Green Refrigeration

MICHAEL GARRY

Earlier this month, the Intergovernmental Panel on Climate Change, an international network of leading climate scientists, released a report declaring that global warming is “unequivocal” — removing for many people any doubt about the reality of the threat.

As users of refrigerants that contribute significantly to global warming when they leak into the atmosphere, food retailers find themselves directly involved in this widely publicized and politically charged issue.

Of course, retailers have been dealing with the environmental impact of their refrigerants for years, but this primarily has to do with refrigerants like R-22 that have a deleterious effect on the ozone layer. Faced with the eventual phase-out of R-22, retailers have been forced to begin switching to HFC refrigerants, which do not harm the ozone layer.

However, HFCs belong to a class of potent “greenhouse gases,” which trap heat in the atmosphere. The buildup of these gases over the past 50 years is now incontrovertibly linked to the global warming that scientists say is contributing to everything from melting glaciers to volatile weather patterns.

How big a role do food retailers play here? According to the U.S. Environmental Protection Agency, if the supermarket industry on a broad scale reduced leaks in its equipment, used advanced refrigeration technologies and adopted better maintenance practices, it could reduce emissions of refrigerants into the atmosphere by 1 million metric tons of carbon equivalent per year. This would be equal to taking 800,000 cars off the road. At the same time, the industry would be saving more than $12 million in operating expenses.

In another measure of retailer contributions to global warming, Wal-Mart Stores has released its 2005 greenhouse gas inventory, or “carbon footprint.” In the U.S., the company calculated that in that year it generated a carbon dioxide equivalent of 15,364,158 tons from a variety of sources, including refrigerant leaks, on-site combustion, trucks, cars, airplanes and purchased electricity. Refrigerants alone contributed 1,553,698 tons, or 10.1% of the total. Of Wal-Mart's “direct” contribution (not including purchased electricity), refrigerant leaks accounted for 41.2%.

For the moment, retailers are under no regulatory pressure to reduce their use of HFCs, although they are required to limit leaks. However, given the enormity of the global warming issue and its widespread press coverage — to say nothing of the possibility that governmental regulations on greenhouse gases will eventually arrive — some food retailers are starting to find ways to cut back on HFC usage.

In one of the newest examples of retailer action, Food Lion, Salisbury, N.C., last month became the second U.S. retailer to test a low-temperature “secondary loop” refrigeration system, which employs 60% less HFC refrigerant (R-507) than a conventional system, an initial savings of 300 pounds. At the test site, a store in Montpelier, Va., the R-507 is confined to the machine room, while liquefied carbon dioxide circulates through the store to refrigerate freezer cases and walk-in freezers. The system, called Second Nature, is provided by Hill Phoenix, Conyers, Ga.

Food Lion, frequently recognized by the EPA's Energy Star program, is also testing a medium-temperature Second Nature system that uses propylene glycol as the main coolant at a year-old store in Dinwiddie, Va. The retailer plans to pilot both medium- and low-temperature secondary loop systems at a store in Portsmouth, Va., scheduled to open in early 2008.

By using a relatively small amount of HFC refrigerant and relying primarily on carbon dioxide or propylene glycol, the secondary loop systems reduce the escape of greenhouse gases. “You hear about global warming every day now,” said Susan Sollenberger, Food Lion's director of equipment purchasing, maintenance and energy. “There are no regulations on global warming yet, but I believe they will be coming. It's nice to be prepared.”

Though carbon dioxide is itself the primary greenhouse gas responsible for global warming, its global warming potential (GWP) is far less than that of refrigerants. For example, carbon dioxide's GWP is 1, while R-507's is 3,850. In addition, commercial carbon dioxide is produced in part by removing it from the air.

Of course, for the secondary loop systems to become a viable alternative for Food Lion, the chain will need to confirm that their energy consumption and total cost of ownership are favorable. “We want to see what it would take to convert to this type of refrigeration system,” said Sollenberger. Meanwhile, in its conventional direct-expansion (DX) systems, Food Lion is using R-507 in new stores and is converting from R-22 to R-507 in existing stores.

The same low-temperature secondary loop system was installed at a Sam's Club in Savannah, Ga., in August 2006, the first U.S. store to receive the system. The Sam's store is expected to save 6,448 tons of carbon over 10 years as a result of the system's reduced refrigerant charge and leak rate, according to Hill Phoenix.

In addition, the Sam's low-temperature system has been able to save that store 239,000 kilowatt-hours of energy on an annualized basis by running at a higher “saturated suction temperature” (minus 21 degrees F vs. minus 27 degrees F) and using compressors, condensers and pumps that consume less energy, said Hill Phoenix.

The low-temperature secondary loop system at Food Lion has become the focus of a new EPA initiative. Dubbed GreenChill, the initiative is seeking the participation of food retailers willing to test environmentally friendly refrigeration systems and take other steps to reduce greenhouse emissions and preserve the ozone layer.

