Do LEDs generate enough lumens for use in fixtures and portables?
Kelly Gordon: That’s the big push. High-power LEDs can produce up to about 80 lumens. A standard 60W incandescent bulb produces about 900 lumens. You have to group LEDs together to approach the light output we need.
RL: Are they efficient?
KG: Incandescent sources produce around 15 lumens per watt, and LEDs are 25 to 40 lumens per watt. Since a CFL is about 50 lumens per watt, LEDs fall in between the two. But technological issues need to be worked out—the most important being heat. LEDs don’t emit
infrared radiation like incandescents; they don’t get hot to the touch. But they do generate heat within the device, and that heat must be moved away. When an LED gets too hot, the light output takes a nose dive.
RL: In what ways are LEDs ready for the home?
KG: Portable desk task lights and undercabinet lights. You can make undercabinet LEDS very low profile. Being close to the work surface, they take advantage of the directionality of the LED light source.
Some LED fixtures and portables are becoming available for the consumer, and some are very intriguing. But the full-scale, practical application of LEDs in resi-dential lighting is still in development. LED lumen output has doubled in the past two years, while the average price has fallen by more than half.
RL: What are OLEDs?
KG: Solid-state lighting encompasses both LEDs and organic light-emitting diodes (OLEDs). LEDs are small, point sources while OLEDs are made in flat and diffuse forms typically used in displays. But they are expected to develop as light sources. Konica-Minolta recently announced a proto-type white light OLED that operates at 64 lumens per watt and lasts for 10,000 hours. At those levels, it would rival compact fluo-rescent lamps. LEDs have much longer lifetimes: around 35,000-50,000 hours.
RL: Will LEDs ever be main light sources in the home?
KG: Eventually. A balance has
to be achieved with product quality, availability and price. We’re used to thinking of the light source as a “bulb,” but that small package typically can’t provide the heat sinking needed for LEDs while generating enough light. Designs that incorporate the LEDs directly into the fixture,
using the housing materials for thermal management, typically do better. There are
new products coming out all the time, and it’s exciting to see the creativity and innovation going on in the industry.
Kelly Gordon of the U.S. Dept. of Energy’s Pacific Northwest National Laboratory (PNNL) is an organizer of Lighting For Tomorrow’s Solid State Lighting contest.
When evaluating new LED products, here’s what to check:
√ Light output: Current LED products may have lower light output
than traditional bulbs, so make sure they are adequate for the application.
√ Color quality: With a “cool” or bluish appearance, some LEDs may not be right for all residential settings.
√ Cost: The long life and energy savings of LEDs may compensate
√ Efficiency: Ask about light output per unit of power consumption—
Source: Kelly Gordon, PNNL