"Lostgallifreyan" wrote in message
...
(Don Klipstein) wrote in
:
I expect about 6.7 watts in the case of a 1710 lumen 100W
incandescent,
if the ellipsoidal mirror is a whole ellipsoid and 100% reflective and
the dichroic filter passes all 400-700 nm light.
As for the rest, approximately or "educated guesses":
UV passing through the glass: .12%
UV absorbed by the glass: .02%
Heat conducted/convected from the filament: ~13%
IR passing through the glass: ~60%
IR absorbed by the glass: ~20.16% ("rounded oddly" to make figures add
to 100%)
I was trying to keep the lumens out of this entirely, but I'll buy it. 
It makes me wonder what the fuss is about actually. While it's better to
get more efficiency, it seems that incandescents aren't so bad we need to
consider banning them, we just need to think more about what source we use
for a given task. As for the case to ban all but halogen types, how much
might be gained? With IR reflection to make them keep the tungsten hotter
for a given input, we get more light, but even so, is there that much
difference? Enough to say that they stay and standard incandescents go?
If LED's ever get a spectral match for a small efficient low-volt halogen,
at least the choice will be easy.
OK, I'm following all this - just about, I think. So let me now throw in a
slightly new set of questions. Back to LED halogen substitutes. Some
distance back up the thread, consideration was being given to losses in the
control circuitry for the LEDs. So, the first question is, just exactly how
are these things ballasted ? The reason that I ask this is that I was in an
electrical cash and carry warehouse tonight, and I picked up a couple of
LED-based GU10 replacements to have a look at. I didn't count the actual
LEDs, but I'm guessing at about 15 or so - let's say 15. Let's also say that
they are bluish types and let's guess at a forward drop of 4 volts. With
them all in series, that's going to be around 60v DC that's needed to run
them.
Now, these lamps were of exactly the same dimensions as a standard GU10
lamp, with the same 'nail head' pins, set in the identical ceramic base.
240v AC rating, stated on the packet. The glass 'cone' was exactly the same
as on a standard GU10, and it appeared, as far as I could see, that for the
most part, it was filled with the LEDs, which looked like 5mm types, and
their support plate. So that leaves very little space for any drive
electronics - certainly not a switch mode PSU, or even for a smoothing cap
on the end of a simple reccy / resistor combination. Not that there would
have been room even, for a resistor of a sufficient power rating to handle
this kind of drop.
Next question. There were two types on offer, one rated at 1 watt, and one
at 1.3 watts, both with a quoted lifetime of 50k hours. So what exactly is
being said here ? Is that 1 watt input from the mains supply, or 1 watt used
by the LEDs or 1 watt of visible luminous output power ? A website that I
looked at quoted the output of a 0.62 watt one, at 20-30 l - I'm assuming
that to be 'lumens'. If correct, and not a misprint, that seems to be a
piddling amount compared to the 950 lumens quoted for an incandescent 240v
50 watt GU10, and yet the text suggests that they are only 'slightly
dimmer'. It also says that these lamps give off almost no heat, and that
they consume only around 10% of the energy of a conventional equivalent
halogen GU10. So for a 50 watt type, that's about 5 watts, suggesting that
around 4 watts is lost in ballasting ??
Setting aside the issues of colour temperature and CRI, which I am sure will
shortly be overcome, it seems to me that these halogen replacement lamps are
even now on their way to bettering CFLs in that they are already exactly the
same pattern as the lamps that they are replacing, so must have sorted the
ballasting problem. And yet there are no plans to phase out the incandescent
version. This flies directly in the face of the proposals to ban standard
incandescents, when the advocated replacement technology (CFLs) is far from
being a satisfactory replacement, on several counts.
Arfa