Split Refrigeration

MICHAEL GARRY

At the Food Marketing Institute's Energy & Technical Services Conference last year, representatives of the Environmental Protection Agency unveiled GreenChill, a new partnership between the EPA and the supermarket industry.

As its name implies, GreenChill aims to find ways to marry environmental progress and refrigeration, the area of the supermarket that probably has the greatest impact on the environment. At the conference, the EPA put out a call for food retailers willing to work with the agency to test new environmentally friendly refrigeration systems that use less of the refrigerants that harm the ozone layer or contribute to global warming when they leak into the atmosphere. Participants will also closely measure and report their refrigerant leaks. EPA plans a full rollout of the program in September.

The first food retailer to join GreenChill was Food Lion, Salisbury, N.C., which announced its participation in January at one of its stores in Montpelier, Va. (Since then, Hannaford Bros., Whole Foods, Giant Eagle and Publix have signed on.) That store happened to be the test site for a “secondary loop” refrigeration system that uses far less refrigerant than conventional direct exchange (DX) rack refrigeration technology. (See story, Page 48.)

Secondary loop systems represent one of the new technologies the EPA is encouraging retailers participating in GreenChill to evaluate. Another is the so-called distributed refrigeration system, which also cuts down on the amount of refrigerant required, and therefore the amounts that might leak into the atmosphere. Rather than concentrate all of the compressors and other refrigeration equipment in one machine room in a store, distributed systems — as the name indicates — split these up into several units located around the store, close to the freezers and refrigerated cases they service.

To the EPA, the jury is still out on which is better, secondary loop or distributed. “Part of the reason for GreenChill is to voluntarily collect data on the different technologies and compare them so everyone can determine what works best for them financially and for us environmentally,” said Dave Godwin, environmental protection specialist, EPA, Washington. “We're open to both types, and others.”

So far, the only North American food retailers testing secondary loop refrigeration for low-temperature store applications are Food Lion and Sam's Club, a division of Wal-Mart Stores, Bentonville, Ark., although Loblaw Cos., Toronto, plans to install a system in September. Many more retailers are using secondary loop setups for medium-temperature applications; nearly 300 such systems are currently installed in North America. Hill Phoenix, Conyers, Ga., has been the primary supplier of these systems.

Far more retailers, though, are using or planning to use distributed refrigeration in new stores and remodels. According to Rajan Rajendran, director, application engineering for the refrigeration division of Emerson Climate Technologies, St. Louis, distributed-system installations have grown significantly, from 4% of new refrigeration systems in 2001 to 15% last year.

Rajendran predicted that the percentage will jump to 50% in 2011, if not a few years sooner. Emerson designs the scroll compressor technology used by all of the manufacturers of distributed systems, including Hussmann, Hill Phoenix, Kysor-Warren and Zero-Zone.

ON TOP OF WALK-INS

One of the retailers implementing distributed systems is Albertsons, a division of Supervalu, Minneapolis, which started installing a distributed system — Protocol, from Hussmann Americas, Bridgeton, Mo. — about a year and a half ago. The system — featuring about six refrigeration units per store, for low- and medium-temperature applications — is now running in 12 to 15 new stores, said Larry Meeker, senior manager, mechanical systems criteria, for Albertsons. One or two units have also been put in remodeled stores that added refrigeration capacity.

Most of the new stores with distributed systems have opened over the last few months, he added. All of Albertsons' banners — Shaw's, Jewel-Osco, Acme, Bristol Farms and Albertsons — have contributed stores to the program.

In the new stores, the six distributed refrigeration units are located on top of the walk-in coolers behind the back wall of the store. They are positioned in pairs, two on each side of the store and two in the middle, in proximity to the refrigerated cases and freezers located in the rear of the store's selling area.

Albertsons has yet to do a complete analysis of the impact of the distributed refrigeration systems on store operations. To date, though, they have “worked quite well for us,” said Meeker. “We're pleased so far.” The company has not made a commitment to using distributed systems across the chain, but for now the plan is to continue to use them in new stores, at least for the Albertsons division, if not yet for all of Supervalu's retail operations, he said. “We see no reason to change.”

Like most retailers, Albertsons is “trying to stay green and save money,” said Meeker. “We're able to meet those goals using distributed systems” in place of traditional systems. The cost savings so far is based on the overall impact of the new system on such factors as building design and resources, including copper piping and refrigerant.

