

MIT Researchers Produce Micro-Light that Outputs More Power Than Applied - jnand
http://www.core77.com/blog/technology/mit_researchers_produce_micro-light_that_outputs_more_energy_than_it_takes_in_22644.asp

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eck
The title (and the first comment on the link) makes it sound like it's a
perpetual motion machine, but as far as I can tell it's more like a tiny heat-
pump: energy is conserved, entropy increases. Still kind of neat though.

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Cushman
Of course they didn't beat thermodynamics, but still, assuming they can scale
the tech up to a useful power, it's a light that's also a _cooling_ element.
That'd be more than kind of neat, wouldn't it?

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Ygg2
But where would you use light that cools?

Fridge lights? House lighting in warm regions? Hmmm. On second thought it
could have interesting applications depending how much it cools.

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mbreese
Lighting is hot. I'd love to have lights that weren't also little heaters. Or,
if the cooling effect is big enough - imagine solid state cooling on devices.
Who needs a fan when you can have a little cooling light?

I doubt that they'll be able to scale this up too much though, since it
probably relies on an effect that only occurs below a certain threshold.

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swombat
Most LEDs don't heat up that much... they're usually cool to the touch.

I'd love a computer that glows brighter to release heat when it gets too hot,
though :-)

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nl
This is one of the best things I've seen invented in a long time.

It's like a peltier cooler[1], but it produces light instead of heat.

I'm thinking of the most amazing beer cooler/Christmas light display ever!

[1] <http://en.wikipedia.org/wiki/Thermoelectric_cooling>

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ars
It does NOT cool things. To use it you have to _heat_ it hotter than wherever
it is shining into.

It uses that heat to make light, but it is not a cooler (i.e. a heat pump).

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davorak
The led itself should cool down if it is producing more power in light then is
being put in electrically. The energy is coming from the the lattice phonons
and as a result the lattice cools down.

The paper[1] behind a pay wall show has a graph showing its cooling power vs
current.

I think where the light is shining into is open space so the source
temperature has to exceed what ever temperature the local background radiation
is at; a common local minimum being the cosmic background radiation.

[1] <http://prl.aps.org/abstract/PRL/v108/i9/e097403>

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ars
Yes, the LED is cooling down, but it will not cool down any lower than the
ambient air. i.e. you can not use this as an A/C - you must _already_ have a
cold source in order to use it.

The cosmic background radiation is not exactly common. You'd have to be in
space.

BTW, I don't think we are actually arguing.

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electrograv
I don't understand. Why can't it cool down more than ambient air? You put in X
amount of power, and you get out 2X amount of power as light -- therefore
additional energy is being taken in as heat and converted to light. Say you
direct that light AWAY from the area through mirrors or something so it
doesn't heat anything nearby up. Then, by simple energy thermodynamics, you
can show that X amount of energy IS being taken away from this local system
and deposited elsewhere as light.

Unless you claim that the LED stops producing the >100% efficiency levels at
room temperature, I don't see why you're claiming it can't cool anything down.

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aqme28
Second law of Thermodynamics. It takes additional energy to move heat up a
temperature gradient, and you're not accounting for that. You can't move heat
from a cold source to a hot sink without paying for it somewhere.

edit: I don't mind a downvote now and then, but I would really prefer a
discussion or explanation to a fire-and-forget downvote.

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Cushman
You pay for it with electricity. That's what a heat pump is, ya?

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sageikosa
Energy input and heat in the "thermodynamic system", versus energy output and
heat remaining stays in balance. If energy input (in electric current) is
higher than energy output, then heat is added to the system. If energy input
is lower than energy output, then heat is lost from the system.

All it takes is the ability to channel some of the light (energy output) away
from the reservoir of heat to show that the reservoir of heat will decrease.

Ultimately you'd expect a temperature gradient at the system boundary to start
transferring heat back into the system. through the first law of
thermodynamics.

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quarterto
In the UK, a microlight is an ultralight aircraft[1]. This would have been so
much more badass.

[1]: <http://en.wikipedia.org/wiki/Microlight>

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ars
Previous discussion: <http://news.ycombinator.com/item?id=3669688>

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beej71
It says it produces too little light for "most" applications... I wonder what
the applications actually are!

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frugalfirbolg
Probably entanglement and other optics experiments if the light produced has
the right properties.

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dudus
I'm pretty sure this is the first step to create an Arc Reactor.

Tony Stark built it in a cave ... with a box of scraps

