Light emitting diodes may be the future of lighting technology, but hurdles remain in the present.

The inefficiencies involved in most general lighting solutions seem to beg for a technological savior in the new millennium. The advances in the evolution of light emitting diodes seem to be the inevitable answer to conventional lighting woes. These small crystal-based bulbs alleviate many of the headaches stemming from fragile, inefficient incandescents. For a number of reasons, however, we are probably years away from seeing LEDs replace traditional bulbs in our everyday lighting fixtures.

First developed in the '60s, monochromatic light emitting diodes - in colors like red, yellow, blue and green - have been a component used in displays and other industrial applications.

One of the classic applications of LEDs has been the exit sign, where a very directional form of light is needed. Exit signs were particularly good fixtures for the LED chips due to the fact that LEDs were only available in red for a time. With the addition of various lenses and new techniques, LEDs can be more versatile, however. As technology advanced, these LEDs could be found in alarm clocks, traffic lights, brake lights, flash lights and all sorts of electronic displays.

The challenge today is to make use of white LEDs (a new innovation in and of themselves) in general lighting. At the LightFair International trade show last April, the three major lamp manufacturers - GE Lighting, Cleveland; Osram Sylvania, Danvers, Mass.; and Philips Lighting, Somerset, N.J. - gave attendees a peek at their LED R&D efforts. They said LEDs could eventually be an alternative to conventional lamp sources for general room lighting if they can develop LEDs that produce white light cost competitively.

Tony Tu, manager of SUNLED (an LED manufacturer)'s stocking branch office in Walnut, Calif., emphasized that it's more complicated to create LEDs that produce white light. "It's somewhat difficult, plus the light that they emit is not exactly true white."

In the past, the only way to produce white light from LED technology was to combine three different colors and shine the light on the same spot. New advances have made this process more efficient, but problems remain.

"(White LEDs) have only been available bright enough to do anything for the last two to two-and-a-half years," said Brian Kennedy, president of Watt-Man L.E.D. Lighting, Charlottesville, Va., "and they're probably anywhere from 10 to 15 times more expensive than red LEDs."

Although LEDs are far more expensive than traditional bulbs, there are numerous reasons why the industry continues to pursue them. Unlike other light bulbs, LEDs are not a component system; they have no filament. LEDs are a multilayered crystal technology that produces light when a current passes through them. Their simplicity makes them durable and efficient. This means they can run more effectively in industrial environments where traditional bulbs would be ruined by vibration and shock. They also generate far less heat than other bulbs. In addition, LEDs don't give off any UV emissions, which can pose a danger to certain materials. These attributes of LEDs translate into more and more new markets; they can be used near clothing, sensitive artwork and other delicate materials. Durability and simplicity make LEDs useful underwater as well. They are well-suited to giving architectural effect lighting in pools, fountains and other exterior areas.

Further, LEDs are 100% dimmable and don't require ballast or harmful, gaseous mercury of fluorescents.

Even more basic advantages stem from the inherent characteristics of LEDs though. The efficiency causes them to draw far less current. In many cases, LEDs use only one tenth the energy that an incandescent would. Furthermore, the durability of LEDs affords them up to 100,000 hours (up to ten years) of longevity in some instances. These benefits can create cost savings of their own.

"If you take an incandescent bulb and you say `that cost me only 50 cents,' but it lasts for 1,000 hours. Then you buy something that lasts for essentially 100,000 hours and you pay $50 for it," said Chips Chipalkatti, marketing and technology manager for LED light sources at Osram Sylvania, Danvers, Mass. But Chipalkatti added that "the costing has to be done as the cost of ownership over the period of time that you own it."

He reiterated that an LED would use only a fraction of the electricity drawn by the incandescent. Factoring that in means more energy savings - in addition to the savings from a reduction in bulb replacement and the manpower required - and LEDs could very well save customers money even before the price goes down.

The likelihood of the average consumer doing that much math may be slim, but Chipalkatti noted that LEDs might be coming down in price before we know it.

"In terms of individual LEDs, I think it's just a matter of capacity that will control the cost. Now I'm shocked that you can buy a VCR for 30 to 50 bucks ... that's a trend that is also sort of imbedded in this semiconductor business of LED lighting."

As the technology advances, companies planning budgets with an eye on the long-term may find themselves using LEDs even before the price comes down.

LED technology may be promising, but there are strides to be made before it becomes a fruitful reality.

Though some LEDs may last for 10 years, blue, green and especially white LEDs have less than half that life span before they are reduced to half of their original brightness.

Also, the inherent advantages of monochromatic LEDs do not necessarily apply to white LEDs. Monochromatic LEDs are more efficient than incandescents because putting a colored filter on a white incandescent light reduces its lumen output. That, and the fact that they are easier to produce, is why monochromatic LEDs have been used in so many applications already. Therefore, white LEDs have a reduced advantage in brightness over incandescents - relative to monochromatics. As Tom Pozda, director of product management and marketing for Gelcore, says, although the market is there, the product has not been developed to the proper level.

"There are very limited applications where you can use monochromatic LEDs. When you start looking at white light, there are a lot of illumination activities, but the challenge is the actual lumen output of the device at this point."

The color quality of white LEDs is also on the cold side; due to the process of producing it, it tends to be a more bluish light. And though they outshine incandescents, getting the necessary brightness out of LEDs can be very expensive at this point.

"I can gang up 200 white LEDs in a fairly tight lamp package, and it will be bright as can be. But the lamp might cost you $600 or $700," Watt-Man's Kennedy said.

The consensus in the industry seems to be that LEDs will be restricted to specialty applications for the next five years or so. But the progression to general lighting will be gradual.

In the meantime, Watt-Man L.E.D. is already selling lamps and other applications. Theledlight.com has a whole line of flashlights and more, and Osram is working with numerous architectural lighting products that are well-suited to the nature of LEDs. Also foreshadowing a rosy future for LEDs, Marktech, Menands, N.Y., is marketing LEDs that outshine and outlast the competition for use in variable message signs (VMS) on roads and highways.