# Pressure Harvesting - from ocean depths

we are extracting potential energy in the form of pressure using air as a medium from an ocean that is providing the energy inputs.
No, you are providing the energy inputs by winching the thing down into the ocean.
Sinking a container of air IS compressing the air in the container.
Yes. So is using an ordinary compressor.
The oceans do provide a natural form of compression as the container sinks.
So does a bicycle pump.

Sink your bike pump (plunger extended)
1. lock of the plunger ( at the depth required)
2. retrieve it
and you have harvested the pressure at depth.
No, you have not.

If you lock the plunger before you start, there is no increase in pressure and lowering it is as easy as raising it (no energy expended, no compressed air.)

If you lock the plunger at the bottom, then it is buoyant on the way down and not as buoyant on the way up, requiring energy to get the pump to the bottom and back up (energy expended, compressed air.) It is the same as using that energy to push down the plunger.

No, you have not.

If you lock the plunger before you start, there is no increase in pressure and lowering it is as easy as raising it (no energy expended, no compressed air.)

If you lock the plunger at the bottom, then it is buoyant on the way down and not as buoyant on the way up, requiring energy to get the pump to the bottom and back up (energy expended, compressed air.) It is the same as using that energy to push down the plunger.
• The pump plunger is extended and not locked down until it is at the desired depth.
• The desired depth could be at any depth on the way down...
• The pump plunger is compressing the air as it goes down reducing buoyancy.
• When it at it's maximum depth the compressed air has reduced buoyancy.

Why is so hard to fathom ( excuse the weak pun) the simplest of scenarios here on sciforums?

You have a bike pump with compressed air in it, at depth.
Now all you have to do is retrieve it...after locking down the plunger.
Once retrieved you have harvested pressure.

Why is this principle so hard to grasp?
What are you scared of?

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Harvesting high altitude low pressure would simply require a glass jar with an air tight lid that you open and close before bringing that jar down to sea level.

If you lock the plunger at the bottom, then it is buoyant on the way down and not as buoyant on the way up, requiring energy to get the pump to the bottom and back up (energy expended, compressed air.) It is the same as using that energy to push down the plunger.
so...what?
You are still harvesting pressure even if you cost you a million USD you are still harvesting pressure...

It is the principle of acquiring potential energy from a non-depleting resource that has you guys so frazzled.
The energy cost of doing so is not the issue...

notes:
the cost of onsite compressed air ranges between 30 -50 cents per 1000 cubic feet
Total cost per cubic foot is any ones guess, but a hell of lot higher than 30-50 cents. Especially if you consider the AGW involved.
Goggle : Cost of compressed air

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so...what?
You are still harvesting pressure even if you cost you a million USD you are still harvesting pressure...
Right. And if you use your arm instead of the ocean you are still harvesting pressure. If you boil water in a secondary loop in a CCS natural gas plant, and use that to spin a turbine, you are still harvesting pressure. But all three of those things require you to input more energy than you get out.
It is the principle of acquiring potential energy from a non-depleting resource that has you guys so frazzled.
You are not "acquiring potential energy." You are just turning one form of energy into another. And in your ocean case, it is the energy required to pull the container thousands of feet underwater.

For God's sake, learn some math.

• The pump plunger is extended and not locked down until it is at the desired depth.
• The desired depth could be at any depth on the way down...
• The pump plunger is compressing the air as it goes down reducing buoyancy.
• When it at it's maximum depth the compressed air has reduced buoyancy.
Exactly. And it has reduced buoyancy all the way back up. So it takes energy to pull it down there, and you don't get the energy back.

Exactly. And it has reduced buoyancy all the way back up. So it takes energy to pull it down there, and you don't get the energy back.
so what?
you are still harvesting pressure....
look.
I place a ten ton anchor on our extended bicycle pump. Drop it over the side, it goes to the bottom traps compressed air, I lock down the pump.
I then drop another similar arrangement of the side which is cable attached to the first arrangement via pulley on the surface.
One goes down the other comes up with a little help.
Harvested pressure...

or do the same with out the pumps... result: no harvested pressure...

No pumps= no harvested pressure
with pumps = harvested pressure.

so what?
you are still harvesting pressure....
Yes. You are harvesting pressure in a steam engine. You are harvesting pressure in a natural gas CCS plant. You are harvesting pressure when you run an internal combustion engine. All those things turn a less useful form of energy (say, natural gas or coal) into a more useful form of energy (motion or electricity.)

All your system does is turn electricity into a less useful form of energy (pressure.)

Yes. You are harvesting pressure in a steam engine. You are harvesting pressure in a natural gas CCS plant. You are harvesting pressure when you run an internal combustion engine. All those things turn a less useful form of energy (say, natural gas or coal) into a more useful form of energy (motion or electricity.)

All your system does is turn electricity into a less useful form of energy (pressure.)
The effective efficiency of harvesting pressure is yet to be determined.
It wont be until the principle itself is understood.
It has taken many posts just to get past all the hysteria.
Member Origin got it in two posts...

So now after many posts you can finally agree that even if it is not cost effective in your opinion, harvesting pressure from ocean depths is possible.

