8 ms·

This news article doesn't even mention the article's name, the authors, or when it was published. It was actually published in January, and has just now been p

by dkbrk 10y ago

This news article doesn't even mention the article's name, the authors, or when it was published. It was actually published in January, and has just now been picked up by the Telegraph. Here is the citation: Ognjen Ilic, Peter Bermel, Gang Chen, John D. Joannopoulos, Ivan Celanovic, Marin Soljačić. Tailoring high-temperature radiation and the resurrection of the incandescent source. Nature Nanotechnology, 2016; DOI: 10.1038/nnano.2015.309 And here is the actual paper, via Sci-Hub: http://sci-hub.cc/10.1038/nnano.2015.309 http://sci-hub.cc/10.1038/nnano.2015.309 The Telegraph's explanation is terrible: "with a special crystal structure in the glass they can bounce back the energy which is usually lost in heat, while still allowing the light through." The tungsten filament is sandwiched between two plates made up of layers of oxides, designed to selectively reflect infrared radiation and transmit visible light. They used a numerical model to design and evaluate various candidate compositions for these plates. For a proof-of-concept, they chose one which uses layers of silicon oxide and tantalum oxide, with 90 layers in total per plate. This reflected about 90% of infrared radiation, producing a luminous efficiency of about 6.6%. This is comparable to commercial LEDs and compact fluorescents, though far from state-of-the-art. However, the results closely matched their numerical model, and a more complex structure comprised of layers of silicon dioxide, aluminium oxide, tantalum oxide and titanium dioxide, with 300 layers in total, should produce a luminous efficiency of 40%. This is significantly better than the state-of-the-art in LEDs (about 15-30%). They did not, however, actually build that one. I have no idea how expensive this would be to commercialise. It doesn't sound like the physics is particularly complex, but manufacturing costs could be prohibitive. I think it's safe to say we won't be seeing it outside the laboratory any time soon.

