U.S. retailer Coborn’s has noticed an average utility savings of 15% when comparing its two new transcritical CO2 (R744) refrigeration installations to similar R448 stores and 25% savings on its refurbished store, and, as a result, the chain is planning to use CO2 in all new builds.

This update was shared by Chris Braun, Project Manager – Refrigeration at Coborn’s during the “CO2 Systems: What Retailers Need to Know” session of the North American Sustainable Refrigeration Council (NASRC)’s online Sustainable Refrigeration Summit 2022. He was joined by Doug Milu of Publix Super Markets, who also shared experiences with CO2.

Coborn’s Inc is a family-owned company started in 1921 in central Minnesota (U.S.). It operates 66 grocery stores plus convenience, liquor and pharmacy outlets throughout the Midwest. The stores vary from 25,000 to 105,000ft2 (2,323 to 9,755m2).

The retailer started its CO2 journey in 2020 with a new store installation. Since then, it has installed CO2 in another new store plus a remodeled store. For the refurbishment, the team managed to switch over the old HFC system to CO2 without any downtime to the store. An adiabatic gas cooler was used for all three installations.

Ready for the future

“Our goals for refrigeration, when we were contemplating between using the synthetic refrigerant and natural refrigerant, was that we wanted to be future-proof,” said Braun. “We want to make sure when we were spending the capital to do a new store or a remodeled store that we were setting ourselves up for the next 20 years plus; that we weren’t going to put something in and have it be regulated out in the next five to 10 years.”

Having good service and installation support was also important for Coborn’s, as was a financially viable upfront cost and total cost of ownership of the equipment over its lifespan. The CO2 installation ticked all those boxes.

“Our plans, going forward, are for all new builds to be transcritical CO2,” noted Braun. The  company also has plans to remodel two existing stores from HFC to transcritical CO2 in 2023 and 2024. “That’s due to the utility savings that we are seeing with CO2 versus standard HFCs. We want to keep doing more.”

Reducing costs with CO2

According to Braun, one of the advantages of going with CO2 is the construction-cost reduction. Coburn’s have been able to eliminate the cost of additional gas boilers thanks to the heat reclaim benefits from the CO2 system.

Another plus is that the CO2 system’s architecture is considerably smaller than that of a standard HFC system, explained Braun. As such, Coborn’s has been able to either reduce the size of the mechanical room or fit more equipment into it without increasing its size. The chain also didn’t have to spend money on the structural steel required to house the fan condensers needed in the past for the HFC systems.

A big benefit has been energy savings, said Braun. When comparing the kilowatt hours of electricity used per square foot in two new build Coborn’s stores, one CO2 and one R448, the chain found that the store fitted with a CO2 system achieved average savings on utilities of 15% per square foot over the R448 store. In a comparison of refurbished stores, the savings went up to 25%.

“Our plans, going forward, are for all new builds to be transcritical CO2.”

Chris Braun, Coborn’s

Lessons learned

Braun explains that it is important to consider the climate when choosing a transcritical CO2 system. For Coborn’s, CO2 makes sense because of the cooler climate and the fact that the system only goes into supercritical mode on average 12–14 days a year – typically only for a couple of hours per day. During this period, the system consumes higher energy and the service calls increase. Technology like adiabatic condensers is key to keeping high ambient conditions to a minimum, said Braun. Other equipment like ejectors and parallel compression also serve that purpose.

It is also important to choose a reputable refrigeration contractor who understands CO2, Braun advised. Coborn’s used the same contractor for all three of its CO2 installations. He also recommended having an electrician who understands how to wire all the equipment correctly. Having an experienced team can make the switch to CO2 much easier, according to Braun.

Another benefit is the cost of CO2, which is significantly lower than that of refrigerants like R448. During a failure at one of the sites, about US$2,500 worth of CO2 was blown off. Had that been an HFC, US$40,000–$50,000 worth of the refrigerant would have been lost, noted Braun.

Challenges in using CO2 include longer start-up after power failures, leaks and the current lack of CO2 cylinder availability for backups.

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