Its certainly possible, but would have to be nearly 3000 feet deep.... quite a engineering feat.
even if you could get to 500psi and double it with heat... What would you do with it?
it would cost 10's of thousands for piping and storage.
Its certainly possible, but would have to be nearly 3000 feet deep.... quite a engineering feat.
even if you could get to 500psi and double it with heat... What would you do with it?
it would cost 10's of thousands for piping and storage.
There has to be something we are missing with regards to PSI of air pressure and the depth the water has to drop prior to dropping off the air. These depths sound insane & not wise to approach.
yer, hw do you maitenance this beast of yours? and we are moving away from the post title of "cheapest." was hoping to find the most cheapest/most economical power source for a househould.
In the end, we all work for ourselves.
well if you have 200ft of fall on your property you've found it.
if you have to drill a 200 ft well with a kick at the bottom its probably not that cheap.
I was talking with a friend last night at length, we reckon the depth is to increase cooling of the air and keep it that way. The venturi principle which is essentially what we are messing with is already in practice in salt water aquariums in the guise of "Protein Skimmers" which works the opposite of the Trompe. In a Protein Skimmer, the air goes up as the water goes down. This causes dissolved organics on the water surface to breakdown into a brown frothy disgusting looking stuff. You can find this exact action on any beach in the world at high tide, you will see a line of brownish foam floating on top of the water. The high tide generally deposits this waste onto the beaches.
So, going back to the Trompe now, the system should be simple to capture. Pressure will be directly related to how well the air housing can hold air, its volume, etc.
Thus, IMO, what we need to do first is not make the trompe device, but first figure out how to house the air cheaply underground, safely. Some thing everyone can do cheaply with materials on hand.
The air will stay at whatever temperature the water is, and pressure will be directly related to height..
making the chamber to hold the air is definitely the biggest engineering problem though for sure.
I disagree. Air temp is cooled on the way downwards, and air temp is maintained by being surrounded by cool earth in the collection chamber. Pressure is related to height, but also to collection. When air is released you have less pressure, and more water in the chamber.Originally Posted by Wolf_rt
when air is released, you will have less air, same pressure, because it still has the same amount of water sitting on it, which is what provides the pressure.
Once the air has been collected at the bottom, it may stabilize to the temp of the surrounding earth, which may be cooler than the water, but that has nothing to do with the air being isothermally compressed, if you heat or cool isothermally compressed air after it is compressed it is still isothermally compressed.
the contrast is against a piston compressor, which will burn you if you touch the output pipe while the compressor is running.
The volume of the storage will not affect air pressure, because if it isn't full of air, it will be full of water. the air/water pressure will be equal at whatever depth you choose, and can be calculated the same as pump head. ie, the 35psi per 15 ft figure you supplied.
If the 'tank' at the bottom, is leaky, that will certainly cause a drop in pressure, and likely failure of the whole system.
The air pressure will vary slightly (in equal proportion to the 15psi-35 foot ratio) as the volume of air increases and forces the water level lower, until the vent level is reached.
I found this more accurate way to determine pressure on wiki...
Pump curves in feet of head can be converted to pressure - psi - by the expression:p = 0.434 h SGso:
where
p = pressure (psi)
h = head (ft)
SG = specific gravity
p= 200 ft (for example) measure from the surface of the water entering the trompe, to the bottom of the vent pipe (or the top of the bend in the input shaft, if no vent)
SG= 1 (for fresh water at 60def F)
so 0.434 x 200 x 1 = 86.8psi for a 200 ft drop.
As far as creating the tank goes, only the section above the vent level needs to be airtight, if water leaks out the bottom it won't effect the operation of the trompe.
also, the pressure of the earth pressing against the sides of the tank increases in the same proportion as the water/air pressure, the further you go down so a particularly strong tank is not required, as long as it is completely buried.
As to how to make a spot for the tank 200ft down in the earth.. its got me stuffed.
I guess you could drill a well large enough to admit a person who could hollow out the bottom of the well as required, would be prohibitively expensive though.
the other option i see, is to build the whole trompe into the side of a cliff/steep hill.. the storage tank would have to be able to handle the pressure on its own though, as there would be little soil above it.
Last edited by Wolf_rt; 21-12-2011 at 10:15 AM.
I had an idea.... if you drilled two wells to intersect at the bottom, then lined and capped one of the wells to act as a tank, with the vent and output coming thorugh it, it may work.
With such a vertical tank though, the air pressure would be quite variable, depending on the water level in the capped well.
I disagree. We are supposed to have a chamber that fills with water and air, that's the beginning basis of the whole system!! As the air fills the chamber, the water level goes down till it is under pressure.
Isothermally cooled is just fancy way of saying the air & water gets cooled by the earth as it travels down the pipe to the collection chamber
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