efficiency of the chiller, the balance may still swing toward higher environmental impact because so much of the energy used by commercial chillers, especially in the United States, is still created by coal. (The United States Energy Information Administration reports that nearly a third of the U.S.’s energy is created in coal plants.) And, when considering the fact that – in an ideal situation – refrigerant is supposed to stay inside the chiller where it has no environmental impact, efficiency seems like the more pressing environmental concern.
That’s why Smith of Johnson Controls said, “Our message and our position on our chiller products is a holistic view of the carbon footprint. Energy efficiency is really the big player. We need to do the right thing in terms of moving to these new fluids, but we need to consider the cost of energy efficiency.”
Companies who want to take a holistic approach and optimize system efficiency can look to new technology. CAREL, for example, offers an evaporative cooler that can boost the cooling capacity of chillers by 30% or more. As Roberto Sandano, CAREL’s Group Head of HVAC Marketing, said, “More and more, what matters is the complete architecture of the system rather than the efficiency of any single unit.” Integrating new technology with new refrigerants can help companies drive efficiency.
Finding the Sweet Spot
Ultimately, every commercial chiller has different refrigeration technology that is ideal for optimizing its unique parameters in terms of efficiency, safety, and cost. Sandano said, “The main difficulty is that the current refrigerants cannot offer a solution for all applications. You need to have a specific approach.”
Ultimately, there is no clear-cut winner in the hunt for an ideal low-GWP, high-efficiency, safe refrigerant. The industry will have to continue to fine-tune the solutions available today. And until an ideal refrigerant emerges, commercial chiller manufacturers and users need to stay informed so they can choose the best option based on the unique specifications of any given application.
To read similar Refrigeration Compressor Technology articles visit https://www.coolingbestpractices.com/technology/refrigeration-compressors.