BCC: Iain gets honourable mention :-)

This is the same material as covered by the [TECH]::LEDS thread of 25-26 Au=
gust.

I wrote a longish response then and won't repeat it here but will make
a few comments based on the specific material posted.

I often  have great  respect for what Sandia does BUT feel that they
have gone severely astray here.

Several comments as reported in that article seem extremely suspect.
It may be that the import of what was said is substantially different
fron what was  reported - as often happens.

> In =A01700 a
> typical Briton consumed 580 lumen-hours in the course =A0of a year, =A0fr=
om candles,
> wood and oil. Today, burning electric lights, =A0he uses =A0about 46
> megalumen-hours=97almost 100,000 times as much.

Assume that the confusion with units is the reporters fault.
For a person to 'use' 46E6 lumen hours per year, assuming that they
use lighting for 12 hours per day (too high) then the mean lumen
illumination energy per person during lighting hours would be 46E6 /
365days / 12hours =3D 10,500 lumen.
For incandescent lighting at say 12 l/W that would require 880 Watt
and at 150 l/W* it would require about 66 Watt.
I use 150 l/W for future lighting efficiency as they are looking at
the year 2030 when LED (or other)  lighting will be far more efficient
than now.
In fact their assumption is "3 times fluorescent efficiency".
Current CFL's give 70 l/W and tube fluros > 100 l/W sop 3x that is
200+ and 300+ l/W.
FWIW 300 l/W is rather close to 100% efficiency for white light
(depending on colour temperature etc - say 80% + - a good trick if
they can do it.
So THEIR claim is say 40 Watt/person.

BUT they say they see no immediate end to the rate of light level requireme=
nts.

BUT I have a 100 Watt CFL in my dining room - equivalent to 5 x 20W
"normal" CFLs - good for say 5000 lumen (ie lower than top CFLs
probably)  or about half the level the report says people will be
using in 2030  say the average person will want for 12 hours/day in
2030. The light is very very ample for whole room lighting for N
people. My son said the light went against the laws of nature - he
said that night time should be dimmer than day time so you get ready
to sleep but that this bulb makes you feel like staying awake all
night :-). ie 5000 lumen is very very very bright. Average usage is <
to << 12 hours per day and if everyone has this much light the world
would be truly awash with light.

They do mention use in other areas - brighter outdoor  lighting etc.
But overall IMHO 5000 lumen is already much too much (even given their
comments about gas flames) and 10,000 more so. Double their claim to
20,000 lumen for 6 hours mean per day.

They say that interior lighting levels are now perhaps 10% of sunlight
on a dull day (which is true enough) but take no account of not only
logarithmic eye response but the fact that an irised eye allows
received light level to be *** the same *** over a wide range of
incident light levels.

Overall it seems to me that their arguments are simplistic. Certainly,
the world COULD use much more light, and will probably do so if not
constrained in some way. But adding only "somewhat" more light will
make a vast difference and the future may be but by no means has to be
as they say. Whatever.




Russell

--=20
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