Ocean thermal energy conversion

[sparks]

A gas is heated to high  pressures by thermal energy collected in an ocean submerged heat exchanger.  The pressure is stored and released by a locked piston.  Upon pressure rise of a certain degree the piston is released. The piston mass energy is deposited on a flywheel via a ratcheting device or any other suitable means.  The sudden drop in pressure allows the piston to return to its initial position due to the heat lag of the exchanger not being able to supply heat fast enough to maintain the temperature of the expanded gas. Gravity returning the mass of the piston to its home position where it is locked and loaded for the next cycle. 

[brian334]

How do you condense the gas to reuse it?

[sparks]

   The gas upon release of the piston expands into the space vacated by the piston converting its thermal energy into the kinetic energy of the piston.  The gas temperature drops drastically allowing for the return stroke of the piston to be accomplished without a phase change.  Phase change could be used but why wait around for that much heat exchange when you can go right to work repressurizing the cylinder?  The gas always stays on the heat exchanger side just expands and contracts depending on how much thermal energy it has in it.

[brian334]

Sparks,
We need a drawing, after the gas pushes the piston down somehow the gas
has to get back into the pressurized area.

[sparks]

  @Brian

   Here is what I had in mind.  The piston in this case does not drive a mechanical device it drives a magnet through a coil which creates and electrical pulse of energy passing first up and then back through the coil.  The walls of the heat exchanger become very cold when the gas is allowed to expand.  Therefore it is important that the walls of the exchanger are thick.  If the walls are not thick enough the pressure of the gas will not drop enough to allow the piston to return to its home position so that it can be latched in place.  Once the piston release has allowed the gas to expand and rush into the column it becomes cool enough and the pressure of the gas drops enough to allow the piston to return to it's home position.  The gas is never allowed to leak to the atmosphere and is stopped at the piston sealing rings.  Refridgerants can be designed to exert a pressure of 450pounds square inch  at 50 degrees.  Atmospheric pressure is about 14psi.  The piston upon release with no load will shoot out of the top of the column like a rocket so there is alot of probelms to overcome getting it to actually work but it is very doable.  The gas does not condense into a liquid like in an airconditioner.  It just goes from a highpressure full of bouncing around molecules to a relatively lowpressure where the molecules dont have enough thermal energy to bounce around as much.
This allows enough time for the piston to return to home position and allow the heat from the ocean to pass through the resistance of the heatexchanger wall to speed them up again.