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Hydrogen

  • Wed, Sep 17, 2008 - 01:10pm

    #9
    srbarbour

    srbarbour

    Status Bronze Member (Offline)

    Joined: Aug 23 2008

    Posts: 52

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    Hydrogen

[quote]First you must hydrolyze water. This is 70% efficient.[/quote]
Closer to 75% actually. Though I’d point out that most good electrolyzes use platinum. There has been innovation on platinum issue though.

[quote]Hydrogen gas is the most voluminous gas of them all. Unless we each want a dirigible in our yard it must be compressed. 10,000 psi would give us a decently small tank. This costs us another 15% in compression efficiency losses.[/quote]

You can use the compression energy of the hydrogen as a power source, so calling it a 15% loss is probably a bit unreasonable. Also, other storage mechanisms have widly varying storage losses, so using this as an example distorts a very complex problem.

[quote] Unless we use it very rapidly, hydrogen boils off and escapes costing us ~3%-4% per day.
[/quote]

What crappy storage tank/storage mechanism was used to conjure these numbers? Sounds exceedingly bogus or old. There are plenty of ways to store hydrogen where losses are much, much less. Near zero actually.

[quote]Then we burn hydrogen in a fuel cell at roughly 50% efficiency.[/quote]

If used now, we’d certainly be burning it in a Internal Combustion Engine: 12-25%.

Fuel cells range wildly in their conversion efficiency anywhere from 30-90% efficiency ratings. However, almost all fuel cells use platinum and only a few can reasonably be used in vehicles. Again, there has been innovation in all the related areas.

[quote]Final take = 0.70 * 0.85 * 0.96 (per day) * 0.50 = 28.5% of the original energy is available for work.

In short, at present hydrogen is a very inefficient battery. Perhaps this can be improved, but that’s how the technology stacks up at present as I understand it. [/quote]

If deployed right now, probably closer to 75% * 20% * 50-90% (Total transport loss is probably ~10-60%+) = ~6% – 13%. Losses could be much lower if used in a power generator — say to store solar energy and release it at night — 75% * 50% (engines which burn for efficiency == much better) * 90% (Short term storage cost) which could be as high as 33% give or take as much as 10%.

Obviously, Hydrogen without good energy converter and without eliminating platinum as much as possible isn’t going to be practical. It would require a massive investment in increasing electrical energy. How much, it is hard to say. Most lists of ‘energy’ used by our fuels directly list the energy of the root oil, or ignore the large transport and conversion losses of gasoline. Which is rather like back tracing the energy consumption of your refrigerator to the energy content of raw coal before it is burnt.

If we can get a good fuel cell with little or no platinum use, and which is suitable for running a vehicle (most fuel cells arent). Then the viability of Hydrogen increases significantly.

Long story short. Cellulosic Ethanol is probably our best interim solution. Until then, we have to wait for the electric industry to switch to more expansionary technologies (fast breeder reactors/solar power) and for a ‘better battery’. Be it improvements in hydrogen, capacitors, etc… I will say though that current batteries will never be good enough and have no real potential for improvement. The jump to Lithium was the last revolutionary step for battery technology, and there isn’t enough lithium in the world to power all our cars.

Don’t get my wrong. We can go hydrogen if we really wanted to. Its just that at this point it is still better to wait as long as possible until the necessary technologies mature and improve …

… short of an onset of peak oil, that is.

Steve