LED'S VERSES INCANDESCENTS - Are they really more energy efficient ?

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We use LEDs. The ones we use in our dining room are very bright and no flicker. They are 15W units.. My wife does her painting there. So yes they are practical and very energy efficient. I don't see why

mtnelect has a problem with that.​

 
It seems pretty clear that mtnelect has a problem with LEDs that don't work properly. I strongly agree on this point.

I've followed the development of LED technology for years, and also followed the hype and misrepresentation by the LED manufacturers.

The technology has matured tremendously, and now LEDs work amazingly well for many (but not all) applications.

I was taking issue with the broad brush misinformation style of talking about LEDs, rather than the focus on the specific and real failings.

If the only factor that we cared about was luminous efficiency, we would be using sodium vapor lamps.

Jon
 
I think I have posted this before. We were in final negations on an industrial project. The chief engineer asked us to use LEDs rather than the usual incandescent lamps for the indicators. No problem. They were a bit more expensive but in the great scheme of things it was peanuts. That was 1992. To date we had no failures with the LEDs. I used them ever since.
 
ggunn said:
I do not see how light can be toxic. Unpleasant, OK; eye damaging if it is too bright, sure, but toxic? Toxicity is a chemical effect.
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Toxicity and deleterious are better stated as "Negative health effects" in recent studies on blue light.
medicalxpress.com

Blue light creates negative physiological changes during sleep

Extended exposure to light during nighttime can have negative consequences for human health. But now, researchers from Japan have identified a new type of light with reduced consequences for physiological changes during sleep.
medicalxpress.com medicalxpress.com
 
I agree it is detrimental to health. When I'm in room with it I want fried food, of course I want fried food in other lighting too.
 
Low pressure sodium was efficient. Its essentially monochromatic light output was horrible in terms of using it to look at stuff, but the astronomers loved it because there was only a single wavelength to filter out.

Jon
 
winnie said:
It seems pretty clear that mtnelect has a problem with LEDs that don't work properly. I strongly agree on this point.

I've followed the development of LED technology for years, and also followed the hype and misrepresentation by the LED manufacturers.

The technology has matured tremendously, and now LEDs work amazingly well for many (but not all) applications.

I was taking issue with the broad brush misinformation style of talking about LEDs, rather than the focus on the specific and real failings.

If the only factor that we cared about was luminous efficiency, we would be using sodium vapor lamps.

Jon
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Actually low pressure sodium is more efficient but the color is not pleasant, the astronomy folks like it.
 
In a lighting class I went to many years ago I remember them saying LPS had the highest lumens per input watt.
 
Touching on a few different points--

The only sensible way to define lighting efficiency (or "Luminous efficacy") is lumens per watt, which conveniently is how we do it. Spectral distribution, color rendering, etc do not enter the concept. To answer the thread's subject question- Yes, they are. And LEDs generally have a much longer life than incandescent.

From what I was just reading, the theoretical limit for a white LED with phosphorescence color mixing is 260–300 lumens/watt which bests LPS but not by that much. OTOH one is much preferred to the other (ex by astronomers, with good reason).

mtnelect said:
the analog sine wave flicker from an incandescent
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Umm, what flicker? Unlike LEDS and discharge sources, incandescent (or "black body") sources have hysteresis, and that's much longer than a half-cycle. So do some of the phosphors used in LEDs and CFLs (which also tend to smooth out their flicker).

A problem with this kind of discussion is that when some points are either nonsensical or easily disproved, the rest of the info presented becomes suspect.
 
mtnelect said:
As shown in the two images, LED light and incandescent light do not have the same characteristics and LED light, by virtue of the excessive amount of toxic blue wavelength light, is a low-quality light.
It should be noted that the reason that the manufacturers use blue wavelength light in LEDs is because this is how they increase luminous efficacy and reduce costs. The industry claims that LEDs are energy efficient are false because LEDs don’t provide the same high-quality spectral distribution as incandescent. If the manufacturers were to make LEDs with the same quality of spectral power distribution as incandescent, the luminous efficacy would be no better than incandescent.

More information to follow ...
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Lots of false statements here. First off the word efficacy means how close the spectrum is to natural mid day sunlight, which is a bluish tinge. Incandescent is too yellow. Many interpretations also include qualitative concerns such as light/dark patterns (evenness) and glare and not just how close we are to mid day sun. Efficiency is something different entirely. It is how many lumens per watt we get out. But that’s not a fair comparison either because incandescent bulbs basically burn a piece of material. We just reduce the oxygen level to the point where it simply smolders for a very long time. Light is emitted in almost all directions. This forces the use of reflective optics and we get a lot of bleed into areas that don’t need lit. So if we designate the foot candles in an area we want to light up, LEDs win the lumens per watt race every time.

Second is the argument about blue light. Are you aware that ALL LEDs only emit a single wavelength of light? You simply can’t avoid this at all. The diode has an electrical property called a band gap. In order for electrons to flow they must cross the band gap. When they do, they release energy. The amount of energy is very precise so we get a single wavelength or color.

