From: dannyb@panix.com (Daniel Burstein)
Newsgroups: rec.autos.tech
Subject: random musings re:EV
Date: 28 Dec 92 01:27:08 GMT
Organization: Panix, NYC

(no flames please, I'm new to this stuff)

1) re: gasoline exploding:  I'm a paramedic in NYC and have witnessed MANY
car crashes.  It is quite rare for the gasoline to leak more than a few
ounces except in extremely rare and/or high velocity crashes.
  when it does leak, it is also quite rare for it to ignite.
  and.. when we -do- get fires, we do NOT (under normal circumstances) get
any serious explosions.
  
  We do, however, see numerous SMALL explosions which are more of a noisy
annoyance than anything serious.  There are all sorts of contained
locations in the car (i.e. tires for one) in which pressures will build up
until the container is breached.
  
   But again, the hollywood type of explosion is EXTREMELY rare.

-----

   On the other hand, there is what is referred to as a BLEVE, or 
     "Boiling Liquid Expanding Vapor Explosion."  Not usually a problem
with cars, but this can happen in, say, a tanker truck (or railroad) accident.
  
  If you take a container of propane liquid and keep heating it, you'll
get to a point where courtesy of a) the increasing pressure, and b)
weakening of the walls, there rwill be a massive and -rapid- failure of
part of the container, causing a huge and sudden fuel leak.  The results
are quite dramatic....  
    Incidentally, in cases of this sort, a water spray is aimed at the
container to keep it cool, but NOT to put out the fire.  A volunteer (in
the highest level of the meaning) firefighter positions the hose, locks it
in place, and runs away)

-------
2) Energy needed to maintin highway speed;

Let's see, my car needs about 2 gallons/hr to cruise along the highway. 
Using the back of an envelope, that's 200,000 BTUs/hr.  Figure on about
25% motor efficiency, so that's 50,000 BTU/hr.

damn, don't have my CRC at hand, so coninuing with back of envelope.
  
roughly 3.5 BTUs /watt, so 16Kw needed 

A horsepower is something like 700 watts, or .7 kw, 
so 16/.7= approx 22 Horsepower needed

note: These figures are -very- rough, but certainly suggest that yes,
indeed, the figure of a 5.5 hp neede by a well tuned Porsche might very
well be correct.  (BUT remember to multiply by four to cover engine
in-efficiencies)

----------

Energy storage: Capacitors

Seems to me there have been some pretty fascinating advances in capacitor
technology courtesy of the Strategic Defense Initiative.  Does anybody
have any info which can be shared with the public as to how much energy can be
stored in something the size of a car battery?  Figures from ten years ago
are hopelessly out of date.

Storage: flywheels

the problems with catastrophic failure have been well described here.  But
a question (or suggestion): Back in the days when we had astronauts using
single-fly space capsules, they had a heatshield attached which diverted
atmospheric frying through the use of "ablative" coatings.  Perhaps
something of this sort, enmeshed in a high tensile strength blanket, could
sufficiently slow down the destruction so as to give the people nearby a
chance at survival?  Afraid I don't even have a back of envelope for this.

Thanks, 
Danny
(dannyb@panix.com>
<dburstein@mcimail.com>