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The force of 9.8 newtons. torque equated to watts

  1. Oct 10, 2012 #1
    Im makeing a hydro gravity genoratetor I need to no how much air to release to give 800w
     
  2. jcsd
  3. Oct 10, 2012 #2

    berkeman

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    Staff: Mentor

    Welcome to the PF.

    Since it's a hydro generator, why are you asking about air? Not understanding the question so far...
     
  4. Oct 11, 2012 #3
    the air is conpressed down 30 feet of pipe in water released into a bag connected to a bike chain the air rises in the water turning a cogg connected to a genorator.
    How much air do i need to release to achive 800w. Or how many kg of force/air to achive 1w of power
     
  5. Oct 11, 2012 #4

    berkeman

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    That's not how hydro generators work...
     
  6. Oct 12, 2012 #5
    I no
    This is a generator that uses water and gravity .What would you call It ?
    Do you no the answer or not ?
     
  7. Oct 12, 2012 #6

    berkeman

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    I do know what a hydroelectric generator is. You are talking about using pumped air for something, so that would be called something different. It also sounds very inefficient. Standard hydroelectric power generation is very efficient (~90%):

    www.usbr.gov/power/edu/pamphlet.pdf

    Why would you want to have to power an air pump to try to tap power out of your arrangement?
     
  8. Oct 12, 2012 #7

    russ_watters

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    This looks a lot to me like a buoyancy-based perpetual motion machine:

    Step 1: Air compressor inflates a bag underwater.
    Step 2: Bag rises, pulling a cable or chain, which turns an electric generator, which powers the air compressor and produces excess energy.
    Step 3: Balloon reaches the surface, deflates, and sinks. Go to Step 1.

    Is this what you are trying to do, thesleeper? If so, it is not possible, as it clearly violates conservation of energy.

    However, the power calculation: power is buoyant force times the ascent rate of the bag. The problems are:
    1. Buoyant force is variable, since the bag expands as it rises.
    2. Ascent rate is difficult, since it depends on the drag of the water and is probably going to want to be a pre-selected value to give you constant RPM in your generator.

    Figure for a rough guess, you'll want the bag to rise at most 1 m/s, so you'll need 800N of buoyancy, which based on water's weight density requires .08 cubic meters of displacement. Pressure is determined by starting depth.

    And if this is about perpetual motion, we'll probably need to lock the thread...
     
    Last edited: Oct 12, 2012
  9. Oct 14, 2012 #8
    Hi Russ
    This is not a perpetual motion machine .
    The compresser is powered by a wind turbine and sola panel.
    Charging a 12 v battery .
    The bouyancy power is an alternative when no wind or sola.
    In theory can bouyancy force run a asinchronised generator to power a microwave 800w if so how much air needs to be released at 10m to achive 800w.
    Or should I work backwards shaft torque is x bouyancy force is y ascent rate is z start depth 10m so y + z = x
     
  10. Oct 15, 2012 #9

    russ_watters

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    .08 cubic meters, at any depth. But it'll need to be deep in order to give you more than a few seconds of power.

    This is not a great way to store energy.
     
    Last edited: Oct 16, 2012
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