In , Lostgallifreyan wrote:
(Don Klipstein) wrote in
:

In , Lostgallifreyan
wrote:
(Don Klipstein) wrote in
:

There are some high power IR laser diodes more efficienct than
LPS.
Other than those, laser diodes are less efficient than most sodium
lamps.

Ok. I thought more laser diodes were but never mind.. Aren't most
class 3B visible red diodes around 20% efficient or more though?
That still leaves a lot of headroom. Tungsten is often said to be 1%
to 2% efficient at making visible light. So a 100W incandescent 17
l/W at 1% to 2%

More like 6-7%. Each watt of tungsten radiation in the 400-700 nm
range
is around 250 lumens.

places the Cree XR-E's 50+ l/W at 3 times that, up to 6%.

Figure around 250-300 lumens per watt of "white LED light". Looks
like
those achieve about 20%.


Watts of emitted light? I just saw a later post of yours that
mentioned "lumens per visible radiated watt". I think that's why we're
discussing such different values. I'm talking about input watts. I
thought we all were, at least Eeyore certainly was, as that's
ultimately watt (haha) is consumed no matter watt is emitted.

Cree themselves don't claim anything like 250-300 l/W for input watts,
at least not yet, though that might not be long awaiting.

So how does a 100W incandescent look in that context?

I am saying that a watt of white light is about 250 lumens, not the
683
some use as the lumen/watt figure for a 100% efficient light source.
A 100% efficient white light source would achieve about 250-300 or so
lumens/watt, depending on what they call "white".

Most of those generating figures of incandescents being 1-2%
efficient
are assuming that they would achieve 683 lumens/watt if they were 100%
efficient.

- Don Klipstein )


Ok, I see that lumens depend on the spectrum, not just the actual visible
watts emitted, but given that there is convection in an incandescent lamp
that makes some of its power emit in the IR, does enough leave that way to
bring the lumens per input watts down to levels that can account for stated
line-power-to-light efficiences of 3% and lower?

Most of the output of an incandescent is IR.

I think when Cree talk of lumens per watt, they're talking of lumens for
each watt of electrical input, and that's how I want to make the
comparison.

I was only mentioning figures of lumens per watt of visible light output
to explain that an incandescent achieving 17.1 lumens per input watt is
nearly 7% efficient.

Put 100 watts into an incandescent that chieves 17.1 lpw. You get 1710
lumens. Each lumen is about 1/250 watt of "white light", not the 1/683
watt assumed by those claiming incandescents are only 1-2% efficient.

- Don Klipstein )