LEDs Light the Way

Nov. 21, 2003
Top Points On Light Emitting Diodes
They’re used as the light sources in traffic signals, automotive brake lights, and animated signage (think the eight-story Nasdaq billboard in Times Square); and the list of possible applications for light emitting diodes (LEDs) just keeps growing.Unlike incandescents and fluorescents (where light is emitted from a vacuum tube), LEDs are small, solid-state lamps that produce light by passing current across layers of a semi-conductor material held inside a package. The semi-conducting material converts electricity into light with virtually no radiant heat.Until about 10 years ago, LEDs were available only in colors. Now, with the advent of the white LED, these lamps have moved into the commercial building marketplace, adding pathway and step lighting, spot and task lighting, and cove lighting to the expanding list of uses. And now that warm white LEDs are available in shades matching incandescent light color, the two can be integrated without anyone noticing the difference. Although white LEDs aren’t yet ideal for general and overhead lighting situations, they’re definitely headed in that direction.When making lighting decisions, both now and in the future, keep these LED points in mind.LED AdvantagesLamps demonstrate quick response time when power is applied or taken away. There’s no need for filters or gels to create colors. “If you use a 1,000-watt traditional halogen light source and put a blue filter in front to aim a spotlight at [someone] on [a] stage, to get the same blue amount of light with LEDs, you only need 65 watts vs. the 1,000 watts. That’s just a huge energy savings,” says Fran Douros, Americas marketing manager, San Jose, CA-based Lumileds.They’re efficient. Today, the efficiency of a high-flux LED can be as much as 24 lumens/watt – incandescent bulbs reach maybe 12 or 13 lumens/watt, according to industry sources.Lamps withstand shock, vibration, frequent on/off switching, and environmental/mechanical shocks.Compact shape allows for new fixture applications. “In the future, you’re going to see a lot more construction that has embedded light sources in it – ceiling tiles, wall panels, floors, and so on. That’s a phenomenal new thing, because it’s not something you could do with other sources. It’s not all about replacing a bulb; it’s about changing the way you light space,” says Makarand Chipalkatti, North American director of lamp modules, Danvers, MA-based OSRAM SYLVANIA. They won’t damage or discolor artwork, clothing, and other items being spotlighted, since there is no UV or IR in the beam. Lamps don’t suddenly go out; they slowly dim over time, which is both a safety feature and a design feature. LEDs have a long life. For a white LED that lasts 50,000 hours at 70-percent of initial light levels: “Assume six hours per day use for something like a step light. That’s 8,333 days. Five business days in a week, and that’s 1,666 weeks. Fifty-two weeks in a year – that’s 32 years. You can see, most likely, that the concrete  the light is set in is going to be cracked before the LED is dim enough to even notice,” explains Douros.These lamps work well in cool outdoor temperatures.They won’t break or shatter; not even during shipping. “A facilities manager could have a central stock of all of these products. Because they are robust, you can ship them from one central location to all these remote locations without having to maintain separate stocks and inventories in different locations. There’s no question about breaking. When was the last time you could do that with a neon lamp, for example? That’s an amazing change,” says Chipalkatti.LEDs don’t contain hazardous fills requiring special disposal.LED DrawbacksThe lamps are not realistically ready for general lighting use in all commercial facilities. “LEDs are still a very directional light source,” explains Jordon Papanier, marketing manager, Torrance, CA-based LEDtronics Inc. “One-third of all energy produced is used for room lighting, so using LEDs as a light source for room lighting would save over 80 percent of the energy currently used on incandescent and 40-percent savings over fluorescent lighting.”These lamps don’t always do well in very hot temperatures (some sources say only up to about 149 degrees F.). A few experts believe that LEDs just aren’t designed well enough yet to function in extremely warm environments.The cost per lamp is higher than other lamp options. “In a high-flux, high-lumen application, there are many more LEDs typically needed in the white light world. The great hope is that price position points continue to come down and that volume goes up. It’s a very volume-dependent business,” says Douros. “[We] could be ready for general lighting if people had an unlimited budget.”Their color can sometimes be inconsistent. “[Companies] are all over the map with their color temperatures,” says Chipalkatti. “A lot of it has to do with the quality of the manufacturing process.” Some white LEDs may look pinkish; others may look like more of a yellowish color. LEDs don’t give off the full spectrum of light in a spherical pattern – they emit one focused beam of color in only one direction. “[It’s] not easy to get an even 360 degrees of light from one LED bulb,” says Papanier.LED LegendsBecause LEDs are relatively new on the lighting scene, not all facilities professionals and building owners are aware of the capabilities and obstacles associated with these lamps. As LEDs move even more into the commercial environment, lighting industry experts are working hard to dissolve some of the myths surrounding these light sources. “This is a technology where anticipation is driving the perception about what [LEDs] do,” emphasizes Chipalkatti.For example, LEDs don’t last forever. Red-colored LEDs (the most common) can last about 100,000 hours before they dim to half their initial brightness. But due to the cost per lamp, some end-users choose to utilize fewer LEDs than the application requires and push those few lamps harder and with higher currents. The end result? The system only lasts for a few thousand hours (just a little longer than an incandescent lamp). “It’s not the LEDs, it’s the misapplication of the LEDs,” explains Chipalkatti. As with any lighting technology, if LEDs aren’t used appropriately and as recommended, facilities managers won’t get the results they want or expect.Many end-users believe LED lamps can get too hot and burn out quickly. “It all goes back to the semi-conductor, but you can’t get too hot inside the chip,” Douros points out. Facilities managers using products or systems that weren’t properly engineered can cause the LEDs to dim much faster. “If the system is properly engineered, that 50,000 hours is very achievable. You just have to remove the heat from the semi-conductor junction. We help people all day long figure out how to remove the heat from the light source,” she says.Brightness levels are at the source of another misconception. Traditional LEDs typically used for indication and signaling purposes are what most people are used to seeing in terms of brightness levels. Because some professionals haven’t ever seen LEDs at work in a commercial setting, there’s a perception (which the lighting industry is working hard to change) that LEDs aren’t bright enough to achieve appropriate light levels. But, “the perception of them not being bright enough has been proven false constantly,” assures Douros. Her advice for this particular situation? Buy from a quality company in whom you have confidence or that can prove it truly engineers LED systems correctly.LEDs’ Bright FutureThe No. 1 priority for the future is making white LEDs a cost-effective solution for general and overhead lighting. “It’s what we all consider the panacea. It’s the holy grail,” says Douros. “With the general illumination lighting market at over $15 billion per year, everyone in the industry is working toward that goal.” “The future looks very bright for LEDs,” Papanier points out. “In 20 years they went from an almost invisible light source to Main Street U.S.A. and the world. Some universities say that LEDs will be used for general room lighting in about 10 to 15 years.”To end-users, Chipalkatti cautions to “use where appropriate.” To light industry professionals: “Don’t push it where it’s not ready.”So, if you’re looking to inundate your parking lot with light for security reasons or to replace the 2x4 fluorescent fixtures in your corporate office ceilings, LEDs probably aren’t your best bet (yet). But just wait ... in a few years, they could be.Leah B. Garris ([email protected]) is associate editor at Buildings magazine.

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