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LEDs for General Lighting

W

Witling

Golden Member
Is it feasible to use LEBs as general household or office lighting? By that, I mean, would it be efficient. I think there are two contexts here. Lamps and overhead or wall lighting, as in most kitchens.
 
This can be done with modern high-power LEDs e.g. the luxeon series which are already used as daytime running lights on some new cars.

White LEDs are roughly the same efficiency as normal halogen lamps but have the advantage of very long life (50,000 hours - much longer than fluorescents), very high reliability and ability to focus the light very accurately, if needed. Note that they use much more power than fluorescent lamps, and most white LEDs give much lower quality colour reproduction. Some very new white LEDs have been optimised for precise colour reproduction (better than most premium flourescents), but sacrifice some light output.

LEDs are also extremely small so can be installed in places where conventional fluorescent or incandescent lighting may not fit. Worktop lighting e.g. in kitchens seems a logical place to use them (though due to the colour distortion problems, this may not be ideal - meat doesn't look very appetising if it has a blue tinge).

LEDs are also expensive - 100 W of LED lighting would cost you over $1,000.
 
Ledtronics sells LED based lights in a variety of form factors as solutions for most any general consumer/business lighting application. General incandescent replacement bulbs run around $50 each.
 
wait, I thought that LEDs had a much higher Efficiancy then Halogen or incandesent. (higher light/watt ratio). As I recall, it is about 75% efficancy in regular LED bulbs, and a possibility of 100% effeciancy. Normal light bulbs run at about 20% and Halogens (again as I recall) where about 50%
 
i think its the nonwhite leds that are efficient.

i saw some led bulbs in a mag recently. shrowded with aluminum heatsinks...multiple leds on a circuit board, and the efficiency was way below cf😛
 
I read an article about someone who outfitted his whole appartment with LED lights probably a year ago. The gist of it said it was feasable, but the high cost of the LED's initial cost would never be made up by the savings on the electric bill. Of course they're cheaper now, but I still think it's cheaper to go with other options.
The other major drawback to it was the unnatural feel of the lights. It's apparently even worse then florecents since the light has so little yellow in it.
 
It's already being implemented or being designed. It's very expensive at the moment with respect to parts, labor and design. A white LED costs as much as a simple incandescent light bulb, and you'll need a few dozen of these to just replace one. Not to mention the added cost of AC-> DC converters. This amounts to much more efficient enery usage and usability with respect to life time, but hell, the start up cost will eat it all away. Also, the phosphor of a white LED has on the order 10k hours of life, which is much shorter than the life expectancy of the LED at 100k hours. So, all those claims of 100k+ hours are moot with white LEDs.
 
Originally posted by: Mark R
LEDs are also expensive - 100 W of LED lighting would cost you over $1,000.
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It's also important to note that a 100w light bulb doesn't put out 100w of light- I beleive it puts out something like 80w of heat and 20w light or something to that effect.

 
It's also important to note that a 100w light bulb doesn't put out 100w of light- I beleive it puts out something like 80w of heat and 20w light or something to that effect.
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Absolutely, incadescent lights are very inefficient. A typical 100 W incandescent bulb produces about 5W of visible light and 95W of heat. With a high quality halogen that may be as much as 10W of vis light and 90W of heat (but in general such high efficiencies are only obtainable in high power halogen bulbs i.e. >500 W).

White LEDs produce roughly the same amount of light per W of electricity as do halogen bulbs. So when I said 100W above, I meant LEDs that consume 100W of electricity (and produce about 10W of light).

Monochromatic LEDs are more efficient (up to 20-25%), and if they replace filtered lamps then huge power savings are possible - decorative signs, traffic signals, etc. are rapidly growing applications. I have a few 3W deep-blue LEDs - these produce about 0.5W of deep blue light each (that's more deep-blue than a 100W halogen bulb - and they are such a concentrated source of radiation that they have to come with a safety warning).
 
Does anyone know why white LEDs are so expensive?
Can they be made using "cheap" fabrications methods or do you need to use for example MBE?
 
Originally posted by: f95toli
Does anyone know why white LEDs are so expensive?
Can they be made using "cheap" fabrications methods or do you need to use for example MBE?
Click to expand...

