Hello guys so I have this idea of mine which I can't get my head around and I need someone to tell me why it won't work, so let's say you have a fully pressurised tank of air and you blow that pressurised air at a turbine connected to a generator, obviously the generator will then start to generate a voltage and when connected to a battery it will charge it, what if you then use that charge from the battery to spin a motor that spins a piston which then repressurises the tank and it creates a cycle again, and also the pressurised air tank at this point is still got some of it's original pressurised air left inside and it won't get used up so fast, think how long it would take to empty a full can of deodorant, also the generator is a 3000w genarator spinning at 2000RPM and the motor is only 200W also spinning at 2000RPM, and even if you include all the losses such at heat, mechanical movement on friction and even sound, then the generator could be outputting let's say 2500W and that's still enough power there to supply the motor, you know what I mean, thank you guys and I hope someone can help me out here.


closed as off-topic by Norbert Schuch, Bosoneando, John Rennie, RedGrittyBrick, user36790 Sep 14 '16 at 8:27

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    $\begingroup$ If you actually do the calculations you'll quickly discover the flaw. $\endgroup$ – lemon Sep 14 '16 at 8:09
  • $\begingroup$ I like to see how things work or why is doesn't work, I don't like to see something work or not work and not knowing why. You know what I mean, could you tell me how it wouldn't work please. $\endgroup$ – ajay123 Sep 14 '16 at 8:16
  • $\begingroup$ @ajay123 Note that mainstream physics don't allow for an infinite energy source, so if you want to ask a question here, you know that there is a flaw in your reasoning. Please see meta.physics.stackexchange.com/a/6097/40681 on how to ask on-topic questions in such a case. (The idea: the question shouldn't be "please find the error" but you should do the work, find the point where your calculations or modelling differ from what would be agreed by mainstream physics. Then if you don't understand why your model is not applicable in that point, you can why it isn't.) $\endgroup$ – JiK Sep 14 '16 at 9:59
  • $\begingroup$ I wonder if you use the electricity obtained from the generator to repressurize the tank, then what's its use? You cant ultimately use it to power any device.It will simply be a machine converting pressure energy into heat energy. $\endgroup$ – Amritansh Singhal Sep 14 '16 at 12:16

Please do the calculations with patience. You'll find out that the energies don't add up. You'll always end up with lower output than what you input. This would be because of several reasons like friction, Eddy current loss and you also need to consider that if you're turning a turbine in magnetic field there'll be an automatic force generated by the current that will oppose the motion of the turbine. So eventually the energy will go down to zero when you let it run for some time(the time scale may be anything depending on the specs of the equipment used). I'm sorry if I'm unable to put it into elegant words. But this is the basic idea.

  • $\begingroup$ Thank your @Pratteek Das, I really appreciate the reply, and I am now starting to get a more understanding of this now, so can you tell me also when you add a load to a generator does the magnetic field get stronger which causes more resistance on the shaft and will is be harder to spin the shaft around this point. $\endgroup$ – ajay123 Sep 14 '16 at 8:28

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