If there’s anything that consumers take for granted in the supermarket, it’s refrigeration. So they are not likely to notice that the systems they rely on to keep products chilled and frozen are beginning to change in profound ways. Retailers, of course, don’t have that luxury.
Many of these changes are being driven by the Achilles’ heel of commercial refrigeration — leaks of refrigerant gas into the atmosphere. These leaks, of course, have caused supermarkets to be subject to regulations by the U.S. Environmental Protection Agency; the rules have particularly targeted refrigerants such as R-22, a hydrochlorofluorocarbon (HCFC) that has a directly harmful effect on the atmosphere’s life-preserving ozone layer.
Food retailers have been replacing R-22 with hydrofluorocarbons (HFCs) that do not contain chlorine and leave the ozone layer alone. This transition away from R-22, years in the making and in conformance with an international environmental treaty (the Montreal Protocol), picked up steam last year when the EPA put a stop to the use of new or imported R-22 with new equipment; by 2020, new R-22 will be forbidden for all refrigeration equipment.
But the considerable effort retailers have been making to switch to HFC refrigerants is hardly the end of the story, noted several retailers at a recent Refrigeration Roundtable co-hosted by SN. Because HFCs have an extremely high global warming potential (GWP) — meaning they have a pronounced impact on climate change, thousands of times greater than that of carbon dioxide — they have provoked a worldwide backlash. Already major European retailers are seeking to replace HFCs with so-called “natural refrigerants” that neither disturb the ozone layer nor contribute significantly to global warming; these include carbon dioxide (R-744, which is natural carbon dioxide, not the kind produced by burning fossil fuels), ammonia (R-717) and hydrocarbons like propane (R-290).
In the U.S., retailers are under no mandate to limit the use of HFC refrigerants but a growing number believe the tide is turning against HFCs. In California, for example, the Air Resources Board began implementing rules this year governing the maintenance of refrigeration systems with more than 50 pounds of high GWP refrigerants such as HFCs. As a result, more retailers are sensing that they will eventually need to employ different refrigerants and refrigeration systems to ensure that they are not adversely affecting the environment — and not putting their companies at risk of having to make costly changes on the fly. Some retailers, particularly those that have joined the EPA’s voluntary GreenChill program, are beginning to test these new refrigerants and systems.
On Sept. 22, representatives of five supermarket chains and four refrigeration contractors discussed their experiences with alternative refrigerants and refrigeration systems as part of a Refrigeration Roundtable in Indianapolis hosted by SN and ContractingBusiness.com (both published by Penton Media, New York). The event, the second such roundtable hosted by the two publications, was sponsored by Hill Phoenix, Conyers, Ga., and Emerson Climate Technologies, Sidney, Ohio. (Other aspects of refrigeration discussed at the roundtable will be covered in future issues of SN.)
The supermarket participants in the roundtable included: Sam Cantrell, mechanical engineer, Raley’s Supermarkets, West Sacramento, Calif.; George Ronn, senior manager, refrigeration compliance and system controls, Supervalu, Minneapolis; Jerry Stutler, vice president of construction and facility engineering, Sprouts Farmers Market, Phoenix; Steve Hagen, procurement and engineering director, Fresh & Easy Neighborhood Market, El Segundo, Calif.; and Gary Cooper, director of refrigeration, Lowe’s Market, Littlefield, Texas.
The contractor participants included: Bill Almquist, president, Almcoe Refrigeration, Dallas; Bryan Beitler, vice president/chief engineer, Source Refrigeration & HVAC, Anaheim, Calif.; Russell Dudan, chief executive officer, Advantage Refrigeration, New Berlin, Wis.; Richard Adkins, sales and marketing, Advantage Refrigeration; and Neil Lansing, owner, Fournier AC & Refrigeration, Jacksonville, Fla. Also participating were Dave Smith, systems specialist, Hill Phoenix; and Tom McFarlane, regional sales manager, West Coast, Hill Phoenix.
Some of the roundtable panelists have embarked on a serious exploration of alternative systems and refrigerants. Fresh & Easy’s Hagen, who is testing a host of alternative options, was particularly bullish about the prospects of the transcritical refrigeration system, which uses only carbon dioxide and not HFCs.
“I’m very convinced that 10 years from now, every supermarket in America is going to be installing transcritical CO2 systems,” he said. “I just think that after test after test in Europe, Canada and Australia and around the world, everybody is ending up at that single defining point — that it’s the best alternative among all of the other technologies.”
He referred to Sobeys, Stellarton, Nova Scotia, which is installing only transcritical systems and has achieved lower initial and maintenance costs for those systems than for conventional direct expansion (DX) systems.
