Green Design

Demonstration Assessment of LED Freezer Case Lighting

The logistics of arranging this comparison test did not allow for relamping of the existing fluorescent case lighting prior to the test and therefore a small portion of the apparent savings may be attributable to fluorescent lumen depreciation. It is more important to note that while the power consumed by the LED system showed a 61% reduction from that of the fluorescent system, a significant portion of the savings has resulted from a 36% reduction in illuminance as determined by relative measured levels before and after the retrofit. This 36% light level reduction accounts for more than half of the savings, which may have been alternatively accomplished with a retrofit of different fluorescent technology in the form of a lower output lamp and/or lower driving ballast. However, the complete retrofit demonstrated here that incorporates step dimming based on occupancy would be difficult with fluorescent technology, given the limited market offerings of specific dimming ballast technology.

The simplest energy reduction is the difference in wattage between the fluorescent and new LED lighting. The average fluorescent-lighted 5-door case has measured amperage of 2.6, while the replacement LED lighting pulls only 1.0 amp. The assumption of a uniform voltage of 120 for both existing and retrofit cases is used and the average wattage reduction per 5-door case is calculated at 192 watts. Based on 24 hour operation of the case lighting (store is open 18 hours per day but the case lighting not turned off after hours), the estimated total yearly energy use of a typical 5-door case lighted with the fluorescent system used at the Albertsons store is 2,733 kWh. The corresponding yearly energy use for the retrofitted LED system is 1,051 kWh. The estimated savings from one 5-door case lighted with LED is 1,682 kWh per year (61% savings – based in part on a relative 36% reduction in case illuminance).