Possible "exotic" thermoelectric power generation

  • An interesting recent Arxiv preprint -

    "Thermoelectricity without absorbing energy from the heat sources"

    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.


  • The (Sept 28, 2015) updated version of the above preprint is available at the same URL --
    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"
    "Thermal Baths as Quantum Resources: More Friends than Foes?"

  • 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.,

    Thermodynamics of quantum systems with multiple conserved quantities
    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 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"
    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"
    - and, an earlier paper-
    "Anomalous power efficiency of a transformer driven by tuned duty cycle pulses"

  • I know absolutely nothing about these particular studies but extrapolating from stuff I do know about, it seems to be a lot of fuss about what are almost certainly measurement errors. There are innumerable ways to get anomalous results from measuring transients, spiked waveforms, and anything which involves high frequencies -- unless you are very cautious about all sorts of things, most notably wiring details and scrupulous calibration with appropriate standards.

    But hey, who knows? Anomalous thermoelectrical generation may be Rossi's next discovery after he gets negative results in his current tests.

  • 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]"....


  • 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.


  • Quote

    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.

    I will believe it the day that I can buy a fridge without electric cord. A self heating / cooling house would also be very nice, thanks.

  • I will believe it the day that I can buy a fridge without electric cord. A self heating / cooling house would also be very nice, thanks.

    I'm a co-author on that pre-print. Our system does not violate or challenge the second law of thermodynamics in any way (and this should be obvious to anyone who has actually read the paper). The negative thermal conductivity phenomenon requires two low temperatures (Tc and Th, Th > Tc) and a hot one (Tw). Energy flows from Th to both Tc and Tw in such a way that the increase in entropy at Tw and Tc together is greater than the decrease in entropy of Th. Therefore, it satisfies dS_tot > 0.

    You can think of it as operating a termoelectric between a temperature of 0 ºC and 100ºC, and using the resulting power to heat a resistor to 200 ºC. In such a system, energy is flowing from the 100ºC reservoir to the 200ºC resistor. Our point is that a simple nonlinear system (essentially a resonating guitar string) can present this phenomenon.

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

    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…

    There is currently much work challenging the absoluteness of the Second Law. There is an AAAS symposium in June in San Diego titled "Challenges to the Second Law of Thermodynamics: Experiment and Theory" which I hope to attend.

  • Your paper doesn't but others do. See;


    BTW, your paper sure goes out of its way to lead to that conclusion when you keep mentioning Brownian motion and Feynman's ratchet and pawl. Maybe you should have been more clear what you are trying to do.

  • BTW, your paper sure goes out of its way to lead to that conclusion when you keep mentioning Brownian motion and Feynman's ratchet and pawl. Maybe you should have been more clear what you are trying to do.

    Neither the Feynman ratchet nor Brownian motion contradicts the second law in any way, and this has been known for more than 60 years. The audience of the paper is expected to know that. Scientific papers are limited in length and thus cannot explain all prior knowledge required to understand them.

  • 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?"

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

  • I've just taken a look at this Quora question and I'm surprised too at the (unusually) poor quality of the answers. I can think of two approaches to see that a system does not violate the second law of thermodynamics.

    The first one is very general: You assume something about the system (Such as that the dynamics of the system [both atoms and pawl] is time-reversible) and derive a fluctuation relation, which tells you that the probability of an entropy-increasing event is always larger or equal to the probability of an entropy-decreasing event. Then you can look at every ingredient in your system to check that it satisfies the assumptions of the fluctuation theorem (For example, motion of a mass-spring system such as the pawl is time-reversible because if you watch the motion in reverse you get an equally physically valid trajectory, which is true for Hamiltonian systems in general).


    This is a very abstract procedure but it guarantees that if your system does not contain 'naughty' elements (That don't follow Hamiltonian dynamics or break time reversal symmetry somehow), then it is not going to violate the second law. There are no such elements in the racthet-and-pawl device as it is typically drawn, with or without gas on the other side.

    The second one (that is probably what you are looking for) is to simulate the system (either using a computer or mentally) and seeing what can go wrong. Looking at this drawing of a racthet and pawl system:


    Let's try a bit of mental simulation: What happens after the pawl jumps from one tooth to the next one. Option (a): The elastic potential energy in the pawl gets dissipated somehow. If that's the case, then we're done. Your system is not Hamiltonian (has energy loss) but it's dissipating energy somewhere (heating a cold reservoir) in addition of producing work. If the cold reservoir is too hot, there will be energy transfer from the reservoir to the pawl (i.e. allowing it to jump up sometimes and letting the ratchet go in reverse). If you include the dynamics of the reservoir that takes the potential energy from the pawl, then the whole system will be microscopically time-reversible and will follow the fluctuation theorems. What if there is no reservoir where the pawl's potential energy can go? Well, then after the first jump it will keep oscillating with an amplitude equal to the height of the teeth. This will allow the ratchet to move in any direction, and the whole system will not work.

    The explanation that I've provided here is very simplistic. There are papers on the topic that are many pages long and provide a rigorous and detailed treatment, but this should give you a rough idea. If you are computationally inclined, it is not *too* hard to simulate a system like this one.

  • 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.

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