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Efficiency Testing for Freezer Case Lighting
Supermarkets use lighted cases to store and display refrigerated and frozen products. LEDs are now becoming common light sources in this application. Current industry practice rewards freezer lighting for its luminaire efficacy measured at room temperature. To obtain realistic data, the evaluation method must consider the application environment. ASSIST has published a technology-neutral method for evaluating the performance of luminaires used in freezer cases.
APPLICATION EFFICACY METHOD
ASSIST’s method calls for measurements of the luminous flux reaching the face of the merchandise. A 60-inch by 60-inch area with 6-inch grid squares was built for illuminance measurements. Measurements are first taken at room temperature (22°C). A scaling factor using the relative light output measured at the proper cold temperature is applied to the room temperature measurements to estimate the cold application’s luminous flux. The luminaire input power and the extra freezer power required to dissipate heat from the luminaire are used to calculate the luminaire’s application efficacy.
PERFORMANCE COMPARISONS
Six commercial LED freezer case luminaires were tested following ASSIST’s method. Comparisons were made between luminaire efficacy and application efficacy and between luminaire power and total system power at both room temperature (22°C) and freezer temperature (–22°C). The results show significant performance differences between room and application (freezer) temperature. For example, luminaire B has better room temperature luminaire efficacy (42 lm/W) than luminaire C (28 lm/W). However, when both luminaires are compared under cold application conditions, luminaire B’s application efficacy is slightly lower and requires 30% more power.
PAST STUDIES
The Lighting Research Center began studying LEDs for freezer case lighting in 2002, and the Alliance for Solid-State Illumination Systems and Technologies (ASSIST) published its recommended test method for freezer case lighting in 2008. Below are summaries of past freezer case lighting research:
Lighting Supermarket Freezers with LEDs (2006)
The LRC conducted an 18-month field study to compare LED lighting with fluorescent lighting in supermarket freezer cases. The study included a survey of shoppers, an energy analysis, and a sales analysis.
Refrigerated Display Case Lighting with LEDs (2002)
Using high-brightness LEDs in refrigerated display cases as a replacement for fluorescent lamps is the focus of this study. Solid-state lighting offers light with less heat.
TECHNICAL REPORTS & PUBLICATIONS
ASSIST. 2008. ASSIST recommends...Recommendations for Testing and Evaluating Luminaires for Refrigerated and Freezer Display Cases. Vol. 5, Issue 1. Troy, N.Y.: Lighting Research Center.
Narendran, N., J. Brons, and J. Taylor. 2006. Energy-efficient Alternative for Commercial Refrigeration. Project report prepared for the New York State Energy Research and Development Authority. 
Narendran, N. 2006. Field Test DELTA Snapshots: LED Lighting In Freezer Cases. Troy, N.Y.: Lighting Research Center.
Raghavan, R., and N. Narendran. 2002. Refrigerated display case lighting with LEDs. Solid State Lighting II: Proceedings of SPIE 4776: 74-81.
Full-text PDF
Project Summary Sheet (2010)
Project Summary Sheet (2006)
2010 SPONSOR
ASSIST
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