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Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: scientizscht on 16/06/2018 19:33:47

Title: Can I store unlimited energy as pressure?
Post by: scientizscht on 16/06/2018 19:33:47
Hello!

Let's say I have a system that can generate 10kg force.

I use this system to compress something, a medium like liquid or gas.

I operate it once and it stores pressure. Can I repeat that until unlimited pressure is stored?
Title: Re: Can I store unlimited energy as pressure?
Post by: Bored chemist on 16/06/2018 20:27:45
It's not clear what you mean. Do you know what force, pressure and energy actual mean?

I read that the total force that the strings put on the frame of a piano is about 30 tonnes.
But none of the strings, by itself, produces anything like that force.
Title: Re: Can I store unlimited energy as pressure?
Post by: scientizscht on 16/06/2018 21:08:20
It's not clear what you mean. Do you know what force, pressure and energy actual mean?

I read that the total force that the strings put on the frame of a piano is about 30 tonnes.
But none of the strings, by itself, produces anything like that force.

OK, I will explain it in other words.
Let's say you can exert a force of only up to 10kN. You physically have this limited capability only, ok?
Can you pump a fluid continuously to generate let's say 100bar or unlimited pressure? Is there any mechanism that will allow you do that?
Title: Re: Can I store unlimited energy as pressure?
Post by: Kryptid on 16/06/2018 21:09:28
Hello!

Let's say I have a system that can generate 10kg force.

I use this system to compress something, a medium like liquid or gas.

I operate it once and it stores pressure. Can I repeat that until unlimited pressure is stored?

I'm afraid not. There will be limits to the strength of whatever machine you can create that is applying the pressure. Any container with a compressed gas in it will rupture if the pressure inside becomes too great.
Title: Re: Can I store unlimited energy as pressure?
Post by: scientizscht on 16/06/2018 21:23:26
Hello!

Let's say I have a system that can generate 10kg force.

I use this system to compress something, a medium like liquid or gas.

I operate it once and it stores pressure. Can I repeat that until unlimited pressure is stored?

I'm afraid not. There will be limits to the strength of whatever machine you can create that is applying the pressure. Any container with a compressed gas in it will rupture if the pressure inside becomes too great.

Oh come on, you still do not understand! Let's say you have very strong container!
Is it possible if you can only exert 10N force, to pump fluid that will reach 100bar?
Title: Re: Can I store unlimited energy as pressure?
Post by: Kryptid on 16/06/2018 21:30:39
Oh come on, you still do not understand! Let's say you have very strong container!

No container is infinitely strong.

Quote
Is it possible if you can only exert 10N force, to pump fluid that will reach 100bar?

On the surface of it, I'd say you can't increase the pressure of a gas any further once the pressure you are exerting on it matches the pressure of the gas itself. Maybe I'm wrong, but that does seem logical.
Title: Re: Can I store unlimited energy as pressure?
Post by: Bored chemist on 16/06/2018 22:11:40
If you use a small enough piston, the same force- say 10KN- will generate an arbitrarily high pressure (until something breaks).

In particular, 100 Bar is 10^7 Pa i.e. 10^7 N/ m2

And you have a force of 10^4 N
So, as long as your piston has an area of less that 0.001 metres square you will get a pressure higher than 100 Bar.

For example, if the piston is 3cm by 3cm (square pistons are odd, but it makes the maths easy) and a force of  10KN you will have a pressure of 10000/ (0.03*0.03*)  which gives 111.111 Bar.
Title: Re: Can I store unlimited energy as pressure?
Post by: chiralSPO on 16/06/2018 22:34:32
I think it is worth pointing out that force can be represented with units of Newtons (N), pressure can be represented with units of Nm2, and energy can be represented with units of Nm. These are all related, but none can be equal to the other because the units are not the same.

I can exert a force of 20 N on a piston with cross-sectional area of 0.001 m2, resulting in an applied pressure of 20000 Nm2. If the piston doesn't move at all, then it doesn't matter how hard I push, no work will be done (no energy added to the system). If the piston moves 0.05 m while I apply a constant force of 20 N (we are assuming that the change of internal pressure is negligible, and the compression happens slowly), then I have done 1 Nm of work (increasing the energy of the gas by 1 Nm).
Title: Re: Can I store unlimited energy as pressure?
Post by: scientizscht on 16/06/2018 22:36:00
If you use a small enough piston, the same force- say 10KN- will generate an arbitrarily high pressure (until something breaks).

In particular, 100 Bar is 10^7 Pa i.e. 10^7 N/ m2

And you have a force of 10^4 N
So, as long as your piston has an area of less that 0.001 metres square you will get a pressure higher than 100 Bar.

For example, if the piston is 3cm by 3cm (square pistons are odd, but it makes the maths easy) and a force of  10KN you will have a pressure of 10000/ (0.03*0.03*)  which gives 111.111 Bar.

Very interesting, so theoretically, you can pump up to very high pressures even if you have weak arms that do the pumping. The point is to have a pump that is very thin, if I got it right?
Title: Re: Can I store unlimited energy as pressure?
Post by: alancalverd on 16/06/2018 23:05:50
That's how hydraulics works.