Because they have to output light on multiple wavelengths, and the wavelengths have to be balanced enough that the light won't have a tinge of some color or another.
 
I'll buy them when they're cheaper and last longer... they'll certainly get better for sure.
 
I hear LEDs are just as efficient as a 60 or a 100W light bulb and pretty much constant regardless of size. This makes LEDs far more efficient than miniature bulbs in flash light. I don't foresee them competing against full size fluorescent for GENERAL lighting. Perhaps for niche market.


Utility companies makes a lot of effort to encourage CFLs, but residential customers aren't anywhere near as concerned about long term cost as they're about initial cost and they keep bying 25 cents a pop light bulbs. Not only do white LEDs have to compete with regular light bulb, they have to compete price wise with CFLs

Commercial customers aren't exactly dissatisifed about 150W lightbulb equivalent 32W fluorescent lamps that lasts 20,000 hours on the average while only costing less than $2 a piece in quantity.

There really isnt't any economical motivation for using LEDs and lack of economic motivation means minimal effort put into developing. Even if white LEDs can match the price of fluorescent, it's going to have to have a much better life and a significant lead in efficiency for commercial users to even consider about retrofitting.




 
I was thinking of using LED's on the under side of my kitchen cabinets to create a track lighting effect onto the countertop. Basically, a high efficiency decorative nightlight in the kitchen.
 
Originally posted by: redly
I was thinking of using LED's on the under side of my kitchen cabinets to create a track lighting effect onto the countertop. Basically, a high efficiency decorative nightlight in the kitchen.
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that would be really nice IMHO. i'm thinking about hanging/placing some above artwork.
 
Originally posted by: jediknight
Well, they're using LEDs for X-Mas lights now.. can't be far off :->

Isn't there a Moore's-law type relation for the flux from an LED?
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LEDs are useful for decorative lighting, because they're quite efficient at producing a very narrow range of wavelength compared to a broadband source(light bulb) with a filter. This isn't representative of the original poster's thread, which is about general lighting.

Even if LEDs could compete with regular light bulbs, it has got no chance unless they can compete economic and effiicnecy with fluorescent lighting.
 
Just bought a 1W LED flashlight yesterday. It's awesome. It's about the same brightness as an equivalently priced regular flashlight (maybe not quite as bright), much smaller, and puts out nearly pure white light.
 
Originally posted by: f95toli
Does anyone know why white LEDs are so expensive?
Can they be made using "cheap" fabrications methods or do you need to use for example MBE?
Click to expand...

The best white LEDs are created using a GaN substrate. The problem is that these substrates are extremely expensive compared with conventional materials. We're talking 10K for a 2" wafer. Bulk production of the material in wafer form has not yet been perfected.

GaN LEDs are still relatively new and their quantum efficiency is low. That means that not all the electron hole recombinations are emitting photons but rather phonons (heat). Researchers are working to increase that efficiency. Until the quantum efficiency can be improved it will be important to have good heat transfer in the packages of the LEDs.

As for fabrication they are fairly complex. They use MOCVD chambers to deposit many layers of materials at various pressures, gas flows and temperatures. The conditions under which each film is deposited can effect the overall quantum efficiency and wavelength of light produced.

This is all based off what I've read, I don't actually work in the LED side of semiconductors.
 
Why focus on white LEDs when we can just use the same principles of light we do to fool our eyes as we stare at our CRT/LCD? Bunch specific wavelength red, blue, and green LEDs together instead of having each LED emit all wavelenghts simultaneously. The only way this would not be effective is if this would not yield a "true white" light, which i suspect is the case... but even still, for general lighting this should be much cheaper and efficient in the near term.
 
The bulk of the cost of white LEDs is in the cost of the blue LED 'pump' used to energise the phosphors. In terms of luminous efficiency, you can get more light per watt from using a 'white' LED, rather than seperate red, green and blue LEDs. The phosphors in a white LED can also be manipulated to give a full spectrum light source, whereas 3 monochromatic sources tends to give less good colour rendering - something very important for illumination sources.

There are a couple of niches for RGB light sources - because they allow a wide gamut of selectable colour. Monochomatic sources are also more efficiently filtered, while retaining a wide colour gamut. Because of this, some very high end LCD screens are now using an array of red green and blue LEDs for the backlight, instead of white CCFLs.
 
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