ohitsdom 10y ago
Thank you, this was so much more informative than the article.
exhilaration 10y ago
Also previously discussed on HN at least twice before: https://news.ycombinator.com/item?id=10916846 https://news.ycombinator.com/item?id=10916846 https://news.ycombinator.com/item?id=10889822 https://news.ycombinator.com/item?id=10889822
buovjaga 10y ago
> It was actually published in January, and has just now been picked up by the Telegraph. The Telegraph article is dated 11 January 2016
- swsieber 10y ago
  It might be back dated then? Or perhaps just slow to publish online? The url implies March 12.
personjerry 10y ago
Why can't we apply the same technique to fluorescent filaments?
- frandroid 10y ago
  Or around candles, while we're at it...
- joshyeager 10y ago
  Fluorescent lights don't use filaments, they use electrically excited gasses. The reason this technique improves the efficiency of incandescent lights is that they produce their light by heating the filament. The hotter the filament, the more light it produces. So by reflecting the heat back towards the filament, you can achieve a hotter filament with less input energy.
  - sitharus 10y ago
    Fluorescent lights do use filaments. At each end of the tube there's a hot cathode - essentially a small incandescent filament designed to emit electrons rather than light. This is the source of the electrons that excite the gasses. While there are some designs that use cold cathodes these are not the common type as they are less efficient. Still won't make this filament treatment help though - sandwiching with layers would probably block the electrons.
  - Grishnakh 10y ago
    So it sounds like this new bulb will have the same problem people complain about with LEDs and CFLs: slow warm-up times. The filament will take longer to warm up to full operating temperature, since you're relying on thermal reflection in the glass to let the heat build up. I guess they could get around this by having a power control circuit in the bulb, to give it a large inrush current to heat up quickly, and then back off once it's warmed up.
vvanders 10y ago
Is that the same oxide as used in Tantalum capacitors? Those things have a tendency to explode randomly if inrush current isn't controlled appropriately. They're also expensive and somewhat of a conflict material from what I understand in the little reading I've done on them(but they're awesome for power circuits).
billiam 10y ago
An additional and important application discussed in the paper for the (relatively) high efficiency infrared reflectors is for thermophotovoltaic systems, which many think will be generating a lot of our electricity in 50 years.
collyw 10y ago
"The Telegraph's explanation is terrible: "with a special crystal structure in the glass they can bounce back the energy which is usually lost in heat, while still allowing the light through." The tungsten filament is sandwiched between two plates made up of layers of oxides, designed to selectively reflect infrared radiation and transmit visible light." Whats terrible about that? Its the same as what you said using words that could be understood by a child.
- refurb 10y ago
  I was thinking the same thing. When I read the Telegraph explanation and was told it was terrible i thought "dam those reporters!". Then I read the actual scientific explanation and thought the Telegraph summary was pretty good.
- deleted 10y ago
  [deleted]
- woodman 10y ago
  Ask the child to draw it, you'll notice the problem. One description makes me think that the glass has some new treatment, the other makes me think that there is a new structure within the bulb.
  - andrepd 10y ago
    Splitting hairs. The point, as succinctly as possible is that: Incandescent bulbs are inefficient because they lose a lot of energy as heat instead of light. This counters that by introducing a crystal that selectively blocks the heat and lets the light through. Maybe the explanation is wrong in the minutiae but it gets the fundamental point across.
    - thaumasiotes 10y ago
      I don't understand how that's supposed to make the bulb more efficient. If you're trying to keep the interior of the bulb hot, mission accomplished. But the problem we're trying to solve is that when we run a current through the filament, some of the energy we supply becomes visible light and some becomes infrared light. We want more of it to become visible light and less of it to become infrared light. How does preventing infrared light from leaving the bulb help with that?
HCIdivision17 10y ago
The manufacturing costs won't be too bad, I'd imagine. At least, in terms of the normal shocking costs of manufacturing. If the design is simple enough, that 300 layers may be just 75 repititions of four layers (no doubt not actually the case, but the machine spraying material onto the plates can adapt). I'm a bit disappointed that the recipe wasn't included; I would have liked to see what the design entailed. All the layers are on dialectrics, and they're all oxides, so the process chambers won't be too hard to control. And I say that knowing full well some poor coater engineer is actually just going to have a devil of a time with it (or not! quarter wave filters are fairly standard stuff). Most of all, the thing I'd be intersted in is how resistant to error is the design? It sure looks like it doesn't need to be too perfect per layer. For a pair of microscope lenses, precision is everything. In a lightbulb you can probably get away with a lot of error (per layer: as a whole you could easily make the color something goofy). Of course, if it's color swings wildly with minor errors in certain layers, well, that could hole the product up in R&D hell.
- venning 10y ago
  > Most of all, the thing I'd be intersted in is how resistant to error is the design? I feel like this is what keeps the most impressive research out of real world application. Yeah, manufacturing is expensive, but tolerances are just so much more controllable in a lab. Manufacturing also produces revenue, whereas funding the years of research necessary just to figure out a new nanometer-precise process is a hard investment for most companies to swallow, especially if the end product isn't guaranteed to produce a profit itself.
  - eru 10y ago
    > Yeah, manufacturing is expensive, but tolerances are just so much more controllable in a lab. Not least because, in a lab you are happy if one out of ten prototypes work for your experiment. You don't want 90% spoil in manufacturing.
  - HCIdivision17 10y ago
    The good news is that the processes I described above are already well established. The trick is always in the dirty, nasty details, but in this case I'd be bullishly optimistic. I haven't personally worked on a large batch coater, so I can't attest to how hard it is to tune the things in, but your typical coater engineer is a bit eccentric anyhow and will no doubt make it work. See, the weird bit of how these coatings work is that it's fairly easy to empirically tune the damn things to be angstrom accurate (-ish), but the geometry of how the material is sprayed messes up the uniformity, which in turn ruins your yields (one square centimeter in the center is good, chuck the rest!). But if the coating can withstand some variation between layers, tuning it such that the layers sorta cancel out in the bulk, you'll lose the efficiency, but your yield can absolutely skyrocket. There will likely be key layers at the optical half, quarter, eighth, etc. thicknesses, but if you get enough layers you can probably get away with a lot. You can also just build really neat source geometries to sorta flatten out the spray over a larger area, but that's something I never worked on. My ignorance of this sort of coating has me worry about it immediately destroying itself from the insane material stresses... Though no idea how well it'll anneal after 1000 hours of constant heat (or worse: on-off heat-cooling cycles!) But since they're all oxides and likely put down together while the substrate stays hot, I bet it works out ok.
paulsutter 10y ago
Upvote for your nice summary, almost went the other way for the undeserved criticism of the article.
PhasmaFelis 10y ago
I'm confused. If reflecting 90% of infrared radiation only produces a luminous efficiency of 6.6%, how can any further increase in reflection lead to 40% efficiency?
- Eliezer 10y ago
  Obvious but maybe wrong answer: because it's not linear, if you trap nearly all the IR it stays until converted to visible, otherwise it still escapes after a couple of bounces.
- pranjalv123 10y ago
  If you reflected all the infrared light, the efficiency would be 100%, since all the light leaving the bulb would be visible. Normally, the vast majority of the light leaving the bulb is infrared, but if you keep 90% of it in the bulb, then 6.6% of the light leaving the bulb is visible light.
daveloyall 10y ago
A bit better: https://www.sciencedaily.com/releases/2016/01/160111135229.htm https://www.sciencedaily.com/releases/2016/01/160111135229.h...
hultner 10y ago
There's nothing state-of-the-art with 15-30% efficiency LEDs, maybe a few years ago but not 2016, blue LEDs are almost at 59% and even the whites are at about 50%.
k_lander 10y ago
Can this method of internal reflection be used to enhance the efficiency of LEDs?

