Gravity Mill - any comments to this idea?

[tbird]

Announce, Announce...

ELSACALC now calculates the recompression requirements and excess water.  Read it 'n weep ('cause we never worked on this earlier).

Anyone care to check my calculations?

http://declarepeace.org.uk/energy/elsa.htm

at the beginning you say "To compress 1 litre of air to twice its volume we need to double the weight on top of it."  twice sounds like just the opposite of what you mean.  that is just a "being tired" mistake.  i understand.

We can compress the air in a cylinder. The smaller the diameter of the cylinder the less weight we need on our piston but we will have to compress it over a greater distance.

i believe this is wrong.  it may work with liquid, but not gas.  if you apply 1kg of weight, that is all the pressure you will gain divided by the area it is applied to.  to gain the whole 1kg., you would have to apply that amount to each square unit you are using.

i'll try to find a website to confirm.  hope i'm wrong, but think not.

tbird 

[ooandioo]

stefan, nice idea - but how will you arrange the whole system (especially the header tube and main water feeding)?
Can you explain more?

Andi.

[prajna]

Yes, tbird, you caught me out with back to front explainations again.  'twice' should read 'half'.

If I have a cylinder full of air it has a weight of 1kg/cm² acting on the top of it (the atmospheric pressure).  If I add 1kg/cm² to the top of it then it will compress it to half its volume. It is now at twice atmospheric pressure.  Double the weight, double the pressure, halve the volume.

Height comes into it when we need to store a certain volume in a particular diameter cylinder.  I managed to confuse myself there I think.  I'll try to clarify my thinking on the page.  The sums should be correct now though, don't you think?

[tbird]

Yes, tbird, you caught me out with back to front explainations again.  'twice' should read 'half'.

If I have a cylinder full of air it has a weight of 1kg/cm² acting on the top of it (the atmospheric pressure).  If I add 1kg/cm² to the top of it then it will compress it to half its volume. It is now at twice atmospheric pressure.  Double the weight, double the pressure, halve the volume.

Height comes into it when we need to store a certain volume in a particular diameter cylinder.  I managed to confuse myself there I think.  I'll try to clarify my thinking on the page.  The sums should be correct now though, don't you think?

i still have a problem with you using absolute pressure.  if anybody should use it, it would be a scuba diver, but they don't.  consider this; if you have an empty container and put a lid on it, how much pressure is inside?  if you use an average gage, say like you use to check the pressure in your car tires, it will read 0.  now if you can apply 1 bar to the container, you could take it to 10m (we'll say that is 1 atmosphere) deep without it being crushed in because it exerts more pressure inside than is being applied outside at any depth less than 10m.  if you try to take it deeper, it will start to collapse.  now at 10m if want to expand the volume, we would need twice the pressure.  that's how we get to the 2nd bar needed to expand the volume to twice at 10m.  compressing the air will change the weigh, but i doubt we could read it on our scales.  to get the container to depth, we have to build i the weight to the container.  a 10kg container with 1 bar of pressure inside will float or sink the same as if it had 2 bar of pressure.  if we allow the container with 2 bar to expand the air volume to twice, then the pressure in both containers would be the same, but the buoyance would be different.

in your example, to read 2 bar, you would have to use an absolute gage.  i don't have one and it won't expand at 10m.  sorry.

tbird

[prajna]

confuses the hell out of me too tbird.  1 bar = 14.503861 psi =  0.9872 atmosphere = 1.02 kg/cm² (which means I should fix my 14.7 psi etc on my site; dunno where I got that figure from).

What is the pressure in a container if I double the volume of air in it?  If you are going by gage pressure then the pressure is 0 psi or 0 bar before I double it.  What is 2 times 0?  Yep, that is why I use absolute pressure because then my unpressurised container has 1 bar or 1 atmosphere or 14.5 psi in it and when I double the pressure it becomes 2 bars or 2 atmosphere or 29 psi.

Don't use my 'absolute gage' when you inflate your tires and I won't use your tire gage when I am calculating pressures.