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Tue, 13 Mar 2012, 2:36pm Electricity from heat »
Registered: Aug, 2008
Last visit: Tue, 01 Apr 2014
Posts: 2385

Prof Neilson wrote:

Pete - you are straining a bit too much to save a broken law.
The analysis that the LED system does not break any laws of thermodynamics is not mine. This is what the paper itself has to say.
Thermoelectrically Pumped Light-Emitting Diodes Operating above Unity Efficiency page 1 column 2 top paragraph :

Beginning with Tauc in 1957, a body of literature theoretically establishing the basic thermodynamic consistency of electroluminescent cooling and exploring its limits began to emerge.

PN wrote:

That you cannot see this and work up a nonsensical analysis is troubling. Then you make hand waving claims like all physicist's.


But really - its much worse. You talk of heat pumps and Carnot efficiency but you have not got a clue.

I have pretty much had enough of this nonsense from you people that have no clue what a heat pump is.

Pete - I refer you to supamark and his analysis of what ails me. Audit a course. I suggest Engineering Thermodynamics. It need not be of ICI quality. Any community college will do.

Or just look at the Wikipedia page.

"The limiting factors are the temperature at which the heat enters the engine, and the temperature of the environment into which the engine exhausts its waste heat, , "

Now to do a proper analysis, please identify Th and Tc in the LED or Graphene experiment.

A heat engine is using a Heat flux to do work. Please identify the heat flux in the LED or graphene device at ambient temperature.
I don't understand the thermodynamics of the graphene experiment in detail, so am going to stick to my knitting - in this case the LED over-unity experiment.

The separate physical synopsis behind the paper also says this.

Physics Synopsis by Don Monroe : Optical Device is More Than 100% Efficient

.. heating the light emitters increases their output power and efficiency, meaning they are like thermodynamic heat engines, except they come with the fast electrical control of modern semiconductor devices.

PN wrote:

The change in ambient temperature does not qualify. The starting ambient temperature is Ts not Th. The ending ambient temperature is Te not Tc. There is no heat flux into the system if you insulate it and Te is lower than Ts. If you don't insulate the system you get a heat flux into the system. This is not the Heat Engine heat flux. That requires a Qh and a Qc. This is a Qambient or some new term.

That you can't even identify a heat engine, its Th and Tc, and it Qh or Qc, then you take a run at me. Its not laughable, its sad. But what should I expect when EE's Physicists, Chemists and whatever Lens is venture outside their education?

To conclude, the LED and Graphene devices are not Heat Engines by definition. They possess no Th and no Tc, no Qh and no Qc. However, they produce work. This is impossible in the existing laws of Thermodynamics.
See below.
So either the experiments are cons or the laws are broken.
The third alternative is that you have not read Landsberg and Evans 1967 - Thermodynamic Limits for Some Light-Producing Devices which defines the thermodynamic quantities you are looking for above.

Here's yet another quote from the abstract

Abstract : Optical Device is More Than 100% Efficient

A heated semiconductor light-emitting diode at low forward bias voltage V<kBT/q is shown to use electrical work to pump heat from the lattice to the photon field.
Thermoelectrically Pumped Light-Emitting Diodes Operating above Unity Efficiency page 4 column 1 paragraph 2 :

Moreover, as sources of irreversibility are removed from the LED, it acts as a reversible Carnot-efficient heat pump operating between the lattice and the photon field.
In most people's language, including thermodynamicists, a device which pumps heat is a heat pump!

So basically the guys writing the paper, and the physicist writing the Physics Synopsis are saying the device is a heat pump and that it obeys the laws of thermodynamics - all of them.


Last edited Tue, 13 Mar 2012, 3:51pm by Technopete

Assumptions: 1) E=1/2CV2. (Only dummies assume this). (I am one of these dummies).