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question about low tech solar water pump

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Posted by chriS RING on February 10, 2004, 5:17 am
a couple years ago on the net, I read about pumping water as follows:
coil about 100' of black poly tubing, with a check valve on each end.
One end goes to bottom of shallow well, bulk of coil lays on the
ground in the sun. The coil must be primed with water to begin.
 1)Sun warms water in coils, water expands, a small quantity exits
coils through upper end (check valve)
 2) Cloud moves between sun and coil, water contracts, pulls water in
through lower check valve.
 3) Cloud moves away, and step 1 repeats.
Has anyone had experience with this pump, any reason it shouldn't
I am curious about optimum tubing size, length, etc.
Chris in Austin, Tx

Posted by Ecnerwal on February 10, 2004, 12:23 pm
 chrisring@austin.rr.com (chriS RING) wrote:

Dissolved gases. The cold water in the well has air dissolved in it.
When it warms in the pipe on the ground, air will come out of solution.
I strongly suspect that it will lose it's prime on a regular basis. I
also expect that if it works, it will have essentially one trickle per
day, not one trickle per passing cloud.

But do feel free to experiment and report back.

Cats, Coffee, Chocolate...vices to live by

Posted by Gary on February 10, 2004, 3:10 pm
 If you assume the pipe itself does not expand,
then for a 100ft of 2 inch pipe for a 100F temperature rise, you would get:

    Water produced = a * V * dT            (a = cubical expn coef of water
                              = (0.000115)(1*1*Pi *100*12) (100) = 43 in^3
(or about 0.2 gal)

But, it looks like most plastics have expansion coefs that are larger than
water, so
the pipe would probably expand more than the water does as it heats up, and
wouldn't get anything??


Posted by Duane C. Johnson on February 10, 2004, 11:16 pm
 Hi Gary

Gary wrote:

Sure you would. Its just that it delivers the water
when it cooles and lifts the water when it heats.

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Posted by Gary on February 11, 2004, 11:05 pm
 Hi Duane,

Yes, I think you are right.
In fact, I think that since the poly pipe has three times the expansion
coef of water, it would work better than a pipe that did not expand at
all -- maybe 2 quarts from the 100 foot hose instead of 1 quart.


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