Information engine operates with nearly perfect efficiency

Physicists have experimentally demonstrated an information engine—a device that converts information into work—with an efficiency that exceeds the conventional second law of thermodynamics. Instead, the engine’s efficiency is bounded by a recently proposed generalized second law of thermodynamics, and it is the first information engine to approach this new bound.

Read more at: https://phys.org/news/2018-01-efficiency.html#jCp

Tau.Neutrino said:

Information engine operates with nearly perfect efficiency

Physicists have experimentally demonstrated an information engine—a device that converts information into work—with an efficiency that exceeds the conventional second law of thermodynamics. Instead, the engine’s efficiency is bounded by a recently proposed generalized second law of thermodynamics, and it is the first information engine to approach this new bound.

Read more at: https://phys.org/news/2018-01-efficiency.html#jCp

> Traditionally, the maximum efficiency with which an engine can convert energy into work is bounded by the second law of thermodynamics. In the past decade, however, experiments have shown that an engine’s efficiency can surpass the second law if the engine can gain information from its surroundings, since it can then convert that information into work. These information engines (or “Maxwell’s demons,”)

Um yeah, I did have a go at designing one of these myself (in theory only) once, without success. it’s the sort of attempt every physicist makes at some time in their life.

> the researchers in the new study designed and implemented an information engine made of a particle trapped by light at room temperature. Random thermal fluctuations cause the tiny particle to move slightly due to Brownian motion, and a photodiode tracks the particle’s changing position with a spatial accuracy of 1 nanometer.

They already have a problem there. The photodiode requires light energy to operate, and this energy has to be added to the energy requirement for operation.

> As a result, almost none of the energy gained by the shift is lost to heat.

True, but they’ve neglected to add that the energy required to operate the photodiode is lost as heat. Unless my brain is functioning less well than I think it is, the energy loss in operating the photodiode always lowers the overall efficiency to less than “the conventional second law of thermodynamics”. Which puts us right back where we started.

mollwollfumble said:

> Traditionally, the maximum efficiency with which an engine can convert energy into work is bounded by the second law of thermodynamics. In the past decade, however, experiments have shown that an engine’s efficiency can surpass the second law if the engine can gain information from its surroundings, since it can then convert that information into work. These information engines (or “Maxwell’s demons,”)

Um yeah, I did have a go at designing one of these myself (in theory only) once, without success. it’s the sort of attempt every physicist makes at some time in their life.

> the researchers in the new study designed and implemented an information engine made of a particle trapped by light at room temperature. Random thermal fluctuations cause the tiny particle to move slightly due to Brownian motion, and a photodiode tracks the particle’s changing position with a spatial accuracy of 1 nanometer.

They already have a problem there. The photodiode requires light energy to operate, and this energy has to be added to the energy requirement for operation.

> As a result, almost none of the energy gained by the shift is lost to heat.

True, but they’ve neglected to add that the energy required to operate the photodiode is lost as heat. Unless my brain is functioning less well than I think it is, the energy loss in operating the photodiode always lowers the overall efficiency to less than “the conventional second law of thermodynamics”. Which puts us right back where we started.

I’m surprised they didn’t already know this. It is pretty well Physics 101 and has been known since at least as early as 1929. What I’ve said is exactly what Leó Szilárd said in 1929. And what is being proposed here is directly contradicted by Szilárd’s work.

By the way, would you like to know the system I came up with for beating the second law of thermodynamics? And why it failed. It failed for a more subtle reason than the method proposed in the OP.

(If you don’t say “yes” I’ll leave the forum and never come back).

Yes. I won’t understand it but didn’t want to leave you hanging.

AwesomeO said:

Yes. I won’t understand it but didn’t want to leave you hanging.

Thanks awfully :-( I really do appreciate that.

OK. Take a tank of gas and hang a lightweight lever in it. As molecules of the gas push the lever they bounce off with less energy and so transfer energy to the lever. And so the gas slowly loses temperature.

To the lever, have a system of rods that transfers the energy transferred to the lever outside the gas tank. Use that energy to generate mechanical power.

We’ve overcome the second law of thermodynamics!

… or not …

Because if the outside of the gas tank is a vacuum then there’s nothing for the rods from the lever to press against so they can’t generate mechanical power. Or if the outside of the gas tank is at the same temperature as the inside then the kinetic energy of the hot molecules outside push back against the rod system and lever exactly nullifying the mechanical power that would have been extracted from it.

That one had me thinking I’d beaten the second law of thermodynamics for about a month.

mollwollfumble said:

AwesomeO said:

Yes. I won’t understand it but didn’t want to leave you hanging.

Thanks awfully :-( I really do appreciate that.

OK. Take a tank of gas and hang a lightweight lever in it. As molecules of the gas push the lever they bounce off with less energy and so transfer energy to the lever. And so the gas slowly loses temperature.

To the lever, have a system of rods that transfers the energy transferred to the lever outside the gas tank. Use that energy to generate mechanical power.

We’ve overcome the second law of thermodynamics!

… or not …

Because if the outside of the gas tank is a vacuum then there’s nothing for the rods from the lever to press against so they can’t generate mechanical power. Or if the outside of the gas tank is at the same temperature as the inside then the kinetic energy of the hot molecules outside push back against the rod system and lever exactly nullifying the mechanical power that would have been extracted from it.

That one had me thinking I’d beaten the second law of thermodynamics for about a month.

What about this one?

Have an enclosed tank containing gas over oil. Float a little sailboat in the centre on the oil with a sail pushed by the random thermal motion of the gas. The boat is pushed a distance proportional to the square root of time. When the sailboat reaches the end of the tank it completes an electric circuit indicating that work has been done on the sailboat by the random thermal motion.

If I want to be more subtle, as the sail approaches the end it restricts the mean free path of molecules between it and the end – hmm, lets not go there because I think there are two effects that may cancel each other out.