by dkbrk 10y ago

ohitsdom 10y ago

Thank you, this was so much more informative than the article.

exhilaration 10y ago

Also previously discussed on HN at least twice before: https://news.ycombinator.com/item?id=10916846 https://news.ycombinator.com/item?id=10916846 https://news.ycombinator.com/item?id=10889822 https://news.ycombinator.com/item?id=10889822

buovjaga 10y ago

> It was actually published in January, and has just now been picked up by the Telegraph. The Telegraph article is dated 11 January 2016

swsieber 10y ago
It might be back dated then? Or perhaps just slow to publish online? The url implies March 12.

personjerry 10y ago

Why can't we apply the same technique to fluorescent filaments?

frandroid 10y ago
Or around candles, while we're at it...
joshyeager 10y ago
Fluorescent lights don't use filaments, they use electrically excited gasses. The reason this technique improves the efficiency of incandescent lights is that they produce their light by heating the filament. The hotter the filament, the more light it produces. So by reflecting the heat back towards the filament, you can achieve a hotter filament with less input energy.
- sitharus 10y ago
  Fluorescent lights do use filaments. At each end of the tube there's a hot cathode - essentially a small incandescent filament designed to emit electrons rather than light. This is the source of the electrons that excite the gasses. While there are some designs that use cold cathodes these are not the common type as they are less efficient. Still won't make this filament treatment help though - sandwiching with layers would probably block the electrons.
- Grishnakh 10y ago
  So it sounds like this new bulb will have the same problem people complain about with LEDs and CFLs: slow warm-up times. The filament will take longer to warm up to full operating temperature, since you're relying on thermal reflection in the glass to let the heat build up. I guess they could get around this by having a power control circuit in the bulb, to give it a large inrush current to heat up quickly, and then back off once it's warmed up.

vvanders 10y ago

Is that the same oxide as used in Tantalum capacitors? Those things have a tendency to explode randomly if inrush current isn't controlled appropriately. They're also expensive and somewhat of a conflict material from what I understand in the little reading I've done on them(but they're awesome for power circuits).

billiam 10y ago

An additional and important application discussed in the paper for the (relatively) high efficiency infrared reflectors is for thermophotovoltaic systems, which many think will be generating a lot of our electricity in 50 years.

collyw 10y ago

"The Telegraph's explanation is terrible: "with a special crystal structure in the glass they can bounce back the energy which is usually lost in heat, while still allowing the light through." The tungsten filament is sandwiched between two plates made up of layers of oxides, designed to selectively reflect infrared radiation and transmit visible light." Whats terrible about that? Its the same as what you said using words that could be understood by a child.

refurb 10y ago
I was thinking the same thing. When I read the Telegraph explanation and was told it was terrible i thought "dam those reporters!". Then I read the actual scientific explanation and thought the Telegraph summary was pretty good.
deleted 10y ago
[deleted]
woodman 10y ago
Ask the child to draw it, you'll notice the problem. One description makes me think that the glass has some new treatment, the other makes me think that there is a new structure within the bulb.
- andrepd 10y ago
  Splitting hairs. The point, as succinctly as possible is that: Incandescent bulbs are inefficient because they lose a lot of energy as heat instead of light. This counters that by introducing a crystal that selectively blocks the heat and lets the light through. Maybe the explanation is wrong in the minutiae but it gets the fundamental point across.
  - thaumasiotes 10y ago
    I don't understand how that's supposed to make the bulb more efficient. If you're trying to keep the interior of the bulb hot, mission accomplished. But the problem we're trying to solve is that when we run a current through the filament, some of the energy we supply becomes visible light and some becomes infrared light. We want more of it to become visible light and less of it to become infrared light. How does preventing infrared light from leaving the bulb help with that?

