Electric vehicle

[Doug Rorem]

>> Date: Thu, 15 Aug 1996 22:38:31 -0500
>> From: Ryan Minnig <Candyman at vax1.mankato.msus.edu>
>> Subject: re: Electric vehicle
>> George M. Dailey wrote:
>> 
>> 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
>>

I think you're somewhat generous with the 25% loss on the lead-acid batteries.
It was my understanding that you lost somewhere around 50% of the energy you
put into them to heat, etc. before getting it back out. That's why
there's interest in other energy storage forms -  flywheels, hydraulic
accumulators and motors, etc.  You pretty much have to rely on wall current
to charge the batteries rather than charging on a hybrid vehicle due to these
losses, and have the engine-generator provide the power needed for cruising
speed.

--
Doug Rorem
University of Illinois at Chicago         (312)-996-5439  [voice]
EECS Department  RM 1120                  (312)-413-1065  [fax]
851 S. Morgan Street                      (708)-996-2226  [pager]
Chicago, IL 60607-7053                    rorem at uic.edu