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Design for a Hydrogen Fuel Cell

  1. May 30, 2004 #1
    Hey guys anyone have an idea for a hydrogen fuel cell. I was thinking about one in which a battery first is used to split water into h2 and o2 using electrolysis. And then the components can be combined to produce energy. Anyone have any other ideas or links? Thanks.
     
  2. jcsd
  3. May 30, 2004 #2
    Here's the simplified problem. "E" and "e" represent energy.

    The splitting-apart reaction:

    water + E = hydrogen + oxygen

    The recombination reaction:

    hydrogen + oxygen = water + e

    The problem is, as hard as you try, E is always bigger than e. That is, it takes more energy to split the water into hydrogen and oxygen than you get back from recombining them back into water. This is why hydrogen is not some miraculous energy source: since we don't have an abundant source of free hydrogen just sitting around, we have to make the hydrogen in an energy intensive process.

    Ultimately, in the "hydrogen economy," hydrogen becomes like a battery: a way of storing and transporting energy. The fundamental problem remains unsolved: finding economical methods for clean and sustainable energy production.
     
    Last edited: May 30, 2004
  4. Jun 1, 2004 #3
    How about in the future, we all fill up our cars from hydrogen blimps, Kinda like pizza delivery?
     
  5. Jun 2, 2004 #4

    russ_watters

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    Staff: Mentor

    In other words, if you already have the battery, the fuel cell becomes worse than redundant.
     
  6. Jun 3, 2004 #5
    I just saw on Power Electronics Journal that sandia / Cal state is starting a big program on fuel cells, maybe you should apply there.
     
  7. Jun 3, 2004 #6
    Alternative

    If I may suggest something, consider running a conventional engine auto using hydrogen. We already have plenty conventional engines, and it will still be a few years before fuel cells can be produced economically for everyday auto use.

    Actually the conventional engine (especially in a hybrid auto using the newer higher efficiency engines) has almost all the advantages of the fuel cell car, except one; oxides of nitrogen. (And without hydrocarbons, nitrogen oxides are much less a problem.) Now all we have to do is find a way to derive, transport and store the hydrogen.

    Consider the website: www.powerball.org
     
  8. Jun 8, 2004 #7
    I read about a great proposed system for preparing hydrogen at low cost.

    At 2,730C (4,946F) water automatically decomposes into hydrogen and oxygen. That temperature can be achieved with a solar reflector (you can vaporize a stone instantaneously with a 20 ft diameter lens - plenty of heat).

    The water would be decomposed and the gasses quenched by injection into water. The gasses are then seperated by gravity.

    The main trouble is that there aren't any materials that can withstand the heat near the focal point of the lens.

    In general, from what I've read, there is alot of head scratching about the best system of storing and then releasing the hydrogen.

    Say you have a great fuel cell and electric motor in your car. When you pull into the gas station, what do you buy? Is there an exchange of cylinders, empty for full? What if your cylinder isn't totally empty? How do they determine how much is left? What if they decide to store it as a hydride?

    Many, many logistical problems to work out. Getting gas won't be the same.
     
    Last edited: Jun 8, 2004
  9. Jun 8, 2004 #8

    Cliff_J

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    Science Advisor

    There is currently a small fleet of cars in California running on hydrogen. They store the hydrogen in pressurized tanks designed to withstand impacts. The hydrogen is generated by reglar PV cells and electroloysis at special 'stations' they have setup. Hydrogen is transferred with pressurized hoses and couplings. So with existing technology they have cars on the road. They are using fuel cells but a regular ICE would keep the costs down for now and provide a transition path.

    Water is abundant - leave the centralized refining model and go decentralized and hydrogen makes a little more sense. Even pressurized the dispersion characteristics make it safer than gasoline. Just need to get those costs in check (economies of scale from mass-production or technological breakthrough) and the biggest challenge would be to get the population to buy it. My two cents anyways...

    Cliff
     
  10. Jun 8, 2004 #9
    Probably the least complicated way of doing it, but I don't think this will translate to self serve stations where old ladies can fill their own cars up without alot of streamlining.

    Is the hydrogen in this case merely under pressure, liquid, or what? How many miles can they get on a "fillup"?
     
    Last edited: Jun 8, 2004
  11. Jun 8, 2004 #10
    Hmmm. This is interesting. I have a book called Fuel From Water Energy Independence With Hydrogen, by Michael J. Peavey.

    On page 21 it says:

    "The smallest amount of energy needed to electrolyse one mole of water is 65.3 Wh at 25C (77F). When the hydrogen and oxygen are recombined into water during combustion 79.3 Wh of energy is released. 14Wh more energy is released in burning hydrogen and oxygen than is required to split water. Extra heat is absorbed from the environment during electrolysis."

    The source he cites for that is a paper called "Fundamentals and Technological aspects of Medium Temperature Electrolyzers" by J. Fischer. The paper was delivered in a seminar on "Hydrogen Energy Vectors" in Luxembourg in 1978.

    He is claiming that since the electrolyis sucks heat out of the environment while it is occuring there is more energy available from the burning of the two gasses than you have to expend in electricity to split them.


    Fuel from Water
    Address:http://www.lindsaybks.com/bks/hydrogen/index.html
     
    Last edited: Jun 8, 2004
  12. Jun 9, 2004 #11

    Cliff_J

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    Science Advisor

    Pretty sure it was still a gas, I don't believe the pressure was all that great. It was featured on something like the 'Techknowledge' show on the science channel. They don't always hand out lots of details and followup on their segments is sometimes seemingly impossible using merely google.

    The system like BMW was using for methanol on their 7-series car would work with the robotic arm to do the refueling duty. But cost-effective?

    EDIT: Just found this via google:
    http://www.ecoworld.com/Home/Articles2.cfm?TID=284

    That is very high pressures at 7000psi. I think I'd rather have the hydride storage.

    Cliff
     
    Last edited: Jun 9, 2004
  13. Jun 9, 2004 #12
    Robot arm is good. General acceptance will be highly dependent on convenience.
    Did you catch about the 5 minute warm up time? That's a bug they'll have to work out.
    Peavy discusses the pros and cons of hydrides from alot of angles without coming to a clear conclusion about how to translate them to use in consumer vehicles. The material itself is problematic because it loses the proper consistancy to hold the hydrogen after so many uses. It starts off granulated and eventually becomes powdery. My impression, though, (just from that one book,) is that it seems to have more promise than high pressure or liquid. He suggests that the powder may have to be exchanged for granules every so often at a special station the way people get their oil changed.
     
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