HCIdivision17 10y ago

The manufacturing costs won't be too bad, I'd imagine. At least, in terms of the normal shocking costs of manufacturing. If the design is simple enough, that 300 layers may be just 75 repititions of four layers (no doubt not actually the case, but the machine spraying material onto the plates can adapt). I'm a bit disappointed that the recipe wasn't included; I would have liked to see what the design entailed. All the layers are on dialectrics, and they're all oxides, so the process chambers won't be too hard to control. And I say that knowing full well some poor coater engineer is actually just going to have a devil of a time with it (or not! quarter wave filters are fairly standard stuff). Most of all, the thing I'd be intersted in is how resistant to error is the design? It sure looks like it doesn't need to be too perfect per layer. For a pair of microscope lenses, precision is everything. In a lightbulb you can probably get away with a lot of error (per layer: as a whole you could easily make the color something goofy). Of course, if it's color swings wildly with minor errors in certain layers, well, that could hole the product up in R&D hell.

venning 10y ago
> Most of all, the thing I'd be intersted in is how resistant to error is the design? I feel like this is what keeps the most impressive research out of real world application. Yeah, manufacturing is expensive, but tolerances are just so much more controllable in a lab. Manufacturing also produces revenue, whereas funding the years of research necessary just to figure out a new nanometer-precise process is a hard investment for most companies to swallow, especially if the end product isn't guaranteed to produce a profit itself.
- eru 10y ago
  > Yeah, manufacturing is expensive, but tolerances are just so much more controllable in a lab. Not least because, in a lab you are happy if one out of ten prototypes work for your experiment. You don't want 90% spoil in manufacturing.
- HCIdivision17 10y ago
  The good news is that the processes I described above are already well established. The trick is always in the dirty, nasty details, but in this case I'd be bullishly optimistic. I haven't personally worked on a large batch coater, so I can't attest to how hard it is to tune the things in, but your typical coater engineer is a bit eccentric anyhow and will no doubt make it work. See, the weird bit of how these coatings work is that it's fairly easy to empirically tune the damn things to be angstrom accurate (-ish), but the geometry of how the material is sprayed messes up the uniformity, which in turn ruins your yields (one square centimeter in the center is good, chuck the rest!). But if the coating can withstand some variation between layers, tuning it such that the layers sorta cancel out in the bulk, you'll lose the efficiency, but your yield can absolutely skyrocket. There will likely be key layers at the optical half, quarter, eighth, etc. thicknesses, but if you get enough layers you can probably get away with a lot. You can also just build really neat source geometries to sorta flatten out the spray over a larger area, but that's something I never worked on. My ignorance of this sort of coating has me worry about it immediately destroying itself from the insane material stresses... Though no idea how well it'll anneal after 1000 hours of constant heat (or worse: on-off heat-cooling cycles!) But since they're all oxides and likely put down together while the substrate stays hot, I bet it works out ok.

paulsutter 10y ago

Upvote for your nice summary, almost went the other way for the undeserved criticism of the article.

PhasmaFelis 10y ago

I'm confused. If reflecting 90% of infrared radiation only produces a luminous efficiency of 6.6%, how can any further increase in reflection lead to 40% efficiency?

Eliezer 10y ago
Obvious but maybe wrong answer: because it's not linear, if you trap nearly all the IR it stays until converted to visible, otherwise it still escapes after a couple of bounces.
pranjalv123 10y ago
If you reflected all the infrared light, the efficiency would be 100%, since all the light leaving the bulb would be visible. Normally, the vast majority of the light leaving the bulb is infrared, but if you keep 90% of it in the bulb, then 6.6% of the light leaving the bulb is visible light.

daveloyall 10y ago

A bit better: https://www.sciencedaily.com/releases/2016/01/160111135229.htm https://www.sciencedaily.com/releases/2016/01/160111135229.h...

hultner 10y ago

There's nothing state-of-the-art with 15-30% efficiency LEDs, maybe a few years ago but not 2016, blue LEDs are almost at 59% and even the whites are at about 50%.

k_lander 10y ago

Can this method of internal reflection be used to enhance the efficiency of LEDs?