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Generate Electricity through compressed air...is it possible

Discussion in 'Alternative Energy' started by aniphics, Nov 11, 2011.

  1. aniphics

    aniphics New Member

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    Well guys , went through the posts, it is interesting. I also want to generate electricity by compressed air, yes the question is from where to get the compressed. I might be wrong but can we get a huge cylinder (like 20 feet long and 4 to 5 feet in diameter) size and diameter can vary, insert a real heavy stainless steel piston , place it vertically along the building and let gravity do its work. I believe when the piston falls it will produce enough compressed air to be stored in the storage tank underground. To take the piston back up we can use a gearbox with a slow motor. It can take few hours to raise the piston. Since the storage tank is underground the the temp around the tank shall be a bit higher than the compressed air in the tank, which will make the compressed air in the tank to expand and produce more pressure...

    Any suggestions guys...yes the measurements of the cylinder needs to worked out, so that it can produce enough compressed air in one , two or three falls in 6 to 12 hours....
     
  2. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Hi aniphics. Thanks for posting a new thread :D

    I am wondering about your suggestion, where you say that to lift the piston you could use a gearbox and a slow motor, why not just use the electricity that drives the motor? I don't imagine the compressed air will generate more energy than what is already supplied to the motor. I think a question similar to this one was asked in the older thread, as well.

    What do you think?

    Regards,
    Der Strom
     
  3. aniphics

    aniphics New Member

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    Thanks storm, yes you are right, to lift the piston electricity to be used to run the slow motor and the gearbox is used to reduce the power intake. (same system used for Car lifts at workshops or the pull chain system, by which you can divide the load of the piston on variable pulleys and supply less energy to lift more weight but it is slow).
    The electricity to run the motor will come from the same source generated by the stored compressed air at the underground tank. As you mentioned "I don't imagine the compressed air will generate more energy than what is already supplied to the motor." The energy generated can be increased by increasing the length and diameter of the cylinder and specially the weight of the piston, because the piston will free fall, since the cylinder is vertically positioned, so almost no energy is required for the piston to come down, yes it will face air resistance, from the air present in the cylinder but the weight of the piston will compress and push the air in the air tank...(MDI the Guy who produced the air car) has developed a electric generator which can produce 250KW for 4 hours with one (6 feet long 12 inch dia) compressed air tank..

    Off course there are lots of calculation needs to be done to make this workable,....

    Needs more brainstorming ...so please put in your suggestions....
     
  4. dave

    Dave New Member

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  5. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    Well, there are a few problems with this idea:

    This is beginning to sound like perpetual motion, which is not possible. Too much energy will be wasted and it will not be efficient.

    This simply re-phrases what I posted above. If the compressed air doesn't generate as much energy as what is supplied to the motor, it is simply wasting it. Therefor, the machine is not only useless, it is also a hindrance.

    Just remember that increasing the weight of the piston will increase the stress put on the motor, making it use up even more energy. Either way, it's a lose-lose situation.

    Hopefully this gives you a little more to go on. Feel free to experiment, but don't expect it to work. I would be very surprised if it works for even a short amount of time, but please fool around with it. It will be a great learning experience either way :)

    Best wishes,
    Der Strom
     
  6. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It's not 'beginning to sound like it', it is simply yet another, obviously non-working, perpetual motion scheme.

    It doesn't matter if you use a geared motor, you still use the same amount of power to move the piston back up, and probably more due to losses in the gearbox.
     
  7. Jugurtha

    Jugurtha Member

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    If I were you, I would *buy* four guys, enslave them, and transform them into human hamsters generating electrical energy.. You know, with the wheels and all.. And still, have some change left.
     
  8. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    All the calculations in the world and then some wont make it work. Physics is physics and it only obeys its rules and mathematics not ours.

    In this reality no. Storing 1 Megawatt hour of energy in compressed air in a tank of that volume is not possible. In fact that tank filled to 100% capacity (35.25 gallons) of gasoline would contain about 1.17 Megawatt hours of energy if it could be burned at 100% efficiency.

    Maybe a 250 Kw for 4 minutes but not four hours. :(

    Sorry but the compressed air car guys are more scam artists than engineers or scientists.
     
  9. Techowest

    Techowest New Member

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    Sorry don't have the answer but another question?
    Theoretical project question.

    How might i calculate the power output in k/w from converting 1,000 cubic meters of compressed air at 1000 psi (Constant)

    Using a rotary turbine connected to a generator for instance.

    Appreciate your advise
     
  10. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    The motor may draw little power but as you say it may take hours to lift the piston back up. All that time adds up and in the end you would be using more power than with a big motor that lifts it in minites.
     
  11. picbits

    picbits Well-Known Member

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    They do this kind of thing in some large hydro-electric generators. During the day when demand is high, they use a reservoir at the top of a mountain to gravity feed the generators. Then during the night when demand is low and there is an excess of generated power from alternative sources (i.e. nuclear) they pump the water back up to the reservoir using cheaper rate electricity.

    Obviously pumping the water back up requires more energy than is harvested when it comes back down but its a good way to have a backup source of energy for peak times.
     
  12. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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    Air is a compressible gas. There is no need for the piston.
     
  13. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Then how would you compress it?
     
  14. picbits

    picbits Well-Known Member

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    In a large tank !
     
  15. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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    With an air compressor.
     
  16. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Which has a piston (or more than one).
     
  17. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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  18. picbits

    picbits Well-Known Member

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    Not if its a rotary vane or screw compressor :p
     
  19. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Which are FAR rarer than piston ones :D
     
  20. picbits

    picbits Well-Known Member

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    If you feed my wife Garlic and/or Onions, she produces an unending supply of compressed air ........
     
  21. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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    Found this about storing energy with compressed air CAES http://en.wikipedia.org/wiki/Compressed_air_energy_storage. It mentions the heat loss that always accompanies compression.

    I was looking for an article on the Ranque-Hilsch vortex tube when I found it. A reminded me of B and while looking for B I found info on A. That sort of thing :)
     
    Last edited: Nov 25, 2011

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