Maxwell's demon and the second law of thermodynamics

[Bender]

Creating a temperature/pressure difference is decreasing entropy, and that is exactly what the demon is doing.

[Moreno]

7 minutes ago, Bender said:

Creating a temperature/pressure difference is decreasing entropy, and that is exactly what the demon is doing.

I don't know. I think demon would decrease entropy if he increase temperature/pressure differences in comparison to some initial state. If he just starts from some initial non-equilibrium state (created not by him) and keeps this state unchanged, where do you see entropy decrease?

[Bender]

If he isn't there, entropy increases. So to counter that increase, the demon has to remove entropy.

Let's try another analogy: an inflatable castle is full of air, but also quite leaky. If left on its own, the amount of air inside decreases. So we install a compressor to keep the pressure constant.

What you are suggesting, is that the compressor does not add any air to the castle, because the total amount of air inside remains unchanged.

[Moreno]

8 minutes ago, Bender said:

If he isn't there, entropy increases. So to counter that increase, the demon has to remove entropy.

Let's try another analogy: an inflatable castle is full of air, but also quite leaky. If left on its own, the amount of air inside decreases. So we install a compressor to keep the pressure constant.

What you are suggesting, is that the compressor does not add any air to the castle, because the total amount of air inside remains unchanged.

Still, there is principal theoretical difference between entropy decrease and entropy unchanged. This is what ideal Carnot engine does:

Quote

 

The maximum efficiency for any heat engine operating between two temperature THTH and TCTC is the Carnot efficiency, given by

eC=1−TCTH.eC=1−TCTH.

 

Such a heat engine produces no entropy, because we can show that the entropy lost by the hot reservoir is exactly equal to the entropy gain of the cold reservoir, and of course, the system's entropy on the net doesn't change because the system undergoes a cycle.

 

https://physics.stackexchange.com/questions/214346/how-is-the-efficiency-of-a-heat-engine-related-to-the-entropy-produced-during-th

[Bender]

19 minutes ago, Moreno said:

Still, there is principal theoretical difference between entropy decrease and entropy unchanged. This is what ideal Carnot engine does:

But we are not discussing an ideal, reversible, carnot cycle.

[Moreno]

5 minutes ago, Bender said:

But we are not discussing an ideal, reversible, carnot cycle.

Why not? I thought to permit the demon to work like an ideal Carnot engine. 

[Bender]

1 hour ago, Moreno said:

Why not? I thought to permit the demon to work like an ideal Carnot engine. 

The demon is not the one creating entropy, everything else in the world is. So unless you also want to transform the planet to a dead equilibrium state, there will be an increase in entropy for the demon to compensate. 

[Moreno]

There are some claims from an authoritative specialist which may sound like perpetuum mobile advancement. John Goodenough definitely doesn't recover all the secrets, but some of his citations sound interesting:
 

Quote

 

Goodenough: We’ve found a lot of things you can do with the Braga glass. It’s gone 4,000 cycles with negligible resistance. We have been demonstrating not only can you do that with her glass at room temperature, and in fact we can go well below room temperature. She’s been lighting an LED with this battery charging itself for two years. It runs on ambient heat.

The Braga battery can last 15,000 cycles. If your battery can last 10 years, people will be satisfied. You do need a long cycle life. Because you have self-charge with her electrolyte, and because you have a big window so you don’t need an SEI there, you can get a long cycle life and lower the cost.

 

https://about.bnef.com/blog/goodenough-making-progress-solid-state-batteries-qa/

Quote

The publication was initially met with considerable skepticism by other researchers in battery technology, with several noting that it is unclear how a battery voltage is obtained given that pure metallic lithium or sodium exists on both electrodes, which should not produce a difference in electrochemical potential, and therefore give no cell voltage.^[4] Any energy stored or released by the battery would therefore violate the first law of thermodynamics.

https://en.wikipedia.org/wiki/Glass_battery

I don't know about the first law, but maybe it has to do something about the second law?

Edited March 25, 2018 by Moreno

[Bender]

The battery has to be charged so even if it works, I see no reason to assume any violation of any laws. At worst its mechanism is misunderstood.

If it works. I guess we have to wait for an independent research group to replicate the results. 

[Endy0816]

2 hours ago, Bender said:

If it works. I guess we have to wait for an independent research group to replicate the results. 

Yeah, actually went looking for this and hadn't found anything.

[Moreno]

57 minutes ago, Endy0816 said:

Yeah, actually went looking for this and hadn't found anything.

Formally, to replicate the results Goodenough have to reveal all the secrets. Who said he did it? So, are you inclined to think it was a hoax? Why would Goodenough do that?

Edited March 25, 2018 by Moreno

[Bender]

I am not qualified to judge this. If it does work, it would not be unreasonable for Goodenough to want to develop it in secret until it is patentable. A lot of money can be made if the claim is leggit.

[Endy0816]

56 minutes ago, Moreno said:

Formally, to replicate the results Goodenough have to reveal all the secrets. Who said he did it? So, are you inclined to think it was a hoax? Why would Goodenough do that?

We've seen battery frauds before. Looking for neverending 'investment' money or fame typically. Not saying this is one but I rationally choose to remain skeptical until I see more than claims(which experts find dubious).

Maybe providing a sealed battery to an independent lab for supervised testing? Can probably think up something reasonable here.

[Moreno]

On ‎3‎/‎25‎/‎2018 at 5:30 PM, Endy0816 said:

We've seen battery frauds before. 

Could you give some examples? I know about "Eestor", but it was rather a capacitor than battery.

[Endy0816]

SEC v. Aquacell Batteries, Inc. and Michael J. Naste, Civil Action No. 6:07-CV-0608-ORL-22-DAB (M.D. Fla.)

SEC Obtains Order Halting $4.7 Million Offering Fraud

https://www.sec.gov/litigation/litreleases/2007/lr20080.htm

Was thinking of another one, but most stories are along these lines.

 

I figure if something is legit, it'll prove itself in time. There's lots of interesting ways to store power that with, new materials, better understanding, etc. may well be the next big thing.