Sorry for bad math skills but does 35000 Kpa = 35000 Joules?
ratio 1:1
ratio 1:1
Pressure Harvesting - from ocean depths
- Thread starter Quantum Quack
- Start date
So are you lying, or are they? Or is it just your ignorance getting in the way? From the article:
"Norwegian research scientists are now working on the concept of storing electricity at the bottom of the sea."
"Many people have launched the idea of storing energy by exploiting the pressure at the seabed, but we are the first in the world to apply a specific patent-pending technology to make this possible."
"This type of power plant is used as a battery when connected to the power grid.”
"In this pumped storage power plant,"
"The process consumes energy from the power grid, just as when one charges an ordinary battery."
"Although a bit more energy is used to empty the water tanks than can be recovered from flooding them . . ."
"According to Schramm, calculations indicate an electric storage efficiency of approximately 80% per power emptying cycle."
KPa is a measure of pressure. A joule is a measure of energy. Different things.
DaveC426913
Valued Senior Member
You've taken a heavy thing that has stored potential energy by virtue of the fact that it starts off 3000m above its lowest potential.
What you have done is equivalent to dropping one large rock off the top of a cliff. The rock started at the top of the cliff. It cannot be lifted back up without squandering everything you've gained.
Yes. You can harvest the potential energy of a raised object (any raised object) by lowering it.
Yes, potential energy can be used to pressurize something.
Once.
Now your device cannot be used again without expending more energy than you got out of it.
Your plan involves littering the ocean with one-time use kilometer-long drums.
An air pump will do the same thing with a far more efficient energy-to-pressure ratio and at a cost orders of magnitude smaller - and no waste.
If your idea is to litter the ocean floor with kilometer-sized empty and useless cans - then a career in eco-engineering may not be in your future.
What you are doing is the energy-equivalent of burning flammable dollar bills in your fireplace in an effort effort to "save money" on wood. "Oh sure " you say," it's less efficient, but the principle is sound! All we need now is to make money cheaper!"
But more power to you.
I know that .. How much energy can 1 Kpa deliver?
I get the impression 1 Kpa m^3 delivers 1 Joule.
but exploit the oceans pressure to store and use air pressure on the surface is definitely possible... and in fact a necessary physical outcome of sinking a variable volume vessel with air inside it.
No it is not just a rock.
It is dropping a compressible gas 3000 meters in a soup of increasing pressure using the weight of the rock to compress the gas with ambient pressure.
That pressure is portable and able to be exploited at the surface 3000 meter up. Hence the use of the term "harvesting".
So we have generated air pressure at a depth of 3000 meters and been able to move that potential energy at no cost back to the surface.
And that's the fascinating thing about this situation.
There is one phase that appears to be missing from a typical energy cycle
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DaveC426913
Valued Senior Member
It is, in every meaningful way, identical to a rock at the top of a cliff.
Put a can of air at the bottom. Drop the rock. Shazam. Compressed air.
Once.
So is the air can at the bottom of the cliff. And you don't need a freighter expedition to get at it.
Yup. Just like picking up the can of air at the bottom of the cliff.
Until you understand why these two scenarios are identical, you will not understand energy generation storage, usage or thermodynamics.
Write4U
Valued Senior Member
There is no pumping involved. Nothing is stored . The ocean pressure trying to fill the empty tanks provide the kinetic force to turn the generator turbine which produces electricity which is immediately transferred to the surface grid. When the tanks are filled with water no further electricity can be generated, until the tanks are pumped empty by the reversible turbine, which is the only time the system actually uses electricity from the surface grid. The question here is if this evacuation of the water uses more more or less electricity than the original forced inward flow of the ocean water actually generates. As I understand it uses mariginally more electricity than it produces but that can be supplemented by excess electricity from the surface grid. And it as long as it is closed the entire system is dormant with only the ocean's pressure against the closed inlet to the empty tanks.
