L David Matheny said:
<snip>
I agree with most of what you say. But the essential feature of a hybrid
for city driving is regenerative braking. Capturing the car's kinetic
energy
and then restoring it as the car accelerates back up to speed is what
allows
high city MPG. And it shouldn't take a very large battery for that.
More important for fuel efficiency is probably the ability to wait until
there is really a load for the engine before running it. At low power levels
combustion engines - especially otto cycle engines - are very inefficient.
Darned Carnot ratio. Diesels are better about that.
You're very right about the storage size for regeneration/acceleration. For
passenger vehicles the gross weight is a design number, and choosing a
target top speed gives the amount of energy needed for that mission. I think
that's why Honda went with ultracapacitors for their concept car; if you
don't need massive storage and the ability to hold it a long time, the high
charge/discharge rates of capacitors are very attractive.
Add me to the list of people who would love to see a Diesel/electric
hybrid.
I think Toyota is working on that for the European market.
