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http://www.theherald.co.uk/display.var.2525038.0.0.php?utag'076

Fascinating concept here from GM. But does anybody understand the
thermodynamics behind this? How does using an internal combustion engine to
charge a battery give such efficiency? It seems to me contrary to the normal
entropic laws where you'd expect energy losses at each level of the system -
from the engine, the battery, and the electric motor - rather than just from
the engine as would be the case with a conventional direct drive system. But
maybe it's to do with the charger engine being able to run at a steady state
rather than being put through all the rigours of acceleration and
deceleration. Does anybody have an angle on this? 

Also, at some point, if you're going to be carrying a ton of metal around as
your means of conveyance, you have to hit on the thermodynamic limits of the
energy contained in a gallon of fuel. Beyond that limit further attempts at
efficiency would be impossible for a given type of primary fuel. Does
anybody know what that theoretical bottom line would be for average driving
conditions? It would be interesting to know as that figure would set the
theoretical bottom line for MPG.

Incidentally, I am sceptical of some of the claims for electric
transportation because they rarely factor in the huge efficiency losses in
generating the electricity, or what the source fuels are. For example,
Eurostar claim an astonishing 18g of C02 per passenger kilometre. But they
buy a lot of their energy from France, which means nuclear. Again, does
anybody consider my scepticism on this unjustified? 

Cheers, 

Alastair.
 
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