Possible "exotic" thermoelectric power generation

An interesting recent Arxiv preprint -

"Thermoelectricity without absorbing energy from the heat sources"

Abstract:
We analyze the power output of a quantum dot machine coupled to two electronic reservoirs via thermoelectric
contacts, and to two thermal reservoirs – one hot and one cold. This machine is a nanoscale analogue of a
conventional thermocouple heat-engine, in which the active region being heated is unavoidably also exchanging
heat with its cold environment. Heat exchange between the dot and the thermal reservoirs is treated as a
capacitive coupling to electronic fluctuations in localized levels, modeled as two additional quantum dots.

The resulting multiple-dot setup is described using a master equation approach. We observe an “exotic”
power generation, which remains finite even when the heat absorbed from the thermal reservoirs is zero
(in other words the heat coming from the hot reservoir all escapes into the cold environment). This effect
can be understood in terms of a non-local effect in which the heat flow from heat source to the cold
environment generates power via a mechanism which we refer to as Coulomb heat drag. It relies on the
fact that there is no relaxation in the quantum dot system, so electrons within it have a non-thermal
energy distribution. More poetically, one can say that we find a spatial separation of the first-law of
thermodynamics (heat to work conversion) from the second-law of thermodynamics (generation of entropy).

We present circumstances in which this non-thermal system can generate more power than any conventional
macroscopic thermocouple (with local thermalization), even when the latter works with Carnot efficiency.

http://arxiv.org/pdf/1508.04368.pdf

The (Sept 28, 2015) updated version of the above preprint is available at the same URL --
arxiv.org/pdf/1508.04368.pdf
Also related, and perhaps of interest are the following preprints which, if correct, indicate that some quantum-based thermodynamic systems may be more efficient than the Carnot bound permits ---
"Efficiency bounds for quantum engines powered by non-thermal baths"
http://arxiv.org/abs/1508.06519
"Thermal Baths as Quantum Resources: More Friends than Foes?"
http://arxiv.org/abs/1509.06318

Another (non-nuclear) preprint proposing that heat can be extracted from a thermal
reservoir, against temperature gradient, in an apparent, but not real, violation of the
2nd law - by increasing entropy in a reservoir of a different conserved quantity, e.g.,
spin.

Thermodynamics of quantum systems with multiple conserved quantities
http://arxiv.org/pdf/1512.01190.pdf
ABSTRACT: We consider a generalisation of thermodynamics that deals with multiple
conserved quantities at the level of individual quantum systems. Each conserved quantity,
which, importantly, need not commute with the rest, can be extracted and stored in its
own battery. Unlike in standard thermodynamics, where the second law places a constraint
on how much of the conserved quantity (energy) that can be extracted, here, on the
contrary, there is no limit on how much of any individual conserved quantity that can be
extracted. However, other conserved quantities must be supplied, and the second law
constrains the combination of extractable quantities and the trade-offs between them
which are allowed. We present explicit protocols which allow us to perform arbitrarily
good trade-offs and extract arbitrarily good combinations of conserved quantities from
individual quantum systems.

Another couple of interesting recent related items --

"Understanding the mechanism for generating electric current without energy consumption at room temperature"
http://phys.org/news/2015-12-m…t-energy-consumption.html

"Perfect heat to work conversion while refrigerating: thermodynamic power of the squeezed thermal reservoir"
http://arxiv.org/abs/1512.07881

Another new preprint proposing a specific method to transfer thermal energy against the thermal gradient (i.e., from cold to hot) without violating an extended version of the 2nd Law - by offsetting decreased thermal entropy with increased information entropy. It would be interesting to know if there are any natural reservoirs of information (or conserved quantum quantity) which can be exploited to provide practical amounts of energy, rather than just interesting experimental results.

"A Maxwell demon model connecting information and thermodynamics"
http://arxiv.org/abs/1601.01124
ABSTRACT: In the past decade several theoretical Maxwell's demon models have been proposed exhibiting effects such as refrigerating, doing work at the cost of information, and some experiments have been done to realise these effects. Here we propose a model with a two level demon, information represented by a sequence of bits, and two heat reservoirs. Which reservoir the demon interact with depends on the bit. If information is pure, one reservoir will be refrigerated, on the other hand, information can be erased if temperature difference is large. Genuine examples of such a system are discussed.

