Carrefour&rsquo;s CO2/NH3 store: energy consumption reduced 20%; cooling equipment footprint reduced 30%

At the end of 2012, Carrefour opened a new store cooled by an NH₃/CO₂ refrigeration system, the La Chapelle Saint Luc hypermarket in the Aube department in North Eastern France. Together with other innovative energy saving technologies, Carrefour aims to achieve 20% energy savings in the new store, whilst the size of its cooling equipment is reduced by approximately 30%.

The hypermarket’s NH₃/CO2 cooling system is a cascade system with pumped CO₂ on the medium temperature side and CO₂ as refrigerant on the low temperature side.

Features of the NH₃/CO₂ cascade system

Ammonia machine room: prefabricated with all the security devices integrated. Ammonia plant air-cooled instead of water-cooled, with a dry cooler for energy savings.
Compressors: three Bitzer screw compressors, two with variable speed drives working at -9°C/+42°C.
MT cooling: 240 kW. All medium temperature cooling with CO₂ as a brine at -6°C.
LT cooling: 40kW at -35°C. Low temperature cooling with CO₂, three reciprocating compressor rack, two with variable speed drives.
Charge: significant reduction charge compared to HFC or glycol. Ammonia charge kept below 150 kg in accordance with French regulation.
Pump: absorbed power of the pump reduced by more than 80% compared to glycol.
Piping: Significant reduction in pipe size.
Pressure: Piping, refrigerated cabinets and evaporator designed for 40 bar.

Thanks to this system Carrefour estimates energy savings of 20% for the cooling machine, compared to a solution using glycol water. Carrefour has calculated a reduction of CO₂ equivalent emissions of about 4000-T eq CO₂ over the lifetime of the plant compared to a conventional HFC system using R404a.

Other energy saving features include, closed refrigerated cabinets for all fresh and frozen products, double-glazed doors on refrigerated cabinets, and LED lighting.

Background information

The store is located right in the centre of the Escapade shopping centre, which covers a sales area of 7,000 m². The Carrefour hypermarket is built based on the “spirit of nature” concept.

Carrefour has installed seven other NH₃/CO₂ brine systems in France for medium temperature applications, one in retail, two in the food industry and four in warehouses.