Nice Car, Nissan Leaf electric car

Discussion in 'NZ Computing' started by William Brown, Apr 13, 2011.

  1. William Brown, Apr 13, 2011
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  2. William Brown

    Matty F Guest

    Matty F, Apr 13, 2011
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  3. William Brown

    Ron McNulty Guest

    But not in the least green....

    NZ peak power comes from fossil fuels. Burning diesel say at Huntly,
    transporting the electricity produced to Wellington, charging a
    battery and then using it to turn the wheels works out at less
    efficient than burning the fuel in a small diesel engine in the car
    itself. And I won't mention the battery replacement cost (money and
    environmental) or the several-hour charging times.

    There is no doubt that fossil fuels will run out some time. But as yet
    we don't have a credible replacement technology. It is a topic that is
    engaging the finest minds in the world today. Unless the problem is
    solved, the 1990s to 2020s will go down in history as the age of cheap


    Ron McNulty, Apr 13, 2011
  4. William Brown

    Boots Guest

    Not relevant when discussing battery-powered devices.

    Please cite the studies that support your assertion that electric
    vehicles are less efficient than petrol/diesel vehicles - especially when
    recharging by means of off-peak electricity generation where the water
    would otherwise be being spilt over the spillway instead of turning

    In case you were not aware of it there are good reasons why Kiwi-Rail
    uses all-electric locomotives over the centre of the North Island.

    (electric traction engines are considerably more efficient at converting
    electricity into kinetic energy than are petrol or diesel engines with
    manual or automatic mechanical transmissions.
    Boots, Apr 13, 2011
  5. Nope. :)

    Not if you use it for around town it's not. Looks like you get ~ 80 to 110
    miles per charge, so more than adequate for most applications. :)
    Now ... how much ? :)
    Bruce Sinclair, Apr 14, 2011
  6. William Brown

    Gordon Guest

    1) OP said peak power
    2) Spilling at hydo dams happens as aoften as we change Governments.

    Okay take 2l of diesel. Lets burn it;

    1) In a diesel engine. 35% efficienty. (Yes it varies, at idle the diesel
    engine is very efficent at turning heat into shaft power.)

    2) Burn in power station. Lets say 40% electricity out the other end. Power
    transmission losses 10%. Battery charging losses 35%. Electric motor loss
    Nil say, although be some small amount.

    So efficiency 0.4*0.9*0.65 = 0.23. cf 30% for the diesel engine, allowing
    for gearbox losses.

    Let us not forget that everyone charging the battery overnight, and
    espically during peak hours will have your lines company very busy putting
    in more lines. More cost to you.
    Gordon, Apr 14, 2011
  7. William Brown

    Boots Guest

    It didn't need to be electrified end to end - only over the part that
    covered the greatest load.
    Boots, Apr 14, 2011
  8. William Brown

    Boots Guest

    You haven't factored in the fact that manual mechanical transmissions are
    inefficient, and automatic ones have even lower efficiency.

    Electric traction is certainly the most efficient way to go.
    Boots, Apr 14, 2011

  9. Most electric cars use a motor to each wheel as electric cars have
    problems with Gear Boxes, too much torque.
    William Brown, Apr 14, 2011
  10. Yes it is: where does the electricty/peak demand generation come from
    (even in NZ): Fossil fuel.

    Yes: the Torque-curve characteristc of a DC machine is excellecnt for
    linear traction applications

    You need to correct for electricity transmission losses, as well as
    the finite battery life (and the energy-cost and environmental impact
    of battery manufacture)
    misanthropic_curmudgeon, Apr 15, 2011
  11. William Brown

    John Little Guest

    Modern gas power stations approach 70% efficiency, so I would expect
    it to be possible to build a similarly efficient diesel station. That
    it's not done I'd assume is because diesel is more valuable for other

    Regards, John
    John Little, Apr 15, 2011
  12. William Brown

    Boots Guest

    Tell us why virtually all locomotive engines are diesel-electric - there
    being no direct mechanical linkage between the engine and the wheels?
    Boots, Apr 15, 2011
  13. William Brown

    Boots Guest

    Since when would anyone with any brains use peek rate electricity to
    recharge night-store heater, let alone an electric car?
    Boots, Apr 15, 2011
  14. William Brown, Apr 16, 2011
  15. Agreed on both counts. :) IIRC, someone in Aus was converting small mazdas
    to fully electric, and they were "only" ~$35k.

    I guess we need to wait for mass production to kick in for the cost to come
    down. Or petrol could go to $25 / L ? :) :)
    Bruce Sinclair, Apr 18, 2011
  16. It was my understanding that a gear box is not required - electric motors
    deliver the same torque at all rpms, and the power used is proportional. So
    the ratio between motor rpm and wheel rpm will be the same no matter how
    fast the car is going.[/QUOTE]

    Maybe. Still need a way to switch from forward to reverse. :)
    Bruce Sinclair, Apr 18, 2011
  17. No, it isn't ... assuming you would charge your electric vehicle off peak
    (eg overnight). Peak is, as you say, a major problem, but not an
    insummountable one.

    I recommend a (free !) net book called sustainable energy without the hot
    air (look for that or sewtha.pdf). One of the ideas proposed is to use a
    national fleet of electric car's batteries to even out peak and off peak. :)

    It's a fine thought provoking read with numbers and written assumptions and
    simplifications (in case you want to calculate for yourself :) ).

    Bruce Sinclair, Apr 18, 2011
  18. William Brown

    Matty F Guest

    Trams have gearboxes, i.e. they have boxes with gears in them. Just
    one ratio! One motor drives two wheels.
    To go in reverse the current is switched the other way.
    The two or four motors may be connected in series or parallel.
    Matty F, Apr 18, 2011
  19. William Brown

    Ron McNulty Guest

    Not quite. A stalled electric motor (i.e. at startup) has a very low
    resistance and demands a lot of current at a relatively low voltage.
    As the speed rises, the current requirement drops away, and
    the voltage across the motor increases. It is not easy to build a
    controller that can service both requirements from a power source like
    a battery (which prefers a constant voltage scenario).

    The traditional way to handle this is to put the rotor & stator in
    series on startup, and switch to parallel once speed builds


    Ron McNulty, Apr 18, 2011
  20. You're unfamnilar with load-flow analysis, and domestic tarriffing, eh?
    misanthropic_curmudgeon, Apr 18, 2011
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