“If you rip out a [conventional] rack system and put a distributed system in, you may not gain all the benefits you're looking for,” said Meeker. In fact, the initial cost of the distributed system is “slightly more” than a traditional system. “But if you look at it holistically — the building, piping and electrical system — that's where you see significant savings.” Albertsons has saved “in the tens of thousands” per store by employing distributed systems over rack systems, he said.

For example, by not having to build a mezzanine to support a rack system's machine room, a retailer can lower the height of the building, saving on building materials such as steel and concrete. And because distributed systems are located closer to the freezers and refrigerated cases, “we substantially cut our use of copper for piping,” Meeker said. Early on, Albertsons executives were impressed with the portability of distributed systems and the ability to easily position them in a store.

Despite those savings, Albertsons is still in the process of evaluating many other aspects of its distributed system. To gauge energy efficiency, Meeker said, Albertsons is getting ready to take measurements and do an in-depth analysis. He said the company's belief is that at a minimum, the energy efficiency is “not any worse” than that of traditional rack systems. According to Emerson's analysis, distributed systems are 5% to 10% more energy-efficient than conventional rack systems, said Rajendran.

Refrigerant reduction is one of the hallmarks of alternative refrigeration systems like distributed and secondary loop units. Meeker said that on average, the distributed systems use 25% to 33% less refrigerant (R-404A) than a rack system.

In addition to using less refrigerant, the distributed systems experience fewer leaks than a traditional system does. The reason is that far less piping is required to reach the cases, meaning fewer joints through which leaks might occur. Moreover, the scroll compressors used in distributed systems keep vibration to a minimum, which helps reduce leaks. “We think we're doing a lot to minimize leaks” with the new system, Meeker said.

Less refrigerant and fewer leaks translate into a more “green” refrigeration scenario, noted Meeker. The green effect is further enhanced by the need for less steel and concrete in construction and copper in tubing.

HFC refrigerants, which many retailers are using instead of ozone-depleting CFC and HCFC versions, are nonetheless harmful to the environment, because they contribute significantly to global warming. For example, R-404A, an HFC refrigerant, has a Global Warming Potential (GWP) of 3,870, which means that one pound of R-404A is equivalent to 3,870 pounds of carbon dioxide, the primary greenhouse gas linked to global warming. “HFC is one of five chemicals singled out by the Kyoto Protocol,” an international agreement on climate change, said Ted Gartland, director of refrigerant and regulatory compliance, Verisae, Minneapolis.

The U.S. Congress is currently considering at least two major bills aimed at reducing emissions of greenhouse gases. A bill introduced this year by Sen. Bernie Sanders, I-Vt., and Sen. Barbara Boxer, D-Calif., specifically targets HFC refrigerants.

On the maintenance side, one of the disadvantages of a distributed system is that it uses control valves that are on the sales floor. “So we went to electrical EPRs [evaporator pressure regulators] that we could adjust over our energy management system,” Meeker said. Overall, the distributed system to date has been “mostly maintenance-free,” though Meeker and staff are continuing to analyze maintenance needs and speak with maintenance departments.

Albertsons is “experimenting” with using the distributed units for heat reclamation, Meeker said. “We can do hot-water heat reclaim off them,” Meeker said. In one store currently under construction, Albertsons plans to do hot-air heat reclaim as well. “We'll monitor it and see of there's an ROI,” he said.

One of the ways retailers control refrigeration costs is by “staging” the use of compressors, running only what is needed to support a given day's refrigeration needs based on the outside temperature at the store. In that regard, the distributed system — spread across six units, with six high-efficiency scroll compressors in each unit — offers “better staging” capability than a conventional system, said Meeker.

Albertsons is also planning to test a digital scroll compressor in a lab that goes operational next month. Digital scroll compressors offer more control over usage than standard scroll compressors. According to Emerson's Rajendran, a digital scroll compressor used in distributed systems can range seamlessly from 10% to 100% of capacity. “It can constantly match a load without turning the compressors on and off,” he said.

ENERGY SAVINGS

Another retailer that has implemented the Protocol distributed refrigeration system is Stemmler Meats and Cheese, Heidelberg, Ontario, which operates one retail store out of a 6,000-square-foot building that also houses its production facility.

Stemmler Meats decided to adopt state-of-the-art refrigeration technology when it opened its current facility last October, explained Kevin Stemmler, co-owner with his two brothers of the 22-year-old company. The building uses two Protocol units containing nine scroll compressors in total and housed in a small mechanical room. Stemmler Meats had employed a conventional rack system in its previous facility.

