6 ms·

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

by 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?
  - Someone 10y ago
    Here’s my take on this (corrections welcome): the thing you need to get light out is a hot filament. You use electricity to a) make it hot and b) keep it hot. Both are easier the better the filament is thermally isolated. Caveat: if that argument is correct, I would think a bulb with triple glazing would help, too. Has that been tried?
    - mapt 10y ago
      The thermal mirror needs to selectively reflect infrared while being transparent to visible light, and it needs to bounce radiation back and forth, which requires a certain geometry. The novelty of this paper is creating a big flat filament sandwiched between high-temperature plates that reflect infrared and can be deposited as layered coatings.
    - eru 10y ago
      > Caveat: if that argument is correct, I would think a bulb with triple glazing would help, too. Has that been tried? The triple glazing is supposed to keep the infrared in (radiation losses), or supposed to keep losses from convection and conduction down?
  - Hayleysaurus 10y ago
    The reflected IR light will be absorbed by the filament, therefore requiring less energy over time to keep the filament at temperature. That thermal energy while lower than the input energy will create a baseline temperature, so now you only need Some of the new energy to output more photons, instead of All the energy.
    - Laforet 10y ago
      Bingo, this is how incadescence work: heating any solid material above a certain temperature will make it glow, all we need to worry about is finding a material that can withstand the temperature and make it into an efficient package. Gas mantles work pretty much the same way. A cage made of ceramic metal oxides (formed by firing a cotton bag dipped in thorium or yttrium nitrate, if thorium is used then every use will release a few microrems of radioactove radon gas) is heated by gas or oil fire to incadescence; because the temperature is much higher than a light bulb, gas lamps actually waste less heat as infrared.
  - ars 10y ago
    > when we run a current through the filament ... becomes ... light Not exactly. It's actually "when the filament is hot it emits light". It has nothing to do with the current (except that the current heats it). So it doesn't matter how you heat the filament - in this case you heat the filament by reflected infrared energy at it. In contrast a florescent light does actually use electricity to make light - heating it would do nothing.
  - InclinedPlane 10y ago
    Think of it like a blanket for the filament. The IR radiation helps keep the filament at the appropriate temperature, so the amount of ohmic heating from electricity can be less.
    - mirimir 10y ago
      Or greenhouse effect ;)
  - mapt 10y ago
    You're trying to keep the filament very hot while spending the least amount of power. Apparently, reflecting the thermal infrared back at the filament lets you spend less power while keeping the filament equally hot and equally luminous in the visible band.
  - amluto 10y ago
    The IR is only a loss if it escapes. Their design tries to reflect it back at the filament to reuse it. A hot filament encased in a perfect window that reflects everything but visible light is highly efficient, simply because there's nowhere for waste heat to go. Check out the wikipedia article on "luminous efficacy". Hypothetical black-body sources truncated to ≥2% photopic sensitivity range are excellent, and that's what this group is trying to approximate.

by 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?
- Someone 10y ago
  Here’s my take on this (corrections welcome): the thing you need to get light out is a hot filament. You use electricity to a) make it hot and b) keep it hot. Both are easier the better the filament is thermally isolated. Caveat: if that argument is correct, I would think a bulb with triple glazing would help, too. Has that been tried?
  - mapt 10y ago
    The thermal mirror needs to selectively reflect infrared while being transparent to visible light, and it needs to bounce radiation back and forth, which requires a certain geometry. The novelty of this paper is creating a big flat filament sandwiched between high-temperature plates that reflect infrared and can be deposited as layered coatings.
  - eru 10y ago
    > Caveat: if that argument is correct, I would think a bulb with triple glazing would help, too. Has that been tried? The triple glazing is supposed to keep the infrared in (radiation losses), or supposed to keep losses from convection and conduction down?
- Hayleysaurus 10y ago
  The reflected IR light will be absorbed by the filament, therefore requiring less energy over time to keep the filament at temperature. That thermal energy while lower than the input energy will create a baseline temperature, so now you only need Some of the new energy to output more photons, instead of All the energy.
  - Laforet 10y ago
    Bingo, this is how incadescence work: heating any solid material above a certain temperature will make it glow, all we need to worry about is finding a material that can withstand the temperature and make it into an efficient package. Gas mantles work pretty much the same way. A cage made of ceramic metal oxides (formed by firing a cotton bag dipped in thorium or yttrium nitrate, if thorium is used then every use will release a few microrems of radioactove radon gas) is heated by gas or oil fire to incadescence; because the temperature is much higher than a light bulb, gas lamps actually waste less heat as infrared.
- ars 10y ago
  > when we run a current through the filament ... becomes ... light Not exactly. It's actually "when the filament is hot it emits light". It has nothing to do with the current (except that the current heats it). So it doesn't matter how you heat the filament - in this case you heat the filament by reflected infrared energy at it. In contrast a florescent light does actually use electricity to make light - heating it would do nothing.
- InclinedPlane 10y ago
  Think of it like a blanket for the filament. The IR radiation helps keep the filament at the appropriate temperature, so the amount of ohmic heating from electricity can be less.
  - mirimir 10y ago
    Or greenhouse effect ;)
- mapt 10y ago
  You're trying to keep the filament very hot while spending the least amount of power. Apparently, reflecting the thermal infrared back at the filament lets you spend less power while keeping the filament equally hot and equally luminous in the visible band.
- amluto 10y ago
  The IR is only a loss if it escapes. Their design tries to reflect it back at the filament to reuse it. A hot filament encased in a perfect window that reflects everything but visible light is highly efficient, simply because there's nowhere for waste heat to go. Check out the wikipedia article on "luminous efficacy". Hypothetical black-body sources truncated to ≥2% photopic sensitivity range are excellent, and that's what this group is trying to approximate.