Alternatives to HCFCs in the Refrigeration and Air Conditioning Sector 66 S ection 02 T o test the efficiency of supercritical CO2 systems, the Norwegian supermarket chain “Rema” selected six medium sized stores for comparison between three supercritical CO2 systems compared to three direct evaporation R-404A systems. The result is presented in a presentation by the contractor (Kuldeteknisk AS, 2009). The design was with air cooled gas-coolers and built in heat exchanger for heat recovery (desuper heater) with 2.7.2 Evaluation of three CarbCarbon Dioxide stores in Norway Fig. 2.21 Comparison of energy (kWh) consumption in six medium-sized supermarkets in Norway. Fig. 2.22 Factory-built CO2 system with combined low and medium temperature circuit.the intention to make cost effective installations with good energy efficiency.The results show that the total energy consumption in the three stores using CO2 were all lower that in similar stores using R-404A (of which one is using significantly more energy without clear explanation and was not used in the comparisons). The plants are factory-built packs with the tubing to the display cases and cold rooms built on site. The operating experience of these plants are reported to be positive and the higher cost of the CO2 packs are compensated by the lower installation cost of the tubing (which have smaller dimensions with CO2 compared to tubes required for R-404A) and lower energy costs. The LCC is reported to be favourable with CO2. To handle standstill without increase of pressure above acceptable limits the systems are equipped with “stand by” cooling units supplied with back-up power (UPS) in case of power failure. This will cool the system to avoid the pressure to increase at stand still. A pressure increase could result in that safety valves open and require recharge of system. temp supercritical COCO2 direct evaporation R-404A 90000,0 80000,0 70000,0 60000,0 50000,0 40000,0 30000,0 20000,0 10000,0 0,0 Rema 1000 Rema 1000 Rema 1000 Rema 1000 Rema 1000 Rema 1000 Hesseng Ankenes S Storsvingen S Storsteines S Skjervøy L Lyngseidet