Those not so green light bulbs

White LED's are blue/ultra-violet LED's with a phosphor element inside. They can allow a certain amount of blue through and mix the phosphor just like they do with fluorescents. There are no "native" white LED's but you can create white by mixing red blue and green LED's.

Ta!

I'll take that as a 'yes' then !

I think you are right, they are in a finite bands of colors...and I'm not sure if you can call them a quantum device someone clarify that... but they add phosphors as filters that glow in the different colors. I think that's how a lot of early white LED's were made (and still made??? correct me if I'm wrong). I think that's why early white ones were so inefficient and had problems with duplicating the same color across the same production line also. (Maybe I was just buying the cheap LED's!). New ones that I've seen have been very very consistent.

I bought a whole bunch of different colored led's a few years ago and besides the regular colors, I had some aqua (or light bluish I suppose) and purple ones that used a phosphor to make the special color. If you looked really close (not directly into them (ouch!), but to the side when on) you could see the blue light from the actual diode that was changed into the secondary special color. I thought that was pretty fascinating that it still produced as much light as it did. So it looks like you can get pretty much any color you wanted with the right phosphor, and that seems to be much more efficient than using a colored filter.

-Nick

Well ultimately it is a quantum device but that part of it pumps a phosphor target that emits broad spectrum light which is also a quantum phenomenon so maybe all we can really say is that the quantum behavior that might produce white light in an LED junction is not currently known. I am not sure if the physics of the phenomenon would allow it but that too sometimes changes when new discoveries are made.

And yes I think it took a while before they got their processes down to where they could produce consistent parts. I think there were also some problems with UV degradation of the package in early parts.

Agreed. I would add that the discharge tube in a fluorescent lamp is equally a quantum device.

There are all sorts of ways to broaden the spectrum of an LED, and many indirect gap semiconductors naturally emit broadened spectra. Obviously, efficiency is degraded - although that could in principle be a smaller degradation than by using phosphors. I suspect the main reason for not developing individual LEDs with broad output spectra is that additional heat is generated in the semiconductor junctions - which is the last place you want it until the technology becomes so cheap that reduced output per LED becomes acceptable. Given the number of separate LEDs in a typical LED lamp, you could also do quite a lot by using LEDs that emit at different visible wavelengths. This could be highly efficient. However, even if current technology allows**, it's unlikely to be economic until production volumes grow.

** I suspect (I'm too far out of touch to know either way) that there are gaps in the available spectrum - but a hybrid of direct and fluorescent would still be a possibility.

Fyz

The CFL equilivalent for a 100W incandescant (Tungsten) Lamp is 26W. The overall energy saving's is 75%. There are other savings as well:

1) CFL's outlast Incandescents 8 to 1 (appox.)-measure the cost of 1 CFL to 8 incandescants.

2) The labor cost of replacing the 8 lamps to 1 lamp-what's your labor cost?

3) When measuring savings include the cost of recycling the CFL for a true cost of energy.

Until the LED technology has produced a user-friendly cost effective alternate lighting source, the CFL's are the way to go. The CFL's are available in all flavors, (2700K, 3000K, 3500K, 4100K, 5000K or 6500K) shapes and sizes.

MrHandyMan

I found some 20,000 hour 100W incandescants for our environmental chambers (over 200 bulbs total) and we now hardly ever change a bulb. At less than 2 bucks a piece they have been a great deal. That bulb lasts more than 10 - 15 times as longs as the average bulb at your corner store... But you don't hear much about them???

We can buy these bulbs. They are just made to run at a lower temperature. For an environmental chamber you need thm as heat more then light.

If not for heat, they are a waste. 20,000 x 100 = 2,000 KW hours at 8¢ per KW hour

= $160.00 over their life

An LED over that time would cost about $15 and burn 200KWH = $15 +$16= $31 and never burn out, but little heat, about ~120 KWH heat over that time

My point was that there are incandescents that last longer than cfl's. The bulbs have thicker filaments and more supports. We cool these room size chambers (20' x 20' x 10') with 2 30hp refrigeration compressors and heat them with 45 kw heaters so the miniscule, no femtoscule, amount of power the lights use is negligible. It's the labor cost and safety risk of changing them that we are now saving that is substantial. Also, I'm glad to hear that in your universe LED's never fail. They do fail, in my universe they fail regularly, and I doubt they would last very long at 100 Celcius. I will look into their temp specs and buy a few for testing if I can find a suitable product, I've thus far only found 80 Celcius as the max, and thermal shock from hot to cold may be a problem as well. I will guarantee you that CFL's will not work for us at -40. Peace!

LEDS can be broken by overcurrent, but used inside their infinite life operating envelope, they are essentially permanent devices.

Many light makes choose to operate withing their 5000 hour, 10,000 hour or 100,000 hour envelope so they can boast extra brighness. This is like the 100 hour photoflood lamps, which you can make from any 120W bulb by using 140-160 volts. You can run them really brightly at 200V for a short time.

In the overall scheme in your case, the power is small. The LEDs would have to be designed for the worst case ambient and could then be made for 100,000 hours, , maybe 25% dimmer than room temp ones, much like the ones you use now, but with white or whatever light color you wanted.

One person alluded to above on what I am going to say. In more formal terms, the concept is a net energy analysis, which is borrowed from the analysis of energy systems. In that context, it compares the net energy delivered to society by some technology with the total energy required to locate, extract, transport, etc. that resource. For example, an analysis of a hydroelectric dam would include the energy 'cost' of the vast amounts of concrete required to build the dam. An analysis of ethanol would include the fuel energy used by the machinery to plant, harvest and transport the grain.

