LED lighting

[Utana]

As a caver, I've been seeing and using various LED headlamps for a while, and have been interested in seeing this technology turn a little more efficient and come into the home. The blue ones are terrible, IMHO, and I think its hard to see true distances correctly with blue light. The newer white lights are way better than the old ones and brighter to boot. Some of the headlamps they are coming out with now a days can make up to 1600 lumens with only 4 bulbs. Amazing! Anyone heard of these Cree super efficient LEDs as mentioned in this article: http://www.ledsmagazine.com/news/7/2/7 Will probably have to wait for the price to come down on these.

I have a few 1 watt LED headlamps and the first time I loaded batteries into them to see how long they would last, they stayed illuminated for a week! Granted only the first 10-12 hours are bright, but its really incredible that they can stay illuminated with such low power for such a long time. I have a few headlamps that have both incandescent and LED bulbs in them. I like the light from incandescents best, but after they wear the battery down and go out I can still turn on the LEDs using the same mostly dead batteries. And they are the only bulb that you can dunk in water time and again and always come back on. I would love to make the switch to LEDs for home lighting, especially for outdoor lighting since they are so darn hardy.

Kelly

[Sunking]

. How are they compared to the T5 fluorescents?

They do not compare. T5HO efficiency is around 105 lumens/watt. Best LEDs you can buy today are around 60 to 70 Lumens/watt..

But here is the catch and it is a big one. The LED light is measured inside the beam the light produces which may be as wide as 120 degrees. Outside of that beam the light level falls to almost nothing as LED light is very coherent like a laser. That makes them good for flash lights and task specific applications.

T5 light level is measured fully around in a 360 degree sphere. Use reflectors and lenses to match the beam angle and that 105 L/watt jumps up to 420 L/watt. So they are not even close.

Now with that said go into any new warehouse, Walmart, office, sporting arenas and look up at the lighting. It is not LED. It is T5HO High Bay lighting. The reason is very simple, they are the most efficient. The US government will not allow LED lighting in any building because they do not meet minimum efficiency standards of 90 Lumens/Watt. Only T5 and T8 can do that for interior lighting.

[jerld]

My friend whose a San Francisco electrician was telling me that the T5 fluorescents are significantly better than the leds, but I haven't heard of tri chip leds. I'll have to ask him about these types of leds. How are they compared to the T5 fluorescents?

[cyberfast]

I have no Problem with leds

if you use tri chip leds they don't produce much heat but put out allot of light.

[alison.drew19]

alison.drew19

why can't you go for recessed lights.

[russ]

For a chart that compares types of lamps please see

http://www.lamptech.co.uk/Documents/SO1%20Introduction.htm

An article about low pressure sodium lamps but the chart is for all types.

[thegreenman]

I have tried several of the LED bulbs currently available in the UK.

Of the 1-3 watt bulbs I have tried the spot type, the ones used in recess lighting are quite good especially as a replacement for halogen.

The LED bulbs as a replacement for CFL are in my opinion dismal and currently far too expensive at around

[Sunking]

By this link you have overstated the case for both CFL and linear fluorescent. I was able to find a 109 l/w tube for sale (which claimed to be the best), and I noticed the wonderful "up to 109" in it's marketing literature.

No not really I said it was an old link, I just used it as it is a good summary and easy for lay folks to see graphically. As for the flourescent bar graph it includes all tubes not just T5HO. And yes I know incandescent goes up to 30 l/w with tungsten high temperature lamps and was my reference for comparison to LED's.

My whole point is folks have to be very careful when selecting a light source specifically those folks using off-grid battery systems. A good example is with CFL's, they are not created equal and run quite a wide range of efficiency. Just recently on this forum a person was shocked when his battery run times were 1/3 of what he expected. What he learned was his 13 watt CFL lamps when ran through the inverter was drawing 55 watts per lamp when he budgeted only 15 watts per lamp. He got snake bit for a couple of reasons.

1. He was using inexpensive CFL's manufactured in China with really poor ballast running a PF of .57.
2. Not considering inverter conversion efficiency. He is running a large inverter on small loads.
3. Using a MSW inverter rather then TSW..

Anyway I think we have both made the same point and agree, LED's are not what they are cracked up to be.

[russ]

Here is a link to an Energy Star presentation that compares different types of lighting.

http://www.energystar.gov/ia/business/networking/presentations/Mar06_Lighting_Tech_Strategies.pdf

[russ]

Welcome BackBlast - The object of the forum is to learn as much as possible and help others where we are able. Note that some are of much more assistance than others due to background.

