exchemist
Valued Senior Member
But the sub has to do work to compress the air it uses to blow its ballast. And this will negate everything.
Pressure Harvesting - from ocean depths
- Thread starter Quantum Quack
- Start date
I thought the air was about increasing displacement... which is primarily about over all size not weight. ( object fully submerged)
If the sub increases it's displacement (Size) it increases it's buoyancy
DaveC426913
Valued Senior Member
Of what??
What weighs 1kg and fills 1 litre? Water. Incompressible water.
Not gas. A litre of gas weighs considerably less than 1kg.
A half litre of gas with a half litre of steel? Steel will not compress. You now only have a half litre of storage.
You will find - not matter how you cut it - you can't do this without either putting energy into the system somewhere, or having zero net effect. (Just like perpetual motion machines - which also fail due to inviolable thermodynamics).
but if the can increases it's sealed size while at the bottom then it will gain buoyancy
DaveC426913
Valued Senior Member
A sub is full of energy needed to do exactly the things you want to do for free. Stop using it as an analogy.
DaveC426913
Valued Senior Member
And how will you do that without inputting energy?
It's compressed for a reason.
I would anticipate that the energy needed to increase displacement of the sub so that it surfaces would be far less than the energy needed to mechanically pump compressed air from the surface to the storage tank.
I am not looking for a free ride. I am looking for an inexpensive ride. One that is free of dirty fuels and waste products as well...
Other than the energy required to sink a large vessel of air.
OK. It unloads its air. It is now very much NOT buoyant. What do you do then to get it to the surface?
Then it is using all the air in the tank (plus a little more) to blow its ballast. No air for you to use. No energy harvested.
You see, there is no submarine in the world that can dive and surface over and over without energy being input. That energy comes in the form of a compressor to pressurize the tanks used to blow the ballast tanks. That takes a lot of energy (and a lot of pressure.) So once again you have an energy dispersal device.
out of curiosity
what happens if we increase displacement by mechanical means.
At least you are getting a better idea of what is being proposed...
I knew jack sh*t about fluid mechanics before starting this thread...and still do. lol
That's entirely possible. It, of course, takes energy as well.
so it all comes down to cost effectiveness of the system and NOT whether it would work.
Once the principle is understood then it's time for the math to work out energy cost effectiveness.
DaveC426913
Valued Senior Member
As we have been trying to point out - even if you eliminate all forms of friction (which you can't), you cannot get more energy out than you put in.
If you could - if you could somehow get more energy out than you put in, then, by definition, you have created an over-unity machine - free energy.
And that's why we keep comparing this to a perpetual motion (more accurately, an over-unity device) setup. It fails for exactly the same reason.
Nope. IT WILL NOT WORK. Period. That's why we have laws of thermodynamics, to explain why such systems will not work. (And yes, people have tried to build perpetual motion machines on the same principles you have listed above.)
When I was 13 I learned that a generator was like a motor, it just worked the other way. After I learned that I had a genius idea - hook the shaft of a motor up to a generator, then run the generator with the motor, and power the motor from the generator! I was so smart. I had just solved the world's energy problems. People kept telling me it couldn't work. I was sure that they just didn't get it.
"The whole system will slow down because of friction," they explained. I had an answer to that - use a set of gears to make sure the generator spun faster than the motor! Then you would get the system to speed up, not slow down.
"Electrical resistance will gradually decrease the energy in the system," they explained. I had an answer to that too. Use an AC motor/generator and use a transformer to boost the voltage! Then you would get more electrical energy, not less, every time it went through the system.
I was convinced this would work for years, and that anyone who claimed it didn't was a dunderhead who couldn't see all the clever tricks I was using to get around the laws of thermodynamics. Those problems were just details, I explained, amenable to clever tricks. Sure, it's not super efficient, but it would still work. It wasn't until the last year of high school that I started to dimly see why it wouldn't work, and it was years later before I understood all the math to prove it wouldn't work.
So you can spend a few years doing that, or take advantage of other people's mistakes and learn from them. Up to you.
ok... I see why there is a problem in the understanding.
Your argument can equally be applied to solar energy or any device that captures potential energy whether that be tidal, wind, or pressure.
Let me explain.
There is energy being input into the system and it is not an over unity device. Nor is it an under unity device.
These "energies" or forces are entirely natural. Pressure is a natural force... ( excuse the loose use of terms**)
The proposal of exploiting pressure is not new.
The principle I am attempting to put forward involves the capitalization on those natural forces. Just as solar , wind, wave or tidal does.
Simple system:
You have a pressure gain as you descend to depth and that pressure can be used to compress air. That compressed air can be transferred to the surface.
true.
Complex system
Same as simple system but with the addition of recycling the air pressure generation system.
not so true but maybe economically feasible.
Motivation:
To produce usable force that is non-polluting and does not involve depletion of natural resources.
(**) I have just researched terminology and found that pressure itself is not considered as an energy. It is considered as a force that can covert to energy.
http://hyperphysics.phy-astr.gsu.edu/hbase/press.html
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hee hee, I have explored numerous PPMM's including historical. some of them are truly fascinating.
All working on the basis of over unity outcomes but fail to see that you have to start with under unity to begin with...and let the universe find unity..but that is another story... lol
This thread is not about an over unity device or even about an under unity device.
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one of the most fascinating was demonstrated recently by an Irish company called Steorn.
https://en.wikipedia.org/wiki/Steorn
I watched this debacle evolve from onset....
Hydropower turbine driving an air compressor. Boom! Done.
DaveC426913
Valued Senior Member
And requires as much (more) energy to do so as it would take to simply compress it on the surface.
Look:
If you arrange your craft so that it can sink without using energy, that's because it is not buoyant, which means it will require energy to lift it again.
If you arrange your craft so that it can rise from depth without using energy, that's because it is buoyant, which means it will require energy to get it down there.
If you try to change the buoyancy while you're down there, that will require forcing air/water in and out of tanks, which means it will require energy to move that air/water.
How does a sub do this? It brings stored energy with it - either on the form of pumps and batteries or in the form of pre-compressed air - which required shore energy to compress it.
TANSTAAFL: There ain't no such thing as a free lunch.
doing a one way trip it wouldn't need much energy added at all...
sink it but don't retrieve it = aka simple system as posted.
but that is referring to the more complex system not the simple system you quoted.