Modelling integrated HVAC and refrigeration systems in a supermarket

Decision makers in the supermarket chains ask with ever increasing strength for a comparison between different HVAC and refrigeration plant solutions, not only in terms of investment costs, but also of energy needs. The option of heat recovery from the refrigeration plant in favour of the HVAC system for space heating is being more and more considered, thus requiring the simulation of a complex system where control strategies play a crucial role. This topic is of great importance also in the view of the reduction of CO2 emissions, because supermarkets are intensive users of energy. In this paper the preliminary results of a comprehensive model of the HVAC and refrigeration systems in a supermarket are presented. This model is developed in the framework of the EU project CommONEnergy, and is based on the Trnsys platform. A cascade refrigeration system to supply various display cabinets and walk-in coolers is considered for refrigeration, while a Water Loop Heat Pump (WLHP) system is considered for HVAC. Heat recovery is performed by collecting heat from the condensers of the refrigeration systems in favour of the WLHP in the cold season. The effect of a water reservoir is evaluated, as heat storage device for the water loop. The capabilities of such a plant scheme are discussed in the view of energy savings for the whole supermarket. Two locations, representative of as many different European climatic zones, are considered. Optimal values of the activation temperatures for heat recovery, auxiliary heating system and cooling towers are discusses as well as the most convenient size of the reservoirs in order to minimize the primary energy consumption.