Paving the Path for a New Generation of High-Efficiency Supermarket Refrigerated Display Cases

Rafik Sarhadian, Ramin Faramarzi, Bruce A. Coburn, and John Lutton, Southern California Edison
Homayun Navaz, Kettering University
David Walker, Foster-Miller Inc.

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Abstract

This paper discusses the results of experimental evaluation of a number of viable and near-term energy-efficiency solutions applicable to open vertical refrigerated display cases. With energy usage intensity of 43 kWh to 70 kWh per square-foot per year, supermarkets are one of the most energy-intensive commercial building types in the United States. A major factor affecting the design and operation of supermarket refrigeration systems is the cooling load requirements of the display cases. Medium-temperature display cases and, in particular, open vertical display cases, are one of the most thermally vulnerable display cases in supermarkets. These display cases, which are typically used to merchandize meat, diary and delicatessen, fish and produce, operate at discharge air temperatures of 28oF to 32oF. They also comprise the largest portion of display case line ups. Historically, display case manufacturers have not invested in energy-efficiency improvements of their products. This has been due to lack of demand from their customers as well as first cost considerations. Furthermore, the absence of energy-efficiency standards for display cases, coupled with supermarkets’ dominant emphasis on merchandising facets have impeded the related research and development efforts.

Laboratory tests were conducted to quantify the impacts of several energy-efficiency measures on the performance of a selected open vertical display case. The result of incorporating these technologies indicated an improvement of 19% in refrigeration effect and reduction of 11% in electric power usage of the refrigeration system (excluding condenser). These improvements were achieved without affecting the target product temperature.