Use LEDs for Refrigerated Display Cases
Ira Krepchin, Associate Director, E Source -- Foodservice Equipment & Supplies, 8/28/2008 7:35:00 AM
Light-emitting diodes (LEDs) have gotten a lot of press lately as the light-source of the future. For some applications, such as general illumination, the benefits of LEDs have been oversold. But one application where LEDs really do shine, is for illuminating refrigerated display cases. LEDs offer several attributes that give them an edge over the fluorescent tubes that have been the leading light source.
Good performance at cold temperatures.
Fluorescent lamps lose a considerable portion of their light output at cold temperatures — they provide about 25 percent less light at display case temperatures than they do at room temperature. LEDs actually perform better when the temperatures are cold. And they last longer as well.
"Lighting energy savings of 43 percent were measured…" |
Directional light output.
Fluorescent lamps emit light in all directions and are typically located near the display case door hinge and use reflectors to direct light onto the case contents. That process results in only about 60 percent of the light getting to where it is needed. LED light output can be aimed just where it is needed. In practice, that can mean the elimination of light-source glare on store floors and provision of even illumination of all products in the case. Tests at the Lighting Research Center have shown that customers like the illumination that LEDs provide.
No IR.
Fluorescent lamps, like most light sources, emit a lot of heat, in the form of infrared radiation, along with the light that they provide. LEDs produce waste heat also, but that heat can be conducted out the back of the LED. And the LEDs can be arranged so that much of the heat can be conducted away from the display case, which reduces the cooling load on the display case refrigeration compressor.
Controllability.
Frequent cycling on and off shortens the life of a fluorescent lamp, but has little impact on an LED. Therefore, foodservice operators can use LEDs with occupancy sensors that turn off the lights when no one is near. The more time the LEDs spend turned off, the lower the load on the compressors as well; and the longer the lamps will last.
The technology has been deployed by a number of companies and field measurements have shown significant savings. For example, field testing sponsored by the Pacific Gas & Electric Co. and conducted by the California Lighting Technology Center, was carried out at a grocery store in northern California. In this demonstration project, LEDs were installed in place of T8 fluorescent lighting in a row of freezer cases. A total of 36 5-foot F58T8 high-output fluorescent lamps and associated ballasts were replaced with 60 LED bars, each 4 feet in length. Lighting demand was cut by about 0.96 kW, and refrigeration load by another 0.46 kW. Lighting energy savings of 43 percent were measured; and the consistency of the lighting between cases was found to be more uniform with the LEDs than with the fluorescent lighting.
In addition, the researchers estimated that more than three cycles of fluorescent lamp replacement will be avoided during the expected 50,000-hour life of the LED system, leading to a reduction in maintenance costs as well. In addition, the fluorescent system that served as the baseline was a fairly modern one — retrofitting older display cases with LED technology would result in even greater savings. LED technology is improving rapidly, so even greater efficiency gains can be expected in the future.
