The Natural Philosopher wrote:
Ian Stirling wrote:
Steve Firth wrote:
On 19 Nov 2006 14:33:10 -0800, wrote:

Are there any commercialy-available low voltage lights which run cool?
Anything other than LEDs?
LEDs do not run cool. No form of lighting runs cool. HTH.

Low pressure sodium comes damn close - IIRC 80% efficient.
'normal' fluorescents are around 50%.

about 20% IIRC. LED about 10%. Incandescent about 1%.

Integrating the minimal power spectrum that looks white and gives a
reasonable colour rendition gives a hard minimum power of about 200lm/W.

Fluorescents get about 100lm/W, the very best white LEDs, run under laboratory
conditions get around 30lm/W, and incandescents get under about 20lm/W.

So, about 50%, 15%, and 10%.

Most white LEDs get substantially less than 15%, even under optimal
conditions. (for example, with the junction temperature at 25C, which is
unachievable in practice usually without heat pumps)