Being from a mechanical background, I am sometimes a fish out of water with electrical thingies. After I retired and we started building homes (great timing) I learned how much I didn't know about many things to do with residential construction!

Lighting, insulation, solar PV and thermal, heating systems, windows and on and on all require a good deal of effort to learn what there is available, what is cost effective and to stay up to date.

Again, welcome and lets us see what we can accomplish!

[BackBlast]

Show me a quote where I said LED's are equal to incandescent. Here is what I did say:

Sorry, my characterization was inaccurate. But you are not being very accurate either, and if we're going to nit pick, well, lets nit pick...

Incandescent ranges 10-17 by your own cite, and for consumer level lighting this IS accurate. 35 is for boutique specialty lamps and I was being rather generous by citing it.

"Not much better than" 10-17 l/w would be somewhat less than 3 times more efficient that a typical LED setup will achieve using your own numbers. This would make LEDs more directly comparable to CFLs rather than incandescents.

It is an old link, or I should say graph, but 110 l/w. I would link to NLI (up to day l/w printed 2-2010) but without an username and password it will not work.

By this link you have overstated the case for both CFL and linear fluorescent. I was able to find a 109 l/w tube for sale (which claimed to be the best), and I noticed the wonderful "up to 109" in it's marketing literature. It would be interesting to see the performance parameters and decay present in those so I can derate the tubes properly besides the known fixture issue.

Anyway, I think we've run the course on this thread. Nice to be on the forum, I hope to learn some things, see you around.

[Sunking]

This is still comfortably above Incandescent levels that you inferred earlier were equivalent, which tops out around 35 l/w. e possible.

Show me a quote where I said LED's are equal to incandescent. Here is what I did say:

Backblast we can agree to disagree, but fact is LED lights are not much better than incandescent bulbs with 40 to 60 Lumens per watt overall efficiency with driver and fixture.

I've never seen anyone claim 120 lumens per watt for fluorescent until now. Do you have a cite I'm not aware of? I'd like to see these new tubes..

It is an old link, or I should say graph, but 110 l/w. I would link to NLI (up to day l/w printed 2-2010) but without an username and password it will not work.

[BackBlast]

Backblast we can agree to disagree, but fact is LED lights are not much better than incandescent bulbs with 40 to 60 Lumens per watt overall efficiency with driver and fixture,

Those numbers are ballpark accurate about 1.5 LED generations ago, the older lower binned Cree XR-E in a fixture would be in this ballpark, though the nicer bins could probably push 80 l/w in a fixture if anyone cared to pay a premium to get them. This is still comfortably above Incandescent levels that you inferred earlier were equivalent, which tops out around 35 l/w. With the lag to production, I actually don't doubt this is all the fixed LED lighting world has really seen yet. So I will largely buy this as the available, not the possible.

...cannot touch T5 and T8 fluorescent lighting at around 90 to 120 Lumens per watt

I've never seen anyone claim 120 lumens per watt for fluorescent until now. Do you have a cite I'm not aware of? I'd like to see these new tubes..

Our Government will not allow LED lighting in any federal building period because they are not even close to being GREEN or ENVIROMENTLY friendly.

I would hardly call our government a sound source of judgment on anything. This is not good supporting evidence.

LED someday might compete and become mainstream, but for now they should only be used for special task lighting like flashlights, tail lights, and landscape lighting…

So my point is valid, forget LED for now.

I do still agree with this, it has a few nitches and nothing more.

[Sunking]

Backblast we can agree to disagree, but fact is LED lights are not much better than incandescent bulbs with 40 to 60 Lumens per watt overall efficiency with driver and fixture, CFL with ballast is 60 to 90 Lumens per watt and cannot touch T5 and T8 fluorescent lighting at around 90 to 120 Lumens per watt. Our Government will not allow LED lighting in any federal building period because they are not even close to being GREEN or ENVIROMENTLY friendly.

LED someday might compete and become mainstream, but for now they should only be used for special task lighting like flashlights, tail lights, and landscape lighting

[BackBlast]

I know this thread is old, but I can't help myself

The problem with LED's are many but the 5 biggest are:

1. Cost.

Agreed.

