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The linked article and the title are pretty misleading. But if you go and look at the abstract for the paper, they mention that the extra energy comes from pum

by jnhnum1 15y ago

The linked article and the title are pretty misleading. But if you go and look at the abstract for the paper, they mention that the extra energy comes from pumping heat out of the environment.

yew 15y ago
Though most inhabited spaces aren't strictly temperature regulated, so there is still some potential for energy subsidization. There might be some applications in solid-state heat pump technology as well. Actually I would think that the more interesting possibility, given that the field is still maturing.
- mvzink 15y ago
  Most cooling systems are seem pretty complex/bulky/energy-inefficient to an ignorant sob like me, but if they can make it simple enough to fit into an LED, and the fact that this cooling system relies only on optical output and electricity, it could have a lot of cool applications we haven't thought of.
  - ars 15y ago
    Cooling systems don't have to be complex - lookup peltier cooler. But they are energy inefficient because the laws of thermodynamics requires it. (You can make them more efficient by not cooling as low - trading temperature for volume. In an A/C that would mean instead of a 40 degree drop, do a 20 degree drop, but with twice the air flow. The net result for the living space is the same, but the efficiency is much improved.)
ars 15y ago
Something is missing here. You can not generate energy just from heat you must have both a heat source and a cold sink. It's en extremely fundamental thermodynamic law. Where is the cold source in this experiment? (I'm not saying there isn't one, just that the article makes no mention of it which is a huge omission.)
- jnhnum1 15y ago
  Energy is certainly not being generated. The energy of the light output will be equal to the heat absorbed plus the electric energy input. If you want to think of it in terms of temperatures, I'm a little fuzzy on the details, but I think in a sense empty space has a temperature associated with it based on the radiation that is present (similarly to how black body radiation is a function of temperature).
  - ars 15y ago
    I guess if the LED was heated more than the room where you receive the light it would work. So you have to put this into an oven for it to work - if you just left it in a room, and expect it to also put light into that room (i.e. the device and the room are the same temperature) it would not work.
  - justncase80 15y ago
    So can we solve global warming by creating a bunch of gigantic LED billboards?
- ajuc 15y ago
  Yeah, if we could cool some place without heating another by more than the amount of heat we cooled this place - it would breake 2nd law of thermodynamics - we could then use difference of temperatures to extract energy and we'll be in the same place, but with more energy. We could then repeat such cycle as many times as we want == infinite free energy.
  - karamazov 15y ago
    The heat absorbed is released as light; conservation of energy is still observed.
    - ars 15y ago
      Conservation of energy is not the issue. It's not enough just to have energy in = energy out. In order to turn heat into any other kind of energy you MUST have a cold sink. If you want to have black body radiation it's not enough to just have a dark area - the recipient of the light must be colder than the source. So this would only work if the LED was heated more than the room around it. I guess if they put it in an oven, and then viewed it from a window in the colder room.
est 15y ago
Also QFT > Although scientifically intriguing, the results won’t immediately result in ultra-efficient commercial LEDs since the demonstration works only for LEDs with very low input power that produce very small amounts of light.
- xtracto 15y ago
  This reminded me of an Asimov short story about an "experimenter" (engineer?) vs a pure scientist. In the story, a ship was trying to enter Jupiter (IIRC) but needed a "force field". The scientist created a force field... which had one problem: It could only be turned on a very small amount of time before it became unstable (and I think exploded). The scientist then spend a lot of his time trying to come up with a better force field which could remain active for more time, but he stopped when he realized it was theoretically impossible (and hence, it was impossible to land in Jupiter). Meanwhile, the "experimenter" achieved the impossible after using the already created field, by turning it on-and-of very quickly and thus, preventin it from destabilizing!. What does it have to do with this? Well, what if we had hundreds of those very dim leds? that might provide usable light.
  - rbanffy 15y ago
    With outputs on the picowatt region, you'd need a couple trillion LED's ;-) But I agree engineers are weird animals. Often people have no idea of what they are really doing when they say "that can't be done" to one of us.

