calling Maxwell's Daemon

[Omnibus]

@nul-points,

Thanks for the link. I'm unable to open any of the links it's supposed to be in but I'll try again later.

Aslo, it's great you'll be doing more of the parallel studies with the unattached cell. I was just going to suggest that. In my opinion it's a very important comparison to do.

Now, in terms of the Nernst equation, notice, that equation is valid only at equilibrium (it is sometimes used in kinetics too but only tentatively). Also, it refers to the potential of just one electrode and not of a potential difference such as the emf of a battery. Further, whether or not the electrochemical system is at equilibrium or not is not determined by the potential but by the current that passes through it. Thus, conditions may be created whereby an electrochemical process (I mean process, that is exhibiting observable current) even when the overpotential is totally eliminated and the electrodes are at their corresponding equilibrium potentials. I have a way of doing it which I have not discussed before and I won't get into it here either because the topic at hand is different. So, under such conditions (carrying out the process reversibly at the equilibrium potentials) we may be able to spend only the deltaG of the reaction (say, electrolysis of water) which means that after producing the hydrogen we may burn it and obtain the enthalpy deltaH, thus "extracting"  for free the bound energy TdeltaS from the environment. Thus, we will have about 22% more heat to use than the energy we've spent to produce it. That's standard thermodynamics, it's largely overlooked but I don't see at this point how it would apply to your interesting experiment.

[nul-points]

Now, in terms of the Nernst equation, notice, that equation is valid only at equilibrium (it is sometimes used in kinetics too but only tentatively). Also, it refers to the potential of just one electrode and not of a potential difference such as the emf of a battery. Further, whether or not the electrochemical system is at equilibrium or not is not determined by the potential but by the current that passes through it. Thus, conditions may be created whereby an electrochemical process (I mean process, that is exhibiting observable current) even when the overpotential is totally eliminated and the electrodes are at their corresponding equilibrium potentials. I have a way of doing it which I have not discussed before and I won't get into it here either because the topic at hand is different. So, under such conditions (carrying out the process reversibly at the equilibrium potentials) we may be able to spend only the deltaG of the reaction (say, electrolysis of water) which means that after producing the hydrogen we may burn it and obtain the enthalpy deltaH, thus "extracting"  for free the bound energy TdeltaS from the environment. Thus, we will have about 22% more heat to use than the energy we've spent to produce it. That's standard thermodynamics, it's largely overlooked but I don't see at this point how it would apply to your interesting experiment.

whoa - too much information for a first date! 

i was just pointing out that the driver (which is a potential) for a cell reaction (and emf potential arises from two half-cell reactions) is due to absolute temperature not a temperature difference (gradient)

the current follows from the combination of the potential, and the internal and external impedances

so - we shouldn't be surprised that we can obtain energy in something which is immersed in a single temperature, rather than having a temperature drop across the system

eg. when we boil an egg, it gains energy from its ambient environment all around - we don't need to only submerse it half-in the water and half-out (although that would also work in boiling the egg, eventually, by conduction inside the egg, of course)

in other words, the cell gains electrochemical energy just by being in an environment at a given temperature - whereas a heat engine, say, requires a temperature gradient to provide the driving force

your hints at other experience of cells sounds intriguing -  i've heard of an energy disparity in electrolysis of water, but seen no first-hand data yet

hopefully we'll hear more of that in due course


hoping to upload that PDF here, if upload restrictions allow

[exnihiloest]

...
whether or not the electrochemical system is at equilibrium or not is not determined by the potential but by the current that passes through it.
...

False statement. There can be no equilibrium and no current, for example with temperature change or chemical reactions which can appear without current, and it can be observed by the potential variation.

[Omnibus]

False statement. There can be no equilibrium and no current, for example with temperature change or chemical reactions which can appear without current, and it can be observed by the potential variation.

It isn't clear at all what you wanted to say.

[nul-points]

the 'sidebar' test on an unattached DIY Zn-Cu cell has only been running a couple of days so far, but it's starting to look similar to the results for the unattached DIY Zn-Ni cell:

  - little or no correlation of the terminal voltage to the ambient temperature cycle;
  - terminal voltage-time trend shows only decrease


the initial 'control' test using a similar LED flasher circuit as a load to 2x AAA NiMH 1.24V cells showed an on-load terminal voltage-time trend which increased for a few days, peaked, and then started to decrease

i've now increased the temperature cycle upper level for this control test
  again, the on-load terminal voltage-time trend is showing an increase - but it's only a few days in so far

it'll be interesting to see if a greater heat input will affect its ability to self-sustain/charge the NiMH cells whilst on-load

meanwhile the main Zn-Cu DIY cell + LED flasher circuit combination continues to run and self-sustain/charge the cells at ambient room temperatures - heading towards its first 1000 hours of non-stop operation