Big LED Breakthrough at Purdue University Could Change the World
by Michael Graham Richard, Gatineau, Canada on 07.22.08
Better, Cheaper LEDs
The incandescent lightbulb that wastes 90% of the electricity as heat is dying, we all know that. But a new breakthrough in solid state lighting might also kill compact fluorescent lightbulbs (CFLs) faster than some expected. Scientists at Purdue University have figured out how to manufacture LED solid-state lights on regular metal-coated silicon wafers (more details below). What this means is: much lower costs.
10% Reduction in Total Electricity Use
And since about 1/3 of U.S. electricity is used to produce light, this is major. "If you replaced existing lighting with solid-state lighting, following some reasonable estimates for the penetration of that technology based on economics and other factors, it could reduce the amount of energy we consume for lighting by about one-third. That represents a 10 percent reduction of electricity consumption and a comparable reduction of related carbon emissions," said Timothy D. Sands, professor of Materials Engineering and Electrical and Computer Engineering states at Purdue.
Old LEDs vs. New LEDs
What makes traditional LEDs so expensive is that the light-emitting layer of an LED light is a gallium nitride crystal and it needs to be treated in various ways with expensive materials.
In sapphire based LEDs, used for green or blue lighting, mirror-like reflectors are need to reflect and resend emitted light, increasing the efficiency. Typically, this layer is extremely expensive to produce, part of the reason the current generation of LED lighting costs so much, costing at least 20 times more than conventional incandescent and fluorescent bulbs. Also, the LEDs are built on sapphire crystals, which provide the color, but are extremely expensive.
But the new LEDs can be made using standard silicon wafers and already existing, less expensive, processes. This would make them competitive with incandescent and CFLs.
The new techniques yield a crystalline structure aligned to the crystalline silicon. This means that the LEDs are less prone to defects and will perform more efficiently [...] silicon dissipates heat more effectively than sapphires. This will reduce damage during operation and lead to longer lifetimes and more reliability..
We might soon have to get used to changing lightbulbs every other decade.
LEDs that are currently available convert electricity to light with an efficiency of 47 to 64%. It is predicted that LED produced with Purdue's process would have an efficiency in the high-end of that range, compared to about 10% for incandescent.
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I can't wait to have 100% LED lights in my house. CFls are okay for now, but it's not a very elegant solution compared to LEDs.
good point about changing bulbs only every other decade. That'll be weird.
Remember everybody; LEDs are actually less efficient in terms of lumens per watt than many other forms of lighting:
Incandescent: 13.8 lm/w (2% luminous efficiency)
Fluorescent: 45~100 lm/w (6~15% luminous efficiency)
Mercury vapor: 50~55 lm/w (7.3~8% luminous efficiency)
low pressure sodium: 183 lm/w (27% luminous efficiency)
LED (currently available) 10~90 lm/w (5~13% luminous eff.)
Source
The stories I've seen here about while LED streetlamps make no sense - the currently available lamps for street lighting are much more efficient than the best available LEDs.
I'm not sure where the 47~64% efficiency quoted in this article comes from. Maybe this is counting light outside of the visible spectrum...
There is nothing magic about LEDs; I'm all for anything that will get people away from incandescents, but there seems to be some confusion about their relative advantage compared to other types of bulbs.
I don't think I'll have a problem changing light bulbs only once every other decade. Makes life very easy.
Cool, but where the heck are you going to get the silicon from? can't forget the shortage......compacts are here to stay.
"Cool, but where the heck are you going to get the silicon from? can't forget the shortage......compacts are here to stay. "
You are confusing a shortage of refining capacity with a shortage of the stuff itself. Silicon is EXTREMELY common, and a bunch of new refineries are coming online very soon. If there's a shortage, it's only temporary.
In many applications, LEDs are actually TWICE as efficient as CFLs at deliverting light on task. That's because they emit light in one direction, rather than omnidirectional like a CFL. In Europe, and some parts of the US, regulations demand a certain amounts of lumens/sq meter on a table or wall- and here LEDs excel. Plus they can be infinitely dimmed, and contain no mercury.
In commercial applications, they return their high intiial costs in about a year- closer to seven years in a residential application. But as the cost comes down, they will completely replace fluorescents.
I'm excited about this! Although I've noticed that with things I do infrequently (like change the air filter) I don't always remember how to do it when the time comes... I hope lights end up in that category!
The properties of light are different than just the efficiency. It has to have a proper color temperature and aesthetic qualities to be tolerated indoors as well as out. LED's can be molded to so so easily because of the lack of heat. LED's are also very small compared to the other options for amount of light per square cm of area. This making light fixtures much smaller, less weight, and therefore cheaper to construct. A single streetlight with 5 LED heads on it covering 5 areas may fit where 5 stands used to be required. There are a lot of things to consider for the uses. I have been trying to imagine a downside to the LED streetlight, but distance of projection is the only thing I come up with, and LED lights are well within range of the normal height. I would think they could easily be solar powered to handle the entire period of darkness that they need be on.