There are practical limits with very thin pipes, where viscosity produces significant energy loss from a moving liquid, but hydraulic jacks and pneumatic tyre pressure  pumps are familiar examples of force multiplication.
Title: Re: Can I store unlimited energy as pressure?
Post by: Kryptid on 16/06/2018 23:16:15
@chiralSPO @Bored chemist

Thank you for that clarification.
Title: Re: Can I store unlimited energy as pressure?
Post by: syhprum on 17/06/2018 06:04:57
There was much discussion about a year ago about clockwork cars that work fine if you use magic gear boxes that output more energy than you put in!
Title: Re: Can I store unlimited energy as pressure?
Post by: PmbPhy on 17/06/2018 11:27:37
It's not clear what you mean. Do you know what force, pressure and energy actual mean?

I read that the total force that the strings put on the frame of a piano is about 30 tonnes.
But none of the strings, by itself, produces anything like that force.
Any string under tension produces a force where tension is defined as a force related to the stretching of an object.

Recall Newton's third law; if I have one end of a piano string which is attached to a piano end and I pull on the other end then the other end will pull back on me using and equal but opposite force. In reality this is true for all matter. For example; I was a weapons mechanic on the A-10. I cleaned and overhauled bomb racks and the 30 mm gatling gun on it. It had a spring composed of a metal allow which were made to sit inside of each other in a stack. To you and me it'd seem just like a stack of metal. However it was that which acted as a spring so the A-10 frame didn't get rattled apart after so long.

As to the OP nothing can be done to create something unlimited. That's an impossibility.
Title: Re: Can I store unlimited energy as pressure?
Post by: scientizscht on 17/06/2018 12:58:58
As to the OP nothing can be done to create something unlimited. That's an impossibility.

You focus on the wrong point. You miss the whole point of the question. You can replace 'unlimited' with comparably very large. Let's not play with words.
Title: Re: Can I store unlimited energy as pressure?
Post by: jeffreyH on 17/06/2018 15:14:54
As to the OP nothing can be done to create something unlimited. That's an impossibility.

You focus on the wrong point. You miss the whole point of the question. You can replace 'unlimited' with comparably very large. Let's not play with words.

In which case why did you include the word unlimited in your question?
Title: Re: Can I store unlimited energy as pressure?
Post by: Janus on 17/06/2018 15:42:15
If you use a small enough piston, the same force- say 10KN- will generate an arbitrarily high pressure (until something breaks).

In particular, 100 Bar is 10^7 Pa i.e. 10^7 N/ m2

And you have a force of 10^4 N
So, as long as your piston has an area of less that 0.001 metres square you will get a pressure higher than 100 Bar.

For example, if the piston is 3cm by 3cm (square pistons are odd, but it makes the maths easy) and a force of  10KN you will have a pressure of 10000/ (0.03*0.03*)  which gives 111.111 Bar.

Very interesting, so theoretically, you can pump up to very high pressures even if you have weak arms that do the pumping. The point is to have a pump that is very thin, if I got it right?
The downside is that as the pump get's thinner, the number of pump strokes you'll need to build up to the same pressure in the container increases, or alternately, the distance the piston travels per stroke has to increase. 
Title: Re: Can I store unlimited energy as pressure?
Post by: PmbPhy on 17/06/2018 17:02:34
As to the OP nothing can be done to create something unlimited. That's an impossibility.

You focus on the wrong point. You miss the whole point of the question. You can replace 'unlimited' with comparably very large. Let's not play with words.
Nope. My point is quite precise at all, contrary to your claim (mind reading are you?) since you quite literally said "unlimited pressure". You also asked about "unlimited energy as pressure". You keep using unlimited then change your tune claiming you meant something else, then claim I miss the whole point. Everyone knows energy is stored in a gas so long as the temp is not 0K (which also is impossible). Any gas can do work as evidenced by cars driving on the highways. Its also use in pneumatics to do work.

As Jeff said, if you didn't mean unlimited why did you use that term? It's you who are playing with words. You may have meant "with a limit" but your claim about comparably large is without basis since you don't know what you're comparing it to. And in science forum we assume what you write is what yo mean.

You appear to have meant quite literally meant unlimiting since it appears to me that he has a perpetual motion machine in mind which produces energy without limit. which of course don't exist.

I'll thank you to stop with the mind reading attempts, shall we? I.e. don't put words into my mouth(/keyboard).

If you meant limited then the answer is still no, depending on what you have in mind. When you place the 10kg on a piston to compress gas then it will only compress it so much, i.e. until the force due to the pressure in the gas yields a force of 10N. Then the piston won't move. So what do you mean repeat? Place another 10 kg weight on the piston and continue the process until you run out of weights?

Exactly what are you trying to figure out? Please give a solid example to help us help you.
Title: Re: Can I store unlimited energy as pressure?
Post by: Bored chemist on 17/06/2018 18:40:54
As to the OP nothing can be done to create something unlimited. That's an impossibility.

You focus on the wrong point. You miss the whole point of the question. You can replace 'unlimited' with comparably very large. Let's not play with words.

In which case why did you include the word unlimited in your question?
Perhaps he expected it to be interpreted figuratively, rather than literally.