From: ems@michael.apple.com (E. Michael Smith)
Subject: steam electric hybrid ...
Organization: Apple Computer Inc.
Date: Fri, 20 Nov 1992 18:26:34 GMT

Thinking a bit more about a steam/electric hybrid ...

How big would a steam turbine and generator be for, say 10-15 kW?

I would expect it to be far smaller than the mass of batteries
it would replace in a pure electric car.  

Assumptions:  An electric car would take about 10-15 kW to run at
freeway speeds.  An electric car would need about 20-30 kWh of
batteries to have a decent range (100-150 miles).  20 kWh of batteries
is about a ton of lead/acid traction batteries.  An acceptable range
for the electric-only mode of a hybrid would be about 20-30 miles (that
would get me to work and back each day, and do most trips 'in-town'
for most folks.

So that leads to the conclusion that about 700 lbs of batteries would
be needed for a hybrid, a weight savings of about 1500 lbs.  Given that
a 10 kW portable generator is far less than 1500 lbs. and of a physical
size that it could be stuffed in the typical space under a hood (if it
were taken out of its mounting cage ...), I think there is evidence that
the concept if physically achievable.

So where are the technological 'gotchas'?  

Complexity?  I can't quite see how a simple steam turbine/generator with
flash boiler for 10 kW could be any more complex than a modern IC engine
with turbo & intercooler & smog gear & ...  Heck, wasn't the Tesla design
for a turbine just recently reserected by someone in a new and improved
form?  (It was, basically, a set of disks on a shaft with steam spiraling
radially between the rotating disks.  Very simple...).

Efficiency?  Fuel being burned external to the boiler will burn cleaner,
but do you loose too much energy in the boiler/turbine/generator/motor,
and occasionally battery charge/discharge, cycle?  Would CAFE kill it?
Given that commercial power steam plants can get to very high efficiencies
I have trouble believing that this is a killer... but maybe it would
cost too much to make small plant that efficient?

Scale?  Is it all a matter of scale?  Would a 10 kW turbine have too
much heat loss or turn at such a speed that it can't be easily coupled
to a generator?  Or be so hard to machine that it would cost the same
for a 100 kW unit as a 10 kW unit?

The idea of an external combustion generator onboard an electric 
hybrid solves a bunch of problems (low smog, lighter weight than
an all-electric, good acceleration from batteries, good efficiency
from turbine, long range on fuel, all-electric mode for short trips, etc.)
so where does it fall down?

At the scale of 10 kW, which electric generating process is most 
efficient, clean and least costly?  Steam turbine, fuel cell,  or ???

Maybe I'm going off the deep end on this, but the idea of three 
gallon size objects under the hood (boiler, turbine, generator)
in exchange for 1500 lbs of batteries, providing an unlimited
range with very low smog production is rather appealing ...

I think it even solves the condenser problem, since at the scale
of 10 kW, I'd expect the condenser to be on the same order of size
as a present IC engine radiator...

-- 

E. Michael Smith  ems@apple.COM

'Whatever you can do, or dream you can, begin it.  Boldness has
 genius, power and magic in it.'  -  Goethe

I am not responsible nor is anyone else.  Everything is disclaimed.