In another demonstration of METRO AG’s commitment to natural refrigerant systems, on 14 September the German multinational wholesale specialist reopened a refurbished 24/7 store in Sofia, Bulgaria, retrofitted with an ejector-based CO2 transcritical refrigeration system. 

The Bulgaria store reopening follows on from previous developments in July and August, when the specialist in wholesale and food retail opened two new transcritical CO2 stores in Russia

To install the new CO2 transcritical system (from global manufacturer Carrier) in the Sofia store, it was necessary to take the old R404A rack and many of the other HFC components, which could not be reused, out of the old refrigeration system.

“A separate machinery room […] outside of the store was needed because the store is open 24/7 – therefore it was impossible to stop the old machinery and install [the new CO2 system] e.g. during closing time,” Olaf Schulze, METRO AG’s Director of Energy Management, investments & technical solutions, told “In the end two systems were operating. It was a huge engineering challenge.”

Removing the old HFC equipment freed up space in the store. “We are using the space from the old machinery for heat recovery,” Schulze told “Heat recovery is engineered by Bulgarian [VLASHKI ENGINEERING LTD] from Sofia in partnership with Carrier.”

Switzerland-based Frigo-Consulting worked as a consultant for METRO on the project. Carrier was the cabinet provider, and the manufacturer and installer of the two CO2 transcritical racks (which provide 68 kW low-temperature and 225 kW of medium-temperature cooling), according to Schulze. Güntner provided the gas coolers.

Given that the Sofia store is open 24/7, the whole retrofit had to be quick. “We pulled this off in a short space of time,” he explained. Open cabinets were used for cooling because of the limited space in the aisles and the high customer frequency.

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