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Old 14th October 2012, 12:17 PM   #21
tvrgeek is offline tvrgeek  United States
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Originally Posted by wwenze View Post
Those "environmentalists" don't dare to compare the efficiency of LED with that of fluorescent tubes.

And they conveniently leave out the power supply when claiming high efficiency and long life.
Current state of the art LED's are, oops, they forgot to tell you, florescent. Anyway, they are very close to a CFL in total efficiency, as in viable light to power used. The 8 foot industrial tube is still the champ. BUT, as LED's are directional, you can use fewer watts to get the same effective illumination on a surface for most applications.

They also forget to tell you that based on hot-wire equivalent, which is how we measure bulbs, no bulb can exceed about 35% efficiency because we do not see all the light in the visible spectrum, we see only three narrow bands. A CFL is between 16 and 18 %, so half way to perfect. Only a sodium is more efficient as it is not wide band white light.

They also forget to tell you the total carbon footprint of manufacturing a LED assembly compared to traditional. Even shipping is higher ( they all come from China) because they are much heavier. Massive aluminum heat sinks. Ever notice how much power smelting aluminum takes?

Me, I have eliminated most of my florescent bulbs because I don't like the hum, flicker, rapid reduction in output, and now a disposal problem. I still use A base incandescent bulbs for light quality. Of course, in the winter, they are very efficient as I am using all that heat. I really like my LED ceiling cans as instead of a vented, heat leaking 75W hole in my ceiling, I have a sealed can using only 12W and get more actual light on the counter. I like my 1W LED bulb I leave on outside because my wife believes our dogs need extra light to see. ( they see fine at night, but never mind). I like LED's for spot task lighting as they can be much closer to you without frying your head. Being closer, far less total light is needed.

Conclusion? "It depends"
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Old 14th October 2012, 11:05 PM   #22
Pano is offline Pano  United States
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Originally Posted by tvrgeek View Post
Only a sodium is more efficient as it is not wide band white light.
Low pressure sodium is monochromatic. But it sure is efficient!
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Old 15th October 2012, 12:06 AM   #23
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CFL bulbs contain mercury and are only a stop gap solution.

Philips makes a LED bulb that puts out a luminescent intensity of 800 lumens at 2700K.
It dissipates 12.5 watts and Home Depot sells them for $26.95
These use a Edison E26 mount (same mount as a regular incandescent bulb).

Philips has a new model that puts out 1100 lumens at 2700K
They dissipate 17 watts - but Home Depot wants $45 for them.

BTW: colour temperature is one spec to to look at.
2700K has about the same warmth as a regular incandescent bulb.
3000K is white light
3400K is starting to be a ghostly blue.

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Last edited by Uunderhill; 15th October 2012 at 12:13 AM. Reason: technical comment needs checking
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Old 15th October 2012, 01:44 AM   #24
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The main reason why I like LEDs is for the lifetime. Yes, their efficiency next to the best CFLs and fluorescent lights is similar, but in applications such as MR16 halogen reflectors...I use some of these and I forever felt like I was changing bulbs to the point where I got fed up and didn't even bother replacing them. I then took the fitting apart and converted the entire thing to LEDs. A couple of years later and they are still going strong.

As Uunderhill says though, you really do need to get 2700k LEDs if you want things to look nice next to incandescents.
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Old 15th October 2012, 02:14 AM   #25
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Lighting is not a straightforward issue, since the human eye has a variable response to frequency, just as has the human ear. The Lumen is a measure of visible light, lumen measurements reflect the varying sensitivity of the eye, raw light power is expressed as radiant flux.

CFLs were still recommended as the leading technology for domestic use by the US Department of Energy as recently as 2011.

While fluorescent tubes remain high in the efficiency stakes, it must be remembered that they are tubes, and overall efficiency depends on the luminaire.

Without entering into a discussion of the issues any deeper than that, LEDs are approaching the best efficiency achievable by any means and with more pleasant colour rendition. They will almost certainly achieve an efficiency unobtainable by any other means, with superior colour rendition, at some point in the future, if they haven't already in laboratory conditions.

As the efficiency of LEDs improves, the heat evolved decreases, so the environmental cost of producing heatsinks can only be expected to decrease.

LED replacement lifetime is better than any competing technology, and LEDs are being adopted for street lighting, for this, if for no other reason.

LEDs are all-round the best technology for flashlights, being mechanically robust.

Cree are probably the leading developers of LED dies.
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Old 18th October 2012, 10:25 PM   #26
tvrgeek is offline tvrgeek  United States
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Saw some 450 L LED's in the store yesterday for $8.50. Now that I can deal with.

Robust. I think of my spelunking days and how many extra bulbs we carried. Minimum two lights each, 2 bulbs for each, a glow stick for good measure and we still had head-lights.

Great where the cost of replacing the bulb exceeds the cost of the bulb. I just hope for street lights they pick a very low temp equivalent, like 2300 degree light. Us old farts do not like blue light at night as the glare makes us blind. Down with HID and Zenon headlights!

Last report I read a lab had a white LED at 22%. As 32% is the theoretical max, it is getting darn close. The only way to get closer is to use three different bands and not generate any mid band output and then further reduce the IR. I doubt we are going to see that any time soon. Darn physics. I don't think that included the power supply.
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Old 19th October 2012, 01:49 AM   #27
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The theoretical limit of luminous efficiency for a white LED is 38.1~43.9%. This depends on the exact hue.

100% conversion of electricity to light yields 683 lumens/Watt @ 555nm.

See Wikipedia - luminous efficacy.
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Old 19th October 2012, 02:14 AM   #28
a.wayne is offline a.wayne  United States
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Originally Posted by Pano View Post
Spoken like a true Canadian!

Lowering the load on air conditioning in southern buildings as well as TV studios can made a big difference. Down South, we use an amazing amount of power to keep cool. Adding even more heat inside the building with lighting doesn't help.
South ...!!!! Your midway and with all that cool mountain air ...
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Old 19th October 2012, 09:12 PM   #29
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One thing that's bugged me about these non LED, energy saving fluorescent bulbs is the noise! You can hear the 50Hz derived buzz they give off. I was having yet another one of those head scratching hum hunting sessions once, only to discover it was the bloomin' lightbulb.
I'm certain filament bulbs didn't do that.
I'm very likely to move to LED, or somehow return to filament for rooms where I may listen to hifi.
Yeah! And I'm running class A! I am an enemy of the environment! No really. I'm terrible. Sometimes, I charge my phone! There, I've said it.
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Old 19th October 2012, 09:22 PM   #30
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LEDs arent always silent either, but that's only if you're using PWM dimming as the inductor can sing at the PWM frequency. At 100% duty cycle though there is no noise.
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