This paper proposes a theoretical study of the potential benefits of a cold storage system in a CO_2 Medium Temperature (MT) plant for supermarkets application. The aim of the plant strategy is the following: during the daily hours the storage can extract heat form the refrigerant leaving the gascooler/condenser, whereas during the nightly hours it can be cooled by the refrigerant before entering the evaporator. Besides, the storage can be used for reducing the electrical energy peak consumption, allowing to size the plant on a lower energy target, and it can influence the choice of the optimisation logic of the plant controller. A model for a MT CO_2 transcritical/subcritical cycle, able to manage the transient due to loads and external conditions change, is proposed to take into account the dynamic behaviour of the system. A daily analysis aimed at understanding the cold storage benefits in different periods of year is conduced based on real data consumption of a monitored MT supermarket. A seasonal analysis is considered too, for appreciating the cold storage benefits in different periods of year. The paper also focuses on the influence of a cold storage on methods and devices used to control the transcritical CO_2 plant working conditions.
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