Seasonal performance of supermarket refrigeration systems.

Different technological solutions are nowadays available to improve energy efficiency in commercial refrigeration units. When considering carbon dioxide systems, a strong effort is taking place to overcome the intrinsic inefficiency of the transcritical cycle so to competitively face warm and hot climate markets. Solutions such as parallel compression, mechanical subcooling or replacement of expansion valves with two–phase ejectors are now offered. The superiority of one options in terms of energy efficiency must be discussed with reference to the climatic conditions of the installation site, the cooling load profile and the
required evaporation temperature, which depends on both evaporators and the way they are controlled. Energy assessment of possible solutions is nowadays performed with different computational tools and comparison between alternative solutions is often difficult. In this paper, a simple figure that allows fair and realistic comparison of different options, for independent evaluation and ease of use of both suppliers and end-users, is proposed for discussion.