Hydrostatic Pressure Piston

[Newbies_Kid]

 

Good day,

 

Our lecturer give us an assignment on renewable energy, he want us to design at least one method of harnessing power from the ocean which still do not exist. So that's why i attached the picture and hope a +ve comment from you guys.

 

Thanks in advance

 

 

p/s: sorry about the mark at the bottom of the picture, i'm in hurry actually

[CaptainPanic]

I am not sure "bottom waves" exist.

 

Also, I am not sure how this will work. The hydrostatic pressure in the cylinder at the place of the valve seems unrelated to the setting of the valve itself. In short: it doesn't matter if the valve is open or closed - the pressure doesn't change at the location of the valve...

 

The only thing that will change the hydrostatic pressure in such a column of water is a (big) wave. Then more water, and thus more pressure is pushing on the column of water.

[Newbies_Kid]

Thanks CP

 

About the bottom wave: i adopt it from an existing devices called "Wave Roller" (below)

 

 

About the pressure: did you mean i need to redesign my devices at sea level? actually i put a value (1000m-2000m) for a purpose, i thought the atmospheric pressure + water pressure would be so great at that deep and enough to produce force to move the piston

[Mr Skeptic]

Thanks CP

 

About the bottom wave: i adopt it from an existing devices called "Wave Roller" (below)

 

 

About the pressure: did you mean i need to redesign my devices at sea level? actually i put a value (1000m-2000m) for a purpose, i thought the atmospheric pressure + water pressure would be so great at that deep and enough to produce force to move the piston

 

Note how this is bright and you can see the surface of the water? This is very near the surface, where waves matter.

 

As for the pressure, it is pressure differentials that provide force (pressure differential times area). Absolute pressure doesn't move anything, and the pressure between the inside of your machine and the outside at the same water level will be zero.

[Newbies_Kid]

Thanks Mr.Skeptic,

 

I think i misunderstood about the underwater pressure, need to open fluid mechanics text book again. Thanks again

[CaptainPanic]

The useful pressure that you can use to generate electricity is the pressure differential after you subtract the hydrostatis pressure.

[Newbies_Kid]

Then how about this?

 

 

 

 

The real problem with this design is how to connect that "wing" with the valve which is at different altitude.

 

right now my group still don't come up with any good idea instead just being obsessed with underwater pressure. Perhaps this is the most tough coursework that we have.

 

 

p/s: once again, sorry with that annoying stamp

[CaptainPanic]

I don't really see the difference with the previous thing, except that you have oil in the pipe now, which will not change anything. As far as I can see, it still contains the same basic flaw:

 

You cannot get energy from the high pressure of the water at great depth.

If you push a pipe (open at both ends) into the depths of the ocean, to 1000 meter or more, then nothing happens. Water doesn't suddenly go up through the pipe.

 

If the water at great depth (and great pressure) would have any desire to go to parts where the pressure is less (like the surface), it would not require a contraption such as this. It would go up through the layers of the ocean all by itself. But, the matter of fact is: the water which is at great depth is quite happy there and has no desire to move up in any way... there is no driving force. The water has no motivation whatsoever to go up.

 

The only thing that generates some energy is the wing. The rest of the contraption will do nothing at all.

[Newbies_Kid]

You cannot get energy from the high pressure of the water at great depth.

If you push a pipe (open at both ends) into the depths of the ocean, to 1000 meter or more, then nothing happens. Water doesn't suddenly go up through the pipe.

 

Sure, this is what i misunderstood in our 1st design. So, in the 2nd design we try to put a "hydraulic jack" into the system. a balloon will explode due to expansion at high altitude and by contraction at -ve altitude because of the pressure different between the inner and the outer of the balloon right?. So this design use this terminology and that's why i change this design into a closed system. when the main valve opened, the higher pressure from the outside will push the hydraulic jack.

[CaptainPanic]

Ok, I understand.

 

But with a hydraulic jack, the thing eventually lifts the car up into the air because you push (high pressure, like the deep sea), then you stop pushing, and you even lift the handle (very low pressure - does not happen in the deep sea), and then you push again, lift again, push, lift, etc.

 

So, if you open the valve, then indeed, the seawater will push on the oil. Depending on the weight of the oil, the piston and the weight, something might move.

But then it stops... and nothing else happens.

[Newbies_Kid]

erm.. there will be something (blue thing in picture) that push the oil not directly from the sea water. The valve (5) is the thing that make the system reset. when the valve opened, the hydraulic system will push up the piston. when the valve closed, no more pressure and the weight push back the oil at initial state. Will this work? your opinion and suggestion very much appreciated

[Mr Skeptic]

Your second attempt is better since the wing is closer to where the waves would be (I'm not sure how well the wing will work without being near the ground btw). However, it still has an extra 950-1950 ft of pipe in either direction, which would provide unnecessary friction losses. Also, step 4 will not work unless your machine leaks oil, and then it will run out of oil and stop working. Once you open your main valve, the pressure of the oil and the pressure of the water will be the same, and closing your valve won't change that -- you'd need to pump the water out of the valve, doing more work than you got by letting it fill.

