I found this info on fueleconomy.gov
Hybrid-electric vehicles are primarily propelled by an internal combustion
engine, just like conventional vehicles. However, they also convert energy
normally wasted during coasting and braking into electricity, which is
stored in a battery until needed by the electric motor. The electric motor
is used to assist the engine when accelerating or hill climbing and in
low-speed driving conditions where internal combustion engines are least
efficient. Some HEVs also automatically shut off the engine when the vehicle
comes to a stop and restart it when the accelerator is pressed. This
prevents wasted energy from idling.
Ok now my question is why not diesel engines? Just think what your mpg's
Maybe it cant be done with a diesel engine? (would the shutting off of the
engine while its idling hurt it?)
You would think they could do something if its just a battery assist .
A hybrid that includes a diesel motor (instead of a gasser) does not reap
the advantages of the low-speed assistance that an electric motor provides.
A diesel typically has greater torque at lower RPM than a gasser does, so it
does not need the assist from the electric motor at low RPM's. Diesels also
use only 1/3 of the fuel a gasser does at idle so it won't conserve as much
if the motor is switched off at idle. In addition, a diesel takes more
electricity to start due to it's higher compression so you won't gain much
A more efficient set-up involving diesels would be similar to that found on
trains and ships - a diesel-electric power plant. In this type of plant,
the diesel turns over at a constant speed and spins a generator (diesels are
far more efficient at constant RPM's), which in turn feeds either a bank of
batteries or directly into an electric motor which turns the wheels (or
propellor, as the case may be). This would eliminate the need for much of a
transmission since electric motors have a very wide RPM and torque range,
and the throttle for the diesel could be completely automatic, increasing or
decreasing as it perceived the need for either more juice to the electric
motor, charging the batteries, or letting the batteries supply the motor and
let the diesel idle down. The traditional foot pedal accelerator would
control the juice to the electric motor, and the computer controller would
decide if that juice would come from either the generator or the batteries.
Combine that with regenerative braking and I think it would be quite
Cheers - Jonathan
I would beg to differ on that, Big Al. The primary reason
diesel-electric locos came into being was the NEED for
smooth but powerful transfer of horsepower to the driving
wheels (automatic trannys or stick shifts coupled to big-ass
diesels were out of the question). Even the monstrous dump
trucks at open pit mines benefited from this combination
(one diesel-generator-motor for each wheel).
For a much smaller application such as a sedan or SUV, a
small turbo-charged diesel engine coupled to a generator
1. provides power to electric motors that drive the wheels
(2WD or 4WD)
2. provides power to charge a bank of batteries that acts as
a float source of power
3. provides power to vehicle's electric components
can be a very efficient setup. If the float source is
small, the diesel will have to run almost continuously. If
the float source is large, the diesel can be shut off, then
be restarted when the float source decreases to a set
threshold. A diesel engine is ideal because of its
efficiency compared to a gasoline engine -- a turbo-charged
diesel just takes it up another notch or two. Use
computer(s) to monitor and control the setup for optimum
performance. An electric motor is ideal because of its
ability to convert electricity into mechanical energy
quietly, very smoothly, and very very efficiently.
Exciting times coming up ahead with the price of gas/diesel
going through the roof... necessity and invention (past the
theoretical part, at least).
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