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Gravitational Potential Energy

  1. Sep 29, 2011 #1
    I want to propose that Gravitational Potential Energy (GPE) is a renewable energy input source but I feel maybe GPE might not be accepted as part of the surroundings acting upon the energy boundary of a system.

    What are the rules of the energy boundary that umpire what is allowed and disallowed? If you know a reliable textbook or article, please let me know
  2. jcsd
  3. Sep 29, 2011 #2


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    Staff: Mentor

    Welcome to PF!

    The concept you need to look into is conservation of energy. Just like with a spring, GPE can't be a continuous source of power: use it once and it's gone unless you use some other source of energy to recharge it.
  4. Sep 29, 2011 #3


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    But it could be a renewable source, depending on what you're actually talking about. Gravitational Potential Energy is a bit general and we already take advantage of that principle in some forms.

    Hydroelectric dams, for example. You're taking advantage of the change in potential energy of water when it's transported to high elevations by snow and rain and then flows downhill again in the rivers.

    The trick is to have some naturally occurring cycle that you can take advantage of since transporting it to a higher gravitational potential energy level yourself would use up more energy than you reap when it comes back down (due to the inefficiency of our means - if we had perfectly efficient machines, we would break even instead of lose on the deal).
  5. Sep 29, 2011 #4
    I want to use a larger opposing GPE to renew the expended GPE so my energy input is GPE. I can't find any energy boundary rules that forbid me from using GPE as an energy input
  6. Sep 29, 2011 #5


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    Staff: Mentor

    Again,(worded differently...) GPE is not an energy input, it is an energy capacity. So the rule you appear to be breaking is conservation of energy.
  7. Sep 29, 2011 #6
    if i can describe my process in a way that is within the constraints of conservation of energy, may i ever define GPE as energy input?

    in other words, as long as i am within the laws of physics that govern this universe, can i ever describe a process with GPE as energy input?

    are there no energy boundary rules except the rules of classical physics?

    i am wanting some rules like quantum mechanic selection rules, rules that umpire fair play

    my superior will present about renewable energy and there is a lot of angst in what label we must use just for completeness. with all the trouble just for a label/name, maybe it is better to invite experts to investigate and discuss the matter after the machine is mass manufactured and deployed. then we all can contribute to accurately define a label as time progresses where there is no time constraint

    this way the system can be accurately described to everyone because its operational logic is really important to see how the GPE is renewed

    GPE can be equated by displacement of force, so I want to say Gravitational Force displacement (GFd) because F = ma = mg and multiplied by displacement GFd has units kg.m2.s-2 = N.m = Joules of energy
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