Hi all
Well here is my half baked idea. My English is not very good, so I hope that you all will understand the principle of how it works.
The idea is a combination of other technologies, that were jet discussed here in this forum.

1.   Hydrogen production
2.   ordinary water turbine-generator
3.   combustion-engine with mechanical-heat-coupling OR hydrogen-oxygen fuelcell

Function:
Let us say we make hydrogen and oxygen via electrolysis in 100 meter depth or deeper. So we have to count with 100% electricity IN. As long as I know the producing of hydrogen via electrolysis has a COP of 0,8 in best case.
Now the hydrogen will raise through a pipe (the oxygen needs an own pipe) 100 meter to the top, because of its lightweight, and will be feed into a combustion engine. (). Through mechanical-heat-coupling this will us produce by a COP of 0,8 (too) heat and electricity (energy OUT).
I choose a combustion engine, because igniting the hydrogen will automatically suck the oxygen through the other pipe.
I don`t know if a hydrogen fuel cell will do the same.
 
Please keep now in mind, that we have a total loss from 40% from our 100% IN.

Now we take the exhaust from the engine, a.k.a. water, collect it in a tank and conduct it through a pipe 100 meter down to operate a water turbine with a generator to get electricity.

Remember 40% losses ??.  BUT we have 100% of the water ?upstairs?.
100% water upstairs means 100% energy stored in the water.

Actually I don?t know the losses from a water-turbine-generator combination. But I guess that it could be around 25% and 35%. So assume 60% energy OUT

The last step to close the circle will be to conduct the water to the electrolysis-tank.

In sum we will have 60% of energy from our engine (mechanical-heat-coupling) and
round about 60% from our turbine, total of 120%.

Well this is half baked idea. I will try to draw a picture of that.
Please correct me if I am wrong with my maths, or better do your own maths and post the results.
I will be waiting for feedback.

Have a nice weekend.

2Tiger

Hi Pirate
Thanks for your reply.
No you understood it well. My intention was to reuse the water.
As long as I know, you can reuse the water if you burnt it in a closed enviroment. The only thing is, that it must be pure and clean water (destilled).

But I may be wrong. Perhaps someone here in the forum has better knowledge in this area.

kr
2Tiger

@tinu

Because of this: Source => Wikipedia

Hydrogen.....With an atomic mass of 1.00794 g/mol, hydrogen is the lightest element.

And if I am wrong, and it wouldn?t raise, we have a 4 stroke combustion engine.
One of the strokes sucks the combustion into the cylinder capacity. The energy therefore is allready
considered in the losses of a combustion engine.
So once started, the engine would help to lift(suck) the hydrogen out of the pipe.
The same will happen to the oxigen.

by
2Tiger

@Tinu

Ever took a mountain trip with your car? Noticed how difficult is for the engine working at high altitude and low pressure? The engine is designed to work at around 1 atmospheric pressure and the additional energy is not taken into consideration.

No I didn?t. But the reason why the the engine has problems is, because the athmospheric low pressure air contains less oxigen in the same amount of volume and this is of cause not good for the mixture (air-combustion) the engine needs to run properly.

Hydrogen is the lightest gas indeed, but it does not know it. It does also not know that it?s air or something else around the pipe. Eventually the pipe itself will float and rise (if light enough) but not the gas inside it.

The hydrogen does not know that? Then why do you think that eventually the pipe (if light enough) will know this?
One real example for this is the famous zeppelin Hindenburg. It "floated" in the air with a gas mixture inside and one of the gases in this mixture was hydrogen.

Assume that the pipe is open on top. The hydrogen will rise in the pipe, because air (heavier than hydrogen) will "fall" in the pipe and displace the hydrogen to the top.
Other example - Fill some oil and water in a glass and you will see, that the oil will float an the surface.
Indeed the oil will not know why it is swimming on the surface, but it does it anyhow.
Does this causes any losses in the system?  No - it is a "natural" reaction between two elements, though physically explained.


kr
2Tiger

Same result with oil, which is pushed up by the water?
   
Unfortunately hydrogen and air mix very well. Once the pipe is open, hydrogen is pushed up indeed, but it dilutes very quickly.

Tinu

A most interesting idea.
It is true that the hydrogen gas produced from the electrolysis of water could be made to rise, but perhaps you would need something like a conveyor belt of balloons (!) to get the hydrogen gas to rise and when it got there you would need to apply energy to compress the gases before combustion would occur. then again, the belt might output energy itself too.
It all sounds very Rube Goldberg but it might work too.
You never know until you try it.

Hi all
The main question I have is, is it possible to reuse the water after electrolysing and burning in order to re-electrolyse it again?
The other question is, where are the losses in the water-electrolysis? Maybe heat?
I would be greatful to hear any answers.

Thanks
2Tiger

The hydrogen will definatly rise thrugh the pipe,it won't mix with the water it's made from,try suspending water over air.In acually generating hydrogen will probably produce pressure in the pipe,as well as the ox pipe.The  trick will be producing enough @700 cfm for a bb chevy per say.And also metering enough ox to have cumbustion.Lets not forget an all stainless motor to inhibet corrosion.Small obsticals sure, practical possibly, give it a whirl on a small scale model maybe 1/6th.