What's wrong with this

[tinman]

  Oh dear Tinman, looks as if you've come a gutser!!

And why is that dear minnie?.

[tinman]

Tinman the conversation has been interesting.  In order to change the buoyant state of a submersible the density has to change.  So, something gives:  mass and/or the fluid volume that the submersible displaces.  If we change the density but not not total mass of material inside a sealed and constant volume container, that container's buoyancy does not change.  That is why I speculated that maybe you were hoping to develop enough pressure in whatever contains the phase change material to change that container's volume, expelling sea water ballast.

From the: "It can't produce free energy." camp,  what you have cycling a submersible up and down are the UP and DOWN states.  We can pretty much ignore everything in between.  In the up state the system including the surrounding fluid is at its potential energy minimum, even though the submersible is at its potential energy maximum.  When the submersible is at the bottom of the travel, the system energy is at its maximum.  Before your submersible can rise you need to change its density.  You can either eject mass, or increase the submersible's volume, or a bit of both.  To do either you must expend work.  Since rising removes energy from the system, expending additional work at the bottom only aggravates the energy loss going from the down to up state.  On the way from the top to the bottom you have to be able to get all the energy that the system lost just to break even.  Sinking the submersible requires increasing its density.  That lowers the center of gravity of the system at the top without changing mass, so system energy is again lost.  The bottom line:  A submersible only moves up or down by expending energy from the system that includes the submersible.  The submersible moves up or down because the end position represents a lower energy state than the starting position.

You do know ofcourse Mark,that the mass of an object can be changed without changing it's size,and also without ejecting any material.

Energy is collected on the way up,once the vessle has surfaced, and on the way down.
I can take a sealed steel sphere and make it sink or rise as i see fit-no ejected mass,no ballast intake or exausting-->nothing enters or leaves the steel sphere.

[MarkE]

You do know ofcourse Mark,that the mass of an object can be changed without changing it's size,and also without ejecting any material.

No that is a new one on me.  If I have some quantity of some material then it has a fixed mass.

Energy is collected on the way up,once the vessle has surfaced, and on the way down.

This is where we are at odds.  I contend based on state analysis that you have to put energy into the system in order to make the submersible fall from its elevated state, or to make it rise from its more submerged state.

I can take a sealed steel sphere and make it sink or rise as i see fit-no ejected mass,no ballast intake or exausting-->nothing enters or leaves the steel sphere.

Are you claiming that you can make that sphere rise or fall without changing either the volume it displaces or the total mass of the sphere and its contents?

[tinman]

No that is a new one on me.  If I have some quantity of some material then it has a fixed mass.This is where we are at odds.  I contend based on state analysis that you have to put energy into the system in order to make the submersible fall from its elevated state, or to make it rise from its more submerged state.Are you claiming that you can make that sphere rise or fall without changing either the volume it displaces or the total mass of the sphere and its contents?

Unless you change the state of that material.
Energy is used to convert the liquid to gas, 75% of which is returned when the gas is converted back to liquid. This leaves the onboard turbines a task of generating the remaining25%

[minnie]

Yes Tinman, MarkE has explained very clearly and you're still skeptical.
  Your videos are brilliant, you explain everything in a scientific way and
  people can understand perfectly. Sometimes you may be wrong with
  your conclusions but your experiments certainly aren't made to defraud.
     This thing now sounds like Tin Man-Tin Brain! Just get a fish tank and
   embarrass me and Mark with your proof.
     I'll certainly believe-if you can prove!!!
                   John.