Has LED lighting efficiency reached a limit?

I've just replaced half of the LED downlighters in a kitchen, and realised that the new ones are exactly the same make and model as the old ones that were installed in 2014.
These are the downlighters: https://www.tlc-direct.co.uk/Products/LTFRD12NW.html
In 2012 I remember seeing LED efficiency improvements each year, but here there's been no improvement in more than five years. So has the LED lighting efficiency reached a limit?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Caecilius wrote:

over 200 lm/W has been reached in the lab, bog standard ikea LEDs are 90-110, some philips ones are 126
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

The 200 lm/W was first reported back in 2010 in the lab.
https://www.cree.com/news-media/news/article/cree-breaks-200-lumen-per-watt-efficacy-barrier
At the time I thought this technology would eventually make its way into real-world lamps, but it's been ten years now so maybe that won't happen.
100 lm/W has been my go-to efficiency level for about five years now. I didn't realise that Philips offered up to 126 lm/W though.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/01/2020 15:39, Caecilius wrote:

Lumens are pretty logarithmic arent they though?
I mean double the power is 3dB brighter and so on..
--
"I guess a rattlesnake ain't risponsible fer bein' a rattlesnake, but ah
puts mah heel on um jess the same if'n I catches him around mah chillun".
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 9 Jan 2020 15:44:25 +0000, The Natural Philosopher

Thanks for that - I didn't realise that lumens incorporated the human brightness perception curve. I'd assumed it was a linear measure of power.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/01/2020 15:53, Caecilius wrote:

You completely misundersand me. What I mean is that double the lumens doesn't look a whole lot brighter So in practice 100lm/W -> 200lm/W is not a giant difference asfar as human perception goes
--
“it should be clear by now to everyone that activist environmentalism
(or environmental activism) is becoming a general ideology about humans,
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thursday, 9 January 2020 15:44:28 UTC, The Natural Philosopher wrote:

NO. PKUATBT.

Irrelevant.
The absolute maximum possible is 683 lumens per watt.
--
(c) Dr. S. Lartius, UK. Gmail: dr.s.lartius@ |

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The person paying the electricity bills!
Keep the brightness the same and use half the electricity, surely that's why we're using LEDs instead of filament bulbs to start with.
--
Chris Green
·

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Caecilius wrote:

I couldn't remember if it was 200, or 300, I do remember that Johnny B Good has been urging us for many years to not buy current LEDs, wait until the 200 lm/W models hit the shelves, any day now :-P
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 9 Jan 2020 14:01:00 +0000, Andy Burns wrote:

Ikea's are poor things - low luminous efficacy (l/W) and hot. 4 years ago I was replacing luminaires and set the line at 100l/w for all but GU10s (the GU10 has a hard life, cap up and in a hole); 3 years ago I was buying 3W 320l COB lamps, 4W 470l, 5W 600l and 6W 800l COBs. Last year's GU10 were 3W 420 lm. A lot of places are still 5W 400l etc., although Home Bargains' 12W 1500l is OK and cheap. I've plenty of stock so will wait until there's an improvement - at my age it'd better be soon!
--
Peter.
The gods will stay away
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yes but for how long and is it mass producible? Impurities are always an issue. Also is it better to use normal leds or some kind of phosphor driven by invisible frequencies? Brian
--
----- --
This newsgroup posting comes to you directly from...
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/01/2020 13:09, Caecilius wrote:

If they are the same why are you replacing them? I thought they were supposed to last more than 5 years
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 9 Jan 2020 14:09:56 +0000, Pancho

I'm replacing them due to failure. Not sure whether it's the driver or the LEDs that are failing though.
They have a five-year guarantee which appears to be about equal to their actual life.
The replacement downlighters are significantly brighter than the remaining old ones though, so I'm not sure I'd want to run them for ten years even if they would last that long.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/01/2020 15:43, Caecilius wrote:

If that is the case it is a bit surprising so many modern downlights don't have replaceable bulbs. I doubt many people want to rewire a new downlight every five years as opposed to just replacing a £2 gu10 bulb.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 9 Jan 2020 16:41:18 +0000, Pancho

It's an easy job if the original installation left enough slack in the cables to pull the lamp and transformer through the hole.
The only potential problem I find is that the edge of the hole in the plasterboard ceiling is fragile, and can be easily damaged by the retaining clips as the lamp is removed and replaced.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thursday, 9 January 2020 16:41:22 UTC, Pancho wrote:

lb.
Consumer devices that are stupidity incarnate surprise you?
NT
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/01/2020 13:09, Caecilius wrote:

The efiiciency of an LED depends on its emitted wavelength, and the most efficient part of the visible spectrum is at the near ultraviolet end where the theoretical limit is around 680lm/W (at 380nm).
For a reasonable colour rendition visible 'white' LED the theoretical limit is around 400 lm/W so we are getting very close!
An equivalent brightness to a 60W tungsten lamp would consume about 2W of power.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Within an order of magnitude, yes. I'd hoped to see real-world examples of those 200 lm/W LEDs that were reported in 2010, but it looks like they never made it out of the lab.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 09/01/2020 13:09, Caecilius wrote:

In practical terms yes. There are advances in maximum brightness LEDs in the laboratory but they are unlikely to make it into mass production until someone finds a way to make them at a high enough yield and reliability. The PSU efficiency is already a factor in consumer devices.
They dim over time as defects in the crystal accumulate. See:
https://www.digikey.co.uk/en/articles/techzone/2012/feb/understanding-the-cause-of-fading-in-high-brightness-leds
The luminous flux at the surface of an LED die is approximately the same as the sun's photosphere and the phosphors are quite close to their limit. Push them much harder and you either need very good heat sinking or a much more robust expensive phosphor. You can never say never in this game - people are working on improved phosphors and better CRI.
https://cen.acs.org/materials/inorganic-chemistry/chemical-search-better-white-light/96/i46
I am a bit puzzled why you need to replace so many LED units though.
The ones in my house are a mixture from different eras using a replace on fail policy. All the spotlights are now LED based. A few filament bulbs persist in seldom used fittings (as do much older CFLs).
--
Regards,
Martin Brown
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 9 Jan 2020 14:47:00 +0000, Martin Brown

I can see that dimming effect myself, as the replacement lamps are significantly brighter than the remaining originals. Given the eye's logarithmic brightness perception they may be more than twice as bright.

I've got 12 downlighters in the kitchen. I've replaced five due to failure over the past year. Given the difference in brightness after five years, I wouldn't want to keep the originals for ten years even if they lasted that long.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.