Thirty-six are transcritical CO2 system, including 11 with parallel compressors and two with ejectors.
Jan Kroll, Carrefour Poland, at ATMOsphere Europe
As it transitions away from HFC refrigerants, Carrefour Poland has converted 46 of its stores to energy-saving CO2 systems since 2013, averaging six-to-eight retrofits per year, according to a presentation last week at ATMOsphere Europe in Warsaw, Poland.
Of its 46 CO2 stores, 10 are cascade, 23 are transcritical booster, 11 are transcritical with parallel compression and two are transcritical with a high-pressure gas ejector system and semi-flooded liquid ejector system (CALM). Danfoss is the supplier of the ejector systems. “They followed the market and technology development for CO2,” said Andrzej Szymanik, Key Account Manager, Cooling for Danfoss Poland, during the presentation.
Szymanik shared the stage with Maciej Szymański, National Senior Manager, Maintenance Department for Carrefour Poland, and Jan Kroll, Senior Manager, Refrigeration & Air conditioning for Carrefour Poland. Carrefour Poland is a division of French mega-retailer Carrefour.
Carrefour Poland, which operates 89 hypermarkets and more than 150 supermarkets, began the transition with both CO2 ascade systems and CO2 transcritical booster systems, but has installed only transcritical systems since 2017, noted Kroll.
CO2 cascade systems, with their lower pressures, were initially viewed as mature and safer than transcritical CO2. “But by 2016, the capex for both cascade and transcritical was the same, so we went with only transcritical,” said Kroll. “After two years, the [higher] refrigeration prices of HFCs convinced us it was the right decision.” Moreover, by then technicians got used to the higher pressures associated with transcritical systems, he added.
Carrefour Poland calculated that its CO2 stores, which also included new cabinets, LED lights, new evaporators and controllers, saved on average 38% in energy costs compared to the HFC systems; the chain estimated that the CO2 refrigeration alone cut energy costs by 20%. While the cascade system provided an estimated energy savings of 9%, the booster system and the booster system with parallel compression reduced energy by 17% and 29%, respectively.
“Each step gave us more energy savings,” said Szymański. "We're seeing a nice savings – higher than expected." He added that maintenance costs have been kept at a "reasonable level."
In its latest retrofit, completed in a 10,000m2 (108,000 ft2) hypermarket in Warsaw in September, Carrefour Poland installed a transcritical CO2 system with a high-pressure gas ejector system and semi-flooded liquid ejector system (CALM). "We are 100% convinced that the [energy] results will be even better than with parallel compression," said Kroll.
The CALM system allows for partially flooding the medium-temperature evaporator; some liquid leaving the evaporator is removed before it can reach the compressor.
"It was a very good decision to switch to CO2," said Szymański.