Danish retailer saves 10% energy with 2nd generation TC CO2 systems

By R744.com team, Oct 28, 2011, 10:57 3 minute reading

Energy measurement data collected between May 2010 and April 2011 by Danish supermarket chain Fakta with 61 transcritical CO2 stores in operation to date, has shown that the retailer has experienced 10% energy savings by applying second generation transcritical booster systems with gas by pass when compared to non-CO2 systems.

This was the conclusion of a case study presented on the first day of ATMOsphere Europe 2011 by Asbjorn Leth Vonsild, R&D Business Development at Danfoss. “What we see today is that CO2 systems are more energy efficient, and we have reached the point where they have the lowest cost of ownership, at least in Denmark”, noted Mr. Vonsild.

30 stores with 3 different system designs monitored over 1 year

A total of 30 refrigeration installations have been monitored during a 1 year period, comprising 10 installations from 3 different refrigeration system designs:
  • 10 stores with parallel R404A systems with very good load adaptation and controlled by ADAP-KOOL® pack controller and AKC 114A case controllers with electronic expansion valve type AKV
  • 10 stores with 1st generation transcritical CO2 booster systems with gas by pass, 2 compressors for MT (33/67%) and 2 for LT (33/67%), mechanical gas by pass valve, controlled by ADAP-KOOL® pack controller, EKC 326 controlling ICMTS high pressure valve, and AK-CC 750 case controllers with electronic expansion valve type AKV
  • 10 stores with 2nd generation transcritical CO2 booster systems with gas by pass, 2 compressors for MT, of which one with AKD inverter and 2 compressors without inverter for LT, controlled by ADAP-KOOL® pack controller, EKC 326A controlling ICMTS high pressure valve and CCM stepper gas by pass valve, and AK-CC 750 case controllers with electronic expansion valve type AKV
Energy consumption results

Mr. Vonsild presented a graph plotting energy consumption per month for the 3 different system types (HFC, Trans 1 and Trans 2) against the average ambient temperature for the month.

When comparing the 2nd generation transcritical CO2 system with the R404A system installed by Fakta until 2007, the measurements indicate about 10% energy savings, with the lowest energy consumption in the cold months.




The results also show a CO
2 technology improvement since 2007 when the first generation of transcritical systems were installed and where the measurement showed about 23% more energy consumption than the HFC systems. The CO2 technology improvement can be attributed to:
  • Improved part load capabilities and smooth control of gas bypass
  • Availability of components in smaller sizes to be able to better match the capacity also for smaller systems
  • A new CO2 injection algorithm in AK-CC 750 case controllers
Further efficiency improvements expected with CO2 supermarket systems in next 10 years

“CO2 supermarket systems today minimise both direct and indirect emissions. We have seen a tremendous improvement over the earlier CO2 systems. But since CO2 systems are still a young technology I would actually estimate that if we look another 10 years into the future, we will see energy efficiency of CO2 systems continuing to improve at a faster rate than HFC systems do”, said Mr. Vonsild. “You will also see the “CO2 equator line” in Europe, north of which CO2 is considered efficient continuing moving southwards”.

There is still room for improvements, including through a new generation of compressors and valves, while also the system architecture and control strategies are expected to improve.

More than 100 CO2 Fakta stores by end of 2011

Fakta operates 61 transcritical CO2 stores out of a total of 378 stores. One of the first movers to install CO2 since 2007, the retailer is aiming to install more than 40 second generation transcritical systems with 9 kW on LT and 28 kW on MT within 2011. 

MORE INFORMATION

By R744.com team (@r744)

Oct 28, 2011, 10:57




Related stories

Sign up to our Newsletter

Fill in the details below