Pressure differentials to generate power?

[athyra]

Now this may seem blatantly obvious, but couldn't naturally existing pressure differentials be used to generate power via a turbine?

Okay, first of all we need to find a permanent pressure differential that is quite powerful. The ocean.

Pressure at say 30 000 feet is hundreds, if not thousands of pounds per square inch. So lets theoretically construct a long pipe, anchored in the ocean floor, that leads upwards to shallow depths.

Midway up the pipe is a turbine.

Now if we induced suction, enough to start the water flowing upwards, would not that flow keep on coming, due to the pressure imbalance between the "mouth" and the exit of said pipe?

Or would the pressure differential not be strong enough to push that much water even with suction starting to flow.

Or am I missing something completely obvious.

 

[Anonymous]

"Or am I missing something completely obvious"?
Gravity

 

[OneWingedBird]

...and the small fact that it's the weight of the water above that's exerting the presure in the first place...

 

[Anonymous]

The oceans are a massive sink of solar energy; just look at the world fom space... the dark blue oceans cover most of the globe, and absorb sunlight quite efficiently, only to power the circulation of the atmosphere and storms.

We can have some of that energy without damaging the cirulation too much; in fact it might be possible to calm the hurricane and el Niño...

Not by utilising pressure, I am afraid; it would quickly normalise, then no more work could be done. I have high hopes for
Ocean Thermal Energy Conversion
OTEC myself.
Manufacure millions of OTEC units and spread them out over the Pacific Ocean.

Tie a few together to make floating hotels, even farms of some sort... we could live on the surface of the sea rather than below it.

Come on then!
it only would take a couple of trillion dollars!

 

[filcee]

Would it be possible to use gravity and a syphoning effect to creat a continuous circuit of water passing through a turbine.
Water is held in a reservoir,and released through a pipe that houses a turbine, to a lower reservoir. As the water turns the turbine, the energy created pumps water from the lower reservoir up a second pipe back to the upper reservoir. At this point we would be showing an energy loss, but if the pipe could then act as a syphon, no more energy would be needed to raise the water to the upper reservoir. So the turbine would have a constant water supply.

Or am I missing something completely obvious, too.

 

[Anonymous]

I ran this past an engineer once who told me that it would steadily 'leak' energy until it stopped working. If, however, part of the turbine's output was permanently set aside for working a water pump...or, say, there were many turbines, one of which generated power solely for the pump...

 

[rynner2]

Would it be possible to use gravity and a syphoning effect...

Or am I missing something completely obvious, too.

Siphons can only transfer water from a higher level to a lower one, although the water in the pipe may temporarily travel above the upper level.

And I think the maximum height of the loop above the upper level is limited to about 30 feet anyway, since a bubble of water vapour would form above that height, stopping the siphon.

Let's face it, so far humanity hasn't been clever enough to get owt for nowt!

 

[athyra]

The only response outlined that actually pertains towards using a pressure differential is gravity, and the main question is, is the pressure required more then is naturally generated by the weight of water, less then is required to over come gravity?

To some of the people having a hard time with pressure differentials: this would be nothing more then constructing a "water volcano"

The earth's crust weighs down upon the magma, creating a pressure differential. When the differential is great enough, it will force it's way through the crust and result in an eruption, hurling magma due to the pressure.

Or compare it to a pressurized oil pocket.

My theoretical idea is no different in principal then that. It is just creating a permanent channel for the "magma" so it does not need to overcome the pressure of all the water above it. Hence the suction to start it flowing.

Something similar is already being done in the volcanic lakes with higher pressure due to co2 extrusion, which builds up until there is some sort of event or catastrophic failure in which the lake layers "turn over" and the water with CO2 in solution is released explosively. Of course, when this occurs, the co2 comes out of solution, and spreads as a ground hugging cloud. This was the cause of a massive animal/human death toll in Africa in 88 i beleive. A simple pipe is used in some locales to bleed off pressure to prevent an explosive "turn over".

If I come across as snarky, I apologize, but some of the answers were snarky in my mind and not applicable.

EDIT: and I don't think this would actually work, or it would have been tried. Rather that from my understanding of physics it would, therefore I want someone more knowledgeable to tell me why it wouldn't. Thus, I learn.

 

[Yithian]

IIRC there was an article on this in New Scientist some years back.

 

[sjwk0]

They kind of do this in Wales, where they have a power station inside a hollowed out mountain - you can have a tour round a bit of it, which I did. Most impressive feat of engineering.

Water flows from a lake at the top down through the turbines into another lake at the bottom, then later gets pumped back up again.
However, it uses more power than it creates, but they use it as an instant-on booster to the standard power stations since in about 10 seconds it can go from 0 to several GW IIRC, ready for everyone turning the kettle on after Eastenders... Then they use surplus power generated by the normal power stations at offpeak hours to pump it back up again. Cheaper and quicker than increasing the output of the standard power stations - in fact they say it paid for itself in a few years.

And completely environmentally friendly too - you wouldn't even know it was there. Environmentally minded types did make them plant all sorts of exotic heathers and so on all over the mountain when they finished, back as it would have been years ago. The same environmental types also made them release a herd or two of goats for the same reasons. The goats promptly ate all the plants they'd spent months growing and planting.

Steve.

 

[filcee]

They kind of do this in Wales, where they have a power station inside a hollowed out mountain - you can have a tour round a bit of it, which I did. Most impressive feat of engineering...

Would this be Trawsffynydd or Dinorwig? I know one is Hydro-Electric and the other is Nuclear. Trawsffynydd was fun for fishing in winter; if it got to cold to sit on the lake shore, strip off and sit in the steaming water .

 

[Anonymous]

The only response outlined that actually pertains towards using a pressure differential is gravity, and the main question is, is the pressure required more then is naturally generated by the weight of water, less then is required to over come gravity?

To some of the people having a hard time with pressure differentials: this would be nothing more then constructing a "water volcano"

oh, I see. No, the pressure is generated by the weight of the water alone, and would only produce enough energy to raise the deep-sea water to the top of the ocean, not above. You could drop a hollow tube, with a sealed end, open the seal, let the water rush in;
the air displaced could run a wind turbine, but the process would stop when the water reached sea level.
It is like a manometer- you would equalise the pressure.
Now it may be worth repeating this process over and over to get wind- powered energy by dropping tubes in the ocean then hauling them up; it sounds inefficient, but if it actually makes a profit in energy it might be worth doing.

The earth's crust weighs down upon the magma, creating a pressure differential. When the differential is great enough, it will force it's way through the crust and result in an eruption, hurling magma due to the pressure.

Or compare it to a pressurized oil pocket.

My theoretical idea is no different in principal then that. It is just creating a permanent channel for the "magma" so it does not need to overcome the pressure of all the water above it. Hence the suction to start it flowing.

The weight of rock stata is much greater than that of water or oil, but the main force driving volcanoes and geysers is subterranean heat- this is not available at the ocean depths; in fact the warmest part of the sea is the top, which is where OTEC gathers it from.

So you are not so very far off, but it would be more efficient to get geothermal energy from volcanoes if it were not so damned difficult. Iceland (and elsewhere) does successfully pull this geothermal trick off,
of course.

 

[athyra]

Thanks Eburacum, yeah I figured something similar was the case. Once you point out the fact that once the tube was filled, the pressure would be equalized at that point, rather then the water flowing out, it is easy to see that that might be the case.

Which brings up all sorts of obvious problems such as how to empty the tube, without using more energy then is generated etc. etc.