As everyone knows by now, the U.S. and most other countries around the world are phasing down the use of high-GWP HFC refrigerants that are used in air conditioning and refrigeration equipment. In the commercial refrigeration industry, this means transitioning away from refrigerants such as R-404A and R-134a, to low-GWP alternatives, such as CO₂ (R-744) and propane (R-290). To make this transition, food retailers will have to completely replace their existing refrigeration systems, as these alternatives cannot be retrofitted into existing equipment.

Not everybody is happy with their existing choices, though, as evidenced by several speakers at the Food Marketing Institute’s (FMI’s) 2023 Energy & Store Development Conference. During one panel discussion, food retailers shared their disappointing experiences with CO₂ systems in particular, citing problems with refrigerant leaks and poorly designed systems that often did not perform as well as they were led to believe. For example, one speaker pointed out that in certain regions of the U.S., systems using HFC refrigerants had an annual energy performance advantage over CO₂ systems, ranging from 16% to 25%.

Another speaker shared how the United Kingdom grocer, Asda, recently replaced a 12-year-old CO₂ transcritical system with a new one that utilizes the mildly flammable, A2L refrigerant, R-454A. The installation took place in 2021, and by 2022, Asda reported a significant decrease in energy consumption and overall CO₂ emissions compared to the replaced transcritical CO₂ system. Indeed, Asda achieved a 34% reduction in energy usage since the replacement, resulting in an annual savings of approximately $51,000.

Worries extend beyond the increased energy consumption of CO₂ systems, particularly in warmer climates, to include concerns over their substantial use of natural resources, such as water. On that point, one food retailer found that the amount of water required to keep transcritical CO₂ systems operating in his stores was approximately 600,000 gallons of water per store per year. In addition, speakers noted that the high pressure and complexity of CO₂ systems require more qualified and experienced technicians to install and service them. And those types of workers are in short supply.

That latter point was discussed in another session that focused on how to attract more technicians to the HVACR industry. While the lack of technicians in the HVACR industry has been a problem for decades, it’s hitting a critical point now, because existing technicians are older and starting to retire. At the same time, there is a lack of new technicians entering the field to fill their positions, which results in increased workloads and unsustainable schedules for the incoming workforce, prompting them to exit the industry, noted moderator, Morgan Smith, program and communications director at the North American Sustainable Refrigeration Council (NASRC).

“There are simply not enough technicians not only to address this transition that the industry is going through right now away from HFCs, but also just to keep up with ongoing operations and maintenance needs,” said Smith.

And the operational and maintenance requirements for CO₂ systems can be significant. During a panel discussion, Shawn Holzschuh, Target Corp.'s director of refrigeration, noted that maintenance of high-pressure CO₂ systems is more complex, requiring technicians to have a targeted focus on the sequence of operations, sensitivity and accuracy of sensors, and maintenance and repair of piping.

“Technicians must also be aware of the pressure in CO₂ systems and what happens if it releases,” said Holzschuh. “They need to understand control sequences to manage rising pressures. They also need to be a master of multiple controllers, and they need to understand how to communicate with various manufacturers’ hardware, all while having a work order load that continues to grow.”

Holzschuh also highlighted a significant operational challenge associated with CO₂ refrigeration systems – the potential total loss of the refrigerant charge in the event of a power outage. This is a major problem, leading some retailers to store a complete backup charge of CO₂ on-site, which has led to shortages of the refrigerant in some areas.

In a separate session, Dustin Lilya, P.E., a principal at DC Engineering in Boise, Idaho, shed light on the magnitude of the leak problem by sharing some of the research he has done on this issue. He conducted a survey across a portfolio of stores in the Pacific Northwest that utilize CO₂ systems and discovered that the average leak rate from 2021 to 2022 ranged between 80% and 130%.

“The survey data is not great,” he said. “If you dig into the data, 80% of the leaks were attributed to venting the refrigerant because of power outages or some other event. A very small proportion was because of identified leaks in the system. It’s pretty compelling that maybe we're not resilient enough in the designs that we're putting forward in order to keep the refrigerant in the system.”

Certainly something to think about.