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Extracting energy out of hydrogen and oxygen

  1. Mar 14, 2007 #1
    The best method of extracting energy out of hydrogen and oxygen

    Which method will deliver the best energy output?

    (1) Fuel cell
    (2) Burning the hydrogen and oxygen and make some steam and send it to a turbine
    (3) Internal combustion engine //piston like a car engine

    And which method will be the best adorable
  2. jcsd
  3. Mar 14, 2007 #2
    apparently the most efficient is Fuel Cell Technology, but it needs a lot of time to start being usefull due to the current infrastructure of the world. My second choice has to be ICE engines, hydrogen has a combustion efficiency of near 60% as compared to the 40% of gasoline. Steam running turbines comes last for me, its really not a practical/usefull/ or liked cycle, i wouldn't ever do it. anyway u sound very interested in this subject, may i ask why?
  4. Mar 14, 2007 #3
    What’s the efficiency of electrolysis of water?
  5. Mar 14, 2007 #4
    Depends on the cycle used. some cycles are joint heating + electrolysis and those are the most efficient. as for electrolysis as is u might want to look it up on the internet..
  6. Mar 14, 2007 #5
    I have: on Wikipedia

    “The energy efficiency of water electrolysis varies widely. Some report 50–70%[1], while others report 80–94%.[2] These values refer only to the efficiency of converting electrical energy into hydrogen's chemical energy. The energy lost in generating the electricity is not included. For instance, when considering a power plant that converts the heat of nuclear reactions into hydrogen via electrolysis, the total efficiency is more like 25–40%”

    To me it have multiple answers
  7. Mar 14, 2007 #6
    that's why i didn't give u an answer. Some researches say that u can go higher than 88% if u use a catalyst in the water solution to conduct electricity better, i don't remember what the catalyst Potassium i think. heating the water mixture results in lowering the amount of electricity needed to break the water molecules. another way would be to use heat and zinc which joins with the oxygen in the water resulting in free hydrogen, this is a reversible process where the zinc is merely a catalyst and breaks free in another process. so reaching above 70% in electrolysis is perfectly logical.but its still a researched area i think
  8. Mar 14, 2007 #7
    Yip, I understand now, hydrogen has its hidden stuff. But still involving electricity + heat to get hydrogen will be better of because, almost no application makes good use of heat beside nuclear.

    And involving zinc will produce Zinc Oxide (Zn0) that a waste, I would be better to make something self sustained hydrogen generator that will totally screw the world over.
  9. Mar 14, 2007 #8
    yeah but there is a way to recover the ZnO cheaply.
  10. Mar 14, 2007 #9

  11. Mar 14, 2007 #10

  12. Mar 14, 2007 #11
    Its ok, no problem.

    I just don’t understand why no body can convert heat to useable electricity, but it takes huge amounts of electricity to product heat?

    And the same with producing hydrogen, I’m seen on TV how thermite makes ice explode, because of the extreme heat that makes the hydrogen and oxygen splits.

    So ways to split water:

    (1) Extreme heat
    (2) Electrolysis of water

    Are there any other ways?
  13. Mar 14, 2007 #12
    Chemical by removing it from other material, like from Methanol or something like that.
    Heat doesn't produce electricity directly but its a combination of heat and pressure. and their are losses due to efficiencies.but heat always produces electricity, there's no better way to produce electricity than heat. and btw. it takes a huge amount of electricity to produce heat, and it takes a lot of heat to produce electricity.
  14. Mar 14, 2007 #13


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    Staff: Mentor

    The course of the discussion doesn't exactly fit the OP: are you asking about the use of hydrogen/oxygen for energy storage or just the efficiency of combustion of hydrogen and oxygen itself?

    As an energy storage system, electrolysis->hydrogen/oxygen->fuel cells fall far short of ordinary batteries in terms of efficiency.
    I'm not following. The conversion of electricity to heat is exactly 100% efficient, but it is irreversible. Due to the laws of thermodynamics, conversion of heat to electricity involves some entropy loss. But obviously we can and do convert heat to useable electricity.
    Last edited: Mar 14, 2007
  15. Mar 14, 2007 #14
    What sounds logic in a way I don’t want to belief, but maybe there a lacking something nobody yet know that can be added to the laws of thermodynamics, that makes the energy more, it’s like a oxidizer in a fire, the more oxygen the bigger your faster it burns, probably the same with fuel cell, if your use hydrogen and Stored oxygen from a tank you get a boost

    To my understanding, using that heat to produce steam and then transfer it to a steam turbine, will have the highest effect in energy gain, thermocouples won’t be that nice.

    I’m actually asking both:

    hydrogen/oxygen for energy storage //the best method of doing

    and then the efficiency of combustion of hydrogen and oxygen might play a big key role
  16. Mar 14, 2007 #15
    Russ what is the comparison in efficiency between a PEM fuel cell and an ICE combustion., both using Hydrogen.
  17. Mar 14, 2007 #16


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    Science Advisor

    A fuel cell will output electrical energy (+ heat) and an ICE will deliver an output of mechanical energy (+ heat). Which is it that you want to use? I think it would only be fair to compare the efficiencies when comparing the energy ouput in the same form, so at least one of the outputs (either from the ICE or the fuel cell) is going to have to be put through another (lossy) conversion.

    PEM fuel cells have an efficiency of about 35% to 60% (chemical to electrical),
    http://www.rmi.org/sitepages/pid556.php [Broken]

    Whereas ICEs have efficiencies probably on the order of about 30-40% or so, I would think, but I have seen estimates much lower,
    says 15% conversion from chemical to 'moving you car down the road', saying that 62.4% is lost during the initial combustion process and then with further loses down the line.
    Last edited by a moderator: May 2, 2017
  18. Mar 14, 2007 #17
    well unfortunately its to give electricity, so i guess a PEM would be better for such a use.
  19. Mar 15, 2007 #18
    It’s just to bad that the big fuel cells only comes in units of +- 88kw, for car purpose only and each unit will cost a banks money.
  20. Mar 16, 2007 #19
    that's why battery powered cars are too heavy, because u got stacks and stacks over each other, that includes fuel cells too
  21. Mar 16, 2007 #20
    No doubt. My brain are out of ideas. :(
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