ECOS 2016: Operation Strategy for Heat Recovery of Transcritical CO2 Refrigeration Systems with Heat Storages

Supermarkets cause about 3% of electrical energy consumption in Europe. Besides its reduction, legal ordinances aim at avoiding synthetic refrigerants and their big impact on global warming. The natural refrigerant CO2 is regarded as a great alternative offering a very low GWP of 1. However, due to its low critical temperature, CO2 sometimes has to be employed transcritical resulting in high operating pressures. Intelligent control strategies explicitly making usage of heat recovery and thermal storages are necessary to minimize energy consumption. In this paper all necessary steps to determine such a beneficial operation strategy are presented. Initially, the relevant refrigeration cycle is modelled in a physical way using the object-oriented Modelica language. Environment data, cooling loads and heating demands are represented as boundary conditions. Due to the usage of heat storages, heat recovery can be decoupled from heating demands. This additional degree of freedom is employed to adjust heat recovery to boundary conditions resulting in a minimized overall energy consumption.

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