> LEDs are only twice as efficient as traditional bulbs?
I didn't see that claim in the article, but I thought these two paragraphs were wonderfully specific:
One quantity that characterizes a lighting source is the so-called luminous efficiency, which takes into account the response of the human eye. Whereas the luminous efficiency of conventional incandescent lights is between 2 and 3 percent, that of fluorescents (including CFLs) is between 7 and 15 percent, and that of most commercial LEDs between 5 and 20 percent, the new two-stage incandescents could reach efficiencies as high as 40 percent, the team says.
The first proof-of-concept units made by the team do not yet reach that level, achieving about 6.6 percent efficiency. But even that preliminary result matches the efficiency of some of today’s CFLs and LEDs, they point out. And it is already a threefold improvement over the efficiency of today’s incandescents.
Comparing theoretical efficiency of new design for incandescent lighting with commercially available LEDs does not make sense, as theoretical efficiency of white LEDs is also around 40%. I'll consider incandescents once the efficiency of commercially available ones reaches the efficiency of commercially available leds. I bet $100 that it will not happen in next 10 years.
Comparing theoretical efficiency of new design for incandescent lighting with commercially available LEDs does not make sense
Yes. They say they are currently at 6% efficiency, which is better than the worst CFL's and LED's, but far from matching the best.
as theoretical efficiency of white LEDs is also around 40%
Yes, although one should probably include the power supply. I think the advantage of the incandescent approach is that there are no losses here.
I'll consider incandescents once the efficiency of commercially available ones reaches the efficiency of commercially available leds.
Sure, sounds wise. Light quality and longevity might be factors too.
But what does this have to do with the claim that the article says "LEDs are only twice as efficient as traditional bulbs"? The article can be read as claiming that the worst commercially available LED's are about 2x the efficiency of the best incandescents, and perhaps this is false, but I don't see this as reason to discount the rest of the details.
Their claimed efficiency is only sort of true, in that it's measuring the electrical input while ignoring the external heat also used to run the light. By similar logic, one could say that a steam engine running in a very hot room is also over 100% efficient.
Also, the "theoretical efficiency of LEDs" is a very different number than the "theoretical efficiency of white LEDs". I think when talking about white LEDs, they are assuming a monochromatic LED pumping a phosphor.
But while it's not that practical, in that it's limited to picowatts (10^-12 watts), it is interesting nonetheless. Another similarly surprising example is that the theoretical maximum efficiency of some fuel cells also exceeds 100%, for similar reasons of extracting heat from the environment.
I didn't see that claim in the article, but I thought these two paragraphs were wonderfully specific:
One quantity that characterizes a lighting source is the so-called luminous efficiency, which takes into account the response of the human eye. Whereas the luminous efficiency of conventional incandescent lights is between 2 and 3 percent, that of fluorescents (including CFLs) is between 7 and 15 percent, and that of most commercial LEDs between 5 and 20 percent, the new two-stage incandescents could reach efficiencies as high as 40 percent, the team says.
The first proof-of-concept units made by the team do not yet reach that level, achieving about 6.6 percent efficiency. But even that preliminary result matches the efficiency of some of today’s CFLs and LEDs, they point out. And it is already a threefold improvement over the efficiency of today’s incandescents.
Which details in that do you question?