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Power generation through endothermic heat absorption.

  1. Apr 14, 2014 #1
    I have been toying with an idea that may break the second law of thermodynamics for a while now, but it is basically this; An endothermic reaction is used to convert heat energy into chemical energy, and then the products of that reaction are used as the reactants in an electrochemical reaction to extract the energy captured by the endothermic reaction. The products of that are then used as the reactants for the endothermic reaction in a continual cycle. If the temperature is too low to allow the endothermic reaction to occur, you have a buildup of reactants for that reaction. If the power draw is too low to keep up with the endothermic reaction, you have a build up of reactants for that. Basically turning this system into a battery / fuel cell that recharges by absorbing ambient heat.

    I should note that I am only a senior in high school with a fairly limited chemistry/molecular level physics education. - Most of it coming from my research into this idea. My particular expertise instead comes in electrical engineering.

    Would this be possible at all? Would it break the second law of thermodynamics as it is skyrocketing past the theoretical maximum efficiency of the Carnot cycle possible in a heat engine? If so, what sort of barrier is stopping this sort of thing from occurring? A theoretical one (The second law - Which could always be disproven as I know of no large parts of physics resting on it. Although please correct me if I'm wrong.) or a chemistry one?

    Thank you for any discussion / answer.
  2. jcsd
  3. Apr 14, 2014 #2


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    The second law of thermodynamics is inviolable in the macro-world. I'll let Sir Arthur Eddington say it for me: "The law that entropy always increases, holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations — then so much the worse for Maxwell's equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation."
  4. Apr 15, 2014 #3


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    A very, very good rule of thumb is if you ever, EVER think you have found a way to break any of the laws of thermodynamics, you'd best just forget about it completely, because you haven't. :wink:

    Also, discussion of over-unity devices, perpetual motion machines, or similar ideas (like this one) are not allowed per PF rules.
  5. Apr 15, 2014 #4


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    I still think Eddington phrased it more elegantly...:tongue:
  6. Apr 15, 2014 #5
    Ah, thanks. Even with reading through the main pages of the forum rules, I never came across that rule, sorry.

    I think it would be better to turn this into a learning opportunity then. How / does this even violate the second law? It was my impression that any device that achieved a perfect or near perfect heat engine efficiency would do this, but is this so and why?

    As for the Sir Arthur Eddington quote
    I am a bit confused on this one. Are you saying that Maxwell's equations somehow prove the second law? I thought that the second law was improvable using math and only created by observation. As well as Maxwell's equations being about electricity and magnetism. (Which on an atomic perspective, I guess they may be able to prove the second law) or are you just saying "Don't even try to go against the second law, you will fail"?

    Oh, and I did find this paper: http://arxiv.org/ftp/arxiv/papers/1203/1203.0161.pdf Although I'm not sure if it is bogus or not. There is not enough followup to tell as far as I'm concerned.
    Last edited: Apr 15, 2014
  7. Apr 15, 2014 #6


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    Not all of the input energy will go to driving your endothermic reaction; some of it will be lost as random heat in the reagents. In fact, your comparison with a battery;
    is pretty good. The way a battery works, I put energy into it, the energy drives an endothermic (energy-consuming) reaction, the energy is released when I discharge the battery and the endothermic reaction runs in the exothermic (energy-releasing) opposite direction. However, charging a battery causes it to heat up slightly as some of the input energy is lost to heat instead of contributing to the battery's charge.

    Two other thoughts here:
    - Your device will only gain energy from the environment if it is at a temperature below ambient.
    - Look carefully at the definition of the second law, including that word "isolated", and be very careful about what you're defining as the "system".
  8. Apr 15, 2014 #7


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