Various technologies and control methods are energy efficiency measures (EEMs) that could be applied to display cases and result in the reduction of the refrigeration load and of the energy consumption of the supermarket refrigeration system. Consequently, the focus of this investigation has tilted toward the open, vertical, multi-deck medium temperature case type. In addition, medium temperature fixtures and storage coolers account for roughly 70 to 75 percent of the total store refrigeration load with open, multi-deck cases contributing about 3/4 of that fraction. Open, multi-deck, medium temperature display cases typically comprise about half of the refrigerated fixtures in a store (ES-3). Figure ES-2 shows the distribution of display cases in a typical supermarket (ES-2). The door anti-sweat heaters represent a major share of the refrigeration load for frozen food door reach-in cases. For example, air infiltration is the most significant portion of the refrigeration load for open, multi-deck cases, while radiation is the largest part of the load for tub-type cases. The impact of each of these elements on the refrigeration load is very dependent more » upon case type (Figure ES-1). (4) Internal thermal loads-the use of lights, evaporator fans, periodic defrosts, and antisweat heaters adds to the refrigeration load of the display case as well as directly consuming electric energy. (3) Thermal radiation from the ambient to the product and display case interior. (2) Heat conduction through case panels and walls. The sources of the display case refrigeration load consist of: (1) Moist and warm air infiltration through the open front of the case-air curtains are employed to inhibit this infiltration, but some ambient air is entrained, which adds a substantial portion to the refrigeration load. The operating characteristics and energy requirements of the refrigeration system are directly related to the refrigeration load. The cases are maintained at air temperatures ranging from -10 to 35 F, depending upon the type of product stored. Display cases are used throughout a supermarket for the merchandising of perishable food products. Over half of this energy use is for the refrigeration of food display cases and storage coolers. Supermarkets represent one of the largest energy-intensive building groups in the commercial sector, consuming 2 to 3 million kWh/yr per store (ES-1).
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