But Cantrell of Raley’s took a more skeptical position on the new technologies. He acknowledged that retailers may eventually face regulations on carbon emissions and be forced to switch from traditional DX refrigeration to alternative systems. But he does not welcome that scenario.
“I really think that’s going to be a tragedy if that happens,” said Cantrell. “You think about the DX technology and all of the body of experience and knowledge about direct expansion refrigeration that exists. I mean, it was invented prior to the car, and that’s a huge amount of experience and knowledge that’s going out the window. In its place we’re getting these new technologies. And who knows? There’s a new bogyman, I’m sure, waiting in the wings to appear after the global warming thing has run its course, and then we’re all going to be moving on to the next thing. I would rather see us getting better at what we know.”
Finding the Right HFC
One area of consensus among supermarket panelists is that they are all in various stages of transitioning away from R-22 to some form of HFC, particularly refrigerants like R-407A and R-407F that have somewhat lower GWP ratings than typical HFCs.
Stutler of Sprouts, for example, said the chain is converting more stores every year from R-22 to R-407F, an HFC with a GWP of about 1,705 (or 1,705 times that of carbon dioxide), compared with a GWP of 3,300 for R-404A. Rather than just stockpiling R-22, he has starting getting rid of it, something he suggests other retailers start doing to avoid having “an abundance of R-22 sitting around.”
Fresh & Easy initially switched to R-407A (GWP of 1,990) but is now using R-407F. For Hagen, the biggest challenge in refrigerant conversions is that compressor manufacturers have not yet rated their compressors for the new refrigerants. As a result, he and other retailers “end up putting in refrigerants that technically void the warranty,” he said. “Usually you can get the refrigerant manufacturer to pick up that risk, but in the meantime you’re putting gas in the compressor racks that haven’t been specifically designed for it.” Even so, he added, that doesn’t pose any issues “other than you’re doing it kind of before the curve.”
In addition to GWP, Fresh & Easy has looked into Total Equivalent Warming Impact (TEWI), which combines emissions and the energy component of a refrigerant to produce the total contribution to global warming. “Some of the advantages of 407A and 407F are that they’re proving to be more efficient in operation,” he said. “So not only are you reducing the GWP on the refrigerant, you’re also saving energy, which hasn’t always been the case with your refrigerant options.”
For Beitler of Source Refrigeration, using refrigerants that have the lowest GWP is one preference in R-22 conversions, along with using the minimum amount (charge) of refrigerant. “The greatest challenge is not just to drop [refrigerant] in but to perform the engineering analysis up front to specify the correct refrigerant type and proper modifications, which might affect efficiency, reliability and leak rates,” he said.
Cooper of Lowe’s Market is transitioning away from R-22 mostly with store remodels and case change-outs. “While the [conversion] problems associated with oil and system contamination can be an issue, we plan to continue with other rack systems as well,” he said. He regards refrigerants such as R-407A and R-407F as good alternatives for medium-temperature systems, “though the capacity issues make them seem limited for low temp.”
Raley’s stopped doing R-22 conversions about two years ago, said Cantrell. Less than 5% of the chain’s total gas inventories is R-22 now, with a “huge stockpile” of recovered R-22 at its maintenance facilities. “We were anticipating this great shortage of gas and it being a really valuable commodity,” he said, though R-22 has turned out to be about $3 per pound less expensive than R-404A.
Raley’s chose to convert to R-404A, which has a high GWP of 3,300, “before any of this global warming nonsense happened,” said Cantrell. “It’s frustrating, because 404A is still such a great gas for our systems.” He pointed to such qualities as energy efficiency and the low “head heat.” “We have such a low amount of maintenance in our newer systems with 404A because in that highest pressure, highest heat part of the system, you’ve got this gas that runs so cool. It really does help with the life of the equipment.”
Still, Cantrell acknowledged that Raley’s would eventually have to make a change from R-404A. “I think a lot of chains are waiting to see what this next great gas is going to be that’s going to maybe leapfrog you over the HFC issues,” he said. He cited HFO-1234yf, a hydrofluoro olefin that has a GWP of 4, as a possibility if its cost can come down (though it has so far been approved by the EPA just for use in automobile air-conditioning). Stutler noted that HFOs may be affordable in systems like the cascade where the amount of HFC required is low.
Variety of Options
While DX remains the refrigeration system of choice and tradition for most food retailers, the need to reduce use of HFCs is driving interest in a variety of alternative systems. One popular alternative is the distributed system, which uses multiple DX-type mini-systems around the store. Other alternatives, such as secondary, cascade and transcritical, rely in part or in whole on carbon dioxide (GWP of 1). Still more exotic possibilities include ammonia as a primary refrigerant and propane as a refrigerant for self-contained cases.
