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:
over 200 lm/W has been reached in the lab, bog standard ikea LEDs are
90-110, some philips ones are 126
If they are the same why are you replacing them? I thought they were supposed to last more than 5 years
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.
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:
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).
57 Lm/W is not very good. The GU10s I get are more than twice that.
I would imagine so. I think there is a theoretical limit to the efficiency of a blue LED
The 200 lm/W was first reported back in 2010 in the lab.
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.
Lumens are pretty logarithmic arent they though?
I mean double the power is 3dB brighter and so on..
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.
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.
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.
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
There is a hard limit on how many lumens per watt you can get for a specified spectral distribution. Monochromatic low pressure sodium lamps held the record at >200Lm/W for a very long time. Luminous efficacy is th key phrase to search for - which includes the eyes sensitivy:
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!Its not that so much, its the dissipation of the losses as heat that holds them back I think. If you cook the active area too much you get early failure. I've seen pulsed ones and steady state ones and all sorts of clever ways to apparently over run the led to get more light out, but there is always a trade off. Brian
Car headlight LEDs are still improving. But still can't match HID.
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
NO. PKUATBT.
Irrelevant.
The absolute maximum possible is 683 lumens per watt.
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