Federica Rossetti, SCM Frigo, and Andrea Zanchetta, Sagat, presenting about transcritical CO2 at ATMO Europe Summit 2023.
Federica Rossetti, SCM Frigo, and Andrea Zanchetta, Sagat, presenting about transcritical CO2 at ATMO Europe Summit 2023.

ATMO Europe: Transcritical CO2 in Cold Storage Facility Offers 19% Energy Cost Savings Compared to R404A

Based on analysis conducted by manufacturer SCM Frigo, cold storage facility operator Sagat will see an ROI in 4.7 years due to lower operational costs.

Italian manufacturer SCM Frigo’s transcritical CO2 (R744) booster system has saved Sagat, the operator of a cold storage facility in northern Italy, 19% on its energy costs compared to those of a still-used R404A system, according to a case study presented by the two companies.

Based on savings in energy and other installation, maintenance and operational costs, SCM Frigo estimates that Sagat will see a return on additional cost of the CO2 system compared to the R404A system in 4.7 years.

Over the system’s 15-year lifespan, the manufacturer says its transcritical CO2 system will be 7.4% cheaper than Sagat’s existing R404A-based units. This includes both capital and operational expenditures.

Analysis of the installation was presented by Federica Rossetti, R&D Engineer at SCM Frigo, and Andrea Zanchetta, a representative of Sagat, during a refrigeration case studies session at the ATMOsphere (ATMO) Europe Summit 2023. The conference took place September 19–20 in Brussels and was organized by ATMOsphere, publisher of R744.com.

Higher efficiency

Sagat has been using R404A at its 52,000m3 (1.8 million ft3) cold storage facility in Treviso, Italy, since 2002. The company first introduced CO2-based systems at its low-temperature warehouse in 2019 in partnership with SCM Frigo and plans to fully transition to R744 by 2030.

The CO2 installation consists of two SCM Frigo transcritical booster systems, which provide 260kW (74TR) of cooling capacity to five of the facility’s cold rooms – totaling 16,000m3 (565,000ft3) – at an evaporative temperature of −32°C (−25.6°F). The units are located outside and include an integrated gas cooler.

For comparison, Sagat’s 10 R404A-based units provide 216kW (61.4TR) of cooling capacity to five other cold rooms at an evaporative temperature of 33°C (−27.4°F) and 180kW (51.2TR) to the site’s loading areas at an evaporative temperature of 0°C (−32°F). The R404A units, which are installed outside and include integrated condensers, service a total of 36,000m3 (1.27 million ft3).

The simultaneous operation of both R404A- and CO2-based systems enabled SCM Frigo and Sagat to compare performance and document energy savings, explained Rossetti during her presentation.

“CO2 offered better performance during the coldest months, with peak consumption during the hottest months,” she said, “while R404A supplied energy savings only during periods where ambient temperatures were higher than 25–27°C (77–80.6°F).”

During the summer, SCM Frigo’s CO2 system consumed an average of 2.9kWh/m3 (0.082kWh/ft3) per month compared to the R404a system’s 2.8kWh/m3 (0.079kWh/ft3).  However, during the winter, the COsystem outperformed the HFC alternative significantly, with a monthly average energy use of 1.6kWh/m3 (0.045kHh/ft3) versus 2.2kWh/m3 (0.062kWh/ft3).

Over the course of the year, the COsystem used 19% less energy per cubic meter compared to the R404A units, Rossetti stated. On average, the systems consumed 2.2kWh/mand 2.7kWh/m3 (0.076kwH/ft3) per month, respectively.

Lower costs

The lower energy consumption of the transcritical CO2 system translated into noticeable cost savings for the end user, said Rossetti.

“The customer paid €1.83 [$2.00] for each cubic meter for CO2 and €2.25 [$2.46] for R404A,” she explained.

Based on the performance and energy data gathered throughout 2022, Sagat saved €6,800 ($7,447) that year. If Sagat were to convert its remaining R404A equipment to CO2, these annual savings would rise to €15,200 ($16,647).

Rossetti noted that the savings helped Sagat offset the higher upfront investment costs of the CO2 equipment.

“The higher cost of ownership of COis balanced out by low installation and maintenance from the energy savings and from the extremely low cost of refrigerants,” she added.

“Considering the energy savings we saw with this installation, we plan to fully replace the remaining R404A units with CO2 technology and invest in technologies to reduce the impact of high ambient temperatures on the performance of CO2,” added Zanchetta. “This will allow us to achieve our final goal of becoming a climate-neutral facility by 2030.”

If the performance of the COsystem improves in comparison to the company’s R404A units, there is a possibility that Sagat might accelerate its plans to transition completely to R744, he said.

“The higher cost of ownership of COis balanced out by low installation and maintenance from the energy savings and from the extremely low cost of refrigerants.”

Federica Rossetti

Improving future performance

While the CO2 system has been optimized, it is relatively “basic” and therefore could be improved with the addition of an adiabatic gas cooler or ejector technology, explained Rossetti. However, due to the technology used by SCM Frigo in this case, parallel compression is not a viable option.

System efficiency could also be boosted by ensuring the outdoor equipment is installed in a shady location or by introducing heat recovery for system defrost, she added.

“CO2 is a good, future-proof alternative to HFC solutions and an excellent solution for more sustainable refrigeration systems,” said Rossetti.

This view is reflected in SCM Frigo’s commitment to natural refrigerants, particularly CO2. The company already produces around 2,200 CO2 units annually and is expanding its production capacity to meet growing demand.

“Our goal is continuous innovation throughout research, design and production of CO2 refrigeration systems,” said Rossetti.

The company first began working with natural refrigerants in 2005 and joined the Beijer Ref group in 2011.

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