trandoductin wrote:
But this is not perpetual motion though, perpetual motion is in a closed system.
This uses abundance of water which is similar to solar that take from external environment.
Like a solar powered toy can move back and forth as long as the sun is shining isn't a perpetual motion machine by definition, even though it can move on forever.
This system takes water so it's like fire burning wood, where the wood is burned, in this sense water the material that feeds the system...but at deep water there's no shortage of water.
You're misunderstanding few things
I'll try to decompose as simple as possible with a different POV
a) - Let say at 200 bar you get a 1 liter bubble in volume, thus it's 200 liters compressed gas at 200 bar in that 1 liter volume, pretend that you use 1 gigawatt to produce that bubble via electrolysis (it's a made up number, but it means it's a big amount of energy).
Why so much energy? because you will need to produce 200 liters of h2 or O2 in a fraction of a second to fill that 1 liter space at 200 bar
b) The max speed: of a BIG bubble going up is around 23-25 meters per minute big max (when you start you recreational diving journey, you learn to never ever go up faster than 18 m/minute in case of emergency, because that's the ascent speed of the tiniest bubbles surrounding you when you exhale thru your second stage)
c) Friction and loss of energy: A bubble going up is already losing energy (continuously expanding and breaking apart = loss of heat), but, that's not the most important, the most important is when the bubbles will hit the fan, at such a slow ascending speed the fans of a turbine (even made of carbon-carbon) won't move fast if it will move at all...
But it's getting even worse, if the fan moves, it will fight against the water's
friction > so air friction against water friction...
![hee hee :hehe](./images/smilies/hihi.gif)
, that "turbine" will never ever produce the amount of energy that you already input in it to make that bubble at 2000 meter, not even 1% of the original amount of energy you did input (even if the turbine is at 10 meter deep it will always "fight" the friction against water).
Thus engineers use the force of water instead of fighting against it > by making a dam.
Or making wind turbines on land using wind in air to not fight against water.
![Big Thumb Up :bigthup](./images/smilies/023.gif)