CO2 refrigeration technology has been blossoming in Romania over the last two years. Following the opening in 2013 of the country’s first CO2 transcritical refrigeration system, in Galati, eight additional stores have been remodelled with CO2 installations. As well as providing refrigeration, these systems also simultaneously recover waste heat for the store’s hot water supply and to heat offices and parts of the sales area. Using this system, stores are able to significantly reduce their carbon footprint.

New system results in 13% energy savings

The success of these CO2 refrigeration systems has increased interest among retail companies in Romania in investing in this modern technology. The Carrefour hypermarket in Timisoara, western Romania has taken further steps by successfully installing a CO2-transcritical refrigeration system with parallel compression and multi-ejector technology. Initial evaluations show that the system is working as expected under normal conditions, and the store expects to make energy savings of up to 13% compared to a transcritical CO2 system with parallel compression.

Two booster racks were installed in Carrefour Timisoara under a collaboration between several companies: Frigo-Consulting Ltd; Danfoss, which was responsible for multi-ejectors and system control; ENEX, which produces booster racks; cabinet manufacturer ES System K; and DAAS, a local refrigeration installer.

The CO2 system’s total capacity is 292 kW for positive and 65 kW for negative temperature demand. The combination of gas and liquid ejectors and parallel compressors facilitates the recovery of energy released during high-pressure expansion and reduces internal throttling losses.

New possibilities for the future

The ejectors raise the possibility of increasing system efficiency by raising the medium suction pressure of the positive temperature range from -7°C to -2°C, depending on evaporator performance. In partially flooded mode, the expansion operation tremendously increases CO2’s heat transfer capacity, allowing for increased evaporation temperatures. This reduces ice formation on evaporators in the cabinets and in cold rooms.

One possible means of reducing energy consumption still further is by using partially flooded evaporators, in which case the evaporation temperature increases to -2°C for positive temperature and to -26°C for low temperature.

Indeed, German supermarket chain Migros – winner of the EHI Retail Institute’s Energy Management Award 2015 for its MMM store in the Mythen Center in the Swiss town of Schwyz – has already shown that using this system triggers energy savings of as much as 25% per year.

About Frigo-Consulting International Ltd.

The company offers services in the field of innovative refrigerating systems, such as design of energy concepts, efficient heat recovery and integral systems, engineering and realisation of sustainable refrigerating, worldwide unique innovations to save primary energy, training and audits.

Author r744