Hmm with this: http://gizmodo.com/5027606/osram-pushes-white-leds-to-world+record-brightness-super-efficiency being read, I wonder how long it will be before we start seeing stuff on the market that can compete with the CFL's...
bird:
Not to be too off-topic here since LED streetlamps were another article entirely, but I can think of quite a few downsides:
-lower efficiency in lumens per watt than low pressure sodium lamps
-much higher initial cost
-more complexity; to reach the same total luminosity, the LED fixture would have to have thousands of LEDs vs. one sodium lamp
-power electronics are needed to bring high voltage AC to the 6VDC that the LEDs need.
granted you might be able to bring down the initial cost in the future, but what exactly is the point if the operating cost is then higher?
Oh boo hoo, whaaaa! I don't like that light. Whaaaaa!
This is exactly what I am talking about!!!! Private companys without any government involvement, and in an industry without any government stupid regulations, making something that the marketplace is screaming for! ECELLENT! NOW if we could get government out of the way in bringing this to the market, we could have this technology in our hands even sooner!
@ Greg
The article doesn't say, but it's probably safe to assume that the same type of pure polysilicon used to make solar cells and computer chips is the same type used to make these LEDs. There has been a shortage in pure polysilicon for the past couple of years, but that finally seems to be easing as many new plants that produce the stuff are coming on line.
You're sourcing stuff from DailyTech?? Wow. Talk about scraping the bottom of the barrel.
At Intersolar there were CFL replacements made from LEDs. Ballasts for the larger tubes included.
A kitchen under-counter one (made of LEDs) would be about 75 USD and is currently available on the market.
Tom: do you have any idea how long an average sodium vapour streetlamp lasts? It's less than a month. I've also seen them die within an hour of being replaced. Switching to LED's would save money not just on power but on the cost of replacing bulbs.
For some reason, the thought of having LED lighting everywhere makes me feel all excitable. It's all a tiny bit thrillingly 60's sci-fi.
Mind you, if we get to the suggested stage where LEDs are sunk into and spread over ceilings, lampshade manufacturers are going to have to start looking for other jobs. I like lampshades. Super.
Joe - www.anewbandaday.com
Ok, time to change this old Wikipedia thing myself. 100lm/W is available since at least a year (check the manufacturers pages, Cree, Luxeon, Seoul Semiconductor, etc.) but this Wikipedia thing gets quoted on and on. I will sign up and change those "old" new.
"-power electronics are needed to bring high voltage AC to the 6VDC that the LEDs need"
The power electronics in low-pressure sodium lamps is much more complicated than that in LED lamps. LED also lacks re-strike problems (turning back on after it just turned off)
"Tom: do you have any idea how long an average sodium vapour streetlamp lasts? It's less than a month"
Low pressure sodium lamps have life-expectancies of 5-10 years as normal-duty street-lamps. What you said doesn't make sense, no city would buy them if they had to change them once a month! LEDs do still last longer, however.
http://en.wikipedia.org/wiki/Sodium_vapor_lamp#Low_Pressure_Sodium_.28LPS.2FSOX.29
I would also argue that the complexity of an LED lamp is less because of its repetitive nature. Large gas lights are also very restrictive in terms of size and shape, not so with LED.
People get caught up in the idea that a light should be like lights always have been, but LED allows designers to change that. Instead of a lamp at the top of a pole, the whole pole could be lit, strings of LEDs could eliminate shadows, glare and the "halo" effect of point source lights. I would definitly call the distributed nature of LED a benefit, not a problem.
Neil,
Not to rain on your parade, but Purdue is a public (government) university. Good try though.
Actually, Purdue was founded by a donation from John Purdue, a businessman.
The bigest problem with CFLs is the mercury in each and every one - about 5 mg. Somehow in our desire to use less energy, we trade one evil for another. I believe LEDs will be as inert to the environment at a traditional bulb. I had already started replacing the bulbs in my house with compacts but will probably stop because of the mercury. While this amount is minimal compared to other products (watch batteries, thermometer, float valves, etc) I stll think that it has a much better chance of getting loose in the environment.
And just think what the batterries for all these electric cars will dump into our ecosystem when they have to be tossed every 5 years!
With regard to streetlight LEDs, check this tech out:
Tictac Bulb @Gizmodo
There are a lot of misconceptions about LEDs. I own a single Cree-based LED flashlight. It's a clean white light that's over 100 lumen. The thing is amazing. I get over 2.5 hours of 100% light output out of a single AAA battery (the light does not diminish as the battery dies, it just goes out). I'd be happy to have that kind of light in my house. It's a whiter light than incandescent bulbs.
Purdue is a public university. It is one of many land grant universities in the country. Regardless of that fact, it's a leading research institution, especially in the fields of engineering. Second of all. Everytime I hear someone say 100% efficiency it makes me cringe. The second law of thermodynamics makes that impossible and those of you reading this should probably know that. And as far as lumens per watt go, who cares. Brightness is rarely the most important part of lighting, because you can always move a light closer.
Anyone know where the above stat/quote can be confirmed? "1/3 of U.S. electricity is used to produce light"
Purdue Sucks
Go Hoosiers
Cheap and good effect, led a very good development
You mean that in my zero running cost eco-home I can charge my Lithium batteries all day, and get most of that energy back as useable light in my LED fixtures - Bravo! The future is near.