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Cause of LED Efficiency Droop Finally Revealed
An anonymous reader writes "Researchers from the University of California, Santa Barbara, in collaboration with colleagues at the École Polytechnique in France, have been able to prove the theory behind LED 'droop.' LED droop is the term for how LEDs emit less light when the amount of current being pushed through them goes above a certain level. 'The cost per lumen of LEDs has held the technology back as a viable replacement for incandescent bulbs for all-purpose commercial and residential lighting.' Now that we understand what causes this, we should start to see research go into technology to circumvent LED Droop. 'LEDs have enormous potential for providing long-lived high quality efficient sources of lighting for residential and commercial applications. The U.S. Department of Energy recently estimated that the widespread replacement of incandescent and fluorescent lights by LEDs in the U.S. could save electricity equal to the total output of fifty 1 GW power plants.'"
A pre-print of the team's paper is available at the arXiv.
>the total output of fifty 1 GW power plants
Soooo... 50 GW?
Climate Progress - Hell and High Water
Over here in sweden it's hard to find a good old light bulb that will dim. But I guess I can live with the non dimming led bulbs for now
Anveto
Yo, genius, you misread the resistor markings when you wired up your Arduino circuit.
It's because of Auger recombination. Basically, you stick in too many electrons, and they all mill around talking with each other instead of getting any work done. This is also known as the 'Water Cooler Effect'.
Of course we would. We all have time machines.
This is why LEDs are already used in traffic lights. If you look at the cost of sending out a crew, putting up cones, flagging traffic around the workers, etc., the cost of replacing a bulb can run into kilobucks. Even if the bulb itself is more expensive, it is far more cost effective to use LED traffic lights to avoid the traffic problems, labor costs, and safety problems of burnt out incandescents.
It links to an .edu, ieee, and arxiv. It is not an advertisement, troll
Climate Progress - Hell and High Water
Leave to our government to have a Department of Energy Energy Frontier Research Center. This just in from the Department of Redundancy Department we can reduce half the E from the DOE EFRC using LED's to become LEED certified says the CEEM.
The little blue LEDs help me when I start to droop. Call your doctor if you don't stop drooping for more than two hours.
You don't even need a resistor, just a smarter hood.
When information is power, privacy is freedom.
So, blaming the LED for the bad design of the cover? Didn't think too much before posting did you?
Pay very close attention to LEDs. Now that we've identified the root cause of one of our biggest problems, in a few years, we'll find ways to work around those problems and extend the lifespan of an LED (and output at higher drive currents) with a minimal loss of light.
This is EXCITING news, as the uses for this across the entire electronics industry are MASSIVE. Higher-efficiency, longer-lasting LEDs means better optical devices and such, as this same tech can be applied down into solid-state laser diodes.
I'm literally about to piss myself from this news. The sheer implications of this knowledge are astounding.
I hope thermal pad and PCB makers are paying attention and prepare, because very soon we'll be pushing a LOT more power through these tiny LEDs, and we'll need the local cooling to compensate.
I only wonder just how far they can defeat or mitigate this effect, and how. Thicker well walls might be an idea, or perhaps a nano-wire-like growth pattern, like we've seen with the recent development of microwires on graphite sheets, can increase the surface area and reduce the available recombination area, thus forcing electron transport.
Something to either attract, guide, or force more electrons across the gap seems to be what is needed.
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.
Basically, past a threshold current, it starts to emit electrons instead of more photons (look up "auger effect").
Thanks again to "editors", illiterate both in English and science.
Fuck systemd. Fuck Redhat. Fuck Soylent, too. Wait, scratch the last one.
You have to be a pretty bad driver to end up on top of a traffic light though.
Mind the frickin' laser...
I'm literally about to piss myself from this news.
That's great, this is why I come here. What other site can you visit where people are more excited about a group of electrons than cute cats?
I'll bet right now you'd rather experiment with electrons than with sex.
"First they came for the slanderers and i said nothing."
The white led are in fact blue LEDs with a phosphor layer which "shifts" the emission spectrum towards green and red. Thus, white LEDs looks bluer or "colder" (associated with ice). The bulbs can be considered as black bodies radiators and thus have their spectrum "coming from" the red part of the spectrum (in fact most of the energy is wasted in the IR as heat dissipation). Their color are more yellowish (centered on green, 550nm) just like the Sun and seems warmer (like a camp fire). Now you can combine few color LEDs to reproduce the the D65 illuminant (Black body at 6500K, like our Sun) by balancing the amount of current in them. Other trick : you reprogram your mind to follow "correctly" Wien's displacement law : blue color is for warmer black bodies compared to yellowish and reddish black bodies (thermal emission). To make sure of that : think of a metallic part you heat up, it will start as black (as in not-emitting) then go to red, then yellowish and then bluish (but you will see it white-blue at this point). So, white LEDs should appear "warmer" when considering true physics...