It would be interesting to see a similiar analysis done on each of the lamp types, where one includes the energy costs of the manufacture and disposal (and ...? )of these lights with the difference in energy use during operation. I am willing to bet there is not as much difference as the propoganda claims.

The claims seem to work out about right if you believe the numbers given for the relative lives of tungsten and of compact fluorescent lamps. I think a major reason for the present higher cost of the compact fluorescent is that the cost of the manufacturing equipment has yet to be amortised.

LED lights have a very small ecological footprint, both in fabrication and in disposal.

Of the input components, only certain phosphors are toxic on release. There are a number of phosphors used and each discrete one will have it's own physical capability and ecological risk. There are some people at work on ways to avoid phosphors totally = better.

CFL lamps have a far higher phosphor load than LEDs, + mercury, so the best way to deal with them is a $1-2 deposit that you get back on recycling. $1-2 will motivate the users and scroungers to find them and get them into the recycling stream. Government should implement this and cover all prior CFLs, even those not bought on a deposit basis. All fluorescents light, the 4' and 8' whould be dealt with the same way. There are large numbers of these bulbs simply crushed and disposed into common garbage now. So it is a cost and an aggravation, it needs to be done.

These deposits will shift the equibrium economics towards LED lamps by 2-3 years closer to the present. with them by 2010 it could be viable. How nice to have permanent lights and no sockets etc

How pleasant to have LEDs
Which give off such volumes of light
Some view them with fearful unease
But most think them pretty at sight.

Their ecology's extremely fastidious,
Their radiance remarkably big;
Their fact'ries aren't totally hideous,
And landfill we needn't dig.

etc...

Fyz (with apologies to Edward Lear)

See here: www.elecosn.com

Here are dimmable LED Bulb, and LED incandescent bulb

"...energy savings don't add up as the Propaganda says they should..."

It can easily be measured. No experts needed here. Each household to their own.

Compact Fluorescent Lamps incorporate an electronic ballast into the base of the bulb. I have had 4 ballasts fail in the past two years. In three cases a resistor burned up, and heated the plastic base casing to the point of turning it from white to brown - with an acrid smell. So the actual fluorescent tube may outlast an incandescent bulb, but the attached ballasts may fail early, so that the Compact Fluorescent Lamp, consisting of a tube plus the ballast, fails when the ballast fails. I happen to have an occupancy sensor triggered ceiling fixture in my main workshop entrance, into which I inserted an incandescent 75 watt bulb and a 25 watt Compact Fluorescent Lamp, utilyzing a "WYE" fixture (0ne screw in male, two female bulb sockets). I did this because it takes a while for the typical Compact Fluorescent Lamp to fully turn on. The interesting fact is that the original 75 watt bulb is still there, but I have had to replace two Compact Fluorescent Lamps in that fixture, with number three now in place. This fixture turns on and off perhaps 20 or more times a day. The other dozens of Compact Fluorescent Lamps I have in other remote workshops are turned on only a few times a day, and they are not burning out early. In that same main workshop I also have 6 conventional dual 40 watt fluorescent tube ceiling fixtures, controlled by a light switch, which are turned on perhaps 5 to 10 times a day. None of these conventional bulbs or ballasts have failed over the same 2 year period. These Compact Fluorescent Lamp ballasts get hot, and when mounted inverted, get even hotter. The claimed 8,000 hour life in this case turns out to be less than the claimed 1,000 hours for the 75 watt incandescent bulb - by a factor of two! Moral: Every exciting new product has a few flaws, or a few application limitations.

Mechanic: I suggest that you try separating the flourescent from the hot 75 watt bulb in your "WYE" fixture. Your problem may be more from heat than from frequent on-off cycles. DickL

I quickly scrolled through this entire discussion and may have missed

any comments about the actual acceptance of the "hue" emitted

from sources of light other than the traditional incandescent lamp.

There's something about fluorescent, and LED lighting

that just plain wears me out.

I wonder if that had/is been factored into the equation when

considering the outright banning of the traditional bulb?

John

CFL's are currently available in a variety of color temperatures, though you may have to look around to find one you like. You probably want a lower color temperature since it will resemble the incandescent you are used to.

White LED's are also being manufactured with a variety of color temperature options and they are also working on LED lighting using red/green/blue devices so you would even be able to dial the color you want.

I believe it's the flicker, not the colour. I use high-frequency (machine-shop rated) fluorescent fittings wherever possible, and these don't have the same effect (on me at least). There are various posts giving more detail in this thread

Fyz

It may also depend on the quality of the lamp. I have measured the light output of a range of quality CFL's and have found the "flicker" to be in the range of 50kHz to 75kHz and I can assure you that unless you are an extraterrestrial that you won't see that. I will check some cheap ones tomorrow and get back to you.

> 50 kHz??? That's the sort of frequency you might get with DC excitation (SFIK not that good for life expectancy) and gas resonances.

I also believe that the flicker shows that the coating has a very short persistence, other coatings have longer and flicker much less or not at all. I would guess some manufacturers are better than others.....

I find that cheap tubes are short lived and blacken quicker....

A subject nobody mentioned is the difference in quality (nominal light output vs real light output and electricity consumption) between "first brand" lamps with the same ratings.

I recently read a report written by a local tech institute about this issue, and differences are really significant!