3 ms·

I am not sure what your claim is in that last paragraph. If it takes heat energy from the thermal bath and produces electrical energy (which is then dissipated

I am not sure what your claim is in that last paragraph. If it takes heat energy from the thermal bath and produces electrical energy (which is then dissipated in a load resistor), in what way is it not a Carnot engine? Are you taking the quoted passage as implying it is performing 100% conversion? This would indeed be a problem, as there is no heat sink at 0K here. That quote, however, is ambiguous, as it says power supplied by the heat bath and not lost from it, and may merely be a statement that it obeys the conservation of energy (i.e. the point being made here may be that the power being supplied to the load comes from the heat bath, as opposed to coming from another possible source, such as the bias voltage supply.) I really should buy and read the paper, but I am not that motivated yet.

gus_massa 6y ago
It is not producing a macroscopic current, it is producing something like Johnson noise https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise (The interesting part seams to be that it has another frequency distribution, but I don't understand the details.) A real engine transform heat into electric energy that can be used to dissipate heat inside a container at any temperature. In particular at a higher temperature that the graphene and the support and the circuit. In the PR they claim that it produce "something useful" that I interpret as "work" or "electrical energy", but in that case it breaks the Second Law even if in their setup the resistor is at the same temperature. After reading the paragraph again, I'm not sure if your interpretation is right and they are claiming that the device is transferring energy from the graphene to the resistor, but that breaks the second law, in spite in the PR they claim it doesn't. I think they never claim a 100% conversion anyway. They just don't have a temperature difference to operate the engine.
- mannykannot 6y ago
  Have you actually read the paper? So far, you have only supported your claims with references to the press release and the abstract. As it stands, you are alleging they have made a pretty serious blunder, which should not be made without reference to the paper itself.

gus_massa 6y ago

It is not producing a macroscopic current, it is producing something like Johnson noise https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise (The interesting part seams to be that it has another frequency distribution, but I don't understand the details.) A real engine transform heat into electric energy that can be used to dissipate heat inside a container at any temperature. In particular at a higher temperature that the graphene and the support and the circuit. In the PR they claim that it produce "something useful" that I interpret as "work" or "electrical energy", but in that case it breaks the Second Law even if in their setup the resistor is at the same temperature. After reading the paragraph again, I'm not sure if your interpretation is right and they are claiming that the device is transferring energy from the graphene to the resistor, but that breaks the second law, in spite in the PR they claim it doesn't. I think they never claim a 100% conversion anyway. They just don't have a temperature difference to operate the engine.

mannykannot 6y ago
Have you actually read the paper? So far, you have only supported your claims with references to the press release and the abstract. As it stands, you are alleging they have made a pretty serious blunder, which should not be made without reference to the paper itself.