That 'ceramic' is still aluminum. Aluminum nitride and alumina mix, to be more precise
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.
but won't somebody think of the Mercury? Or toxins, or radio waves, or autism that LEDs cause?
What mercury? Ain't none in LED's.
LED's don't emit radio waves. The power supply might ( but utterly harmless levels ), but not LED's
LED's don't cause autism.
LED's don't do anything, except emit light and get a bit warm.
OP: Education. Get one.
The cost per lumen of LEDs has held the technology back as a viable replacement for incandescent bulbs for all-purpose commercial and residential lighting.
Really? CREE started distributing LED bulbs a month or two ago through Home Depot for less than $10 each. I own two of them.
450 lumens for $9.97 is 0.0222 per lumen. It's rated to last 22.8 years. That's $0.0010 per lumen per year of use.
Let's compare that to an "equivalent" (the cree is a 40-watt equivalent bulb) incandescent bulb. $8.77 for a pack of 6 is $1.46 per bulb.
300 lumens for $1.46 is $0.0049 per lumen. But it's only rated to last 0.9 years. That's $0.0544 per lumen per year of use. It's more than 54 times more expensive than the CREE. That's before you look at the electricity you'll be saving (6 watts to get more light than you would out of a 40 watt incandescent).
Home Depot is also selling CREE's 60-watt equivalent:
800 lumens for $12.97 is 0.0162 per lumen.It's rated to last 22.8 years. That's $0.0007 per lumen per year of use. The incandescent is 77 times more expensive.
As much as I love CREE LEDs in general, I prefer Philips 10.5-watt bulb. The bulb itself it more aesthetically pleasing (in my opinion) and it diffuses the light better (the CREE focuses all the bulbs in one area and its very apparent from the very bright spot in the middle). I own six of them. Home Depot sells them for $27.97 for a two pack.
800 lumens for $13.99 is $0.0175 per lumen. Rated to last 18.3 years. That's $0.0010 per lumen per year of use. If I'm going to spent the next two decades with a bulb, I'll spend the extra three hundredths of a cent per lumen on something I really like. Still less than one fiftieth the cost of an incandescent per lumen.
The only things I see holding back LED bulbs are misinformation and lack of availability (Home Depot is the only major brick and mortar store I've found that carries them). That, and some freaky designs that don't look like light bulbs... I bought one of these out of curiosity, and its appearance, on or off, just irritates me for some reason... if I was redesigning my living room to look like Quark's, I'd go with these all the way, but since I'm not "that guy" it's in a lamp that I almost never use. Which means it will probably outlive me. It may even survive to the 24th century and end up in Quark's.
If only they lasted. We've had LED traffic lights in areas of Silicon Valley for most of a decade, and many of them are failing, one section of LEDs at a time. There's a huge bin of partially failed traffic light round LED panels at Weird Stuff Warehouse in Sunnyvale. Mostly red and green; the yellows aren't on as much.
The problem is outright failure, not dimming. That's an indication of a manufacturing problem, like a joint that fails under thermal cycling. Many pre-2004 LEDs are prone to this problem
Whoosh. Sense of humor. Get one.
...autism that LEDs cause?
You forgot to mention the idiotism that it provokes.
LED's don't emit radio waves.
Then you should take them back to the store for a refund.
but won't somebody think of the Mercury?
Good ol' Freddy, we still miss him
The main emission peak is mostly centered at 450nm, not quite UV...
http://en.wikipedia.org/wiki/File:White_LED.png
http://en.wikipedia.org/wiki/File:Cone-fundamentals-with-srgb-spectrum.svg
LED's do not emit a sense of humor.
LED's don't emit a 'whooshing' sound (unless you catapult them or use a trebuchet)
PocketPermissions Android Permission Guide
Horses and dogs are mammals, but dogs aren't horses. Light and radio waves are EMF, but light isn't radio waves.
Free Martian Whores!
That sounds like a challenge to me...
Slashdot still doesnâ(TM)t support Unicode after it was added to the HTML standard in 1997.
Cancer causes LEDs!
I'm sure there was an xkcd with the proof...
No sig today...
That must be a very large LED!
For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...