When the tanks are empty they are again ready receive the pressurized water from the ocean, which turns the generator turbine. The system can be expanded by adding additional tanks which allows for longer generating times, but also use more time to empty. But the system is versatile and can be customized for many uses.
This system is useful as a supplemental energy source, when winds are down or at night when solar-panels are dormant .
I believe the guy who wrote the review did not fully understand the system . He called the tanks the storage system which is completely wrong. The tanks merely provide water storage of the "used" water which has already passed the generator turbine and produced electricity.
When the tanks are filled no electricity can be generated at all until they are emptied and ready to receive inflowing water which provides the kinetic force to turn the turbine generator which is located at the water inlet valve, and which also functions as the water outlet for the evacuation of the excess water, pumped by the reversible turbine, the only time the system uses electricity from the surface grid. It is a very simple system but that makes it versatile and easy to manufacture and maintain. The illustration shows its elegant simplicity.
DaveC426913
Valued Senior Member
So, a direct contradiction.
So it takes less energy to reset it than it does to use it.
So, an actual Free Energy device. Hmmm...
I wonder what would happen if you added up the energy requirement from the pump with the energy requirement from the surface grid...
Hmm...
He is completely right.
They are similar sure... but this does not change the fact, in fact it even reinforces the fact, that ocean pressure is exploitable.
But there is one thing you are missing from your "Rock on can" energy cycle. Do you know what it is?
Do you wish me to tell you?
You don't seem to have had the seeming conundrum presented in p9 #174 resolved.
This is simply a variant on say lowering a mass down a hole in the ground, via a winch at the surface attached to say an electrical generator. A one-way conversion of potential energy to electrical. In your conundrum it's not immediately obvious where the trade between potential energy and pneumatic energy arises. It occurs at the bottom when the air is being compressed, not on the way down. Hauling the compressed cylinder back up to the surface now takes energy since the vessel is now far less buoyant, despite a small overall reduced mass given air has escaped to the surface via the attached air-line. I won't bother doing explicit sums to prove it - what I wrote in #128/#134 covers all possible variations within the basic theme. If the source is a conservative field no net changes in overall energy are possible.
Also note that a bird's-eye view must take into account a very tiny lowering of ocean depth when the submerged cylinder is compressing (it was initially raised when the cylinder was completely submerged near the top - Archimedes principle). Overall then merely trading one source of PE for another - compressed gas. With the attendant losses thrown in.
DaveC426913
Valued Senior Member
It is as exploitable as rocks found the top of a cliff.
Heck, you don't need rocks. There are way more trees than rocks.
You can fell trees and pressurize containers.
Of course, now you've cut down all the trees...
There is a very long list of things on the planet that are above their lowest potential. We could put a compressor at the bottom of a pit and throw all sort of things on top of it. For a while.
And way more accessible than the ocean.
These are all identical to your idea. But cheaper, more convenient and more cost effective than going out to the middle of the ocean to dump tonnes of iron trash cans.
You are making a mess of our planet by turning the convenience of air pressure directly into trash - at an alarmingly high rate for what you get.
It doesn't matter.
You can't cheat thermodynamics, no matter how many valves and tanks you add to your contraption.
You are failing in exactly the same way every PMM-inventor does.
OK say we consider you rock off a cliff for a moment.
You drop a rock weighing 1000kg's of the cliff and it falls 1000 meters onto a large can with air in it...
The impact of the rock compresses the air in the can.
the compressed air is transferred to an appropriate pressure vessel.
ok... no problems simple yes?
continued....
cont...
You then pipe the compressed gas back up to the top of a cliff 3 times the original height and transfer it again to an appropriate vessel.
Now do your thermodynamic accounting... what do you end up with...?
Part of the rocks energy potential is now 3 times higher than it was to start with.
Remember ambient air pressure is diminishing as you go higher..
You then pipe the compressed gas back up to the top of a cliff 3 times the original height and transfer it again to an appropriate vessel.
