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Power generation using buoyancy, gravity and compressed air

  1. Mar 23, 2012 #1
    Hi all, this is my first post. I was wondering if it would be possible to use a deflatable/inflatable bladder inside a housing with an air valve at the top and bottom of said bladder secured through the housing. The housing material would be heavy, placticised metal or stainless steel. This housing would travel up and down jnside a guide. The guide would be part of a complete frame secured under water either inside a container or in a body of water ie: ocean. The frame structure would have a compressed air chamber with air lines running to the top and bottom. When the bladder is deflated it would sink traveling down the guide to the bottom of the frame docking onto the bottom air line with the valve in the bladder housing. The airline would release compressed air into the bladder inflating it. The docking mechanism would release the bladder housing allowing it to rise through the guide to the top of the frame structure again docking with the top airline. Here the bladder housing would be deflated and the docking mechanism would release allowing the bladder housing to sink. The bladder housing would have magnets attached and the guide would have a wire coil attached around it.
    I am not very educated and there are many questions of this idea I can not answer as how compressed air acts under water, How long/tall could this structure be, could the deflated air be saved and reintroduced to the compressed air tank? I know the magnet and coil principle is used to produce electricity but would this idea be workable? I appreciate your comments and if it is bunk i accept the views of you learned lot and hope to learn a little more on this topic. Thanks
  2. jcsd
  3. Mar 23, 2012 #2
    You would lose energy from doing this and would not be a suitable power generator.

    The main reason is that you would expend more energy compressing the air than you would get back in the end. Even if you add all kinds of fancy tricks (magnetism, gravity, etc...) you are actually making the system less efficient because of friction.

    You should probably read up on thermodynamics and perpetual motion machines type 1 & 2.
  4. Mar 25, 2012 #3
    There's no point of using an ocean: if you have compressed air you can run it through a displacement engine and it is the same result except much simpler.
  5. Mar 26, 2012 #4
    Thanks for the feedback. Where would the friction develope? The bladder housing should rise and fall in the guide easily as it would be a smaller size and as far as the fancy tricks go gravity, buoyancy and magnetism are not so much fancy as they are constant forces that are used in many applications. I will read up your suggestions though as I want to learn. Thanks again.
  6. Mar 26, 2012 #5
    Yes, I suggest you learn about perpetual motion machines and compare your contraption with some examples of PMMs.

    I'm not saying yours is necessarily, but you have to think of the entire "life-cycle" of what you are trying to do INCLUDING pumping the air in to begin with.

    Here is an excerpt from wiki:
    A perpetual motion machine of the first kind produces work without the input of energy. It thus violates the first law of thermodynamics: the law of conservation of energy.

    A perpetual motion machine of the second kind is a machine which spontaneously converts thermal energy into mechanical work. When the thermal energy is equivalent to the work done, this does not violate the law of conservation of energy. However it does violate the more subtle second law of thermodynamics (see also entropy). The signature of a perpetual motion machine of the second kind is that there is only one heat reservoir involved, which is being spontaneously cooled without involving a transfer of heat to a cooler reservoir. This conversion of heat into useful work, without any side effect, is impossible, according to the second law of thermodynamics.
  7. Apr 2, 2012 #6
    I came across an interesting YouTube video. Someone came up with this idea already (and I thought I was so clever). I didn't know how to post the link but its under HIDRO+ Emission Free Renewable Energy. This is pretty much the exact idea I've tried to explain and it seems that he has it working. Give it a look and see what you think. Thanks
  8. Apr 2, 2012 #7
    This is not a perpetual motion machine, but where do you get the gas, how much energy does it cost to pump it in and out of the reservoir, what are the efficiencies of each step of the process, what is the net energy exchange (output - input)?

    I have a hunch that calculations will show a negative net energy (as in you lose energy by doing this).

    If only, somewhere on earth, there was this huge reservoir of compressed gas (stored energy) that could be used as the source for this power generator. However, if such a reservoir was discovered (like methane gas), there would be more efficient uses for this energy (like running a line into a chemical plant for processing).
  9. Apr 2, 2012 #8


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