Mailinglist Archive: opensuse (5130 mails)

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Re: [SLE] Warning to Americans!(now going OT)
  • From: Bob S <usr@xxxxxxxxxxx>
  • Date: Thu, 4 May 2006 00:58:12 -0400
  • Message-id: <200605040058.13092.usr@xxxxxxxxxxx>
On Wednesday 03 May 2006 15:39, David McMillan wrote:
> Kevanf1 wrote:
> > On 02/05/06, James Knott <james.knott@xxxxxxxxxx> wrote:
> >> Kevanf1 wrote:
> >> > There are alternatives but one is branded a conspiracy theorist if you
> >> > so much as hint at the oil companies perhaps keeping them quiet. There
> >> > is no reason why we shouldn't have safe engines running on
> >> > water. There is no need to have a tank of highly flammable hydrogen
> >> > gas (from the split H20) as it can be split in small quantities and
> >> > fed into the engine that way.
> >>
> >> ????
> >>
> >> Splitting water into hydrogen and oxygen takes energy. Where does that
> >> energy come from? Remember, you can never exceed 100% efficiency and
> >> are unlikely to even reach it.
> >
> > Solar power. Admittedly, solar panels take energy to make them but I
> > don't think they break down fast. So, this would mean that the energy
> > put into making them can be regained from the use of the sun over its
> > lifetime. The solar energy is then used to split the water. It
> > doesn't take much in the way of electrical power to produce the two
> > gases after all.
>
> ..have you ever done the energy calculations for this? I doubt
> there's a solar array on Earth small enough to fit onto a car that can
> crack water into H2/O2 fast enough to keep up with the demands of an
> internal combustion engine. Solar is good for a slow, steady *trickle*
> of electrical power.
> Not to mention, H2 as a gas is compressible -- water is *not.* And
> H2, even if you liquify it, is a huge headache for storage, handling,
> and has literally the worst mass/volume ratio going -- ask any rocket
> scientist. The *only* reason that it's used in rocket engines is that
> it gives just about the best ISP possible for current technology in an
> engine that has enough thrust to get from sea level to orbit (ion
> engines and their kin have much higher ISPs, but have thrust levels
> measured in ounces). There's a vigorous minority among rocket
> scientists who believe that LOX/Kerosene comes close enough to matching
> LOX/H2, once you consider the mass savings in the huge cryogenic tankage
> that H2 requires, that if you're going for overall efficiency rather
> than max performance, LOX/Kerosene probably makes a better choice.
> To match the total energy of a tank of petrol, you have to have a
> *much larger* volume of H2 -- the fuel/air ratio is backwards. An ICE
> burning petrol uses a small amount of fuel combined with a large amount
> of air. An ICE burning H2 would have to use *twice* as much H2 as air,
> even if the air was pure oxygen -- with open air being largely N2, it's
> even worse (note to chemists: I'm leaving aside molar numbers vs volume
> for the sake of simplicity). You can beat this to a certain extent by
> using compression, but H2 doesn't compress well, being the lightest
> element (hence the headaches for rocket scientists). And sufficient
> compressions produce explosion (from pressure, not falmmability) and/or
> cryogenic hazards.
> This is all why most of the leading work in H2-powered automobiles
> has been concentrating on using H2 "sponges" or fuel-cell equivalents,
> rather than gaseous H2. If carrying a tank of water and electrolyzing
> it on-the-fly were *that* easy, we'd be doing it already. And if the
> automotice companies weren't, then the DIYers who build their own
> electric cars would be.

Hmmmmmm........Ya know, when I was a little kid, (long long time ago) they had
these little toy wind-up cars with a big spring in them. Maybe we should
revisit that. :-)

Bob S.

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