Laboratory Assessment of Propane Type Horizontal Self-Contained Display Cases

Refrigerated display cases are used in grocery stores to merchandise perishable food products. Based on the stored product types, temperature requirements, the refrigerated display cases are categorized as either medium-temperature (MT) or low-temperature (LT). The MT display cases are used to merchandise meat, deli, dairy, produce and beverages. The LT display cases are used to merchandise frozen food and ice cream. Refrigerated display cases are either self-contained or are served by remote refrigeration systems. Currently, the U.S. Environmental Protection Agency (EPA) is considering a proposal that will push many refrigerated display cases to use natural refrigerants in the near future. The use of natural refrigerants in these units includes propane, carbon dioxide (CO2), and isobutene. Natural refrigerants have a potential for significant energy and demand saving, as well as environmental benefits primarily due to their low global-warming potential when refrigerant escapes into the atmosphere. Provided that there are about 3,000 large size supermarkets (greater than 1.6 million kilowatt hours (kWh) per year) in Southern California Edison’s (SCE’s) service territory that use multiple self-contained display cases, the potential savings can be substantial. The potential for savings can be enhanced by inclusion of smaller retail stores that also use self-contained cases. The objective of this laboratory assessment is to quantify the actual energy and demand reduction potential for self-contained cases with natural refrigerants as compared to baseline systems with traditional refrigerants. The results will be used to develop an incentive measure for the technology. This assessment was performed in a controlled laboratory environment. It involved establishing the baseline scenarios by testing a LT horizontal display case that uses traditional refrigerant, R-404A. Another set of testing was done on an identical LT horizontal display case that uses natural refrigerant, propane or R-290, to establish the measure scenarios. The instrumentation and testing followed the American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 72 in conjunction with the Air-Conditioning, Heating, and Refrigeration Institute Standard 1200. For all test runs, data was collected over a 24-hour period, monitoring 22 data channels with 5-second sampling intervals. The obtained data was then used to compare energy usage and power demand. Results indicated that the compressor of the display case with natural refrigerant required about 40% less power. The lighting system power was about the same for both unit types. Accordingly, total power demand of the case with natural refrigerant was lower. In relation to the baseline unit (conventional refrigerant), the compressor of the display case with natural refrigerant ran longer. This was attributed to the fact that the compressor was a variable speed drive. Though the refrigeration system ran longer, the daily energy usage of the display case with natural refrigerant was lower by little over 20%, 7.7 kWh/day vs. 6.0 kWh/day. Data obtained here substantiates the benefits of LT cases with natural refrigerant in terms of power demand reduction and energy savings. On the other hand, it would be beneficial to evaluate other types of self-contained cases, like open vertical, with natural refrigerants. Encouraging results obtained in this project leads to recommend refrigerated cases with natural refrigerants as part of the rebate program offerings.