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B HHO Easy Recombination to get electricity

  1. Mar 29, 2017 #1
    I was just wondering if there is an easy way to recombine hydrogen in a fuel cell style but effectively by doing electrolysis in reverse. Splitting is really easy but is there a way to get the HHO to recombine into water and release electricity effectively by reverse electrolysis? I get that there are fuel cells but they are expensive and I am not made of money. Looking for a decent scalable output. Really just a hydrogen battery
     
  2. jcsd
  3. Mar 29, 2017 #2
    As a somewhat flippant response, your post strikes me a bit as a "get cheap energy with this trick companies hate" question. I mean, fuel cells exist for a reason.

    A more physical answer, I think you will have two problems: how to meaningfully convert the recombination energy into something usable, and secondly, how to store the hydrogen in the first place. Because that's the two main problems a fuel cell solves. Storing hydrogen at a reasonable volume, other than binding it chemically like in the fuel cell, is only possible by storing it in liquid form. That takes very cold temperatures and high pressure, a very dangerous combination.
    Converting the recombination energy into usable energy, well, since chemical conversion is out of the question, the thing left is to just plain burn it, and make use of the heat. very inefficient, and you need a lot of oxygen too.
     
  4. Mar 29, 2017 #3

    berkeman

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    Welcome to the PF.

    You don't get more energy out than you put in to split the water. You do understand that part, right?
     
  5. Mar 29, 2017 #4

    Drakkith

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    If you're looking to generate power, the easiest way is probably just to burn the hydrogen by letting it recombine with oxygen and then use the heat generated to power a generator. I believe there are already generators out there that run off of hydrogen that you can purchase.
     
  6. Mar 29, 2017 #5

    russ_watters

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    How about a steam engine turning a generator? Efficiency's about the same as a fuel cell.
     
  7. Mar 29, 2017 #6

    Mark44

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    Recombining them is really the easy part -- just apply a spark in the presence of hydrogen and oxygen. That's what happened to the Hindenburg in 1937.
     
  8. Mar 30, 2017 #7

    fresh_42

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    And not to forget the "modern" incidents at which this exothermic reaction took place: Chernobyl and Fukushima.
     
  9. Mar 30, 2017 #8
    The part about liquid requiring low temperatures AND high pressure is wrong. Low temperature is all it takes and the liquid is at a low pressure. As the temperature increases the pressure would increase. That is how hydrogen rockets work, pump liquid H2 into big tanks which do not require super hard shielding from high pressure, just strong enough to take the weight of the H2.
     
  10. Mar 30, 2017 #9
    Yes, that was worded imprecisely by me, sorry. The point being, keeping hydrogen liquid is not exactly a "backyard scientist" kind of thing. If your cooling fails and your hydrogen starts to boils, you DO have a pressure problem, and a massive one. That's why hydrogen tanks are rather sturdy structures themselves.
     
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