The creation of white light emitting diodes (LEDs) represents a huge shift from current lighting paradigms and is expected to result in the establishment of new lighting fixtures, controls and power supplies, in addition to new application and installation practices and codes; today, the domestic market for traditional lamps, ballasts, lighting fixtures and lighting controls is about $12 billion in the United States and about $40 billion worldwide. With 22 percent of the United States’ electrical energy running lights, and with incandescent lamps consuming electrical energy equal to the output of more than 40 large power plants, white LEDs could be the answer to the energy-efficiency problem in the lighting industry.
Commercially viable colored LEDs (primarily blue, red, yellow and green) have been around for some time and are widely used in traffic signals, roadway signs, exit signs and LCD backlighting in cell phones and other electronic devices. According to Kraig Kasler, vice president of marketing for GE Consumer & Industrial’s LED business, Lumination, Cleveland, the global LED market in 2004 stood at $3.7 billion, with white LEDs accounting for about half of that.
However, according to Michael Neary, senior applications engineer for LED systems at OSRAM Sylvania, Danvers, Mass., LEDs currently account for less than 1 percent of the total general illumination market in the United States.
“Where LEDs have made headway is in traffic signals, exit signs and exterior signage, and they’re now just starting to enter the high-end residential and new commercial building markets,” Neary said. By 2030, it is estimated that 20 percent of the total lighting market will be LED-based.
Making white LEDs
The first and most basic way to make a white LED is by mixing red, blue and green LED solid state chips to make white light. However, using a blue LED and coating it with a yellow phosphor to produce a broad-spectrum white light is growing in popularity.
“The phosphors are stimulated by the blue light to produce a white-colored light,” said Jeff Quinlan, director of engineering at Lithonia Lighting, Conyers, Ga., an Acuity Brands company.
The third method is to use a near-blue ultraviolet LED chip and add triphospors to it.
Rather than emitting a single color through a discrete wavelength to create moods, themes or to be used as accents, as colored LEDs do, white LEDs emit a broad spectrum of light and can be used, as they grow more efficient, in general illumination applications.
“Using the blue LED chip as its base, white LEDs can more efficiently produce a bright white light in cooler color tones. Ultraviolet chips, however, are more efficient in producing warmer tones,” said Alex Mier-Langner, director of LED product development for Lightolier, Fall River, Mass., a Genlyte Group company.
Other than the use of phosphors, the most significant differences between white LEDs and their colored cousins are cost and performance.
“Red LEDs are the most advanced, efficient and inexpensive because they’ve been around the longest. As the newest entrant into the field, white LEDs are more expensive and don’t have performance levels as high yet,” Kasler said.
Performance and color quality
On the color rendering index (CRI), white LEDs don’t currently have a solid or definitive rating. They are comparable to good fluorescent or incandescent light sources, according to Quinlan.
“Electrical contractors need to be sensitive to the CRI variation between each batch of LED chips manufactured to ensure that the color temperatures emitted operate as specified by the project,” he said. However, according to Mier-Langner, manufacturers are working to produce white LEDs that can be measured with the same CRI as traditional light sources.
“The CRI of white LEDs can vary from 40 to 90 today. Electrical contractors should choose a product based on the need for color quality,” he said. For example, signal lights in an automobile can have a lower CRI rating and still fulfill the application’s lighting and efficiency needs.
The efficacy of white LED luminaires is currently between 35 and 100 lumens per watt.
“In laboratories, researchers have gotten LEDs to produce lumens per watt in the 100s,” Mier-Langner said. The trick with measuring white LED efficiency is that you have to differentiate chip efficiency with total fixture efficiency to ensure that the product is producing the required lumens per watt for the application.
“Electrical contractors need to focus more on the fixture, rather than on the efficiency of the chip itself,” he said. According to Kasler, those white LEDs that produce warm light and are closer to the color of incandescent lamps are currently producing around 30 lumens per watt. “Cooler, bluer white LEDs, at 6,500 Kelvin, currently have efficiencies between 40 and 50 lumens per watt,” he said. However, these numbers represent a 30-fold increase per decade in terms of efficiency since 1968.
Clearly, white LEDs have to improve their efficiency before they can compete in the general illumination market with linear fluorescent (which produce 3,000 lumens per lamp), standard incandescent bulbs (which produce 2,000 lumens per lamp) and halogen lamp sources (which produce from 150 to 4,500 lumens per lamp).
Ups and downs
Long life really makes LEDs shine. “White LEDs will generally last from 50,000 to 60,000 hours,” Neary said. Compare that to the life cycle of fluorescent lights at 25,000 to 30,000 hours, halogen at up to 6,000 hours and incandescent at a mere 2,000 to 3,000 hours, and the benefits of decreased maintenance costs of white LEDs becomes clear.
“When the technology becomes more cost-effective to produce and provides a better light output, it will become a lamp source of choice across all illumination markets,” Neary said.
Other benefits of white LEDs are their small size and low profile, which provide users with significantly flexible design options; lack of mercury; robustness; and easy integration with backup power systems.
“LEDs’ flexibility allows them to be configured in different ways to create a host of luminaires for various applications,” Mier-
Langner said. And with no glass to break, they are more durable than traditional light sources. In addition, they are easily dimmable and provide a very directional light source that reduces light pollution.
However, the current initial cost of white LEDs is probably their largest barrier to market acceptance.
“There is currently a huge degree of variation in cost, depending on the size of the chip and the application,” Quinlan said. For example, a 60-watt incandescent light bulb costs about $.0003 per lumen. A white LED today ranges from 8 to 10 cents per lumen, which is 200 to 300 times as expensive as an incandescent bulb and 30 or 40 times as expensive as a CFL. However, over the past 40 years cost has been decreasing constantly in lumens per watt by a factor of 10 per decade.
Another disadvantage, according to Mier-Langner, is the difficulty in determining by sight examination whether the product is designed properly and manufactured correctly. “Contractors have to rely on the manufacturer’s expertise,” he said. In addition, the higher-powered LEDs produce significant heat, there is a lack of industry standards and there is an extensive engineering process required to incorporate LEDs into existing fixtures.
On the horizon
Although no one can predict how many years it will be before white LEDs gain widespread market acceptance, Quinlan predicts in the near future white LEDs will become more efficient and will continue to drop in cost in relation to current light sources.
“We will see an increased incorporation of white LEDs into existing products in general illumination applications, from residential to commercial, institutional and retail,” he said. When the payback, in terms of total cost of ownership, approaches two to three years, people will begin to rapidly adopt the technology.
“White LEDs should reach the point within the next decade that professional lighting designers and electrical contractors widely apply this new technology,” Quinlan said.
They already are being used in downlighting and task lighting applications and in refrigeration cases and retail displays. They are growing in popularity because of their long life in hard-to-maintain areas, such as tunnels, roadways, bridges and in high-ceiling environments.
“White LEDs are also being used today in landscape and pathway marking and in exterior illumination in parking lots and on roadways,” Neary said.
According to Mier-Langner, manufacturers are investing in research and have gotten excellent results in laboratories.
“Promising advances in color and efficiency is driving further research forward in an attempt to bring white LEDs to general illumination applications in the next five to 10 years,” he said. Also within the next decade, there should be an influx of nicely designed fixtures that offer high energy-efficient packaging of white LEDs. “As the technology continues to improve and is used in more applications, the cost will continue to decrease,” Neary said. EC
BREMER, a freelance writer based in Solomons, Md., contributes frequently to ELECTRICAL CONTRACTOR. she can be reached at 410.394.6966 or by e-mail at firstname.lastname@example.org.