This article discusses design and developments in the refrigeration and compressor fields to deal with Montreal Protocol’s announcement of expiration of R-22 as refrigerant. The Montreal Protocol dictates that by 2010 no new refrigerators or air conditioners will use R-22, a hydrochlorofluorocarbons (HCFC), as a refrigerant. The replacement, known as R-410A, is an HFC (hydrofluorocarbon) rather than an HCFC. Jim Crawford, director of regulatory affairs at The Trane Co., a heating and air conditioning company in Tyler, Texas, said that industry is adopting R-410A primarily in air conditioning. Companies like Trane have used the time allotted by the Montreal Protocol to design, test, and build R-410A equipment for 2010. Compressors have had to be optimized both for the refrigerant and the application. Since the heat characteristics are different between the two refrigerants, heat exchangers must be made larger or smaller. Many new air conditioners, like Trane’s XL16i, already use R-41OA, which contains no chlorine.
By international agreement, industry around the globe is preparing to stop using the last refrigerants that threaten Earth's protective ozone layer. But the question of what to replace them with turns out to be a bit more complicated than it might seem at first. A one-far-one swap won't be enough, according to some experts. The very rules that have gone a long way toward preserving the ozone that blocks much of the sun's ultraviolet radiation are encouraging the use of refrigerants that may contribute to global warming.
The Montreal Protocol was an international effort to deal with what was once a growing ozone hole. Drawn up in 1987 and put into effect by '89, it has been a great success in phasing out refrigerants that contain chlorine, thought to be a destroyer of the ozone layer. The protocol, originally signed by 23 countries and now ratified by more than 180, immediately banned the manufacture of any appliance that used chlorofluorocarbons (CFCs), one of which was the refrigerant R-12, commonly used for automotive air conditioning and found in older household air conditioning units. Thanks largely to this initiative, chlorine levels in the troposphere, which contains 10 percent of the Earth's ozone, have stabilized, and in the stratosphere, where the ozone layer is found, they've even been measured at reduced levels.
But the protocol also addressed less egregious ozone destroyers, While CFCs can remain in the atmosphere anywhere fiom 50 to 1,700 years (65 for R-12), hydrochlorofluorocarbons (HCFCs) stay in the atmosphere between a year and a half and 20 years . Starting in 1996, use of HCFCs has been scheduled to end as well. This group of chemicals includes R-22, or Freon, which is found in refrigerators, household air conditioners, and cooling devices large and small. Although existing devices that already use R-22 and existing stockpiles of the fluid will not be banned, no new appliance of any kind can use R-22 once 2010 comes along.
But while the phase-out of both CFCs and HCFCs has certainly begun to effect change in the composition of what's above us, the future, as dictated by the protocol, holds many challenges for engineers, refrigeration manufacturers, and air conditioning repairmen alike. The 2010 deadline, to say nothing of the eventual ban on R-22 production altogether by the year 2030, looms like a massive-if melting glacier. Buy a new fridge four years from now and it'll have something other than R-22 in its tubes, If you keep your current one and puncture it while improperly defrosting your freezer in 23 years, you may not be able to refill the charge.
Manufacturers have had enough time to prepare for 2010, and an alternative has been widely accepted as the replacement for R-22 in residential equipment for the near future. The replacement, known as R-410A, is an HFC (hydrofluorocarbon) rather than an HCFC. The missing "c" is chlorine. But just how long R-410A will last as the staple of the coolant world remains to be seen.
Jim Crawford, director of regulatory affairs at The Trane Co., a heating and air conditioning company in Tyler, Texas, said that industry is adopting R-410A primarily in air conditioning, "In the US., for residential size, that's the only direction we're moving," he said. "The HFCs are part of the solution in the Montreal Protocol, but they're part of the problem in the Kyoto ProtocoL"
The European View
Bruce Hunn, director of technology at the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, said, "I have heard refrigerator/freezers run on isobutane.
