Cost optimisation of supermarket refrigeration system with hybrid model

Refrigeration systems based on vapour compression cycle are one of the largest energy consumers in supermarkets. In this paper a hybrid model of a refrigeration system is developed, in order to estimate the benefits of energy optimisation measures. The refrigeration model comprises the refrigerated display case dynamics, food products dynamics, evaporation model, and ice formation model, and is further extended with the discrete events that are typical for normal operation of a refrigeration system (i.e. customer interactions, product refilling, defrosting). Model parameters are identified from the measured data, equipment specifications and estimations of some conditions in a supermarket case study. The simulation software AnyLogic is used to realise an agent-based model of the display case that allows us to extend the model to the entire store-wide refrigeration system. The analysis demonstrates the use of the model for system optimisation purposes. The defrosting schedule of a single display case as well as for the complete store is optimised considering the overall running costs, food quality, and maximum peak power. Moreover, several energy optimisation measures are compared and evaluated in terms of their contribution to the overall savings and food quality degradation.