Energetic Analysis and Optimisation Strategies of a Modern Northern European Supermarket

Abstract

Supermarket refrigeration systems are responsible for more than 30% of the refrigerant greenhouse gas consumption in Europe. The share of supermarkets in total energy consumption in Europe is about 3%. The aim of this thesis was the analysis of energy consumption in supermarkets and the investigation of saving potentials. In this context, field measurements were carried out in a Norwegian test supermarket. Detailed evaluations were carried out in order to gain all relevant information. The measurement results indicated a good performance with an average energy intensity of 488.9 kWh/m2 sales floor area in 2014. The most important conclusions from the measurements were that there was more need for cooling than for heating and that only a small part of the available waste heat from the refrigeration plant was used for heating. Moreover, main saving potentials were assigned to the refrigeration plant and the air handling unit. Based on this knowledge, an overall control concept for refrigeration systems was developed. Simulations were carried out in order to investigate two optimisation approaches: in case a, the control concept was applied; in case b, the plug-in cabinets were replaced by remote refrigeration, more efficient illumination was used and the control concept was used. A highly dynamic overall supermarket simulation model was developed for this purpose. The predicted energy savings were about 6% in case a and about 16% in case b. Furthermore, an improved indoor temperature control was achieved in both cases, especially in case b. These results show that even in a cold country like Norway, internal heat loads can be extremely high. The consequence is that the high cooling demands cannot be satisfied completely. It can be concluded that one of the most crucial stages in supermarket design is the investigation of heating and cooling demands. Heat loads like waste heat from plug-in cabinets should be kept considerably below the overall heating demand. A detailed analysis of the interactions between refrigeration plant, HVAC, heat recovery and building was carried out. It was shown that high energy performances could be achieved. Even though the newly developed optimisation strategies and the control concept cannot be adopted automatically by other supermarkets, some of the general conclusions can contribute to the development and further investigation of energy efficient supermarket concepts.