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Water lifted by weight?

  1. Jan 31, 2007 #1
    water lifted by weight??

    Well I was just roaming through some renewable energy options and came across hydraulic energy. I realize that this usually requires a dam, stream, river, and or a waterfall of some kind at the desired location and typically is used in larger applications.

    What I was wondering is could it be possible to do it with water holding tanks? Tank 1 would be elevated higher with a minimum downward pitch being 25 degrees, the water travels down to Tank 2 which is significantly bigger and is already 3/4's full. As the water from Tank 1 begins to travel into Tank 2 it reaches full, a sensor is triggered and a valve opens in the bottom. The weight from the water pushes it back up to Tank 1 and you create a continuous cycle

    Any insight would be greatly appreciated
  2. jcsd
  3. Jan 31, 2007 #2


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    No, a continuous cycle with no net energy input would be perpetual motion, which we do not waste time discussing here on the PF. Hydraulic energy sources work in real life because thermal energy from the sun fuels the evaporation stage of the water transport.
  4. Jan 31, 2007 #3


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    Draw yourself a picture. It should be evident why this doesn't work.

    Just make sure you get one basic point about pressure: pressure depends only on the depth of the water. With that fact in mind, you should be able to see that it is not possible for a tank of water to push water out the bottom and back up above its level.
  5. Feb 1, 2007 #4
    I have seen some sites with a water spring on a hill, but yet the main source of water was below it. If it was the weight I thought perhaps you could copy what nature does but on a smaller scale.

    I suppose even if you put solar pumps into the mix you are useing energy to create energy, there are ram pumps but too much water waste.

    Anyway thanks for the insight, thought it would be a cool way to recharge a battery bank...Someone would have surely thought of it already though
  6. Feb 1, 2007 #5


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  7. Feb 1, 2007 #6


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    What you have seen uses the motion of the water running down hill to pump a fraction of it uphill to where it needs to be.
  8. Feb 1, 2007 #7
    A short walk from where I live the canal that served the stone mines runs parallel to the river. There is a lovely little pumping station thats been there since before the 1800's that pumps water from the river into the canal using the force of the river. It's been doing it for 200 years so has probably covered it's installation costs by now. I would have thought that if it was possible to create free power from water they would have done it by now.

    This is the 3rd or 4th water based perpetual motion thread I have see in the last two months (not having a dig at you Rand, curiosity is what got Einstein where he is today... dead, hmmm maybe not the best analogy)
    Is this common or are we in a post Christmas "I hate work and will now make my fortune by selling perpetual motion machines" type thing?
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