A CO2 cascade refrigeration system met engineering chief Paul Anderson’s efficiency requirements, but victory on total costs remains down the road.At ATMOsphere America 2014, Paul Anderson, Target’s Engineering Chiefannounced that retail giant would shift to CO2 hybrid systems for new stores and major remodels.In the cover story of issue 3 of Accelerate America, Paul Anderson provides an exclusive insight intowhy Target has committed to CO2.
Prototype result in $2000 (€1726) energy savings
In terms of energy performance, the prototype system did not initially meet Target’s requirements. In 2012, Anderson reported that Target’s CO2 systems were consuming more energy than a DX system using R404 in the same market. But at the 2014 ATMOsphere America meeting he revealed that the Conyers and Columbus hybrid cascade systems were saving about $2,000 (€1726) annually in energy costs compared with the standard DX unit. (The prototype system also produces enough heat to provide hot water in the store.)
In order to achieve that energy saving, Target had to compensate for the energy penalties inherent in the heat exchanger, rack valves and other components in a CO2 design. That required honing in on the optimal component selection and system design by submetering the energy consumption of many components.
“When we set up the initial stores, we would spend up to seven months fine-tuning the system to identify the barriers to improved efficiency,” he said. “We kept tuning the component selection to fit the application.” Anderson, who before joining Target worked as an engineer for John Deere, Taylor Industries and Eaton Automotive, strongly believes in tailoring components to the size of a system.
Current cascade system costs expected to come down in three to five years time
The efficiency improvement, however, has not been enough to compensate for other cost requirements of the hybrid cascade system. For example, capital investment in the technology is still 25% -30% higher than that of the DX system, while installation costs about 5% more. Moreover, maintenance expenses run about $2,300 per year more than for a DX system. Overall, incorporating efficiency gains, the cascade system costs $60,000 to $80,000 more than the conventional model in incremental cash flow, said Anderson.
But he is seeing a slow decline in equipment and installation costs for the cascade system. That won’t be reflected in the two 2015 stores, but should come over the next three to five years as production grows, he said.
At the ATMOsphere America conference, even as he announced the new prototype Anderson acknowledged that there’s still work to do with respect to the total cost of ownership. “But we believe advances in CO2 technology are absolutely viable,” he said. “We look forward to working with our partners to develop solutions that eliminate barriers that still exist today.”
Reducing maintenance costs
Meanwhile Target is doing all it can to reduce maintenance costs. During the months spent fine-tuning a new system, the chain works with manufacturers and contractors “to ensure that contractors truly understand how to keep systems operating efficiently,” Anderson said. That includes getting accustomed to the higher pressures inherent in the system, including 200 psi on the low-temperature side, 400 psi for medium-temperatures.
In terms of leaks, Anderson found that by switching from R404A to R134A, a lower-pressure refrigerant, leak rates dropped. It’s still too early, he said, to assess leak rates for CO2.
Target employs a refrigerant management system (from Verisae) that tracks refrigerant usage, including leaks, across the chain, helping the chain to comply with the record-keeping requirements of Section 608 of the Clean Air Act.
Carbon impact reduced by 65%
In regard to Anderson’s last bucket, sustainability, Target’s selection of a CO2 cascade system has been a major plus. The system’s lower energy consumption compared with a traditional DX unit, combined with its reduction of HFC charge and GWP, cuts carbon impact by 65%, eliminating more than 150 metric tons of CO2 equivalent annually per store.
In its 2013 Corporate Responsibility Report, Target put forth specific company-wide goals for greenhouse-gas-emission reductions it wanted to reach by fiscal 2015, using a 2007 baseline: a 10% emissions drop per square foot and a 20% drop per million dollars of retail sales. Through fiscal 2013, it had reached 7.1% and 7.4% declines, respectively.
On transcritical CO2 not making the cut
In addition to its three pumped-glycol tests, Target considered other possible prototype systems, including transcritical, and pumped CO2. “The other systems we looked at have not met our internal hurdle for new technologies we want to apply going forward,” said Anderson.
Though transcritical systems can work well in the cooler climates typical of Target’s home state of Minnesota, Anderson’s team has found them unsuitable after many years of testing. The issue for Target, he explained, is that PFresh stores use fewer refrigerated and frozen cases than a conventional supermarket, and therefore generate less waste heat. As a result, there is not enough waste heat to compensate for the efficiency penalties experienced by a transcritical system, he said.
But what about SuperTargets, which have as much refrigerated and frozen food as conventional supermarkets? “That might be a place where transcritical would work, but we’re not building any more SuperTargets,” he said.
One advantage of transcritical refrigeration is that by eliminating HFCs (including R134A) it protects companies from future HFC regulations. As an HFC user, Target is paying close attention to the Environmental Protection Agency’s current plans to delist certain high-GWP HFCs such as R404A and R507A by Jan. 1, 2016. Even R134A is slated for delisting for new stand-alone food refrigeration and new vending machines, though not in store-wide systems. “We’re always monitoring the situation,” said Anderson.
The full article and Issue 3 of Accelerate America is available at http://accelerate.shecco.com/
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