Analysis and Modeling of Energy Demand of Retail Stores

A retail store, especially a grocery store, has a high energy density due to decorative illumination and refrigerated cabinets. The purpose of this paper is to measure and analyse energy consumption of a grocery store and develop an energy demand model. The measurement revealed that energy consumption of refrigeration accounts for 60% of the total consumption and an air leakage has an effect on heating and cooling. Thus, we developed a refrigeration equipment model, enabling to calculate energy consumption for refrigeration and to take into account air-leakage from refrigeration cabinets in heat load estimation for calculating energy consumption for air-conditioning. Finally, we apply the model to a general merchandise store to confirm its applicability. INTRODUCTION The energy consumption of retail stores accounts for approximately 40% of the consumption of Japanese commercial sector. It has been increasing due to an increase in the total sales area and an increase in the energy consumption per sales area. Studies on energy consumption of retail stores are very limited because there are a variety of service and form in which the service is provided. Moreover, retail stores in general has a significantly high energy density. For example, while average primary energy consumption of office building is approximately 1,500 MJ/(m 2 ∙year), that of grocery store is approximately 6,000 MJ/(m 2 ∙year). Thus, this paper introduces a simulation model of a grocery store. By combining this model with existing building performance simulation tools, a variety of retail stores can be modelled. Jenkins proposed a simulation model that estimates the energy consumption of a grocery store (Jenkins, 2008). In this model, thermal load from equipment and occupant in the store is given based on the actual condition in order to calculate the energy consumption of HVAC systems. The thermal load of the air leakage caused by the refrigerated display cabinet was calculated while assuming that the temperature surrounding the display cabinet is stable. However, the air leakage does influence on the cooling and heating demand. The air leakage increases the thermal load of the refrigerated display cabinet. In this paper, we present the result of measurement on energy consumption of a grocery store. The measured consumption was classified into end-use categories in order to develop a bottom-up simulation model capable of dealing with the whole energy consumption of the grocery store. We especially focus on the refrigeration equipment, as explained later, more than half of total energy consumption of the grocery store was occupied by that for the refrigeration equipment. In its model, the heat balance around the display cabinet is modelled using the temperature and humidity measured around the cabinet. The refrigeration equipment model was combined with an energy demand model to calculate the whole energy consumption of the grocery store with 1-hour time resolution. This model enables to take into account the effect of the air leakage from the refrigerated display cabinet in the estimation of cooling and heating demand. Finally, the result estimated by the simulation was compared to the measured energy consumption in order to validate the accuracy. We applied the energy demand model to a general merchandise store to confirm the applicability of the simulation model. Figure 1 Inside grocery store MEASUREMENT We measured the power consumption of the grocery store in order to clarify its structure of energy consumption. We called the store Store A. Store A locates in Hyogo prefecture in Japan. Its business hours are from 9:30 to 21:00. Figure 1 and 2 show a picture and the floor plan respectively. While the main activity is food sales, its sales of food accounts for most of its total sales. As shown in Figure 2, groceries are divided into two types: refrigerated and Proceedings of Building Simulation 2011: 12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November.