TOPICS > Science

Light Bulb Technology

November 10, 2005 at 12:00 AM EDT


SPENCER MICHELS: In a lighting designer’s studio in San Francisco, a sales rep for Color Kinetics shows off a new kind of lighting that may revolutionize how we light our homes and offices.

JENNIFER PANKO: I’m going to zoom this in, and you’ll see how the colors don’t shift. Now let’s bring it back up.

SPENCER MICHELS: What Jennifer Panko is pushing are LEDs, a 35-year-old technology that is finally coming into its own. LEDs, or light emitting diodes, are thin pieces of various materials that emit light when electricity goes through them. But they use far less energy than traditional lighting, while providing flexibility in color and intensity.

While colored LEDs are already used for decorative lighting, when the industry perfects white light, it could well signal the biggest advance since, well, since Thomas Edison invented the electric light bulb in 1879.

Old fashioned incandescent bulbs use a lot of energy. In fact, lighting makes up 22 percent of the U.S. electricity budget. George Craford, chief technology officer of Lumileds in California’s Silicon Valley, showed us how much less energy LEDs use.

GEORGE CRAFORD: So, if you’ll just turn the crank you can light that, but it takes some effort to do that.


GEORGE CRAFORD: Now, if we switch over to the LED you’ll find that there’s a big difference.

SPENCER MICHELS: Oh, yeah. Hardly moving it and the LED goes on. And we’re getting essentially the same amount of light from both sources.

Craford says a switch to energy-saving LEDs could sharply reduce national energy consumption, and save $40 billion a year.

GEORGE CRAFORD: The world is in an energy crisis, and the fact that we can make a real dent in that is a key thing.

SPENCER MICHELS: Instead of using a filament like a conventional light bulb, LEDs use a wafer, much like a silicon chip which is coated with various materials that might include the element gallium or industrial sapphires.

When stimulated by electricity, the LED emits light, the color dependent on the elements used.

In a lab at the University of California at Santa Barbara, Steve DenBaars is a leading LED researcher.

STEVE DEN BAARS: It’s very similar to baking a cookie where you have 26 ingredients you can put into it. There’s so many variables that it’s very difficult to determine what the best cookie’s going to be. So, you know, we spend a lot of time varying the temperature, the chemical ingredients, the pressure that you grow it under, the time. All those things are very difficult to optimize.

SPENCER MICHELS: LEDs that emit colored light are already on splashy display around the world, lighting up retail stores, casinos, stages and bridges.

In Philadelphia, the famous boathouses along the Schuylkill River are now lit by LEDs. On a smaller scale, they light up keypads mobile phones, and they have become popular in flashlights, whose batteries last longer because the bulbs don’t need as much energy.

GEORGE CRAFORD: Like five times longer battery life. And for military applications, the batteries are a key issue because the troops have to carry a lot of weight, and the less batteries they carry the better and it’s also very rugged. The advantage of LEDs is that they are virtually unbreakable.

SPENCER MICHELS: And they are increasingly used in traffic lights, both because of low energy use and the fact that they last for a long time, saving money on replacing bulbs. Unlike conventional stop lights that used colored glass, the LEDs emit colored light. At UC Santa Barbara, Steve DenBaars has an experimental version of the LED traffic light.

STEVE DEN BAARS: In California, about 50 percent of the traffic signals, both the green, red and yellow, are LED-based because they use just one-tenth the energy.

SPENCER MICHELS: They use so little energy because they don’t waste it on heat, the way today’s light bulbs do, says Chris James, a vice president at Cree, a manufacturer of LEDs.

SPENCER MICHELS: Show me about the heat. These really don’t have much heat?

CHRIS JAMES: Here. Put your finger on that. That’s about as bright as your eye can stand.

SPENCER MICHELS: No, it isn’t hot. You don’t feel anything.

CHRIS JAMES: There’s no heat at all.

SPENCER MICHELS: The major thrust of much research today is the production of reliable, strong white light from LEDs. Shuji Nakamura, a Japanese researcher now at Santa Barbara, pioneered the development of high performance blue light, which when combined with a phosphor emits white light. And it is perfecting that light that researchers and graduate students here are exploring.

Still, problems remain, says Robert Steele, an industry market research analyst and a chemist.

ROBERT STEELE: There is no native device that will just emit white light. The light comes in narrow slices of color, a blue or a green or orange or red.

SPENCER MICHELS: Steele says that effective and powerful white LEDs are still a ways off.

ROBERT STEELE: The sources are still small in terms of the amount of light they produce compared to an incandescent lamp or a fluorescent tube. So you’d have to have a big assembly of these things to give you, you know, enough light to light a room. And then in doing that, it’s still very expensive.

SPENCER MICHELS: Still, says Cree’s Chris James, progress is being made.

CHRIS JAMES: The lighting industry’s been able to double the brightness of this material about every 18 months, and that’s going to have a huge impact.

SPENCER MICHELS: And, he says, the price will come down.

CHRIS JAMES: This is probably, you know, a $2 light bulb, and an LED ready to go to plug in is probably $30. But if you count the electricity it takes to run this for a year and the electricity it takes to run the light-emitting diode for a year, you’ll actually find that the LED Is cheaper than the bulb. That’s today.

SPENCER MICHELS: And eventually?

CHRIS JAMES: Eventually much cheaper.

SPENCER MICHELS: While experts agree that savings from LEDs won’t take place for several years, and white light needs more development, the industry is still worth $4 billion a year. That’s a result of the appeal of flexible, colored lights, says market analyst Steele.

ROBERT STEELE: Imagine being able to walk into a room and going to the wall and turning a dial that says “Maui sunset” and your room is flooded with light that is representative of a Maui sunset that you saw on your vacation, and you loved it so much you wanted to bring it home, and you can do it. I’m not exaggerating at all. This is entirely possible. You could do it today.

SPENCER MICHELS: But the big future of LEDs will be their everyday use in homes around the world. Estimates range from three to 10 years before they start replacing traditional lighting. By then, the industry is predicted to grow worldwide to 10 times its present size and change the way we see things.