London Banter - View Single Post - Electric or Hybrid Card or something car, suggestions?

Sales! · April 13th 04, 01:53 PM posted to uk.rec.cars.misc,uk.transport.london

Apparently on date 13 Apr 2004 05:37:26 -0700, (Ian
Johnston) said:

(D.P.Round) wrote in message ...

(Electric motors don't *have*
to suffer transmission losses because they can be designed to pretty
much any set of torque and speed specifications.)

Which is fine if you want a particular torque speed combination only.
In an application like a car, where you need to have power delivered
across a large speed range, efficiency considerations may well require
a gearbox. And anyway, unless the motor(s) are built into the driven
wheels, there will still be transmission losses.

Not wanting to support electric vehicles particularly, there are some features
which make perfect sense. Your energy comparison is ok, but the 48000 Kj of
energy in the petrol would have to then be converted into kinetic energy of the
vehicle. A petrol engine won't deliver 48000, it won't even deliver 24000, it
will end up more like 12000 Kj of vehicle motion, what with one thing and
another.

Of course, if taxed at the same rate, mains electricity would then cost four
times as much as the petrol, so it balances out much the same anyway.

And the electricity, that's already useable energy so you can use it to power
something like linear accelerators acting on the disc brakes where better than
90% of the energy does turn directly into forward motion, saving any
transmission losses which you do definitely have with a combustion engine
design.

There are also some other gains from the petrol engine, notably the heat which
most of the energy ends up as, can be used to keep the passenger compartment
warm, whcih saves carrying around large amounts of insulation and having to
spend some significant portion of your electricity in heaters, or making the
humans suffer from the cold of a metal box passing through cold air at speed.
This isn't a trivial matter, either, although in hot summer days I daresay it
would be a mere inconvenience and sometimes even an advantage.

The real strength of an electric vehicle is that the motor will be a fraction
of the weight of an equivalent combustion engine, and doesn't need to be
started, you just pump electrical energy into the motor and get instant torque.

The real weakness of it, is how you carry about enough energy. Batteries weigh
far too much for their capacity, and cost a lot more than a fuel tank as well
as needing to be replaced a lot more regularly. Electric motor designs cost a
lot more over the life, because of this, as well as not being able to have
decent range.