LEDs’ Shopper Appeal

Afield study conducted by the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute, Troy, N.Y., demonstrates the appeal of LED technology.

“This field study confirmed that shoppers overwhelmingly prefer LED lighting in the cases,” said LRC spokesman Keith Toomey.

Several years back, LRC conducted a laboratory study and concluded that LEDs would work well in freezer/refrigerator cases. In the more recent study, the LRC evaluated a four-door prototype freezer case with white LED lighting standing side by side with a freezer case with standard T8 fluorescent lamps at a Price Chopper supermarket in Rotterdam, N.Y.

The freezer, built by Tyler Refrigeration, a unit of Carrier Corp., was outfitted with several 1-watt, high-output white LEDs in a lighting system designed by Lumination (formerly known as GELcore), a subsidiary of GE Consumer & Industrial. The LEDs were mounted vertically at 1 inch. An additional line of LEDs was mounted horizontally at 2-in. spacing along the top of the case, behind the door header.

Over the course of the study, the LRC investigated shoppers’ preference for an LED-lighted freezer case compared to the matching freezer with conventional lighting. Overall, shoppers said products were more appealing and the lighting was brighter and more comfortable to look at inside the LED freezer.

The study had two parts. In the first, when the average lighting on the merchandise was kept at similar levels in both cases, more than 86% of shoppers selected the LED freezer as the one they liked the most. In the second, the light level inside the LED freezer was dimmed 25% lower than the fluorescent freezer. Even after dimming, 68% of shoppers preferred the lighting in the LED case. (The lighting did not affect sales.)

Cold Temperatures Impact Fluorescents

While fluorescent lamps provide superior energy efficiency in many lighting applications, they are not that well-suited for use in refrigerators and freezers, according to the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute, Troy, N.Y. Cold temperatures have a negative impact on the mercury-vapor pressure inside fluorescent lamps, reducing light output from the lamp and reducing lamp life. Also, because fluorescent lamps produce diffuse light in all directions, some portion of the light does not illuminate the products directly.

Additionally, LRC says that the poor configuration and mounting location of fluorescents in refrigerated cases negatively impacts their performance. Since some cases minimize space between door and shelves, light distribution may be concentrated near the lamp rather than spreading uniformly across the merchandise on display. Fluorescent lamps also produce radiant heat, contributing to the heat gain inside refrigerators and freezers, and increasing the need for cooling.

“Even though the average illuminance level of the fluorescent-lighted freezer was slightly higher, the uneven distribution of the fluorescent lighting led to areas at the center of each glass door that had roughly half of the average LED light level,” said N. Narendran, director of research, LRC, the leading university-based research center devoted to lighting.

While the fluorescent freezer had dark areas at the center of the case, the light levels were more uniform all the way across in the LED freezer.

“This likely led to the perception that the LED case was brighter,” said Narendran, who added that the sparkle the LED lighting created within the space also led to its high marks.

Energy: The prototype LED freezer at Price Chopper was built to measure shoppers’ preferences, not to show energy savings. But the LRC estimates that, using current white LED light sources with an average efficacy of 45 lumens per watt, an LED lighting system dimmed to a level that maintains shopper satisfaction would save 14 watts over fluorescent lighting in a four-door freezer similar to the one tested in the study.

In addition, because LEDs last much longer than fluorescent lamps in freezer environments, they provide a much lower life-cycle cost for owners.

“Our customers like the fact that the maintenance has been significantly reduced by eliminating the need for regular lamp and ballast replacements,” said Rick Waldron, senior product manager, Tyler Refrigeration. Tyler plans to have LED lights in its door-case production in the second quarter of 2007.

Some retailers are already deploying LED technology. Wal-Mart Stores, for example, will outfit low- and medium-temperature refrigerated display cases in more than 500 U.S. stores with a new LED solution from Illumination. The chain expects to net more than $2.6 million annually in energy-cost savings vs. standard fluorescent technology.