NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/sci/electron/21473

Internet Message Format | 1992-12-23 | 5.3 KB

Xref: sparky sci.electronics:21473 sci.energy:6409 rec.autos:30408
Path: sparky!uunet!gatech!udel!darwin.sura.net!seismo!skadi!stead
From: [e-mail] (Richard Stead)
Newsgroups: sci.electronics,sci.energy,rec.autos
Subject: Re: Flywheel batteries as EV power source
Message-ID: <[e-mail]>
Date: 23 Dec 92 17:29:31 GMT
References: <[e-mail]> <[e-mail]> <[e-mail]>
Sender: [e-mail]
Followup-To: sci.energy
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Nntp-Posting-Host: skadi.css.gov

In article <[e-mail]>,  writes:
> In article <[e-mail]>, [e-mail] (Richard Stead) writes:
> > must do work against the molecules to separate them, but once separated,
> > they snap back, releasing the acculmulated strain energy as heat.  That's
> > right, energy is conserved, and a pile of shredded composite does not
> > represent more energy than the whole piece.  Entropy simply means that
> > energy has been converted to heat.
>
> Unfortunately wrong, and very sloppy.  Take a ream of paper and turn it into
> scraps and tell me you haven't expended energy.  That energy came from the
> flywheel hense the fluff does not have the same energy as the initial flywheel.

Wrong youself, bub, and indeed very sloppy.  All the work you did on that
paper is now represented as heat in the pile of shreds.  It's just not
all that much heat, because it is so little work.  And I can hear you now
whining about how much your arms would ache after doing that, but then, I'll
just have to remind you that your arms ache from the work of moving your
arms during the shredding, only a small fraction of the total work you did
went to shredding the paper, and that energy is still all there in slightly
warmer paper.  Of course, it takes so long to shred the paper this way
that the power is very low, and most of the heat is able to diffuse into
the surrounding air while you are still tearing.

Why do you insist on such inappropriate analogies?  The energy and material
physics regime for tearing paper or falling fluff are entirely another world
when compared to microsecond failure of 400 MJ of energy failure.  You think
that by trying to draw analogies to something safe from everyday experience
will make the flywheel safe - it won't.  For your paper tearing example,
you would have to shred 100's of reams to microscopic fibers in nanoseconds
to get anywhere close to the power we're talking about.  Such occurances
simply aren't everyday experiences.

> Energy has been used bending molecules, which may or may not snap back, but

So you're telling us that the "fluff" is going to store a significant
fraction of 400 MJ as strain energy????  Get real!!  You know mothing
about the energy of the bending of these molecules, nor of strain in
materials in general.  That much strain energy would literally make
the fluff explode.  Just try converting the energy of bending you propose
into a pressure exerted by the bent molecule.  You'll find a pressure
larger than that at the earth's core.  The substance would violently
fly apart.

> more significantly in breaking bonds which originally held the flywheel

Obviously, you know no chemistry either.  For the big molecules in the
composite, that bond stores chemical energy (It took energy to get all those
atoms together into that big molecule, an endothermic reaction, the reverse
would be exothermic).  Breaking it represents a net release of energy.
This is why gasoline works - those bonds have energy - you break them
and they release it.  It may take work to break the bond (activation
energy), but the final state recovers all that work plus the energy in
the bond and releases it as heat.

So, please note, you have just made your position more difficult, because
you have all the bond energy of the composite now to deal with as well as
the rotational energy stored in the flywheel.

> together.  Now if you've got the inter fiber bond strength of a material of
> carbon carbon fibers we could use for a fly wheel, your a hell of a lot
> farther ahead that most in the carbon carbon field.  Now is this energy enough
> to make the fluff safe, I don't know, that's why I asked.  Remember that

No - because it is energy ADDED to the problem, not subtracted!!

> I guess you'd better keep your gov job.  This sort of attack science doesn't
> cut it out here.

I don't have a government job - shows how bad your reasoning is.  I attack
because the post I reponded to was yet another in a long series in this thread
that was simplistic, wrong, ignored all the detailed technical arguments
that had preceded it by only a day or two, and was a smug attempt at a flame
itself.  Just try a similar comment at a scientific conference sometime.
They'll rip you to shreds - few scientists would have as much patience
with this crap as I do, and you should be glad to have so many of them
taking the time to post to the net.  Maybe you should bother to read some of
the posts instead of just mouthing off on things you have no knowledge of.

But I will apologize to the rest of the readers here for flaming - the goal
is patience and I fell short.  This will be my last flame-ridden post on
the subject, I will practice better netiquette from now on.


--
Richard Stead
Center for Seismic Studies
Arlington, VA
[e-mail]