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Permanent magnet alternators on Japanese vehicles?

  1. Jun 23, 2009 #1
    I am incorporating a solar chimney in my house build in Thailand, this will have a venturi to create the suction for removing warm air from the building and I intend to use this high air speed area to generate electricity. As air speed will be dependant on the Sun and not the more fickle wind [here in Thailand anyway] I don't anticipate the problems associated with low air speeds and am therefore considering a vehicle alternator. I have read that a PMA [permanent magnet alternator] is the most effective type to use but are these fitted to production vehicles and does anyone know of a Japanese manufacturer who fits them so I can look in local scrap yards; which are full of Jap vehicles here.
  2. jcsd
  3. Jun 23, 2009 #2


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    When you suck the air out of your house, the air from outside will come into the house to replace it. When it does that surely the fan will stop rotating because the temperature difference will be lost?
    In any case, this effect would only happen in for a short time in late afternoon when the house is hotter inside than the air outside.
  4. Jun 23, 2009 #3
    And alternators are only good at high speeds.
  5. Jun 23, 2009 #4
    I was hoping for a knowledgeable response to my question rather than an opportunity to explain how a solar chimney actually works; simpler if you go to Wikipedia and look up 'Solar Chimney'.
  6. Jun 23, 2009 #5
    No idea what a PMA is then!
  7. Jun 23, 2009 #6
    Actually, just about any generator is only good at higher speeds. If you don't operate at higher speeds then you don't generate any voltage. You will probably need a gearbox of some sort going from your turbine to generator/alternator.

    I would imagine any of the higher end more pricey models would have PMAs in them.
  8. Jun 23, 2009 #7


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    Kenward, have you made any estimates of how much energy this is expected to generate?

    Personally I'd be surprised if you were looking at more than about 10 watts continuous output power, but I don't know the size of the dwelling or solar chimney. I'd imagine that a 10W solar panel would be easier and cheaper if that level of power is any use to you.
  9. Jun 23, 2009 #8


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    Wikipedia says that :
    "Automotive alternators invariably use a rotor winding, which allows control of the alternator generated voltage by varying the current in the rotor field winding."

    That means no permanent magnets.

    I've heard of permanent magnet washing machine motors being used as generators. The good ones are apparently the flat "pancake" type.

    How tall are you thinking of making this solar chimney?

    I suspect there might be a better thread like General Engineering for the solar chimney aspects of this question.
  10. Jun 23, 2009 #9
    I suggest building your own generator/alternator of the type used in DIY windmill setups. There are several free plans available on http://www.instructables.com/
  11. Jun 24, 2009 #10
    Hi uart

    I am looking for 50-60Watts. As a basic car alternator, not a high performance or PMA unit, can generate 60amps at 12V at optimum RPM I don't quite follow your 10 watt limit. I am no expert and understand the many areas where generated power can be lost, or not generated if you can't make the RPM, but please let me know why you believe such a low output would result.
  12. Jun 24, 2009 #11
    Thanks for your follow up:

    The washing machine motor is a helpful suggestion for future investigation but to 'prototype' the system I would prefer a 'plug n play' unit such as a PMA vehicle alternator, I know they do exist but just need to track one down that can be inexpensively procured as a test subject.

    For commercial applications height is a big factor in generating air speed but nobody wants a 30 metre chimney sticking out of their house roof; or a 300m one as proposed in Australia. Therefore it is more a factor of efficiency in capturing the infra red waves via a collector; the resultant heat generated seeks an escape route and a carefully designed venturi will theoretically generate very high air speeds which can be harnessed to drive the alternator. I am not expecting to hit the ground running on this but know it has the potential.
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