A GREENCHILL PARTNER

Food Lion last month became one of the first U.S. food retailers to join the GreenChill partnership, in a signing event at the Montpelier store. As part of the program, the chain agreed to participate in research to assess the performance of the low-temperature secondary loop system at the store. Food Lion also pledged to maintain an “inventory” of its leak-induced refrigerant recharges, and to equip all new stores and upgraded stores with ozone-friendly refrigerant.

The EPA is hoping that the GreenChill program will lead to “broad adoption of advanced refrigeration systems that are ozone-friendly and significantly reduce emissions of greenhouse gases,” said Jeff Cohen, manager of the EPA's Alternatives and Emissions Reductions program. In combination with leak reduction and improved maintenance, the adoption of new technology would lead to the EPA-estimated reduction of 1 million metric tons of carbon equivalent per year.

The secondary loop system is “a technology we want to promote [because] it will have much smaller refrigerant emissions,” Cohen told SN. However, the system will have to pass muster in evaluations of energy efficiency by industry and government experts. “If the technology is a winner, that's the best way to propel it in the market,” he said.

Besides Food Lion and Sam's Club, another six food retailers plan to test the low-temperature system over the next six months, according to Scott Martin, director, sustainable technologies, Hill Phoenix. Loblaw Cos., Toronto, has confirmed it is one of the six retailers.

Other retailers have told SN that secondary systems are under consideration. “We are evaluating [carbon dioxide secondary systems] as well as other options, as we recognize that ultimately our objective needs to be to minimize the HFC charge in the store,” Kenneth Welter, manager, refrigeration engineering, Stop & Shop, said last fall in an email. Supervalu “is just starting to look at carbon dioxide systems,” emailed George Ronn, manager, EPA compliance and system controls, Supervalu.

In evaluating the costs of the low-temperature secondary loop system, Food Lion has found its initial cost to be “slightly higher” than a conventional direct-expansion system, noted Sollenberger. In addition, Food Lion has invested in a backup generator for the system to ensure that the carbon dioxide remains fluid and at low pressure.

“If you have an extended period where you lose power, you couldn't keep the pressure down and you would have to vent the [carbon dioxide] charge into the atmosphere,” said Ted Gartland, director of refrigerant and regulatory compliance, Verisae, Minneapolis, which markets maintenance-automation and asset-management software.

Another issue Food Lion is addressing is its maintenance technicians' lack of experience with secondary loop systems. “We have to make sure they're comfortable with it and understand it,” said Sollenberger.

On the other hand, Sollenberger acknowledged that the cost of carbon dioxide is far less than that of the HFC refrigerant. While conventional refrigerant runs between $8 and $9 per pound, carbon dioxide costs only 50 cents per pound. Moreover, by using carbon dioxide, the secondary loop system can employ thinner copper piping. At Food Lion's Montpelier store, this resulted in a 50% reduction in the weight of copper pipe used in the store, a savings of 1,040 pounds, said Hill Phoenix.

In testing the secondary loop systems, Food Lion has been able to consult with its parent company, Brussels-based Delhaize, which uses both medium- and low-temperature secondary loop systems. Because of greater regulatory pressures in European countries, retailers there are much farther ahead of U.S. retailers when it comes to using advanced refrigeration systems.

In fact, some European retailers use carbon dioxide not as a secondary refrigerant, but as the primary refrigerant in what are called subcritical systems. Compressors for these high-pressure systems and related transcritical systems have not been approved by Underwriters Laboratory for use in the U.S., though approval is expected to come soon, said Martin of Hill Phoenix.

LOBLAW'S EXPERIENCE

Though Food Lion is still evaluating its medium-temperature secondary loop system, Loblaw has been using these systems for six years, and now has them at 50 of its stores, according to Mark Schembri, vice president of maintenance and equipment purchasing. “Our strategy is to incorporate secondary systems in our new full-service conventional supermarkets,” he said.

In September, Loblaw plans to install its first low-temperature secondary loop system incorporating carbon dioxide in a store that will also feature a medium-temperature secondary system, Schembri said.

The biggest impact of the medium-temperature secondary system has been a “significant” reduction of conventional refrigerant charge, said Schembri. This in turn has resulted in a reduced leak potential compared to medium-temperature systems at other stores. “If there is a leak [of conventional refrigerant], it's isolated to the compressor room and it's easier to detect,” he said. Elsewhere in the store, propylene glycol, as a liquid, is easy to spot when it leaks.

Another advantage of the medium-temperature secondary system is that because the cooling process involves a smaller temperature difference than in a DX system, there is less of a drying effect on food such as service deli and meat, Schembri said. As a result, shrink of these products has been reduced, he added.