The distributed refrigeration system is probably the most widely adopted alternative option. Rather than concentrate all of the compressors and other refrigeration equipment in one machine room in a store, the distributed system is split up into several units located around the store, close to the freezers and refrigerated cases they service, saving on construction costs and cutting down on the total amount of refrigerant required.
Sprouts, with stores that average 25,000 square feet, uses two distributed systems, mostly along the perimeter, on top of walk-in coolers on either side of a store. “It reduces the amount of refrigerant, but it’s going to increase the amount of equipment,” said Stutler. “For our footprint, I think distributed is a simple answer.”
Supervalu has also made a hybrid distributed system — one with a secondary component — standard for its full-size stores (excluding Save-A-Lot), said Ronn. The distributed system combines a DX low-temperature side with a medium-temperature glycol side. “We don’t build new conventional DX [stores] anymore,” Ronn said. In its typical store design, Supervalu has three of these distributed units in the backroom (including one near the bakery or deli area), as well as one on top of the meat cases, one on top of the walk-in boxes for frozen food, and one on the other side of the store. (Not all units may be used in the same store.)
Distributed systems can pose a challenge to contractors, noted Beitler. It can complicate the service process “by having key components on the roof and not part of the indoor equipment package.”
Cantrell cast doubts on the effectiveness of distributed systems. “Maybe there are store formats where distributed systems make sense,” he said. “But for us, what you’re really afraid of with refrigerant leaks is gas that leaves the system, and gas leaves the system through potential leak points. If you triple or quadruple the amount of moving parts in a store with distributed systems, then you’ve tripled or quadrupled the amount of leak points.”
Secondary systems are another increasingly popular option. As in Supervalu’s hybrid distributed system, they typically employ glycol as the cooling agent for medium-temperature cases (such as dairy, fresh meat) and carbon dioxide as the cooling agent for low-temperature (frozen-food) cases, with a downsized amount of HFC in the compressor room.
Adkins of Advantage Refrigeration, for example, observed that some of his retail customers have been converting most of their medium-temperature fresh meat service cases to a secondary glycol system. “I suspect that is for numerous reasons, but one is the freshness and the integrity of the product that they achieve,” he said.
But some retailers have observed paying an energy premium for glycol systems. Fresh & Easy plans to install a compact chiller CO2/glycol secondary system in the next few months, but Hagen projected that the system, which uses about 72 pounds of R-404A, will be a few percentage points higher in energy cost. “You always pay a penalty in energy for glycol,” he said.
Raley's has one secondary system that’s uses R-404A as the primary refrigerant and liquid CO2 and glycol as secondary refrigerants. However, the system is “considerably more expensive, has a significantly higher service cost and uses about 3% more energy,” said Cantrell. “So really there’s no incentive in my mind for pursuing this. I understand it was a good experience to get our minds around what was involved if we were forced into it — if DX just becomes cost-prohibitive because of regulations.”
Succeeding With Cascade
Retailers in the roundtable reported having successful tests of cascade refrigeration systems. This system may vary in design but often combines a conventional DX system (for low-temperature cases) and a secondary system (for medium-temperature), with carbon dioxide as the cooling agent circulating though all display cases; it uses a relatively small amount of HFC.
A Sprouts store in Thousand Oaks, Calif., which received a GreenChill platinum award in April, operates a carbon dioxide-based cascade refrigeration system from Hill Phoenix. The system has 235 pounds of HFC refrigerant (R-407F) confined to the motor room, compared with 2,000 in Sprouts’ original systems and 600 to 800 pounds in the distributed systems currently used. The cascade system benefits from the low cost of carbon dioxide — about $1 per pound vs. $10 to $12 a pound for R-407F.
Since it was installed in late April, the cascade system “has operated flawlessly,” Stutler said. While the initial cost of the equipment exceeds that of a conventional system, “if we can get more of the supermarket GreenChill partners to jump on this bandwagon, we would hope that the cost of this system would be reduced.”
Sprouts’ cascade system is consuming a higher amount of energy than a traditional DX system, but it is still in the test phase, Stutler said. “Even if you’re 5% higher, with the reduction of the HFC refrigerant that you pulled out of the store, the carbon footprint reduction far outweighs the energy increase.”
And given the tendency of systems to leak, “I believe over time that there’s going to be a payback on the [cascade] system with the reduction of refrigerant,” he said. All things considered, he added, “If it were up to us, all of our stores would be cascade going forward.”
Fresh & Easy also operates a carbon dioxide-based cascade system. Unlike Sprouts, Hagen noted that the cascade system is about 5% more efficient than the chain’s current DX system design. In terms of maintenance, the cascade system was “not the most flawless or problem-free installation to start with,” said Hagen. However, since changing the pressure on a couple of valves, “I don’t think we’ve had a service call in the store in 90 days.” Carbon dioxide systems, he added, “are really proving to be very reliable and almost bulletproof in their normal operation.”
