Lights with low heat output

[denbigh1974]

Are there any commercialy-available low voltage lights which run cool? Anything other than LEDs?

[Ian Stirling]

Assorted fluorescant or electroluminescent, with their own inverter. No 'native' low voltage lights.

[Steve Firth]

LEDs do not run cool. No form of lighting runs cool. HTH.

[Andrew Gabriel]

There are low voltage fluorescents. You haven't given enough info for any detailed reply. LEDs you are likely to find used in most lighting are similar efficiency to filament lamps.

[Ian Stirling]

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

Not to mention that at low enough powers, most forms of lighting won't heat up much.

[Dave Fawthrop]

|On 19 Nov 2006 14:33:10 -0800, [e-mail] 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.

Depends what you mean by cool. LEDs do not run *cold*, (at ambient temperature) but run at a low lower temperature than incandescents, halogens etc, which in my book classes as

*cool*

[Ian Stirling]

They generally produce the same amount of heat for a given amount of light - it's just spread out more. And the LED junctions themselves have to remain at a moderately low temperature (

[Dave Fawthrop]

|Dave Fawthrop wrote: |> On Sun, 19 Nov 2006 23:12:53 +0000, Steve Firth |> wrote: |> |> |On 19 Nov 2006 14:33:10 -0800, [e-mail] 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. |> |> Depends what you mean by cool. |> LEDs do not run *cold*, (at ambient temperature) but run at a low lower |> temperature than incandescents, halogens etc, which in my book classes as |> *cool* | |They generally produce the same amount of heat for a given amount of |light - it's just spread out more.

Just not true :-( Almost all the power used by a 100W incandescent bulb goes into the room as heat, only a tiny amount as light. Everyone who has burned a hand on a lit light bulb will know that. A 22 watt energy saving bulb with equivalent light output to a 100watt incandescent can only emit under 22 watts as heat. They only feel warm to the touch

[Ian Stirling]

You specifically mentioned LEDs, and my response was clearly about LEDs. And the tubes of most CFLs hit 100C.

[denbigh1974]

I want to light an alcove by mounting a "strip light" of some sorts on a nearby beam. But the beam is only 4 feet above the floor so I want to install a light which has less risk of burning or shocking the kids if they accidentally break it.

[The Natural Philosopher]

Actually they are about ten times as efficient..

[The Natural Philosopher]

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

[The Natural Philosopher]

LEDS die at around 100C. The reason they are used increasingly in traffic lights is energy efficiency.

[Ian Stirling]

There are many, many enclosed strip-lights. It may be appropriate to paint the bit next to the beam brilliant white, and mount it on the side of the beam.

[denbigh1974]

Yes, Ian, I had the same thought about mounting. With regards to a low volt + low heat strip light though, which would you suggest I take a look at?. There seem to be a few LED strips and that's all.

[stevelup]

Hi

Surely the primary reason for using them in traffic lights is to reduce ongoing maintainance costs?

Steve

[The Natural Philosopher]

That as well. But there are enormous energy savings to be had as well.

[Ian Stirling]

What sort of quantity of light are you thinking about?

[Ian Stirling]

However, this is not the case for white LEDs. For traffic lights, it's true, for a couple of reasons.

Firstly, most of the light in a normal light is absorbed by a filter, and secondly, the bulbs are very inefficient as they are run at a low output to increase time between failures.

LEDs produce light at one wavelength only, so need no filters. And the way they are used in traffic lights, where there may be hundreds per light means that they fail gradually.

[Ian Stirling]

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)