Electric vehicle

[Ryan Minnig]

George M. Dailey wrote:
> 
> At 05:03 PM 8/9/96 -0700, you wrote:
> >.... Hmmm, let's see...  How about electric motors
> >mounted in the hubs of each wheel that will not only be motors, but
> >regenerative brakes ... Let's put an onboard turbine engine to
> >generate power for these things so we have some acceleration,...
> 
> Consider this, 4 off the shelf electric motors. Ridgidly mounted to chassis
> and connected to the wheel via cv joints.  A battery pack per current
> electric vehicle standards, and one off the shelf small gas engine DC
> generators. I think you know where I'm going. Generator is sized to propell
> the car at 55mph, stand alone. Generator and battery pack combined might
> give you 0-60 in 3 seconds.  Of course, all of this would require
> micro-processor control.  Ok experts, what are the real world physical limits?
> 
> Thanks, GMD

I can speak from experience with electric vehicles.  I was the
electrical man for TWO solar electric vehicles for Mankato State Univ,
in MN for Sunrayce '93 and Sunrayce '95 respectively.  Battery
technology sucks.  So does Solar power.  The most affordable
photovoltaics per energy output cost ~$5000 for 8m^2 which produces 1KW
of electric energy, not good only about 12-14% of the energy hitting the
earth from the sun.  Anyway on to your question.  Since batteries suck,
the only affordable batteries are lead-acid which are heavy and have a
very low energy density, the most reasonable thing to do is just build a
car that uses a 5hp gas motor.  Sure electric is very clean, but
performance is terrible.  Consider this, if you run a gas motor to
charge the batteries and run the electric motor you only get about 75%
of the energy that the gas motor outputs.  Try to follow me.

Gas -->  output to shaft.
100%     -2% from mechanical resistance  =98%

Gas -->  Generator  -->       Electric motor  -->    output to shaft.
100%    -5% elec. resistance  -5% elec. resistance   -2% from mech.
resistance  =88%


Gas -->  Generator  -->  Battery sotrage -->       Electric motor  --> 
output to shaft.
100%   -5% elec. resist. -25% chemical resist.   -5% elec. resist.   
-2% mech.  =63%

In each instance follow the path that the power has to change states. 
Remember NOTHING is 100% efficient.  Even if the motor and generator
were made form superconducting wire, there is resistance from the
contact points and very very very small ohmic resistance in the wire. 
Even just using a belt or chain drive loses about 1-5% due to friction
in the chain or belt.  We will eventually have to use someithing other
than fossil fuels, but the technology has to come a long way.  We still
have a lot to do with gas engines.  With all the refinements made to
engines we only get about twice the gas mileage as compared to a Model A
FORD.  

I don' mean at all to shoot your idea down, I think it is great that
someone else is interested in doing something innovative, these are just
some of my experiences and the hurdles to overcome.

Any other thoughts??     -Ryan