But wait you say, we have white LEDs. White is not a wavelength. But we can make use of pigments called phosphors. When a phosphor is struck by light, it absorbs it and then re-emits the light at a different, longer wavelength. By mixing phosphors which are just a coating we control the color output and spectrum of the light it produces. This is the exact same technique that has been used for decades in fluorescent tubes. The light in a tube is mostly UV. It is a purple color. Coating the bulb converts it to white light. Similarly we can do the exact same thing if we start with a blue LED. The only limitation is longer wavelengths waste more energy converting blue light to say red. The energy in light is related to its wavelength. Obviously the most efficient LEDs would be no phosphor coatings at all. Early “white” LEDs use clusters of multiple colors. This works at a distance but it’s pretty obvious that it is a cluster of red/green/blue LEDs…color rendering is not good.

It is true that “cool white” LEDs are about 20% more efficient than “warm white” ones. But we are working at over 200 lumens per watt with cool white output. Dropping to warm white puts you at “only” over 160 lumens per watt. Over at team burning filaments, size matters. The bigger the bulb the more efficient it is, s simple fact completely missed by the Bushes. A 100 Watt incandescent bulb hits an efficiency of 16 lumens per watt. So with this basic comparison an LED is 10 times more efficient even using the lower efficiency warm white LEDs. This isn’t taking the efficiency of the optics or beam patterns into consideration. It’s just raw light output.

As to the blue light hysteria, it’s utter nonsense.

www.aao.org

Should You Be Worried About Blue Light?

When you stare at a screen for hours at a time, whether it is a computer, TV, phone or tablet, you are exposed to blue light from the device. But there is no scientific evidence that blue light from d
www.aao.org www.aao.org


No credible scientific evidence has linked blue light to eye damage. UV-B certainly but not blue light. There is an obvious reason why.


Visible light is only a very tiny part of the electromagnetic spectrum. The UV spectrum is far larger. UV-B is the middle of the spectrum and causes sun burns and skin cancer and macular degeneration. UV-A has the leg set wavelengths and makes your skin tan but does not cause burns. It is closest to visible (blue) light. So if UV-A is OK (and it is), so is blue visible light.

The blue light people would have you believe that the damaging effects of light would skip over UV-A and violet, causing problems at blue only, even ignoring indigo or green light as well.
 
winnie said:
The technology has matured tremendously, and now LEDs work amazingly well for many (but not all) applications.
Click to expand...
One application where some LEDs do not do well: My sister gave me for Christmas one year a BBQ light - a battery operated LED set on a gooseneck with three strong magnets to attach it to the grill frame. It works great except for one rather important thing. The light from it has virtually no red component, so rare meat is indistinguishable from well done. I use it for a reading light; it is fine for that.
 
Without resorting to actual numbers, probably the least "efficient" lamp in the last 40 years was the 93w incandescent; slightly less heat but even less light :ROFLMAO:. They were on the market for, what, a year or so? Then the rightly vanished.


For reference, the ideal black-body radiator at 4000 deg K has a luminous efficiency of 7.0% or 47.5 lumens/watt (roughly double that of a tungsten filament quartz-halogen lamp). Crank the BB up to 7000 deg K and those almost double.

(Sung to the tune of "My Bonnie Lies over the Ocean"--
Black bodies give off radiation,
and do so continuously,
Black bodies give off radiation,
and do so to Planck's theory.)
 
zbang said:
Without resorting to actual numbers, probably the least "efficient" lamp in the last 40 years was the 93w incandescent; slightly less heat but even less light :ROFLMAO:. They were on the market for, what, a year or so? Then the rightly vanished.


For reference, the ideal black-body radiator at 4000 deg K has a luminous efficiency of 7.0% or 47.5 lumens/watt (roughly double that of a tungsten filament quartz-halogen lamp). Crank the BB up to 7000 deg K and those almost double.

(Sung to the tune of "My Bonnie Lies over the Ocean"--
Black bodies give off radiation,
and do so continuously,
Black bodies give off radiation,
and do so to Planck's theory.)
Click to expand...

That applies to light bulbs which are basically BB radiators or close. Nothing is ideal. With even metal halide we are converting UV from a basic mercury lamp to visible light. So it does not follow a black body Planck spectrum at all. LED and fluorescent HO are even further from a true BB emitter. Which is why it is very far from “ideal”. In reality l there are no perfect black body ir white body emitters, only grey. Hence we use emissivity but even that’s a problem. It assumes that emissivity is uniform at all wavelengths, which it isn’t.

So I don’t see where BB/WB has a place here.
 
ggunn said:
I use it for a reading light; it is fine for that.
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Don't you get hot?
biggrin.gif
 
ggunn said:
One application where some LEDs do not do well: My sister gave me for Christmas one year a BBQ light - a battery operated LED set on a gooseneck with three strong magnets to attach it to the grill frame. It works great except for one rather important thing. The light from it has virtually no red component, so rare meat is indistinguishable from well done. I use it for a reading light; it is fine for that.
Click to expand...
I'd say anyone that marketed it as a grill light is who went wrong here.
 
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