When Stemmler Meats installed the distributed units, it was told to expect a 36% energy savings compared with the conventional system. “That proved out — plus,” said Stemmler. Although Stemmler Meats tripled the amount of refrigerated space at the new facility, “our energy costs only increased 50% to 60%. We found that amazing.” Based in part on that savings, Stemmler estimated that the distributed system, which cost 20% to 30% more than a conventional system, will pay for the difference in 1½ to 2 years. The initial cost of the Protocol distributed system and evaporators was $76,500, not including installation.

The store also saves between $1,000 and $2,000 per month on hot water costs by virtue of the heat reclamation achieved through the distributed units, Stemmler said. On the resource side, the system uses two-thirds less copper piping than a conventional system, as well as less refrigerant.

Food Lion, which is testing a secondary loop system for low- and medium-temperature applications, also tested a Protocol system in one store that opened in 2005 as part of a project with the U.S. Department of Energy. However, it only used two Protocol units that were linked together in a hybrid “mini-rack” configuration supporting low-temperature freezer cases.

“We chose not to go with a conventional distributed system,” said Susan Sollenberger, Food Lion's director of equipment purchasing, maintenance and energy. One reason for that decision is that the chain, which operates more than 2,000 stores, concluded that distributed systems sacrifice too much staging capability compared with conventional rack systems — despite what other retailers have experienced.

Another reason is that Food Lion believed that it could not do effective heat reclamation with a distributed system. “Heat reclamation is big for us,” said Sollenberger. She also felt that maintenance of refrigeration equipment is easier to control when it is all contained in a single machine room rather than spread around the store.

In its one-store test, which Food Lion continues to monitor, the retailer tied the two distributed units together to facilitate staging, and also as insurance, “so if we lose one compressor, we don't worry about product safety,” said Sollenberger. “In a true distributed system, you have to be extremely proactive servicing any compressor failure so you don't lose temperature.”

Wayne Rosa, Food Lion's energy and maintenance manager, noted that Food Lion would not want to sacrifice sales space to house distributed equipment, and it avoids putting equipment on the roof at its stores.

Rajendran pointed out that refrigeration manufacturers are designing distributed units to include doors that flip open and create a sheltered area, making them easier to work with on rooftops.

Sollenberger acknowledged that while Food Lion is satisfied with its stance on distributed systems, “it does warrant that we run the numbers again.” She can also foresee using a distributed unit in a remodeled store that is extending its chilled or frozen product lines.

Secondary Loop Update

As the first retailer to join the Environmental Protection Agency's GreenChill partnership with the supermarket industry, Food Lion, Salisbury, N.C., agreed in January to participate in research to assess the performance of a low-temperature secondary loop system at its Montpelier, Va., store.

The secondary loop system, from Hill Phoenix, Conyers, Ga., uses 60% less HFC refrigerant (R-507) than a conventional refrigeration system. The refrigerant is confined to the machine room, while liquefied carbon dioxide circulates through the store to refrigerate freezer cases and walk-in freezers. (See “Green Refrigeration,” SN, February 12, 2007.)

Food Lion is also testing Hill Phoenix's medium-temperature secondary loop system, which uses propylene glycol instead of carbon dioxide, at a store in Dinwiddie, Va. The chain plans to test both medium- and low-temperature secondary systems at a store in Portsmouth, Va., set to open in early 2008. The test of the technology will run for two years.

Asked for a progress report, Susan Sollenberger, Food Lion's director of equipment purchasing, maintenance and energy, said the low-temperature system's energy usage is “very comparable” to that of a conventional refrigeration system.

Wayne Rosa, energy and maintenance manager for Food Lion, observed that as the chain becomes more familiar with using carbon dioxide, “we'll better define the parameters and should have it more energy-efficient than a standard system.”

The medium-temperature unit is consuming more energy than a conventional system, but “we want to see how [the medium- and low-temperature systems] perform together” in the Portsmouth store, Sollenberger said.

A big win for Food Lion, Rosa said, is that the secondary loop system, like a standard system, allows the chain to reclaim heat for heating air and water. “That's a significant savings,” Rosa said.

Another plus is that Food Lion is not using any copper in the piping that carries the carbon dioxide. “That may be a bigger factor than anything, given the availability of copper,” she said.

While the secondary systems have not exhibited any refrigerant leaks, Sollenberger said that Food Lion's conventional systems already have a low leak rate.

As a GreenChill partner, Food Lion has begun sharing leakage and energy data from the secondary loop projects with the EPA. “We're a wide-open book for them,” said Sollenberger.
— M.G.