[FoRK] 230% efficient LEDs seem to violate first law of thermodynamics

Kevin Marks kevinmarks at gmail.com
Thu Mar 8 14:20:42 PST 2012


69 picowatts? So a billion or so for a dim screen? I suppose that's a
really hi res display
On Mar 8, 2012 2:09 PM, "Jeremy Apthorp" <nornagon at gmail.com> wrote:

> Looks like we've got some totally bling fridges coming our way :)
>
> On 09/03/2012, at 8:40, Stephen Williams <sdw at lig.net> wrote:
>
> > If verified and generalizable, this would be amazing.
> > Did anyone else read the Uplift series?  Chasing mister saucer eyes...
> >
> > http://dvice.com/archives/2012/03/230-efficient-l.php
> >> <http://dvice.com/archives/2012/03/230-efficient-l.php>
> >>
> >> 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
> >>
> >
> >
> > sdw
> >
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