Alternatives to HCFCs in the Refrigeration and Air Conditioning Sector 62 S ection 02 The conclusions of the independent analyses performed in this test are that for conventional northern European houses with a relatively high heating demand, this CO2 design does not achieve the same annual COP, but if the main demand is hot water production, the characteristics are more favourable and good COPs can be achieved with CO2. Measured COP at 0°C ambient temperature and 31°C water in to gas cooler and 61°C water out was 2.51 which at this water temperatures would be acceptable relative conventional technologies. The water flow in these tests was much lower than what would be used in most systems. If the same heat rejection would be desired in the radiators with a higher flow the conventional heat pump would use 20% less energy whereas the CO2 heat pump would not increase its performance due to higher return temperature. With the ongoing development of low energy housing, the amount of heating needed is decreasing which will make the ratio of hot water versus heating more favourable than in most existing houses. Future optimisation of installations in the house and CO2 heat pumps will show where they will be competitive, but carbon dioxide is expected to be one of the refrigerants used in future heat pumps in particular if high water temperatures are required. More and more compressors and other components designed for carbon dioxide systems are becoming available in the market and the products for new segments are being developed. 2.7 Carbon dioxide in supermarkets Su mmary researarch prproject evaluauating two supupermararkets with carbon dioxide refrigeraration operarating in supercritical systems in Sweden, and a field test in six stores in NorwayThe reports evaluate the technology and environmental impact of these systems, and also provide an LCC analysis. At higher temperatures, carbon dioxide as a primary refrigerant is one of the more innovative technologies developed to reduce the use of high-GWP refrigerants such as HCFCs and HFCs. This has required the development of new components for the high pressure side including compressors, heat exchangers and control valves. There are two main characteristics to take into consideration the low critical point (31.3°C) and the high pressures. The low critical point and high pressure result in a need to redesign the heat exchanger and a rethink on how to use CO2 without causing increased energy consumption. CO2 supercritical systems are introduced in many countries in supermarket refrigeration and many evaluations are on-going. Different studies and reports are showing different results. The development is rapid and further improvements of the technology can be expected as it becomes more established. The conclusion of one independent evaluation reported below is that the tested stores would have higher energy consumption than those using conventional technologies and that calculations indicated that the use of CO2 in the low temperature stage and another refrigerant in the high temperature stage would have a better energy performance. This solution would often result in a more complex system and thus be less attractive than a single stage system. The COP of a CO2 supercritical system will depend on the climate where the installation is installed. A warmer climate will have a more negative impact on COP in these systems than on a conventional system making it more difficult to make them