LEDs for general home lighting

[amorrison]

Whats the light quality,energy efficiency and cost effectiveness of LEDs for general home lighting in 2004.
Lots of hype starting - see -

http://www.luxeonstar.com/

One watt this year,ten watts next year, 100W after ? ?
Streetlights in five years ? ?

 

[advidana]

in las Vegas they are using it for traffic signal lights.

 

[IRstuff]

Not just in Vegas...

While LED's provide the directional lighting required for traffic signals and possibly street lights and other directional lighting like spotlights and tensor lights, it's not clear if general purpose. omni-directional lighting is an efficient usage of LED's.

The reason is that anything that you use to alter the directionality of the LED lighting will reduce the overall efficiency of the system, which means that only in the case where you don't want to be bothered to replace lights would you use LED's for that purpose.

As for reliability, LED's are not quite there yet. Southern California started converting to LED traffic signals last year and one particular signal on the way to work is now completely dark. It started with a small cluster that grew larger and now the entire array is dark; possibly due to poor design.


TTFN

 

[IRstuff]

And also, LED's have some stiffer competition from compact fluorescent lighting. 1400 lumen from 23watts

TTFN

 

[bbop]

We here in Saint Paul have been using LED's for traffic signals for 3 years now and have had no problem with their output. One thing we do get complaints on are the lights which don't have LED's as there is a noticable difference.

 

[IRstuff]

But, there's a big contrast (!) between the directional lighting from a traffic signal and home lighting.

Traffic signals have (?) <45° cone angle AND you are trying to look directly into the light stream, while in most home lighting, it's desireable to have >45° cone angles and you're looking at reflected lighting.

One personal comment about the brightness of LED traffic lights is that they are so much better during the daytime, but tend to be overly bright at night, particularly after being dark-adapted. The first couple of months after the changeout, I would look directly at the LED lights at night and my eyes would actually hurt, but since then, I've adapted by not centrating on the lights at night.

I could see(!!) using LED's to replace tensor/reading lamps, since those applications demand cone angles substantially smaller than 45°.


TTFN

 

[hbendillo]

I think we are looking at big things for LED's in the future. The big advance in recent years is the near white light LED source. Probably the biggest uses are for accent and step lights. If you have a high end home and wish to add effects and accents LED's could be a good choice. We are not quite to the point where they are very effective for task lighting but it may be some day on a limited basis. I can see it being used for night ligting in facilities where not much illuminance is required. Take a look at what these guys are doing with LED's:

http://www.colorkinetics.com/

 

[peebee]

Interesting comment you make, IR, about reliability not being up to snuff with LED's. I generally think of LED's as being more reliable than just about any other source out there (I might need to look up some specs on induction lamps first, that's the only other source I can think of which might match the reliability of LED's). For colored lights (stop lights, taillights, exit signs, indicating lights), you can't beat an LED for reliability & long life. My guess is that you experienced a manufacturing defect.

My understanding is that LED's biggest hurdles to entering the general purpose white-light illumnation markets are:

1. Lousy color rendition
2. Low power densities (which means big sources & poor light control/focus & large fixtures)
3. High cost

All three of these are slowly being improved.

There are actually two manufacturers out there (that I'm aware of) making LED fixtures for the architectural lighting market -- ColorKinetics is one. . . And the name of the other slips my mind right now. . . .

Anyway, they both offer big flat LED array panels. Interestingly, you can control the color output from these things to any color of the rainbow. On some models, you can even drive them somewhat like a very low resolution TV (200x200 array or something like that).

But those things are very high priced.

And the white light that they generate doesn't come close to traditional white light sources -- if you want real white, or color rendition, stick to incandescent or fluorescent or metal halide.