Solid-state lighting coming into focus

The digital revolution is coming at last to the $100 billion global lighting industry. Energy-efficient LED lamps that replace the glowing-hot filaments of incandescent and halogen bulbs—and the harsh light of compact fluorescents—are finding favor with early adopters, who swallow hard and pay the hefty premiums with an eye toward energy savings. Even the superefficient T8 fluorescent tubes are in the sights of industrial giants such as General Electric, Osram Sylvania and Philips as those companies pursue roll-to-roll web printing of cheap plastic lighting panels using organic LEDs.

Traditional lighting doesn’t require electronics, but electronics technology is transforming the lighting market. Just as the modern automobile has become an electronics platform, the lighting solutions of the future will be chock-full of electronics, from the basic semiconductor emitters to smart compensation circuitry that will continuously optimize color temperature and composition for the time of day, the type of task and the differing life cycles of the components.

Solid-state lighting is already successful in niche markets, such as those for architectural, security, industrial and entertainment lighting. Specialty markets justify the premiums paid for SSL by reaping the benefits of zero warmup; integrated data signaling; and the ability to generate pure colors by mixing red, green and blue, instead of using energy-wasting white-hot arcs with color filters.

In the commodity lighting markets, LEDs are starting to penetrate specialty fixtures. For instance, Denny’s Restaurants recently announced it was going green by replacing all of its downlights nationwide with LED versions.

“LED lights will generally last 25 to 50 times longer than your standard incandescent light, but with the same color of light and same quality of light—and only use 20 percent of the power, on top of all that,” said Paul Scheidt, LED marketing manager at Cree Inc. (Durham, N.C.), maker of the downlight chosen by Denny’s .

Cree’s LR6 downlight taps patented color mixing to create light comparable to that produced by incandescents, but uses about 85 percent less energy and lasts up to 50 times longer. SOURCE: Cree

Even users of compact fluorescent lamps (CFLs) are upgrading to LED versions, which offer a more pleasing light than fluorescents. Last to be replaced by solid-state lighting will be the T8-format fluorescent bulbs.

U.S. Department of Energy comparison of lumens per watt for various lamp types shows that LEDs provide the most illumination and last the longest in the field. (a) correlated color temperature; (b) color rendering index; (c) high-intensity discharge SOURCE: DOE Solid-State Lighting Research and Development: Multi-Year Program Plan Click on image to enlarge.

The drawback to SSL is the sticker shock. Expect to pay about $40 for a Philips AmbientLED A19-replacement lamp today (predicted to drop to $10 by 2012), vs. less than $1 for incandescent bulbs. A few T8 LED prototypes have been shown, but only organic LEDs made on web printing presses are likely to offer competitive prices to the superefficient fluorescents—and probably not until around 2020.

“Near-term costs favor [inorganic] LEDs dramatically,” said Jim Jenson, vice president of marketing for the MOCVD Business Unit at Veeco Instruments Inc. (Plainview, N.Y.), maker of the metal-oxide chemical vapor deposition (MOCVD) equipment with which most LEDs are made. “OLEDs, on the other hand, are still high up on the cost curve.”

Until 2020, LEDs will likely remain the dominant solid-state lighting technology, offering a point source of light, like a halogen or incandescent bulb, but from a gallium nitride chip. An LED lamp can be custom designed to perform the same task as an existing bulb, but with higher efficiency and with an expanding palette of options, including electronically tunable color (temperature) and composition (measured by the color rendering index [CRI])—and, someday, even Web access using visible-light communications.

Cree crams 12 LEDs into a single package for customers who are designing MR16 halogen bulb replacements. SOURCE: Cree