2. Efficiency is exaggerated and does not conform to NLI standards. As mentioned the problem is with the driver circuits and heat. You will see claims as high as 100+ Lumens per watt. When the ballast or driver power is included as with all other lighting, the efficiency is not much better than incandescent

This is a terrible overstatement of the problem. LED manufactures typically DON'T MAKE the current regulators that are required to run their product. They are rating their product and not the SYSTEM you buy, and it's the SYSTEM you must compare to get apples to apples. You could well be right on the money as far as the terribly conceived and built "replacement bulbs" around that snooker people into them buying based on general LED hype and claims. But you're way off base in applying it to properly designed LED oriented enclosures and systems. It's pretty easy to maintain 100+ l/w with the latest and greatest LEDs in a properly built and executed system. Current top bin is ~143 lumens/watt @ 25C junction, which gives you a 30% margin for power supply and die heat losses before you get below 100 lumens/watt. Still costs way too much $/lumen to do though.

CFLs and the like have ballast losses as well, and they certainly are not on the order of 70-85% loss you are assigning to LED regulators.

3. Next on the efficiency hit list is LED's produce the highest output when they are cold. So when the measure the Lumen output with a very short pulse of a few milli-seconds so the light does not warm up. Once the light warms up in real use, the output drops considerable.

I would put heat as the #2 issue rather than 3. It's a problem. They use a small pulse because you want to compare apples to apples, 25C die temp. The efficiency over the temp range is also characterized and rated as well as the package thermal path, you can keep the output fairly good with a good thermal path. This has been one of the most focused on areas of LED development because heat ultimately limits how much power you can get through a single package.

You can't keep an LED at this rated level in most cases, but you can keep heat losses to 5-10% with ease. Over driving LEDs for the thermal path available is easily the most common mistake in poorly conceived systems. The need for this thermal path also means LEDs do not work very optimally in current standard lighting fixtures unless they are mostly a heat sink and very low power because they lack that thermal path, and this adds yet more cost to their adoption for well built systems. You NEED a designed thermal path and most-to-all other currently lighting systems don't have one beyond generous access to open air.

It is useful to note here that CFLs have the opposite problem - they struggle in the cold. Not a big deal in the house, but in a garage or outside are a different matter in the winter. Refrigerators are great candidates for LED lighting and I'm surprised more manufactures haven't figured this out.

4. Last on the efficiency list is the directional nature of LED light and where they take the measurement. They measure on the lights focal spot. Move a few degrees in any direction and the light falls off the cliff. Great for flashlights and effect lighting, terrible for indoor area lighting.

There are many different beam profiles, many are much smoother than you describe and many are quite suitable for general lighting, and I would even say that the typical LED beam profile can even be an advantage - you don't need to waste a massive amount of your light going directly back into your fixture and needing to be reflected back out (if you manage it at all) like many bulb and tube style lights do, which can easily be a 30-40% or more lumen loss that LEDs can completely avoid. I'd say this can be a solid advantage rather than a disadvantage.

It is true that if you concentrate all the LEDs in one spot in the same direction the light will likely not be uniform, that's a system design issue that makes it a bit more complicated than "put one in any orientation that you like in the middle of the room" but not completely unmanageably so. Even with simplicity, you can take a lumen hit to make the light uniform with a diffuser - it certainly need not be any worse than the above mentioned fixture hit.

5. Color Rendering Index. LED's CRI is horrible with an extreme amount of Blue light pollution.

CRI on some LEDs is very very good. It's even more expensive, less efficient than run of the mill, so a ridiculous candidate for general lighting. Regardless, it exists, so if this really is a problem it can be addressed.

While CRI is an interesting standard, many people have lived with and dealt with poor CRI bulbs before. LEDs aren't any worse than most of the CFLs out there and many people use those just fine. So I don't really see this as an impediment, it's certainly "good enough" in it's current state and much much better than it was 5 years ago.

Warm white LEDs have toned down the blue spike significantly and have slightly better CRI than the current cool white (80 vs 75). I would not describe the warm white LEDs I have experience with as having any "blue light pollution".

The most efficient lighting one can use in your home is fluorescent T5 tubes which has a true 100 Lumens per watt and excellent CRI. Next in line is CFL of 60 to 80 Lumens per watt, and then LED with a real rating of around 30 to 6 Lumens per watt.

I can't argue with your recommendations, they are spot on. Even if I think you tend to poo poo LED tech more than you should But perhaps you do it because there are so many poorly conceived LED products out there - and that I can certainly sympathize with that.