NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/sci/electron/21494

Internet Message Format | 1992-12-24 | 5.2 KB

Xref: sparky sci.electronics:21494 sci.energy:6420 rec.autos:30445
Newsgroups: sci.electronics,sci.energy,rec.autos
Path: sparky!uunet!usc!sdd.hp.com!spool.mu.edu!umn.edu!csus.edu!netcom.com!netcomsv!butch!enterprise!news
From:  ()
Subject: Re: Flywheel batteries as EV power source
Message-ID: <[e-mail]>
Sender: [e-mail]
Nntp-Posting-Host: 129.197.148.130
References: <[e-mail]> <[e-mail]> <[e-mail]> <[e-mail]>
Date: Wed, 23 Dec 92 21:13:50 GMT
Lines: 93

In article <[e-mail]>, [e-mail] (Richard Stead) writes:

>> 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????

No I'm saying that it probably won't contribute a significant amount of energy.  Vaporization will, (might, we haven't yet done the math).

>> 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.

Unfortunately, your probably kicking yourself now.  If you read your own posts.
You apparently understand the concept of endo and exothermic so I'll make it
simple:  The formation of a large molecule from atoms is exothermic (molecules
have a lower energy state, otherwise we'd be living in a plasma).  Therefor the
conversion of a molecule into atoms (the vaporization your so hot on) is
endothermic.

To use your own words "Why do you insist on such inappropriate analogies?"
Your use of gasoline in your own words is "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."

Please make a note so you won't make the mistake again.  Gasoline consumption
and CO2 and H2O production is exothermic because the products are at a lower
chemical potential energy than the reactants (gasoline and oxygen).  Please
get a high school  chemistry book and figure this out for yourself.  I
clearly agree that if this hot fiber fluff is exposed to air one would get
something like an air gas bomb reaction.  Which brings up an additional
safety issue of making sure this stuff is contained in vacuum or inert gas.


>I will practice better netiquette from now on.
--
>Richard Stead
>Center for Seismic Studies
>Arlington, VA
>[e-mail]


Just for the rest of you, and to save a post.

I was talking to some of the individuals involved in the Stanford Gas
and Electric Car.  They are trying to build a car that will run a gas
engine (constant RPM) and use it to charge a battery for an electric
motor.  The advantages are that the gasoline engine is only run at
peak optimization and does not have to idle at stop lights while doing
no work to move the car, etc.  The power of gasoline and air combustion
is stored in standard lead acid batteries.  Thus a massive weight
savings, as you have fewer batteries than a standard EV, and as gasoline
holds energy more effectively than batteries (and you don't have to carry
the air).  This results in a car that is better than a standard car, from
the stand point of MPG (including the losses of an additional step between
the engine and the wheels).  However it is less effecient that a total EV
from the stand point that each car still makes its own electricity and one
losses the economies of scale for a central power plant.  For those of you
for whom this is review apologies.

The upshot of this conversation turned on regenerative breaking.  It turns
out that there are massive losses using a braking motor to charge a battery
as the battery would like to be charged much more slowly that you will
probably have to break.  The solution is yet another system to store the
breaking energy, and slowly bleed the energy into the battery.  The two
most promising systems are a large capacitor and a flywheel.  Apparently
the capacitor currently has the inside track as it can be done with off
the shelf technology, where the problems with the flywheel are the
consequences of massive failure.  However, massive failure is not
apparently enough to totally eliminate the flywheel idea.

Darin Olson
R&DD
LMSC
Palo Alto, CA
___
Hell if I knew everything I'd claim to be Richard Stead.


>