Refrigerated display lighting (RDL) represents one of the more perfect applications for LEDs. Because fluorescent tubes can be replaced with LED strips and reduce energy usage by 60%, retailers are beginning to implement LED case lighting on a wider scale. Typically, a store can realize return-on-investment (ROI) after 2-3 years using LED-lit coolers. In addition, since LED commercial lighting wholesale give off little heat relative to a fluorescent tube, an additional energy break is realized on compressor cooling. "LEDs love the cold; the colder they are the longer they last We are able to design fixtures that are rated for 100,000 hours, "said Jamie Pearson, senior value stream manager of Lithonia Lighting, part of Acuity Brands..
Fig. 1. An all-LED supermarket in Portugal used Arquiled fixtures and controls and Oslon LEDs from Osram Opto Semiconductors (photo courtesy of Arquiled / Osram).
Fig. 1.
Fluorescent tubes provide a diffuse light in all directions, whereas LED lighting fixtures have been designed to provide directional illumination at 70-160 ° as needed in the case. Importantly, the quality of light in the case can also be improved to reduce glare, eliminate hot spots and make the food and packaging more appealing through better color rendering. "We recognized early on that many company's products would be within 10% of each other in energy savings. So we focused on providing the best light with the best color rendering and greatest uniformity, "said Paul Kelly, vice president of market development for Nualight.
This merchandizing effect of LED lighting is being applied beyond the refrigerated cases themselves. Many grocery stores, specialty shops and convenience marts have decided to implement LED lighting throughout the store and in outside parking lots and gas stations. For instance, Jerónimo Martins Group (Fig . 1 and 2) recently installed LED lighting inside and outside its supermarkets in Portugal, which we will cover in more detail below. Notably, Walmart has set a goal to use 100% LED lighting in all of its 5366 stores through new construction and retrofitting .
As will be discussed, the adoption rates of RDL differ among Europe, North America and Asia. The fastest adoption has been seen in North America, where incentives have shortened the time to ROI.
Refrigerated case lighting options
Refrigerated display cases are available in many styles and sizes, but the market overall generally comes down to vertical freezer cases with doors and horizontal refrigerated cases without doors. The lighting in the vertical cases run vertically along each side of the door, and is generally 5 -ft tall. In horizontal cases, typically there are one or two 4-ft fixtures that run at the top of the case (canopy lighting) and the base of the case (shelf lighting). In Europe, another common design employs a row of vertical coolers on top and horizontal coolers on the bottom.
Fig. 2. The gas station uses controls to further reduce lighting costs (photo courtesy of Arquiled / Osram).
Fig. 2.
The worldwide market for lighting in refrigerated display cases is huge, especially the retrofit market. Case makers such as Hussmann and Kysor / Warren are selling new refrigerated cases with LED lighting already equipped in the case. But for existing stores, new cases cost in the range of $ 5000 for a three-door unit, so most managers choose to retrofit the case lighting.
In a study from 2010, Osram Sylvania estimated that there were roughly 10 million vertical case freezer doors available for retrofit, and nearly 20 million horizontal linear 4-ft fixtures in open refrigerated cases available for retrofit in the US. The study estimated there were 14 million single-lamp fixtures and 6 million dual-lamp fixtures in horizontal cases available for retrofit, according to Cheryl Ford, vertical marketing manager for Osram Sylvania.
The vertical units are used for packaged foods, while the horizontal cases are used for fresh dairy and meats. Though an ingress protection (IP) rating is not common for the freezer lighting fixtures, many users specify an IP rating of IP64 or IP65 for the horizontal cases to ensure the fixtures can withstand wet cleaning.
At first glance, it would appear that food and beverage retailers have countless options when it comes to choosing a provider of LED refrigerated display lighting. Providers include well-known companies such as Acuity Brands, GE Lighting, Nualight, Osram Sylvania, and Philips Lighting , but there are numerous other providers from Europe, North America and Asia. The qualified product list of the DesignLights Consortium (DLC), which includes both vertical and horizontal RDL, contains products from 19 manufacturers.
Fig. 3. The Shiver fixture from Lithonia Lighting uses a 90 ° cutoff angle to reduce glare on merchandise and keep light inside the case (photo courtesy of Acuity Brands).
Fig. 3.
The DLC relies on LM-79 data from a qualified third-party testing lab to demonstrate that fixtures meet minimum performance criteria. These include a luminous efficacy of 55 lm / W, CRI of 70, light output of 50 lm / ft for end fixtures or 100 lm / ft for center fixtures, and a zonal lumen density of 90% from 0-90 °. Fig. 3 shows a typical light distribution when zonal lumen density is concentrated in this way.
A 5-ft fluorescent tube uses 60W of power (total wattage for 58W lamp and ballast). Today's 5-ft LED fixtures typically use 12W (right or left end unit) or 18-24W (center unit). Both bi-pin and bracket-based versions are offered (Fig. 4). A driver is needed to step down from mains power to 24V. It is typical that one driver is required per door (2 fixtures).
Some LED fixtures use a series of low-wattage LEDs, typically 0.5W or 1W, along a strip, while others use high-powered LEDs spaced along a metal fixture. Most units have specially designed optics. Some companies offer broad product lines in a range of sizes and color temperatures, while other companies target only the most common case sizes and product depths.
Retailers typically choose LED fixtures with cooler color temperatures for freezers whereas a warmer CCT of 3000K is more suitable for meats, fish and seafood. Products with a color rendering index (CRI) of 70 to as high as 95 are commercially available, which compares to a CRI of 85 for fluorescent lamps. For instance, Philips offers its Affinium LED modules (Fig. 5) in color temperatures of cool white (5600K) or neutral white (4100K).
Fig. 4. The LEDstixx fixtures in bracketed or bi-pin versions. The driver can handle 4-6 fixtures, reducing installation complexity (photo courtesy of Osram Sylvania).
Fig. 4.
Though a higher price is associated with the higher CRI LED fixtures, retail store owners understand the greater visual appeal associated with better color rendering. While initial use may be confined to high-end products such as meats and cheeses, the more LED pricing comes down , the easier it becomes to afford the better light.
Susan Fowler, LED refrigerated lighting product leader for GE Lighting summarized the design of the Immersion RV40 LED commercial lighting wholesale , as products that "optimize energy savings while providing 750-1100 lx, hiding the view of the light source, focusing light on the packaging versus spilling onto the floor or doors, and creating uniform light in the case. "GE offers these fixtures in 3500K, 4000K and 5000K color temperatures and sizes of 30, 36, 48, 60 and 70 in. The 60-in , 4000K model produces 1070 lm (213 lm / ft) and requires 18W of power.
Regional differences
Retailers in North America, Europe and Asia are at different stages of RDL adoption. The types of cases and sizes differ by region as well. Fowler noted that North American stores tend to be larger in general than stores in Europe. She stated that while all regions are interested in reducing energy cost and maintenance cost with LED fixtures, western countries tend to focus on energy and light quality, while eastern regions tend to focus more on payback.
In North America, the utility rebates have accelerated adoption. "North America is miles ahead of Europe," said Kelly. "Perhaps 40% of the North American market has been retrofit in the freezer segment," he added. Kelly predicted that LED lighting for all refrigerated cases will become the de facto standard in North America by 2014.
Another difference is that product tends to be situated closer to the door in cases in the US. Some companies offer a product line that accommodates these differences. Speaking to Osram's approach, Ford said, "The distance of the lighting fixture to the merchandise is key . If your shelf depth is up to 4 in - one product is used, 4-8 in - a second product and 8-10 in -. a third product "
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