The difference between harvesting pressure from conventional sources is that that pressure costs a lot to generate, where as the oceans can generate that pressure for free.
Costs of mining coal vs costs of mining oil vs the cost of mining uranium etc all non-renewable and dirty.
The cost of mining pressure from the oceans is yet to be determined. But it is a clean and infinite resource that will be around as long as the oceans exist.

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The point is that pressure can be mined as a primary resource. You could even use your back yard swimming pool say (6 feet deep, 17.36 psi) if you had a need for low pressure pneumatics.
If your pool was 30 feet deep you could pump up your car tires to 28psi with mined pressure.

Or build a 100 meter by 30 meter dia. tall water tank to harvest 160psi for higher pressure needs.
Essentially where ever there is a sizable body of deep liquid it is mine-able for pressure.

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The effective efficiency of harvesting pressure is yet to be determined.
It is very easy to determine. Use math.
It wont be until the principle itself is understood.
The only person who does not understand the basic principles here is you.
So now after many posts you can finally agree that even if it is not cost effective in your opinion, harvesting pressure from ocean depths is possible.
It is not practically OR theoretically possible to "harvest energy from the ocean depths" and get net energy out. Period.
The difference between harvesting pressure from conventional sources is that that pressure costs a lot to generate, where as the oceans can generate that pressure for free.
You have already admitted that you need energy to get the container down there and back up. So it's not free.
Costs of mining coal vs costs of mining oil vs the cost of mining uranium etc all non-renewable and dirty.
The cost of mining pressure from the oceans is yet to be determined. But it is a clean and infinite resource that will be around as long as the oceans exist.
To "harvest energy from the ocean depths" you need to put in more energy than you get out - so you have to burn coal or use uranium to get your pressure.
The point is that pressure can be mined as a primary resource. You could even use your back yard swimming pool say (6 feet deep, 17.36 psi) if you had a need for low pressure pneumatics If your pool was 30 feet deep you could pump up your car tires to 28psi with mined pressure.
Two questions for you.
What pressure will you see at the bottom of a 30 foot deep pool?
How would you use that to "pump up your car tires?"

It is not practically OR theoretically possible to "harvest energy from the ocean depths" and get net energy out. Period.
Pressure harvesting is harvesting potential energy..

Pressure harvesting is harvesting potential energy.
Nope. It's just physics that doesn't get you any more energy than you had before.

Again let's do the math. You posted above that you can "use your backyard swimming pool" to "pump up your car tires." Let's see if your idea works in reality.

What pressure will you see at the bottom of a 30 foot deep pool?
How would you use that to "pump up your car tires?"

Nope. It's just physics that doesn't get you any more energy than you had before.

Again let's do the math. You posted above that you can "use your backyard swimming pool" to "pump up your car tires." Let's see if your idea works in reality.

What pressure will you see at the bottom of a 30 foot deep pool?
How would you use that to "pump up your car tires?"
So you think it is an exercise in futility but harvesting pressure is possible?
In the mean time you could quote me posting the pressure at 30 feet in an earlier post.

So you think it is an exercise in futility but harvesting pressure is possible?
You keep using that word "harvest." If you think it means "see high pressure" then yes, you will see high pressure at the bottom of the ocean. If you think it means "get some renewable energy from all that pressure" then no, you cannot.

Important points:

There is high pressure at the bottom of the ocean.
You can use that to compress things.
You will ALWAYS use more energy to accomplish that compression than you will get out of your system.

You keep using that word "harvest." If you think it means "see high pressure" then yes, you will see high pressure at the bottom of the ocean. If you think it means "get some renewable energy from all that pressure" then no, you cannot.

Important points:

There is high pressure at the bottom of the ocean.
You can use that to compress things.
You will ALWAYS use more energy to accomplish that compression than you will get out of your system.
I am mobile but I'll give it a go on the fly.
Going down:
The extended pump will loose it's displacement as the plunger side of the chamber fills with ambient water. It will loose buoyancy as the plunger compreses the trapped air and sink with out any aid all the way till it rests on the bottom.
So going down costs no energy.
Going up:
As the pump is self adjusting it's buoyancy as it descends it remains slightly buoyant (weighs less) at the bottom.
As it is being raised to the surface it will gain weight due to the compressed air being retained after being pressurised.
When it leaves the water the pump will weigh it's original weight plus the extra weight that the compressed air would impart. ( neglible in this case)
Summary
The only energy cost is in the retrieval and in the case of a simple bike pump a fishing rod and reel would suffice.
Re: Archimedes' principle, Fluid Mechanics

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I am mobile but I'll give it a go on the fly.
Going down:
The extended pump will loose it's displacement . . .
You keep using words you do not understand. Use math instead.

Choose a volume of air. Calculate the work needed to get it to some depth. Calculate the work you will get back (if any) as it rises with a smaller displacement. Then calculate the potential work that can be done by the compressed air.

If you can't do the math, you aren't capable of understanding your error.

You will ALWAYS use more energy to accomplish that compression than you will get out of your system.
The compression itself requires no added energy.
It is the retrieval of that compressed air that may require energy.