Now do your thermodynamic accounting... what do you end up with...?
Part of the rocks energy potential is now 3 times higher than it was to start with.
Remember ambient air pressure is diminishing as you go higher..
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DaveC426913
Valued Senior Member
OK, you can lead a horticulture but you can't make her think. I've led you for 200+ posts and you still have no clue about conservation of energy.
Best of luck to you. Call me when you win the Nobel Prize for your free energy device.
Best of luck to you. Call me when you win the Nobel Prize for your free energy device.
it's not a free energy device but there is something strange going on. There will be a way to explain it all with out resorting to sulking off...
Conservation of energy is an absolute requirement and not just a law..
The amount of potential energy being transferred to a higher position will always be less than the original every time... so perpetual energy is not possible.
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Write4U
Valued Senior Member
Yep. There is no energy stored anywhere except as potential of the ocean's pressure against the closed inlet valve of the empty tanks.
No, it uses marginally more energy to pump the tanks than it generates, but not much different than any other electricity generator. All systems lose power. None of them produce 100 % of available energy
I think it said this system generates about 80 % of total use. But The surfac grid often has excess energy and can supplement the underwater system when it needs to pump out the water from the tanks, which is the only time the system uses energy instead of producing it.
One of the advantages is that it can operate under all weather condition and at night when solar goes dormant.
You mean calling it a storage system? But it does not store anything except water which has already been used to generate power and needs to be pumped out, which uses power, not store it.
Perhaps I misunderstand the word "storage"? Like keeping something stored for later use?
The system does not store electricity, it is not a battery. It produces electricity, by means of a water powered turbine generator and sends it directly to the surface grid. No electricity gets stored for later use anywhere in the system. It's not necessary
I can think of a possible use for a battery, if the surface grid goes completely down and you need to pump out the full water tanks in order to produce power independent of the grid.
It's like having a home generator . Power goes out, you start your generator and power comes on. But instead of gasoline this system uses the kinetic energy provided by freeflowing high pressure ocean water to drive a turbine generator, which does not store but sends the electricity it generates directly to the surface grid. I'm sure you can add batteries, but that just complicates the underwater housing and why use batteries when you are directly connected to the surface grid?
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and using the ocean depths instead of a hole in the ground is no different...in thermodynamic principles
Yes?
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No different in overall principle - only in particulars. In every 'gravity fueled' scenario possible, there is simply exchange of one form of energy for another. With no cyclic gain possible. Let's run through the specifics quoted in p9 #174:
Initially a fully expanded cylinder containing air is poised just above the ocean surface. There experiencing just gravitational force of magnitude mg. Lowering it till just fully submerged has steadily reduced the effective weight to zero when fully submerged. There has been a loss of cylinder PE and a concomitant gain in ocean PE, since it's level must rise against gravity during this process. Further lowering the cylinder - now having neutral buoyancy - entails no appreciable further energy exchanges (finite compressibility of the cylinder is entirely material dependent thus not fundamental to the basic physics, and at any rate will be very small).
At the bottom, the cylinder is allowed to compress piston-like. The ocean surface level now drops back to almost the level initially before cylinder submersion - reducing it's PE accordingly. But that merely accounts for almost the initial PE gain when the cylinder went from dry to just fully submerged. It does not account for the huge driving pressure at the ocean depth creating much more pneumatic PE than that involved in the initial submersion energy exchanges. Where then does the extra energy come from?
The answer is there in plain sight. Compressing the cylinder at depth has simultaneously lowered the PE of the cylinder - it's no longer at neutral buoyancy and weighs almost as much as when suspended in air. Hauling it back up accounts for all the apparent magical gain in pneumatic energy of compressed air.
To repeat from p7 #128, for a gravitational field
∇ x -∇φ = 0. Zero curl. The latter is a fundamental mathematical fact and excludes any possibility of net gain or loss of energy over a closed path. One-way trips are pointless, as stated many times this thread.
Are we finally done here?