Japanese cold storage operator Yoshio Ice Manufacturing & Refrigeration (Yoshio Ice) is continuing to see a significant energy-use reduction with its second installation of a transcritical CO2 (R744) refrigeration system.

The company presented operational data on the system during the ATMOsphere Japan 2021 conference, held online on February 15 and organized by shecco, publisher of this website.

In February 2020, Yoshio Ice retrofitted an existing R22 system with a “Super Green” CO2 transcritical system at one of its cold storage facilities in Fukuoka, Japan. The CO2 system, supplied by Tokyo-based manufacturer Nihon Netsugen Systems (NNS), began operating in April 2020.

For the period from April–December 2020, the facility saw a cumulative energy-use reduction of almost 22%, according to data presented by Yoshio Ice President Shigekatsu Koganemaru at the conference.

Yoshio Ice first installed transcritical CO2 systems for one of its newly built cold storage facilities in Fukuoka in April 2018.

During the ATMOsphere Japan 2019 conference, NNS President Katsuhiko Harada presented energy performance metrics for this first installation from April–December 2018. Power consumption for the period was 27 kWh/m³, less than what was predicted (around 35 kWh/m³), and far less than Japan’s industry annual average of around 61 kWh/m³.

It was these good results, Koganemaru said, that led the company to move forward with the most recent transcritical CO2 installaton in February 2020.

In the latest installation, while CO2 was a contributing factor to the energy drop, Koganemaru explained that the company’s load-following inverter controller was the major factor in maximizing energy efficiency.

“The results of the installation of this equipment are not only due to the characteristics of CO2 as a refrigerant,” said Koganemaru. “It’s the flexibility of our operation through advanced equipment control that makes these numbers possible.”

The 2020 data told a seasonal story. In the summer, when the load was at its peak, there was little difference in the amount of electricity used compared to the original R22 system, as shown in the following graph. In August, for example, the operating data showed only a 5.8% reduction in energy use.

Yoshio Ice ATMO Japan 2021 Presentation
The title reads “Comparison of power consumption and overall reduction rate” with the R22 system’s power consumption in blue, the CO2 system in orange, and the reduction percentage in black. See the full presentation here.

However, during winter, the inverter controls’ impact on energy use became apparent. In particular, data for November 2020 showed a 38.8% reduction in energy use compared to the original R22 system. The CO2 system, Koganemaru said, is also equipped with an inverter for the fan on the cooling side to increase efficiency and reduce the number of defrosts needed.

“Today, the technology being used for equipment efficiency and production processes is growing every day,” said Koganemaru. “Since there is no significant difference in equipment efficiency, how to control them will be a major factor in improving COP [coefficient of performance].”

The Super Green CO2 system, Koganemaru added, also employs a heat recovery system to store heat in a brine tank. The heat is then used for defrosting, further increasing the system’s overall COP.

See Yoshio Ice’s full presentation here (Japanese).