And then there's that issue of global thinking. As Reinhard Radermacher, a professor of mechanical engineering at the University of Maryland's Center for Environmental Energy Engineering, sees it: "In Europe, people seem to say, 'First, we have to do what's right for the environment, and then solve the other problems.' "
The European way of thinking means that individuals take on more personal risks to reduce the risk of global catastrophe. But the individual risks may not be as great as they seem initially, according to Glenn Hourahan, vice president of research and technology at the Air Conditioning Contractors of America, a trade association.
"Yes, Americans are skittish about using flammable or toxic refrigerants," Hourahan said. "Part of it is our litigious society, but you should also keep in mind that, besides the Europeans' having a higher tolerance for risk, the equipment activities are very different. The typical European propane system contains a smaller charge than the typical US. counterpart."
Eckhard Groll, a professor at Purdue University's School of Mechanical Engineering, pointed out that the personal risk is not as great as others we take for granted. A grill on the porch deck may have seven or eight pounds of propane, while a residential air conditioning unit would have less than half a pound. And, of course, in the garage there are other highly flammable materials we take for granted. "The way we use gasoline-we grew up with it," Groll said. "In those applications, we don't give it a second thought."
Propane has no ozone depletion potential and a much lower global warming potential than hydrofluorocarbons (11 compared to anywhere from 140 to 11,700 for HFCs). The US. Air Force sponsored tests on the safety of propane as a refrigerant for its field-deployable environmental control units, which can be used to regulate temperatures in portable shelters and to make contaminated air breathable. Researchers from Mainstream Engineering in Rockledge, Fla., tested a system using propane by firing 30-caliber bullets into the condenser coil, which did not explode or catch fire.
For years, Groll's research focused on how to make CO2 both efficient and effective. It was widely used a century ago, before manmade refrigerants took over. While Groll is the first to admit that CO2 may not be most effective in a home air conditioner, he is eager to point out that "when the application calls for very compact equipment, it may be very hard to beat CO2.''
One of those applications is the automobile air conditioner. According to Groll, automotive systems have been shown to leak 50 percent of their charges over two years, thanks to the necessity of flexible hoses, the open-drive compressors with shaft seals, and continuous vibration.
"So we're releasing one pound per two years per car," he said. "Now you have to consider we have over 200 million cars on the road in the US. alone. That's about 100 million pounds of refrigerant." CO2, of course, will also leak, but as it's harvested from the atmosphere in the first place, it presents less environmental risk when it re enters the air.
Groll considers his CO2 research more or less complete. "We have investigated long and hard," he said. "We know what the fluid can do, we know what the applications are, but unless we see real applications in the field, there's not much left to do."
Not everyone agrees that such a change is necessary, or likely to happen. "I currently drive a car that is six years old," said Jim Crawford at Trane. "The air conditioner hasn't been serviced. It's not serviced every two years, and it hasn't been losing half its charge every two years. It's just not happening." Although Crawford agrees that CO2 may be the best refrigerant in certain applications, like water heating and heat pumps, as someone who works for a company that builds commercial air conditioning units, he finds it unlikely that CO2-or propane or ammonia- will be a major competitor against R-410A.
"What I see as an observer is that most manufacturers, dealers, and customers are staying with known territory to a remarkable degree, while we're all preparing at breakneck speed to effect a smooth transition to R-410A. We all have it in the field; we all have it in the market. But even the most ambitious advocates for R-410A have not moved rapidly to phase out R-22. People don't like change, I suspect," Crawford said.
Companies like Trane have used the time allotted by the Montreal Protocol to design, test, and build R-410A equipment for 2010. Compressors have had to be optimized both for the refrigerant and the application. Since the heat characteristics are different between the two refrigerants, heat exchangers have to be made larger or smaller.
