[FoRK] 230% efficient LEDs seem to violate first law of thermodynamics
sdw at lig.net
Thu Mar 8 13:40:35 PST 2012
If verified and generalizable, this would be amazing.
Did anyone else read the Uplift series? Chasing mister saucer eyes...
> Physicists hellbent on destroying the universe have come up with a tiny LED that produces 69 picowatts of light while using just
> 30 picowatts of power. That's an efficiency of above 100%, which should be impossible, but isn't. And in other breaking news, up
> is down, black is white, and zebras <http://dvice.com/archives/2011/12/nasa-wants-to-s-2.php> look the same.
> Last week, physicists from MIT published a paper in /Physical Review Letters/ entitled "Thermoelectrically Pumped Light-Emitting
> Diodes Operating above Unity Efficiency." My guess is that most physicists cringe a little bit when they see the phrase "above
> unity," because that's another way of saying either "perpetual motion machine" or "free energy," both of which are likely to get
> you branded as either an eccentric (if you're lucky) or a total crackpot (if you're not).
> Over-unity machines may be impossible, but the LED in this paper definitely put out more than twice as much energy in the form of
> photons as the researchers fed it in the form of electrons. They found that as they decreased the electrical voltage that went
> into the LED, the emitted light decreased by a direct proportion, while the input power decreased exponentially. In other words,
> the less power you put into an LED, the more efficient it gets at producing light, and if you decrease the power enough, you can
> blow right past the 100% efficiency mark.
> So, how does this not totally and completely invalidate the conservation of energy? We have to look at how energy flows through
> the /entire/ system, not just at the electricity in and light out. When the LED gets more than 100% /electrically/ efficient, it
> starts to cool itself down, which is another way of saying that it's stealing energy (in the form of heat) from its environment
> and converting that heat into those over-unity photons.
> This cooling effect has some interesting implications for low-power electronics, but most importantly, we can all rest just a
> little bit easier knowing that the basic physical rules that frame our perception of the universe have survived for one more day
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