DOE Shines $21M on Advanced Lighting Research

coondoggie writes to mention that the US Department of Energy is planning to fork over close to $21 million for 13 projects promising to advance solid-state lighting research and development. "SSL lighting is an advanced technology that creates light with considerably less heat than incandescent and fluorescent lamps, allowing for increased energy efficiency. Unlike incandescent and fluorescent bulbs, SSL uses a semi-conducting material to convert electricity directly into light, which maximizes the light's energy efficiency, the DOE said in a release. Solid-state lighting encompasses a variety of light-producing semi-conductor devices, including light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs). "

Comments

Re:Can't beat incandescents

[GregPK]

The best flourescent out there gets roughly 70 lumens per watt. LED's have already passed the 100 lumens per watt barrier.

What rubbish

[EmbeddedJanitor]

LEDs are far more efficient than incandescent. I have an LED/incandescent flashlight that lasts far longer in LED mode than incandescent mode but is not quite as bright. ie. Led brightness * LED time far greater than incandescent brightness * incandescent time.

Re:The Real Questions

[Anonymous Coward]

Where do I buy them now

EarthLED Light Bulbs which are more efficient, last longer, use less energy, and are greener to produce than even CFLs (which are greener than incans).

Do they fit...

Yes!

... as much ... light?

Yes! I own two (would own more but see price). etc. etc. Read the page, it answers your questions. They are dimmable, etc. etc.

suckered!

[Quadraginta]

Blacklight Power is a well-known combination of perpetual-motion and pyramid scams.

Re:Color Issues??

[Overzeetop]

There are no good white basketball players...

Oh, sorry, I had a top secret flashback for a moment. White LEDs, iirc, are essentially fluorescent light sources which use the LED to stimulate emission in several bands based on the phosphors used. As such, they are still discrete (though not monochromatic) frequency lights and cannot creat and exact replica of incandescent (i.e. blackbody) radiation. I've not seen much on LED CRIs or color temps...most people are just so amazed that they produce "white" light that they don't seem to care. White LEDs, as a result of how they work, are only about 1/2 as efficient per watt as their more efficient monochromatic counterparts.

Re:Color Issues??

[MasterC]

As such, they are still discrete frequency lights and cannot creat and exact replica of incandescent (i.e. blackbody) radiation.

However, that is irrelevant due to the biology of our eyes. IOW, it doesn't matter if you see light of a violet frequency or, instead, a combination of red and blue (aka purple). Really, the LED needs to just mimic the spectral sensitivity (570nm, 540nm, & 430nm) of our cone cells. This means we don't need actual white light (frequencies ranging from red to violet) to have white light insofar as our eyes care.

And, no, LEDs are not fluorescent. Fluorescent bulbs stimulate mercury to emit UV light. The UV light hits the phosphorus which makes it fluoresce and produce visible light. LEDs work by jumping electrons across a band gap and a photon is emitted when it jumps back down. The high efficiency comes into play because it doesn't take much more energy than that of the band gap to make an electron jump.

White LEDs are different

[sd.fhasldff]

And, no, LEDs are not fluorescent. Fluorescent bulbs stimulate mercury to emit UV light. The UV light hits the phosphorus which makes it fluoresce and produce visible light. LEDs work by jumping electrons across a band gap and a photon is emitted when it jumps back down. The high efficiency comes into play because it doesn't take much more energy than that of the band gap to make an electron jump.

*White* LEDs don't work that way. You might assume that white LEDs are simply three (or more) normal LEDs combined in a single package. While it is possible to make white LEDs this way, it's not the method usually used (for several reasons, including "color integrity").

Instead, white LEDs are typically made by coating a BLUE indium-gallium-nitride (InGaN) LED with phosphorous. This is not all that different from a fluorescent bulb, which is what the GP postulated.

Different color temperatures can be achieved by varying the phosphorous coverage. Lower coverage lets more blue through (cooler temperature), whereas higher coverage causes more blue to be absorbed and thus more of the phosphorous emission spectrum to be emitted. The dominant line in the most commonly used phosphorous for LEDs is around 580nm (yellow).

It's also possible to get white LEDs that are made by coating a near ultra-violet LED with phosphorous (thus getting even closer to the fluorescent bulb of the GP).

This might change in the future, with serious work being conducted in the field to improve on reliability, efficiency and color characteristics. To the best of my knowledge, however, none of the new methods (go search for yourself) are commercially available and as we all know, many things that seem promising in the lab never make it to market for any number of reasons.

For reference, red diodes emit at ~ 630nm, blue diodes at 470nm, green at 530nm. The exact wavelength of the emitted light depends on the materials used in the LED, of course.