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 (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. The analysis demonstrates the use of the model for system optimisation purposes. The defrosting schedule 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.
Refrigeration systems are one of the largest consumers in supermarkets. In order to evaluate different refrigeration system conditions and to properly monitor the hazardous nature of the stored food, we have developed and presented a hybrid model of the display case. The model considers the main discrete display case events and also the identified temperature dynamics of the stored food and display case. The model was used to analyse how the defrosting strategy, the frequency of food loading and the frequency of door openings influence the total operational cost and the product quality.
The ability to predict and to manipulate with consumption is becoming more and more important as wide range of demand response schemes are expected in near future. This paper introduces a new control scheme for adjusting the current consumption of the refrigeration system in shopping center. The control scheme enables us to perform short term adjustments of the refrigeration system consumption, while still guaranteeing the HACCP temperature limitations. With smart shifting of the refrigeration load it is possible to shift some consumption to more favorable time period and, therefore, reduce overall electricity costs. The scheme can be easily expanded on all refrigeration display cases in a shopping center and on several centers. The approach was verified on the simulation model of the refrigeration system where reference tracking performance of the controller was verified.
The paper presents some methods of optimizing energy costs, which are based on remote control of the central cooling systems. The optimisation can be achieved by exploiting heat capacity of the system (including food) and the change of the price of electricity during the day. The paper shows the basic scheme of the system and the proposed optimization algorithm. In the case of double billing rates during the day, the proposed optimization algorithm achieved over 9% savings in electricity costs in the simulated environment.