Energy Usage in Supermarkets - Modelling and Field Measurements

This thesis investigates a special type of energy system, namely energy use in supermarkets through modelling, simulations and field studies. A user-friendly computer program, CyberMart, which calculates the total energy performance of a supermarket, is presented. The modelling method described in this thesis has four phases: the first phase is the de-velopment of a conceptual model that includes its objectives, the envi-ronment and the components of the system, and their interconnections. The second phase is a quantitative model in which the ideas from the conceptual model are transformed into mathematical and physical rela-tionships. The third phase is an evaluation of the model with a sensitivity analysis of its predictions and comparisons between the computer model and results from field measurements. The fourth phase is the model ap-plication in which the computer model answers questions identified in the beginning of the modelling process as well as other questions arising throughout the work. Field measurements in seven different supermarkets in Sweden were car-ried out to: (i) investigate the most important parameters that influence energy performance in supermarkets, (ii) analyse the operation of new system designs with indirect system implementation in Sweden during recent years, and (iii) validate the computer model. A thorough sensitivity analysis shows a total sensitivity of 5.6 %, which is a satisfactory result given a 10% change in the majority of input parame-ters and assumptions, with the exception of outdoor temperatures and solar radiation that were calculated as extreme values in METEO-NORM. Comparisons between measurements and simulations in five supermarkets also show a good agreement. Measurements and simula-tion results for a whole year were not possible due to lack of data. CyberMart opens up perspectives for designers and engineers in the field by providing innovative opportunities for assessment and testing of new energy efficient measures but also for evaluation of different already-installed system designs and components. The implementation of new energy-saving technologies in supermarkets requires an extensive inte-grated analysis of the energy performances of the refrigeration system, HVAC system, lighting, equipment, and the total energy usage. This analysis should be done over a long period, to evaluate and compare the real energy performance with the theoretical values calculated by Cyber-Mart.QC 2010033