The system is also able to defrost cases at a lower temperature, resulting in less temperature fluctuation for the food in the case, said Hill Phoenix's Martin.

By using propylene glycol as a secondary coolant, the medium-temperature system is able to employ ABS plastic piping instead of copper piping, reducing maintenance and energy costs. Sam's Club in Savannah and Food Lion's Dinwiddie store both use the ABS piping, and Loblaw expects to employ ABS piping in September in medium-temperature equipment in the same store where it will install its first low-temperature secondary carbon dioxide system.

The cost of the secondary equipment is slightly higher than that of DX equipment, while installation cost is comparable, Schembri said. But with ABS piping, he expects those costs to be less than those of a DX system. The energy consumption of the secondary system has been about on par with that of a DX system, he said.

Though Loblaw's contractors were apprehensive about the secondary system when it was first installed, they have become accustomed to it, and in fact report that it requires less maintenance than traditional systems, Schembri said. “It's a simple system. It doesn't have as many variables as a DX system,” he noted.

ANOTHER OPTION

Secondary loop systems are not the only alternative refrigeration systems retailers are looking at. Another important option is distributed compressor systems, which are small racks located close to food display cases in order to shorten the connecting refrigerant lines. Distributed systems, which have been available in the United States for about a decade, also fall under the advanced systems being evaluated in the EPA's GreenChill program.

Because of their proximity to display cases, distributed systems reduce the amount of refrigerant charge required as well as the amount of energy consumed in the cooling process, said Bryan Ware, product manager, refrigeration systems, Hussmann Americas, Bridgeton, Mo., which manufacturers the Protocol distributed system. The Protocol system experiences low leak rates — 5% or less of refrigerant — because of the reduction in brazed joints and limited vibration.

Unlike conventional refrigeration compressors or even secondary loop systems, distributed systems don't need to be housed in a separate motor room.

“You place distributed systems where you couldn't put anything else — over a cooler or freezer or on a part of the floor that can't be merchandised,” said Ware. The average supermarket would use between six and eight distributed systems. The current base of refrigeration technicians are more familiar with distributed systems than other alternative technologies, he noted.

Popular in Europe, distributed systems have been attracting renewed interest in the U.S. over the past three years as a result of cost increases for refrigerants, energy and installation, as well as the growing awareness of global warming, said Ware.

According to Hussmann, more than 5,000 Protocol units have been installed in hundreds of U.S. supermarkets for full-store and remodel applications.

Plugging the Leaks

There's a very simple solution to the environmental problems posed by in-store refrigerants, one that would obviate the need for alternative refrigeration: Prevent all the leaks in refrigeration equipment.

“From a purely factual and technical basis, a well-designed, leak-free and hermetic HFC system can be better than any carbon dioxide system from an environmental impact point of view,” said Rajan Rajendran, director, application engineering, Emerson Climate Technologies refrigeration division, St. Louis.

But preventing leaks is no trivial assignment, given the temperatures and pressures refrigeration piping endures on a daily basis. Leak rates for conventional direct-expansion systems still average 20% of initial refrigerant charge or higher, said Jeff Cohen, manager of the Environmental Protection Agency's Alternatives and Emissions Reductions program.

Yet refrigeration manufacturers have made strides in developing systems less prone to leaks. “In 2005, our leak rate was less than 1% of what it was in 2001,” said Scott Martin, director, sustainable technologies, Hill Phoenix, Conyers, Ga.

Some retailers have been helping manufacturers by anonymously submitting leak data to an ongoing study conducted by the Food Marketing Institute and the Commercial Refrigerator Manufacturers Division of the Air-Conditioning and Refrigeration Institute. Retailers are encouraged to submit their data at www.ari.org.

Of course, retailers are required under the Environmental Protection Agency's Clean Air Act of 1990 to repair, replace or retrofit their refrigeration system within 30 days if they have an annual leak rate of 35% or more. New leak regulations to be proposed this fall may lower the 35% maximum, said Cohen.

Individually, retailers are pursuing preventive maintenance programs. Food Lion, Salisbury, N.C., performs leak checks at least four to six times annually, said Susan Sollenberger, Food Lion's director of equipment purchasing, maintenance and energy. As a result, “our refrigerant expenses are less today than they were in the late 1980s,” despite the dramatic jump in the price of refrigerants, she said.

Hy-Vee, West Des Moines, Iowa, has been using software from Verisae, Minneapolis, to more precisely describe and narrow down the location of its leaks, employing standard terminology shared by other retailers. “We'll have consistency in our chain, with all of our contractors using the same leak locations,” said John Scanlon, Hy-Vee's service administrator. “We'll have a better grasp of what our leak rate is.”

Scanlon said he plans to share leak data gathered through this process with the FMI-CRMD study.
— M.G.