by jnhnum1 15y ago

The linked article and the title are pretty misleading. But if you go and look at the abstract for the paper, they mention that the extra energy comes from pumping heat out of the environment.

yew 15y ago

Though most inhabited spaces aren't strictly temperature regulated, so there is still some potential for energy subsidization. There might be some applications in solid-state heat pump technology as well. Actually I would think that the more interesting possibility, given that the field is still maturing.

mvzink 15y ago
Most cooling systems are seem pretty complex/bulky/energy-inefficient to an ignorant sob like me, but if they can make it simple enough to fit into an LED, and the fact that this cooling system relies only on optical output and electricity, it could have a lot of cool applications we haven't thought of.
- ars 15y ago
  Cooling systems don't have to be complex - lookup peltier cooler. But they are energy inefficient because the laws of thermodynamics requires it. (You can make them more efficient by not cooling as low - trading temperature for volume. In an A/C that would mean instead of a 40 degree drop, do a 20 degree drop, but with twice the air flow. The net result for the living space is the same, but the efficiency is much improved.)

ars 15y ago

Something is missing here. You can not generate energy just from heat you must have both a heat source and a cold sink. It's en extremely fundamental thermodynamic law. Where is the cold source in this experiment? (I'm not saying there isn't one, just that the article makes no mention of it which is a huge omission.)

jnhnum1 15y ago
Energy is certainly not being generated. The energy of the light output will be equal to the heat absorbed plus the electric energy input. If you want to think of it in terms of temperatures, I'm a little fuzzy on the details, but I think in a sense empty space has a temperature associated with it based on the radiation that is present (similarly to how black body radiation is a function of temperature).
- ars 15y ago
  I guess if the LED was heated more than the room where you receive the light it would work. So you have to put this into an oven for it to work - if you just left it in a room, and expect it to also put light into that room (i.e. the device and the room are the same temperature) it would not work.
- justncase80 15y ago
  So can we solve global warming by creating a bunch of gigantic LED billboards?
ajuc 15y ago
Yeah, if we could cool some place without heating another by more than the amount of heat we cooled this place - it would breake 2nd law of thermodynamics - we could then use difference of temperatures to extract energy and we'll be in the same place, but with more energy. We could then repeat such cycle as many times as we want == infinite free energy.
- karamazov 15y ago
  The heat absorbed is released as light; conservation of energy is still observed.
  - ars 15y ago
    Conservation of energy is not the issue. It's not enough just to have energy in = energy out. In order to turn heat into any other kind of energy you MUST have a cold sink. If you want to have black body radiation it's not enough to just have a dark area - the recipient of the light must be colder than the source. So this would only work if the LED was heated more than the room around it. I guess if they put it in an oven, and then viewed it from a window in the colder room.

est 15y ago

Also QFT > Although scientifically intriguing, the results won’t immediately result in ultra-efficient commercial LEDs since the demonstration works only for LEDs with very low input power that produce very small amounts of light.

xtracto 15y ago
This reminded me of an Asimov short story about an "experimenter" (engineer?) vs a pure scientist. In the story, a ship was trying to enter Jupiter (IIRC) but needed a "force field". The scientist created a force field... which had one problem: It could only be turned on a very small amount of time before it became unstable (and I think exploded). The scientist then spend a lot of his time trying to come up with a better force field which could remain active for more time, but he stopped when he realized it was theoretically impossible (and hence, it was impossible to land in Jupiter). Meanwhile, the "experimenter" achieved the impossible after using the already created field, by turning it on-and-of very quickly and thus, preventin it from destabilizing!. What does it have to do with this? Well, what if we had hundreds of those very dim leds? that might provide usable light.
- rbanffy 15y ago
  With outputs on the picowatt region, you'd need a couple trillion LED's ;-) But I agree engineers are weird animals. Often people have no idea of what they are really doing when they say "that can't be done" to one of us.