When it comes to dispelling the dark of night, not much has changed since Thomas Edison's first electric light bulb of the late 19th century.
Today's incandescent light bulbs produce light by passing electricity through a thin metal filament, causing it to glow brightly.
While such simplicity has worked beautifully for the last 120 years, conventional light bulbs still haven't made much gain in energy efficiency. As much as 95 percent of the energy used by a light bulb is given off as wasteful heat. Such heat is also one of the key reasons light bulbs have life spans of only a few hundred hours before they burn out and need to be replaced.
But several companies believe that the time to throw out the standard bulb is close at hand. And the potential successor to Edison's bulky bulb is the solid-state, light-emitting diode, or LED.
LEDs have been around since the early 1960s. They produce light by passing an electrical charge through a solid semiconductor material.
Robert Steele, an analyst with market research firm Strategies Unlimited in Mountain View, Calif., says the nonmetallic materials used in early LEDs didn't produce much light, and the only color light was red.
"For many years, they were just indicator lights," says Steele. "They were small and produced just enough [visible] light — if you looked directly at them."
However, over the last decade, researchers have been able to greatly improve the quality and quantity of light that can be produced from LEDs. And rather than just a single color, the new LEDs can produce so-called white light, which, like sunlight, contains every color of the rainbow.
One such LED, called Luxeon, is produced by LumiLEDs, a joint venture between Agilent Technologies and Philips Lighting. The San Jose, Calif., company says the device is just 5 millimeters wide, but one of the brightest, white-light LED devices currently available.
The key to Luxeon is a special phosphor compound that coats the top of the LED. When the device's semiconductor is charged with electricity, it produces an intense blue light that strikes and "excites" the phosphor. As a result, the phosphor produces a yellowish glow that, when combined with the blue light, produces an extremely close approximation of white light.
Mark Swoboda, a vice president at LumiLEDs, says the Luxeon device uses just five watts of energy to produce 120 lumens — the same amount of light as a 10-watt halogen bulb but without the wasteful heat.
"We can typically see a 90 percent energy savings [with a Luxeon]," says Swoboda.
More importantly, without the high operating temperatures, fragile glass structure, and thin filament design of traditional light bulbs, Luxeon LEDs have a life span of about 50,000 hours — more than eight years.
LED to New Uses
Although a single bright-white LED like the Luxeon wouldn't replace a single conventional light bulb, LumiLEDs says several companies are expressing and experimenting with using LED arrays for a variety of applications.
Robert Miller, a senior partner and managing director of BrightLights Technologies in Detroit, for example, says several car companies are already using LEDs for brake and turning signal lights in certain luxury cars. But his company has also developed LED-based headlights for concept vehicles such as the Tomahawk, a four-wheeled motorcycle designed by Chrysler.
Miller says LEDs make ideal light sources for such vehicles because of their inherent ruggedness.