Source Refrigeration installed the Fresh & Easy cascade store, and from a contractor’s standpoint, “it was a good learning experience,” said Beitler. “We used different tools, hoses and gauges. We bought a helium leak detection system,” he said. He also employed different wall-thickness tubing, charging techniques, operating pressures and fixture piping criteria. “These are not terribly unique but do require a different level of training commitment.”
Transcritical systems, which are based on DX technology with very high pressures (up to 1,200 pounds per square inch), use only carbon dioxide.
Fresh & Easy has a transcritical system slated for next year, Hagen said. “For us, it’s about testing what’s available so that when R404 or R407 is $80 a pound we know which way we want to go, instead of losing millions of dollars while we’re trying to figure out where we’re going.”
Hagen sees a bright future for transcritical systems as manufacturers “overcome the few minor UL [Underwriters laboratory] issues” pertaining to high pressures. “Transcritical is really just another refrigeration system,” he said. “It doesn’t really work significantly differently. It’s just about being able to live with the high pressure.”
Stutler observed that only a very small portion of transcritical systems run on high pressure, “and the majority of it will be running at the same pressures that a typical cascade CO2 system will run at.”
Hagen acknowledged that transcritical systems work better in colder climates. “It’s not going to be very applicable in a desert,” where cascade systems may need to be used to keep pressures down, he said. Elsewhere there will be variance in energy usage. “In San Francisco, you’re going to save energy over a DX system. But in Atlanta, you pay a small premium in energy. I think some of that will probably get worked out to make it more efficient over time.”
Ammonia and Propane
Despite its notorious pungent odor, ammonia, one of the very first chemicals ever used in refrigeration, is also being considered as a possible replacement for HFCs by some roundtable panelists.
Supervalu is building a store in California that will be its first to employ ammonia as a primary refrigerant and CO2 and glycol as secondary refrigerants. Fresh & Easy’s ammonia/CO2 system, scheduled for early next year, will be the chain’s first to not have any HFCs. Hagen estimated that the ammonia system, like the cascade system, will be about 5% more efficient than a DX design.
In many applications, ammonia is contained in seven or eight roof-mounted modules, each containing about 9 pounds, mitigating the risk of a major leak. The small amount of refrigerant enables stores to evade most codes, but Ronn urged retailers testing ammonia to alert local authorities and neighbors of its presence. “You always have the possibility of air inversion or fog that’s going to hold the odor if you have a leak, but the amount of ammonia involved is not enough to be considered toxic unless in a confined space,” he said. “In most instances, even if there were a leak, ammonia is lighter than air anyway, so it’s going to rise.”
On the other hand, noted Cantrell, “all it takes is one busybody neighbor to start raising hell about health problems and trying to take you to court because they’re saying that their kids are having problems because there’s ammonia in the air.”
Another somewhat controversial refrigerant is propane, which Fresh & Easy is testing in small quantities (4.1 ounces) in self-contained coffin cases from AHT. Among propane’s advantages are that it is reported to be more energy-efficient than refrigerants such as R404A, has a GWP of only 3, and is only $2 per pound.
“I think [propane] is probably the future for small self-contained cases,” said Hagen. Fresh & Easy is authorized to test self-contained propane equipment via the EPA’s Significant New Alternatives Policy (SNAP) program, but the chain has limited its trial until the final rules for the use of this refrigerant are released.
While propane as a refrigerant raises safety concerns due to its flammability, Hagen believes it is safe in limited quantities in cases. “It is definitely more flammable than the other refrigerants but almost everybody in America has a five-gallon propane container in their barbecue grill,” he said. “And if you walk into any Wal-Mart or a Target, and you walk to the camping section, they have 50 or 100 14.1-ounce propane cans in a self-contained case. The ones we use have 4.1 ounces.”
Stutler, however, pointed out that “you typically don’t have a refrigeration contractor with a torch running around on the shelves of a Wal-Mart, but you may have one at a case that has propane in it.” Hagen countered that in Europe retailers are using a stronger enclosure in propane cases. “But you definitely have to train technicians about what’s there because they tend to put torches on things they shouldn’t.”
With all of the refrigerant and refrigeration options available, Raley’s continues to prefer a DX system that it designed about 15 years ago and has gone through several revisions since then. Commercially available via Hill Phoenix, the system employs an open drive with big industrial compressors and a single pipe loop. It uses about 25% less refrigerant than conventional compressors, consumes 10% to 20% less energy and saves 30% or more on service, said Cantrell. “It’s really hard for us to give that up to try something unproven.”