Another fairly recent paper claiming (non-nuclear) anomalous energy gain.
Definitely would involve "new physics", and probably incorrect, but easily testable.

"The experiment of Self-charging Inverter driven by the 3rd Positive EMF"
http://www.aias.us/documents/m…/SelfChargingInverter.pdf
- and, an earlier paper-
"Anomalous power efficiency of a transformer driven by tuned duty cycle pulses"
http://ac.els-cdn.com/S1875389212025035/1-s2.0-S1875389212025035-main.pdf?_tid=777f3e14-b65a-11e5-b030-00000aab0f26&acdnat=1452293717_9fb338cbae44241160cdf82b07c50312

A related item in the popular science press on the extended 2nd law of thermodynamics ---
"Autonomous Maxwell's demon displays chilling power"

Key excerpt: ... In the latest work, Jonne Koski, Jukka Pekola, and colleagues at Aalto University in Finland have instead made a demon that acts without external control....The device is described in Physical Review Letters and in an accompanying commentary, Sebastian Deffner of Los Alamos National Laboratory in the US says that the Finnish team has made the autonomous version of Maxwell's demon "a physical reality". The new device, he says, "fully agrees with our simple intuition – namely that information can be used to extract more work than seemingly permitted by the original formulations of the second law [of thermodynamics]"....

http://physicsworld.com/cws/ar…n-displays-chilling-power

In his comment below, Marc Serra, one of the preprint authors, justifiably takes exception to my too quickly worded description (in quotes):

"An Arxiv-preprint which, if correct, appears to challenge the 2nd Law" ---

I should have written that it "... at first impression poses an apparent, but not a real, challenge to the 2nd law. It's a clever design, producing a counterintuitive effect that many would not have thought possible.

A mechanical autonomous stochastic heat engine

ABSTRACT: Stochastic heat engines are devices that generate work from random thermal motion using a small number of highly fluctuating degrees of freedom. Proposals for such devices have existed for more than a century and include the Maxwell demon and the Feynman ratchet. Only recently have they been demonstrated experimentally, using e.g., thermal cycles implemented in optical traps. However, the recent demonstrations of stochastic heat engines are nonautonomous, since they require an external control system that prescribes a heating and cooling cycle, and consume more energy than they produce. This Report presents a heat engine consisting of three coupled mechanical resonators (two ribbons and a cantilever) subject to a stochastic drive. The engine uses geometric nonlinearities in the resonating ribbons to autonomously convert a random excitation into a low-entropy, nonpassive oscillation of the cantilever. The engine presents the anomalous heat transport property of negative thermal conductivity, consisting in the ability to passively transfer energy from a cold reservoir to a hot reservoir.

http://arxiv.org/abs/1601.07547

Marc,
First I wanted the word "appears" to convey that an "apparent" but not real
violation of the 2nd law seem to occur - as your paper clearly states.
(Ambiguous word choice. See the edit to my posting.)

Second, Contrarian brings up the interesting Feynman ratchet-pawl example.
While I believe that it does not violate the 2nd law, I am still perplexed by the
following question posed on Quora.com --

"In the Brownian ratchet, what if there is a vacuum on the side of the pawl that
eliminates the pawl from being hit by particles and knocked loose?
Would this violate the second law?
The Brownian ratchet cannot extract energy from room temperature because the
pawl is also hit with particles causing the ratchet to fail.
What if there is a vacuum on the side of the pawl?"
https://www.quora.com/In-the-B…is-violate-the-second-law

I do not find the answers on Quora convincing.
Do you have an opinion on the subject you are willing to share?

Thanks Marc,

I agree. Assuming perfect rigidity renders the system non-Hamiltonian.

Seems like it might be similar to the old paradox of the long perfectly rigid pair of
scissor blades apparently able to transmit information superluminally (by the speed of
the blades crossing point.) - but, the paradox disappears when the blades are
more realistically modeled as flexible.

Another paper illustrating the relation between information and thermodynamics ---

Physicists create first photonic Maxwell's demon
http://phys.org/news/2016-02-p…otonic-maxwell-demon.html

Preprint -- "Photonic Maxwell’s demon"
http://arxiv.org/pdf/1510.02164v1.pdf