[Newbies_Kid]

and closing your valve won't change that -- you'd need to pump the water out of the valve, doing more work than you got by letting it fill.

 

Yes, you are right and i just notice that. So.. how about if i put a one way valve between the main valve and the piston "blue color"? or perhaps can you suggest me anything better. Also, how about if i change oil with gas? this should increase the force transferred right??.

 

 

Drawing is easy but it sure gonna make me crazy when i have to apply the control engineering and some mathematical modelling especially if using matlab which i'm sucked most....

[CaptainPanic]

Will this work?

No. It won't.

 

I cannot explain it any better than I already have. Water at great depth in the ocean cannot provide any energy. You can replace whatever with whatever in your contraption, it won't change the principle.

 

Just look up the Bernoulli equation for incompressible fluids here, will you please? Notice that the equation includes a term for the height.

 

For a machine like yours, it is absolutely vital that you understand this equation. Also, it will show that there is no energy to be gained from this machine.

[Mr Skeptic]

Right, you'd be better off attaching a turbine to the valve you are opening and closing via wave power, than any other part of your contraption. Incidentally, if your machine worked the way you seem to think it does, then you wouldn't need wave power to open and close a valve, since you could power it with your perpetual motion machine.

[Newbies_Kid]

Captain Panic: I had look up at the link given but why it is bernouli equation? As far as we understand, there is no laminar or turbulence flow involved because this is just a simple hydrostatic force on submerged planes right?

 

 

 

So we put some calculation in the picture and conclude that the smaller area of contact between fluid and the main piston the more force will be transferred.

Edited September 23, 2010 by Newbies_Kid

[CaptainPanic]

Captain Panic: I had look up at the link given but why it is bernouli equation? As far as we understand, there is no laminar or turbulence flow involved because this is just a simple hydrostatic force on submerged planes right?

 

 

 

So we put some calculation in the picture and conclude that the smaller area of contact between fluid and the main piston the more force will be transferred.

Now we're getting somewhere

 

You're absolutely right that the sea at such a depth can exert a force.

But, in order to use a force to do work (to make energy), it must cover a certain distance.

It is this distanc which is missing all the time... since (on a longer timescale) there is no flow, and the components remain on teh same place (although they seem to move up and down a bit).

[Newbies_Kid]

Right, you'd be better off attaching a turbine to the valve you are opening and closing via wave power, than any other part of your contraption. Incidentally, if your machine worked the way you seem to think it does, then you wouldn't need wave power to open and close a valve, since you could power it with your perpetual motion machine.

 

 

Yes, i will save a lot of time if i just do as you suggest. But the Wave Roller is one of the existing devices which extracting wave power to move the turbine.

 

Here i list some of the method which exist today to generate force from ocean power. You can search those in google for more info.

 

1. Salter duck (Wave)

2. Sea snake (Wave)

3. Ocean thermal energy conversion (temperature different)

4. Wave Dragon "tapchan" (Wave+gravity)

5. Wave roller (Wave)

6. Oceanlinx's oscillating water column (Compressible fluid + wave)

7. Sea Gen (under research) - Wave farm (wind farm like)

 

So our lecturer need a new kind of method which still do not exist, although this coursework just contribute 50% from our total mark, our dean is looking forward to it. If we can design a new method, he want to apply a grant for further research.

At current state, me and my group decide to use the extreme pressure of ocean's floor as the main energy contributor.

[CaptainPanic]

At current state, me and my group decide to use the extreme pressure of ocean's floor as the main energy contributor.

You should change your name from "Newbies_Kid" into "Stubborn_Kid".

 

Energy ≠ Force

 

The pressure in the ocean can exert a force (in the form of pressure). But you cannot get energy from it.

[Mr Skeptic]

At current state, me and my group decide to use the extreme pressure of ocean's floor as the main energy contributor.

 

Well, it would be more convenient and certainly less expensive to just use the pressure of a pile of bricks as your energy source, and it will work just as well (neither will work at all). Just remember: to get a force from pressure you need an area (force = pressure * area). To get work from a force you need a distance (work = force * distance). To follow the laws of thermodynamics, the thing you're getting energy from must lose energy. And what you're trying to build looks an awful lot like a perpetual motion machine, except that for some reason one of the parts that does roughly zero work uses wave power.

[Newbies_Kid]

Yes, sorry for the misconception.

 

As you said before, "in order to use a force to do work (to make energy), it must cover a certain distance"

 

 

From above we finally get : Work (in) = W (out).

So to do this work, we must have an equal energy.

 

Take potential energy;

 

PE = mgh

= Fh

when h= d

 

PE = Fd = Work

[Mr Skeptic]

Yup, and to get your machine to work more than the first second, you need to be able to reset it, which will cost you energy.

[Newbies_Kid]

And what you're trying to build looks an awful lot like a perpetual motion machine, except that for some reason one of the parts that does roughly zero work uses wave power.

 

I could felt the same thing, the machine is just way too simple but very efficient. So i decide to convince my team to find another sources instead just being obsessed with the undersea pressure.

 

Ocean wave should be a potential sources as it already contains the energy and we just need to find out how to transform it into desired energy.

 

Thanks for your great advices!

Edited September 24, 2010 by Newbies_Kid