As lighting designers turn to nontraditional light sources, LEDs and fiber optics could have a bright future.
Light emitting diodes (LEDs) and fiber optic cable aren't new technologies — not by a long shot. Chances are, if you use a cordless phone at home, you're exposed to both every time you pick up the receiver. That little red light that blinks to tell you you've got a message? It's an LED. And the line along which your mother's voice travels to ask, “Why don't you ever call?” is most likely fiber optic cable. Both have been around for decades. So why the big fuss about them now? LEDs and fiber optics are beginning to make inroads in a field for which neither was primarily intended: general illumination. And advances in both technologies are giving lighting architects two more weapons in the constant battle they wage against the dark.
From indicator to illuminator. On some level, it should come as no surprise that LEDs have made the step toward general indoor lighting — after all, they do produce light. But in the past, those little red embers were capable of doing nothing more than flashing on a computer console or letting you know that a piece of your stereo equipment was on; by any measure not enough light to lead you to the bathroom in the middle of the night, much less illuminate an assembly line. And the biggest obstacle to taking that next step was the inability to create bright, white light.
Yet once pioneering manufacturers like Nichia, Tokushima, Japan, strayed from the standard aluminum gallium arsenide (AIGaA) semiconductor material that creates low-level red light and developed stronger blue, green, and amber light from other organic materials like indium gallium nitride (InGaN) and aluminum gallium indium phosphide (AIGaInP), the possibilities of general and task lighting became more realistic. With the advent of the blue LED, engineers could create the elusive white light by combining red, green, and blue diodes in an array or by layering the plastic dome of a single blue diode with a phosphor coating, producing a mixture of wavelengths that are perceived by the eye as white.
A feature of LEDs that has made them attractive to lighting architects all along is their size. The combined profile of a typical LED and the circuit board to which it's attached is less than an inch — drastically less than that of the standard fluorescent lamp and accompanying fixture and ballast — reducing the space needed in the plenum.
But that very feature that makes installation easier makes illumination more difficult. Measuring only a few millimeters, one LED produces a minimal amount of light; hundreds and even thousands would be necessary to produce the same amount of light given off by a typical metal halide lamp. Not only that, engineers have failed to increase the efficiency over 20 lumens per watt, far below that of fluorescent or metal halide.
Another obstacle to the mainstream adoption of LEDs in commercial and industrial settings is their color temperature. Thanks in some degree to the development of the blue diodes that made white light possible, current LEDs produce a color temperature between 5,000°K and 6,000°K, which strays too far into the blue-white range for comfortable indoor lighting.
Although these problems may sound like too much to overcome, Jeff McDonald, a consultant to the Lighting Research Office, Cleveland, says LEDs can reach the promised land of task and general indoor lighting — but it's going to require a greater effort on the part of large-scale integrators and fixture manufacturers.
“It's going to take a financial, R&D, and application commitment to successfully move through the hurdles of the marketplace,” he says. “As it starts to move through the rest of the marketplace, you're going to need people like Genlyte and Lithonia and Cooper to step up and start offering some products they've done all the testing and all the engineering on.”
All of which isn't to say LEDs haven't moved beyond the indicator function they've been known for up until now. Nor is it unrealistic to expect that they'll show up in more mainstream, general illumination applications in the commercial and industrial markets. McDonald says LED manufacturers are aiming for wider market adoption by the end of the decade; in fact, he predicts LEDs will begin to play in areas like task, under-desk, and under-cabinet lighting in 2 yr to 3 yr (Photo on page 20). For the time, however, manufacturers have focused on niche markets like the automotive and signage industries where LEDs' lightweight, shock-resistant designs are more applicable.
When LEDs finally make that next step into general illumination, McDonald believes the ability to control and alter their intensity more easily than today's standard light sources will be a major selling point. “You're not talking to a filament; you're not trying to dim fluorescent lamps that don't want to be dimmed,” he says. “You're able to control it through a reduction in current or varying currents going to the different LEDs. And that's the really cool thing about it.”
Light those hard-to-reach places.
Having a little more luck in indoor illumination is fiber optic lighting. No longer a novelty item used to light up hats and T-shirts, it has found its way into more respectable markets like display lighting in museums, theaters, and cathedrals. Pioneered in Europe and using the phenomenon of total internal reflection, in which light from a single halogen or metal halide source is transported as much as 72 ft by way of plastic or glass strands to any number of places, fiber optics drastically reduce the number of lamps necessary to light a space, thereby cutting down on maintenance and relamping concerns.
The common mental image of fiber optic cabling as gossamer-thin strands of flimsy plastic may make it hard to believe it can withstand the corrosive effects of standard lamps or produce sufficient amounts of light, but the structure is more conducive to lighting than that picture suggests. A single “tail” is made up of multiples of 400 strands — usually made of glass and measuring 50 microns in diameter — that transport and emit light from their ends; a size 1 tail holds 400 strands, a size 2 tail comprises 800 strands, and so on. Though the light footprint isn't ideal for ambient lighting, it's well-suited for spotlight display cases and wall-mounted objects.
What has made the technology so attractive to lighting architects designing installations in places like art galleries and museums where the items on display can be ruined by excessive, intense light is the virtual nonexistence of heat or UV rays (Photo at top). Because the tails carry light by reflection, they leave the heat and damaging rays behind at the source. This same characteristic makes it possible to use fiber optics under water in pools and fountains because they do not conduct electricity.
Gersil Kay, founder of architectural lighting firm Conservation Lighting International, Philadelphia, points to the low-maintenance nature of fiber optics as one of its greatest advantages. “If you have a very high ceiling where you can't get up to change the lamps, you have to use fiber optics,” she says. “People don't realize the cost of maintenance in an instance like that. No lighting is good if you can't readily access it to maintain it.”
Recent strengthening of restrictions on energy efficiency have also forced building owners to consider light sources that produce improved lumens per watt output and less heat — two things fiber optics offer. In particular, ASHRAE 90.1 has put the squeeze on builders to reduce energy consumption, and as older buildings come due for retrofits, Kay believes fiber optics are the way to go.
“Now that we have this standard, there's going to be a tremendous market in retrofitting to comply with the restrictions,” she said. “And I maintain that if you start with the most energy efficient light source that you can use, even if the people ignore the wattage restrictions and the controls that are mandated by the standard and which will be enforceable in every building code in every state, you'll be saving energy.
“Glass fiber optics is eminently suited for existing buildings, because first of all it's miniaturized. It's also unobtrusive and energy-efficient, and it gives you really sophisticated lighting.”
However, like most new technologies — especially those developed overseas — glass fiber optic lighting has yet to gain mainstream adoption in the U.S. lighting industry, and Kay blames a combination of unfamiliarity and lack of adequate education for lighting manufacturers, designers, and architects for the slow progress the technology has made stateside.
“The United States thinks we're the center of the universe — if we didn't think of it first, then it doesn't exist,” she says. “People who are successful lighting designers figure if it ain't broke, don't fix it. And besides, people hate new things. Whether they're good or bad, they're suspect of them.”
Despite the obstacles preventing LEDs and fiber optics from entering and becoming major players in the general illumination market, both McDonald and Kay are confident that the technologies will continue to find the niches that need scratching and provide lighting designers with options they didn't have before.
“You have to pick and choose,” Kay says of the light sources. “You have to see what the lighting wish list of the client is and then you figure out what lighting tools you need to achieve that particular goal.”