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“We continue making improvements with each [carbon dioxide] system and believe that advancing CO2 technologies in supermarket refrigeration systems is absolutely vital."
— Paul Anderson, engineering group manager, Target
Target’s Test Results
Over the past few years, Target has remodeled more than 1,100 stores, greatly expanding its grocery and fresh food selection — and thus its need for refrigeration systems — in what is called the PFresh format. In a 2-year-old store in St. Paul, Minn., the chain has been testing a CO2 secondary system that uses CO2 to cool frozen cases and glycol to chill dairy and meat cases; R-404 is the primary refrigerant. In a year-old store in San Clemente, Calif., Target has been testing a cascade system that employs CO2 for low-temperature cases, glycol for medium-temperature cases as well as R-134A. In June Target opened a store in Conyers, Ga., with a cascade system, and this month plans to open a “small, urban-format store” in Los Angeles that will have a cascade system.
In comparing the total cost of ownership of the test-store systems with that of a conventional DX system, Target looked at energy usage, capital investment in equipment and installation, uptime, maintenance and carbon impact. The St. Paul store’s secondary system, for example, consumed 24% more energy, cost 18% more for equipment and 21% more for installation and was equal in uptime; but its carbon impact, factoring in both the direct impact of refrigerant leaks and the indirect impact of electricity consumption, was 40% less.
The San Clemente store, which runs a cascade system, has used 10% more energy, cost 35% more for equipment, 18% more for installation and was equal in uptime. But its carbon impact was 65% less.
The maintenance and repair for the systems in both stores have been greater than for a traditional system. “We have had more work orders for the CO2 systems initially but over time maintenance and repair will be equal,” said Anderson. “But to make it happen we have to pay more attention to detail in the installation and startup.” He also encouraged a “time commitment to fine-tuning the system” as well as having contingency plans for power loss, doing scheduled maintenance, and making sure parts and CO2 are available.
In reporting that Target’s overall carbon emissions were 40% lower for the St. Paul store and 65% lower for the San Clemente store, Anderson also pointed out that the direct annual leaks of refrigerant were 66 metric tons and 32 metric tons of CO2 equivalent, respectively, compared to 174 metric tons for the DX system. He did not indicate the cost savings in refrigerant for the two test stores, but it would likely be less than the premium paid in energy. Thus a low carbon footprint in these stores may not compensate for the current energy cost premium.
Fresh & Easy has installed two cascade refrigeration systems, one in Rosemead, Calif., in 2010 and one in Folsom, Calif., in 2011. The Rosemead store, which uses CO2 to cool low- and medium-temperature cases in conjunction with R-134A, also employed an emergency system with a small generator that could cool the CO2 and prevent losses of the gas during power outages. “That’s a lifesaver because they lose power in that area,” said Thomas Hutchison, chief executive officer, Enreps, Phoenix, who spoke at the session on behalf of Fresh & Easy. “That helped on the maintenance side.”
According to Hutchison, the Rosemead store consumed 9.4% more energy than a conventional DX system while incurring 27% more in maintenance costs; its equipment and installation costs were 50% and 35% higher, respectively. But its carbon emissions were 41% less.
The Folsom store’s system, which uses CO2 only for low-temperature cases, was designed to minimize the amount of R-404, which represents only 10% of the refrigerant used. That system experienced a 30% higher energy consumption during its first four months compared to a DX system; it also required higher initial and installation costs, by 50% and 25% respectively.
Fresh & Easy is designing a cascade system for a store in Sacramento, Calif., that will use only natural refrigerants — about 30 pounds of ammonia as a primary refrigerant along with CO2 for low- and medium-temperature cases. An ammonia/CO2 system has already been installed in an Albertsons store in Carpinteria, Calif., and the Defense Commissary Agency (DeCA), Fort Lee, Va., is preparing to install an ammonia system at the Lackland base in San Antonio.
Hutchison noted that new refrigeration systems require training for technicians to remove the “fear of the unknown.” He expects technicians to become more comfortable with the systems and for maintenance costs to drop over time.