In the real world, the compressors are put through a rapid series of seasons to see how they withstand the punishment of extreme weather. Each test model is placed in a simulator and subjected to temperatures ranging from deep winter freezes to desert heat. According to Crawford, Trane will alternate between heat and the cold multiple times in 16 weeks. "Wednesdays are wonderful," he said. "We have ice and snow. It's great to walk into it in the middle of summer in Texas."
Just as Europeans have deemed propane acceptable for home air conditioners while the United States has rejected it, ammonia may face a similar difference of opinion. However, there are arguments for using it in a large contributor to refrigerant leakage in the United States the supermarket walk-in refrigerator. According to Groll, "There's a tremendous amount of piping, and lots of soldering and valves, and not all the people in the field are taking good care of those connections. Studies have shown 30 percent of leakage per year, and a supermarket charge is 2,000 pounds."
Supermarket freezers are usually kept away from customers and are large enough to have a separate system for the ammonia itself. Because ammonia is a cheaper refrigerant than anything on the market except for CO2, it becomes an economical alternative to R-22. A secondary loop would be used, keeping the toxic ammonia in a separate shack outside the supermarket building. Some companies have developed a system that sprinkles water to absorb ammonia as soon as it is detected in the air. Research in the United States has shown that should there be a leak, the entire charge can be absorbed into an active carbon.
According to Groll, ammonia is not as dangerous as its reputation suggests, and it is easily detected. "The whole issue is way too dramatized," Groll said. "You can detect ammonia in one or two parts per million. It's only toxic when it reaches 1,000 parts per million. We have an excellent detection system: the human nose. Immediately, you know something is wrong and you get the heck out of there."
It's unlikely that ammonia will have any acceptance as a refrigerant in U.S. homes in the near future. Glenn Hourahan at the ACCA pointed out, " Insurance and U.S. safety and municipal codes have limited its use to commercial applications with limited exposures to occupants or building visitors in the event of accidental releases. Typically, it is used in process applications, warehouses, and so forth."
The dual-loop supermarket solution doesn't make as much sense for the home. "Perhaps you'd use ammonia in a small chiller outdoors," Crawford said. "The question is: Why did I do that? If I did it because of the global warming potential of HFC, and I have to use a second loop that reduces efficiency, have I really helped with global warming or is it a detriment? It looks like you don't break even. So will these things be decided on the basis of ideology or will they be made on the basis of science and technology?"
Harvested from the atmosphere in the first place, CO2 leakage will have no detrimental effect on it.
Many new air conditioners, like Trane's XL16i, already use R-41OA, which contains no chlorine.
No Rest for the Innovative
In the next quarter-century, we' ll have to work out which applications get which refrigerants, but for the longer term we may require greater innovation, especially if the use of HFCs is significantly limited.
Radermacher said he believes that if refrigeration were invented today, R-410A would be the refrigerant of choice. But he adds that we have to aim our scopes a little farther into the century. "We'll have to start looking at whole other ways," he said. "The alternative may not be what people expect at first glance."
Some of those ways may be better insulation and zero-energy houses. Others may be things that seem almost laughable now. "What if the screen of your computer pours out cool air? You don't need to air condition the whole building," Radermacher said. Another idea is " displacement ventilation," where the floor is elevated and perforated so cool air rises only where a person stands or walks. "Wherever you are, you take the plume with you," he said.
Despite the many alternatives available for the future, great and Sl1ull, there are plenty of knotty political problems to work out before then.
Tom Werkema, director of regulatory affairs for Atofina Chemicals Inc. in Philadelphia, said he recently attended a Montreal Proto col meeting in New Delhi and was convinced that even further reductions are needed, and soon. "Developing countries have no current HCFC reduction schedule, except for termination on January 1, 2040," he said. "In fact, they must freeze at 2015 levels in 2016, but have unlimited growth until then."
As Guy Hurdy, president of the U.K. Institute of Refrigeration pointed out, technology is not what's standing in our way: "The major hurdle will be to get users to realize the urgency of the situation."