In article ,
Martin Bonner writes:
On 12 July, 18:45, wrote:
Tim Streater wrote:

Further, 5 of them, drawing 60W in total, will also I assert emit less
heat than a single tungsten, because more of the energy supplied goes
into producing light, and less goes into producing heat.
Less, but not much less. One lumen is 1/683 W. According to
http://www.mge.com/home/appliances/l...comparison.htm, a good

That's a good chart, although I can't see why it's done as flash.

A couple of points - LED lights that achieve even 50 l/W are
currently prohibitively expensive, never mind the 60 figure it
suggests. Most of the cheap consumer LED lamps are same effiency
as halogens.

A shame it's missing low pressure sodium - the higher power ones
are around 220 l/W, and are the most efficent mass produced light
source available.

An interesting problem is that they are too efficient to heat
the sodium enough. If you run one in an oven, they reach
300 l/W, but take it out of the oven, and at 300 l/W there's not
enough heat being generated to keep enough sodium vaporised so it
will dim back down until its efficiency is reduced to the point
where it generates enough heat, and settles at about 220 l/W.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]