From: philw@vice.ICO.TEK.COM (Philip W White)
Newsgroups: rec.autos.tech
Subject: Re: Flywheel batteries as EV power source
Keywords: flywheel, IEEE Spectrum, graphite
Date: 7 Jan 93 03:38:20 GMT
Organization: Tektronix Inc., Beaverton, Or.


Anyone interested in Electric Vehicles might want to look at the November
1992 issue of the IEEE Spectrum magazine (ISSN 0018-9235).

There is a sidebar on flywheel energy storage, unfortunately without
any references to other more detailed publications.  From that sidebar:

Richard F. Post of Lawrence Livermore Nat. Lab., CA  and  Univ. of California
Davis proposes a small flywheel for use in vehicles.  It would rotate at
10,000 radians/sec (95,500 rev/minute?) and store 1 Kilowatt-hour
(1.34 horsepower-hour).

A vehicle would use 20 to 30 of these.

Specific energy for the system, including containment structure, estimated
by Post at 150 Watt-hours/kilogram (= 0.2 hp-hr/kg = 0.44 hp-hr/lbm).

I calculate 30 such flywheels, storing 30 KWhrs, have a mass of 200 Kg
(440 pounds storing 40 hp-hours?). Obviously not a real long-range
vehicle but none of these EVs have been so far.

Rotor to run on magnetic bearings in a vacuum chamber.  Containment structure
is outside the vacuum chamber and separate from it.  Vacuum chamber mounted
on gimbals inside containment to handle what folks in this thread have
called the "gyroscopic effect".  Vacuum chamber running at 1 to 0.1 
millipascals (I don't have a conversion table for pascals...) giving a
rotor rundown time of "several months".

Rotor constructed of composite based on graphite fibers.
"Unlike massive steel rotors, which can fail in a spectacular fashion,
throwing off large chunks of shrapnel, fiber-based composite rotors tend
to fail by disintegrating into a mass of fairly benign 'cotton candy',
to borrow Post's descriptive phrase."  That is a direct quote so if you
want to flame it we all realize you are questioning Post's idea,
not mine.

Containment box of "3-dimensional composite" to retard crack propagation.

Rotor has permanent magnets attached and motor/generator windings run
up a tube at the rotor's rotational axis.  That tube is part of the
vacuum chamber wall, so the windings are outside the vacuum chamber.

One big advantage claimed is that these flywheels can deliver power
at the rate of at least 5000 watts/kilogram, while an internal combustion
engine would do 800 watts/kg at best.  (800 W/kg = 2.3 hp/lbm, would be
460 hp from a 200 pound engine).  Of course the
weight of the electric motor and controls must be added to the flywheel
storage system but still I think the flywheel system would have a big
power/weight advantage over the internal combustion engine, especially as
the weight of the tranmission must be added to the IC engine system.


Also in same magazine, Chrysler claims regenerative braking (w/ chemical
batteries) extends range by 8% on a standard SAE driving route (the "C cycle").

      Phil White   Tektronix, Beaverton, OR
USENET:  philip.w.white@tek.COM
 US Mail: Mail Stop 59-432, P.O. Box 500, Beaverton OR 97077-0001

From: david@trsvax.tandy.com
Date: 04 Jan 93 18:15 CST
Newsgroups: rec.autos.tech
Subject: This gives me gas!
Message-ID: <107200003@trsvax>