Water

Discussion in 'Chemistry' started by thecollage, Nov 28, 2007.

  1. Read-Only Valued Senior Member

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    10,296
    That's just taking the long way around to say: electrolysis.

    Where are you getting the electricity?
     
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  3. ray gun Registered Member

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    just back to that water thing, surley using water for fuel would be crazy when we have so many other sources to use like solar, wind, hydro electric from damns etc, if they can build a tunnell under the english channel to france, i would imagine they could build a few hydro electric plants enough to supply the best part of western europe, i have a few friends only a few mind, that have switched to solar, but they sem to make it so expensive, there is so mch energie out there, but it all boils down to one thing.
     
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  5. sreeja Registered Member

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    BY using electrolysis to break apart the H20 (water) into H (hydrogen) and O (oxygen), and using the H (hydrogen) as the fuel.But it takes more energy to break the molecular bond than you get from the hydrogen.
     
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  7. Positron Agony: Not all pain is gain Registered Senior Member

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    Sheesh Dragon! Water is actually a pretty common compound universally. Hydrogen is common as...well, Hydrogen, and Oxygen having a low atomic mass is also common, this is a generalization so correct me if i'm wrong but C, H, and O compounds are the most common I would assume, probobally with a large number of Na compunds as well.

    As for this "burning up hydrogen nonsense" the byproduct of using hydrogen as a fuel is water, it comes back. Conservation of mass and energy means that we cannot "use up" all of our water doesn't it?

    We get water back as showcased by the combustion reaction for Hydrogen.

    2H2 + O2 = 2H2O + ENERGY

    Hey look! water as a byproduct!? NO WAY!

    I don't mean to offend you personally, but from what i've seen your knowledge of Chemistry is a bit...lacking. Well so is mine, but at least I remember basic concepts.

    Perhaps to refresh you on said basic concepts you could look at this and stop making ridiculous claims
    http://witcombe.sbc.edu/water/chemistryelectrolysis.html
     
    Last edited: Dec 3, 2007
  8. Positron Agony: Not all pain is gain Registered Senior Member

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    sorry forgot about the topic at hand. Ah yes, water, I love water. seperating the water is very doable process, the key is to try and get the seperation process cheaper (in terms of energy) so that it can be used much more economically. Although it already costs pennies doesn't it?
     
  9. Read-Only Valued Senior Member

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    10,296
    Actually, the heart of the whole thing is that you never get back as much energy as you put into splitting it. Any energy converson process has losses and splitting water and then using the hydrogen are two stages of converson. To put it into common terms, energy-wise you are going in the hole (loosing).
     
  10. Positron Agony: Not all pain is gain Registered Senior Member

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    171
    I see, so is the net gain entirely negative? or is it even slightly positive? If so, What are the mechanical reasons that we can't get a net gain? Can the conversion process' be combined at all? Does this sound like a test question?
     
  11. Read-Only Valued Senior Member

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    10,296
    It can never be even slightly positive. For example, the theoretical maximum efficiency of electrolysis is between 80 and 94%. Let's be generous and just call it 94%, and that means you've already lost 6% there alone. Now consider the hydrogen - what are you going to do with it to provide useful energy, burn it? If so, there will be wasted heat that cannot be recovered - more loss. And are you burning it to produce steam to run a turbine generator? Not all the heat can be extracted from the steam (more lost), the turbine/generator is only about 85% efficient at the most, so there goes another 15% at least.

    Perhaps instead of all that you want to use it in a fuel cell? The MOST efficient ones currently top out at about 85% - a loss of 15%.

    So even assuming the best possible conditions and the highest conversion factors (electrolysis with 6% loss and fuel cells with 15% loss) you still have lost 21% of your original energy in those two conversion steps. It's a no-win situation no matter how you arrange it.
     
  12. Positron Agony: Not all pain is gain Registered Senior Member

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    It would seem that nuclear energy is still the cleanest and most efficent then wouldn't it. Darn.
     
  13. Read-Only Valued Senior Member

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    10,296
    Yes, in terms of practicality. Things like solar, etc. are nice but they will never generate enough power to meet the world's growing energy needs.

    That's why I keep saying that fission is the best solution for the short term until fusion finally becomes a reality in another 50 years or so. Hopefully, less than that - but fission will carry us far beyond that point anyway.
     
  14. Positron Agony: Not all pain is gain Registered Senior Member

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    I know the French have really jumped on board with building more nuclear reactors, but Germany is doing just the opposite and pushing coal for some reason. I think it has something to do with environmentalists. Here in Kansas where I live, we have had a contract to build a nuclear plant for quite some time now, but instead they are gonna build a coal one and even send OUT the power, but the CO2 emissions go on our record.:bawl:
     
  15. Read-Only Valued Senior Member

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    The good news is that world-wide there are something like 167 nuclear plants either being planned for or in the approval process. There are several in the U.S. alone and Japan is also joining the rush.

    The people - and governments - have slowly come to realize that it's the ONLY way to increase energy output without generating excess CO2. There's no real alternative at all waiting in the shadows. Yes, coal is pretty cheap and we'll still have to deal with it for a very long time.
     
  16. Nasor Valued Senior Member

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    To put it simply, the only energy that you can get back from burning hydrogen and oxygen is the energy that you put there with electrolysis. So you can't get back more energy than you put in, any more than you could get more energy out of a rechargeable battery than you added to it when you charged it.
     
  17. Read-Only Valued Senior Member

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    But the bigger - and even more important truth - is that you can never get back all that you put in in the first place.
     
  18. Chatha big brown was screwed up Registered Senior Member

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    If the hydrolysis of water is so inefficient, then how come they use it in space rocket fuels?
     
  19. Read-Only Valued Senior Member

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    Simple. Cost isn't the main consideration - energy density is.
     
  20. cosmictraveler Be kind to yourself always. Valued Senior Member

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    Using wind, water or sun to make hydrogen wouldn't cost that much to build the devices in order to produce the hydrogen. Once it was built it will last a very long time, like windmills, photovoltaic solar cells and dams that use water to produce electricity.

    Here is but another methold to extract the hydrogen from water.....

    http://www.youtube.com/watch?v=aGg0ATfoBgo&feature=related
     
  21. Read-Only Valued Senior Member

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    10,296
    We've already discussed that video. It's just another case of getting out less energy than is put into the system. No help there.
     
  22. kevinalm Registered Senior Member

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    993
    They don't. Hydrogen is obtained by cracking it out of hydrocarbons, usually natural gas and propane. Then cooling to the liquification temp. They get the oxygen by cryogenically liquifying air and distilling. (iirc nitrogen boils easier than oxygen)
     
  23. Forceman May the force be with you Registered Senior Member

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    Yes, of course because if we are to colonize mars ( another planet of the habitable zone) we will have to find an external source for water, no matter what state of entropy, until we can stabilize Mars's atmosphere and terrain
     

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