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Reducing energy consumption in industry has become an important aspect on a global scale. Energy efficiency is one way of reducing energy consumption and promoting competitiveness. Increasing energy costs, security of energy supply, emissions from energy production have shown that current freezer design solutions are not sustainable. The food industry has a common tendency, whereby energy costs are only of secondary importance, unlike other production costs, resulting in minimal monitoring of energy consumption. Electricity consumption for freezer operation amounts to 20 % of total electricity consumption. Within the framework of this study, electricity consumption for fish freezing and storing frozen fish and finished products, as well as the coefficient of performance (COP) for compressors and parameters affecting COP were analyzed. From the results it can be concluded that the specific consumption of electricity in freezing of fish is lower than that of frozen fish storage. The two-stage compressor COP ranges from 2.4 to 3.7, but the single-stage compressor COP ranges from 3.7 to 5.5. The pressure in the condenser and ammonia vapor temperature after the compressor is affected by the temperature of the water used to cool the condenser and compressors. As the temperature of the water used for cooling increases, the condenser and ammonia vapor temperature after the compressor increase, which in turn reduces the compressor COP.

Unlike energy efficiency, in terms of exergy efficiency it is possible to compare the existing operation of an energy conversion system with the ideal operation. Exergy loses and exergy destruction make it possible to identify the shortcomings of an existing system, which should be improved immediately. With exergy analysis, it is possible to identify the priority actions that need to be taken in order to improve the functioning of the system: greater exergy loss prevention is the highest priority. Energy efficiency refers to the useful work and investments needed to obtain useful work and investments needed to obtain energy efficiency; this is important to some extent, but the effectiveness of exergy makes it possible to compare system performance with the ideal. Results shows that the highest exergy destruction of a single-stage compressor refrigeration system from all working condition is found when ambient temperature and freezer temperature difference is 10 ºC, pressure in compressor is 0.62 MPa, ammonia temperature after compressor is 90 ºC, total exergy destruction of single-stage compressor refrigeration system 97.84 kW. The highest exergy efficiency of a single-stage compressor refrigeration system from all the working conditions is found when ambient temperature and freezer temperature difference is 39 ºC, pressure in compressor is 0.45 MPa, ammonia temperature after compressor is 128 ºC, exergy efficiency of a single-stage compressor refrigeration system is 59.76 %. The highest total exergy destruction of a two-stage compressor refrigeration system from among all the working conditions is found to be when the ambient temperature and freezer temperature difference is at 13 ºC, pressure in compressor 0.44 MPa, ammonia temperature after compressor 76 ºC, total exergy destruction 83.86 kW. The highest exergy efficiency of a two-stage compressor refrigeration system from among all the working conditions is found to be at an ambient temperature and freezer temperature difference of 39 ºC, pressure in compressor 0.56 MPa, ammonia temperature after compressor 92 ºC, exergy efficiency 53.55 %.