Technology's Twists and Turns Opens Up New 'Bulb' Choices

By Charles Linn

A light bulb is a light bulb, right? Not so, say those who reviewed lamp manufacturers’ offerings at Lightfair, an annual trade show held May 8-10 in New York City.

LED array.

 “Change is being driven by energy codes,” says lighting designer Robert Dupuy, associate principal at Interface Engineering,  Portland, Ore. These demand that designers squeeze every possible Watt out of a lamp and fixture.” And, newly available lamps that allow specifiers to balance the need for efficiency and color rendering quality while maximizing lamp life are challenging conventional wisdom about which lamp is best for a given situation.

Developments in light-emitting diode (LED) technology lead the way in challenging the technological status quo. These tiny, bright lamps were so ubiquitous at the trade show that Tim Haley, a commercial lighting engineer for Osram Sylvania joked, “This event should be called, “LEDFair.”

Osram Sylvania
Ceramic metal halide light source.

Manufacturers are trying to substitute the small, bright lamps for conventional lamps in every conceivable application. They have moved quickly away from individual lamps, such as those used in traffic signals, and turned to surface-mount technology, where the lamp, wiring, heatsink and circuit are integrated. Some manufacturers are putting phosphor-coated domes over blue lamps to produce what has been LED’s Holy Grail—pure white light. Others are mixing blue, green and red lamps to make white and every other color.

But not everyone is a believer, yet. Part of the problem is that “the lighting world is colliding with the semiconductor world,” Haley says. “What is considered warm-white light for them is cool-white for us.”

It also is difficult to manufacture quantities of LEDs that all produce the same amount of light, and there are no standards for how light output should be measured. According to Haley, some manufacturers say they are getting 16 to 34 lumens per Watt, but that is either equal to the efficiency of a 100-Watt incandescent lamp or twice as efficient.

Either way, LEDs produce lots of heat, which under some conditions can destroy circuits. Some fixtures are designed to shut down if they get too hot.

T8 fluorescent tubes are gaining ground in high spaces.

Cost also is an issue. “We’ve seen samples of LED strip lights that cost $300 per ft,” says Dupuy. But, virtually everyone agrees that LED lighting technology is advancing and costs may tumble.

Another major shift is toward high-output T8 fluorescent for high interior spaces such as warehouses and big-box stores. They are replacing metal halide (MH) lighting sources, which have dominated that application for the last 15 years. The color rendering of fluorescent has always been superior to metal halide, and energy efficiency, cold-temperature operation and service life have improved.

New electronic ballasts make it easy to dim or step-control the tubes when used in conjunction with skylights. Electronic ballasts also help extend tube life to nearly 30,000 hours, which is as good or better than MH, Haley says. “With the T8’s efficiency, you can save 40% to 50% over the MH product,” he adds.

LED integrated circuit is an all-in-one light source.

For almost 40 years, high-pressure sodium (HPS) lamps have been the predominant choice for roadway and industrial lighting even though their orange-white light renders color poorly. Re-

search indicates that vision is so improved when white-light sources are substituted for HPS that brightness, and therefore Wattage, can be reduced. This is giving a new generation of small, very efficient ceramic metal-halide lamps a boost. Not only is Wattage reduced, but the smaller lamps also have a higher lumens-per-Watt output than HPS.

But Dupuy notes that induction lighting is rapidly gaining acceptance. Induction lamps have no electrodes and use electromagnetic induction-excited phosphors to produce white light with better color rendering than even non-ceramic MH. Although their initial cost is much higher than HPS, they can last up to 100,000 hours. “Wherever lamps are difficult to change, service life is as important as color,” he says. That can take the sting out of their higher initial cost.