Pressure Harvesting - from ocean depths

Discussion in 'General Science & Technology' started by Quantum Quack, Mar 8, 2020.

  1. DaveC426913 Valued Senior Member

    Messages:
    18,895
    Sorry. What do you think the pressure is inside a sub at-depth?

    OK, Ex beat me to it. The pressure inside a sub is 1 atmosphere. That's why they have to be rigid, and why they implode if you look at them funny.
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. billvon Valued Senior Member

    Messages:
    21,607
    Yes. You can build an arbitrarily strong container; then the internal pressure does not change (much) no matter what the external pressure does. And you can make it arbitrarily heavy so it sinks.

    Now - how do you think it rises again?
    At first when you posted stuff like this I assumed you were joking. I have come to realize you simply have no clue.
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. DaveC426913 Valued Senior Member

    Messages:
    18,895
    Give him a break. He's at least open to learning. That's a big plus around here.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    23,328
    How do you think a submarine rises?
     
  8. billvon Valued Senior Member

    Messages:
    21,607
    I would like to believe that. He spends a lot of energy intentionally not understanding. However, he has learned in the past, so there is hope.
     
  9. DaveC426913 Valued Senior Member

    Messages:
    18,895
    The problem here is you're off on a wild goose chase. A submarine is not an analogy to a pressure harvesting setup. A submarine is not a source of energy - it's a sink.
    Let's not waste dozens of posts convincing you you can't make a sub into an energy source.
     
  10. billvon Valued Senior Member

    Messages:
    21,607
    Agreed. Let's wait for him to get back on topic.

    Ball is in your court, QQ.
     
  11. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    23,328
    ok... so... how does knowing that effect the ability to sink a Variable volume storage vessel (VVSS) and deliver air compressed on descent to a bulk storage facility and then return to the surface to do it again if wanted.
     
  12. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    23,328
    well ... if a sub can do it .....
     
  13. exchemist Valued Senior Member

    Messages:
    12,373
    Whut?

    Try again?
     
  14. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    23,328
    Perhaps you guys are still fixated on perpetual energy devices...
     
  15. billvon Valued Senior Member

    Messages:
    21,607
    So far you have been the only person to claim to be able to "harvest" free energy from pressure.
     
  16. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    23,328
  17. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    23,328
    as I posted earlier I used the term Harvest because...see post#71
     
  18. billvon Valued Senior Member

    Messages:
    21,607
  19. exchemist Valued Senior Member

    Messages:
    12,373
    Now you clever chaps are on line I have a puzzle for you.

    I imagine a simple scenario with a 1 litre container weighing 1kg, so its buoyancy exactly matches its weight. This can descend, without any work being done at all, say to 100m depth, at which point the ambient pressure is about 10 atm. QQ then opens the valve. The air is compressed to 10atm, isothermally, because of the water all around. The work done by the water to compress it is given by W=nRTln(V0/V) which I work out to be about 230J*. This is then the stored energy QQ can "harvest" when it gets back to the surface.

    However the volume of water displaced by this device is now only 0.1litres, so its apparent "weight" is now 0.9kg, i.e. 9N. So to pull it up to the surface one has to expend 9x100 = 900J. Nearly 4 times the stored energy. But I can't think where in the energy balance for this operation, the rest appears. So I'm wondering if I have made an error somewhere. Any ideas?


    (*I found an engineering source on line that quotes the equivalent of about 270J, but that was adiabatic, I think)
     
  20. billvon Valued Senior Member

    Messages:
    21,607
    I strongly suspect it is present in the additional heat the now-compressed air contains.
     
  21. Quantum Quack Life's a tease... Valued Senior Member

    Messages:
    23,328
    well done!
    So stored pressure is delivered to the surface with out having to add energy to the system.

    All we have to do now is get the air down to the storage facility also with out adding energy.
    So we use a specially designed submarine that sinks down to the storage unit compressing on board variable volume storage while it does so.
    It docks with the storage unit and transfers the pressurized air to supplement the bulk storage unit.
    The sub then blows it's ballast and surfaces to do it all over again...
     
  22. exchemist Valued Senior Member

    Messages:
    12,373
    I don't think so because I've said this is isothermal and I've used the gas equation formula for isothermal processes.
     
  23. DaveC426913 Valued Senior Member

    Messages:
    18,895
    exchemist likes this.

Share This Page