From: stead@skadi.CSS.GOV (Richard Stead)
Newsgroups: sci.electronics,sci.energy,rec.autos
Subject: Re: Flywheel batteries as EV power source
Date: 22 Dec 92 22:44:50 GMT
Followup-To: sci.energy

In article <1992Dec22.204130.18133@enterprise.rdd.lmsc.lockheed.com>,  writes:
> In article <51694@seismo.CSS.GOV>, stead@skadi.CSS.GOV (Richard Stead) writes:
> > 
> > Flame on.
> > 
> > The rampant idiocy on flywheels just continues.  How many ways do people have
> > to be told about conservation of energy?
> 
> Conservation of energy exactly, where do you think you get the energy to 
> turn a carbon carbon fly wheel into cotton candy from?  Before you start
> flaming at others for not doing the math, do it yourself.

Now you look like a real butt-head.  Look back a week or so on this subject.
You will find so much math and material physics posted by me that it could
choke a horse.  All accurate, all referenced.  Now, butt-head - go read it
and come back with something constructive.  You obviously haven't a clue.

> Wrong again, a hyper speed carbon carbon flywheel is not designed to fail at
> once it is designed to fail a bit at a time, as cotton candy, using up a 
> significant fraction of the energy stored in the disk over a period of time 
> (although that time may be microseconds).  

Wrong yourself, pup.  You want to remain ignorant, it is clear.  However,
just referring to fiber as "cotton candy" or "fluff" does not change the
energy involved.  Afterall, a hydrogen explosion is never anything more than
air.  If fluff isn't dangerous, shouldn't air be less dangerous?
Look back a couple days, and you'll find a post by me that shows the power
involved if the flywheel takes a full millisecond to fail.  Many gigaWatts.
Just try containing that kind of power - it doesn't matter if it's carried
by a Mack truck, fluff or just air.  It will blow you to bits.
 
> > You think fluff is harmless?  Let's tie you down and hit you with "fluff"
> > traveling at several km/s and at a temperature of a few thousand degrees.
> > Let's see if we can find any teeny parts of you after the impact.
> 
> Obviously this fluff created by a failed flywheel is not exactly safe.  But
> you contain this fluff inside another carbon carbon shell such that the
> expanding hot fluff makes more fluff until the energy is such that it can
> be contained by a container.  The object is not to stop the flywheel failure
> at any given point, but to slow it down and cause it to loose energy.  

And I can calculate how much that is.  The energy available will melt over
200 kg of steel.  How much composite can it melt?  Depends on the heat capacity
of solid composite and the heat of fusion of the composite and the melting
point.  I'll give you the benefit of the doubt and say that the energy
required to melt a kg of composite is the same as that for a kg of steel.
That's 200 kg of composite, now all melted and very hot.  No fluff.
It actually now doesn't matter how long the failure takes - whether
shreading composite or banging off the sides or whatever - the energy
must end up as heat, and sufficient heat will melt the composite.
And in melting a material, the same total energy is used whether you shread
it first or not.  A few times that mass might completely contain the
explosion, but now you have a much heavier car than with lead-acid
batteries, and do you have any clue how big, say, 2000 kg of
light-weight composite is?

> What I would like to see is a good treatment of the energy needed to turn a 
> flywheel into cotton candy.  This gives everyone a better idea of how 
> much energy is left yet to be contain by the next carbon carbon shell.

A negligible amount compared to melting it and the energy is sufficient to
melt a couple hundred kg.  Also, the way the molecules work is that you
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.

I repeat for the billionth time, energy is conserved!

> > I'm really tiring of this nonsense, so while I politely corrected the
> > first posters in their misconceptions - you get flamed, boy.
> > 
> > > >My opinions are my own.
> > 
> > Good thing - they're pretty damned stupid for anyone else.
> 
> Gee thanks for your help in keeping this discussion open and moving forward.

You're welcome.  Why don't you try helping a bit instead of flaming
when you don't know what you're talking about.
--
Richard Stead
Center for Seismic Studies
Arlington, VA
stead@seismo.css.gov