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Posted by CT on January 9, 2006, 4:57 pm
 
This was awesome. Thanks!!!!!


Posted by dold on January 9, 2006, 11:53 pm
 


I wandered around your site, including plugging in the values for my home,
(214 degree face, 26 degree roof, 38.8 latitude, 1100 foot elevation.)
I looked at some of the referenced links.

I don't see anything about using a solar powered pump in conjunction with
the solar collectors.  Doesn't that seem like a good idea, or is that an
investment with too long of a return?

My 12x32x4 semi-above ground pool is in a courtyard, and gets a lot of
shade.  There's no room for anything but a roof mount collector, and my
current pump was not thought to be up to the task of pushing water to the
roof.  The buried plumbing is all on the wrong side of the pool anyway.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA  38.8,-122.5


Posted by Gary on January 10, 2006, 2:05 am
 dold@XReXXSolar.usenet.us.com wrote:

There is some stuff on the site about solar pumping here:
http://www.builditsolar.com/Projects/WaterPumping/waterpumping.htm

These applications are more like well water pumping, stock watering, and some
low flow solar water heating.

I've never seen any mention of running a pool type pump on solar.  Maybe this is
because they tend to be quite large pumps and it would take a lot of PV panel
area.  The solar pool heating applications I've seen make use of a portion of
the water ciruclated by the regular pool pump for filtration.  Maybe the
thinking is that since you need this pump to circulate water for filtration
anyway, that you are getting the solar panel circulation for "free"?

In your situation, maybe adding a separate and smaller pump just to circulate
water to the collectors might be in order.  I am guessing that this is still
likely to be a pretty large pump to do on solar.  If the collectors drain down
when they are not collecting, then the pump has to have enough head capability
to initially push the water up to the collectors.  Once the water has filled the
whole collector circuit, the head requirement goes way down, but you still need
a pump that can produce the high head at startup.  In solar hot water heating
systems for houses, this type of drain back system is not typically done with a
solar powered pump, because the PV panel size needed to drive such a high head
pump is large.

I think that by the time you built a solar electric system capable of driving
one of the large pool pumps, you would be better off just to do a regular grid
tied PV system for the house that could serve other house loads (or the grid)
when the pool pump was not pumping.  This would make better use of the money
that went into the PV system?

What I know about pools would fit on the head of a pin -- maybe others have some
thoughts on this?

--


Gary

www.BuildItSolar.com
gary@BuildItSolar.com
"Build It Yourself" Solar Projects









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Posted by dold on January 10, 2006, 8:53 pm
 
Ooo.  Good stuff.


My solar projects are PV panels (done, 3.8KW), Domestic water heat, pool
heat, Solar Sponge space heat, and cold water.  I have a 100 foot hill, so
I want to pump up from the well to a tank during the day.


Maybe that's where I've gone wrong.  Maybe I am underestimating the size of
pump that I need.  I'll visit your referenced pages for more clues there.


But it's not free, because my pump isn't running during the day, unless I'm
in the pool.  I think it's convenient for plumbing, keeps the cost of the
system down to $00 for a couple of black panels, and there you go.


That is likely.  I need to crunch some numbers.  For the well, I can trade
power for time.  I can't pump 20GPM, but I can pump all day to a storage
tank at a lower rate, and gravity feed at 20GPM for a while.


I don't think the head changes.  Getting the first drop of water 20 feet
high requires the same head pressure as keeping it going.


If you say that's true, then I am surprised.  In a closed loop, some of the
water will be siphoning, but I got the impression that the drain down was
open at the top, and didn't use siphoning.  Maybe that's the startup cost.

Why use the drain back system then?  The pool use will be discontinued long
before we have a freezing night.


Sigh.  I guess so ;-)
I don't know what flow rate I need.  I need about 20 feet of head.  That
doesn't seem like a large pump, but i haven't looked at numbers yet.


The fact that no one is marketing it suggests that it might not be a good
idea.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA  38.8,-122.5


Posted by SolarFlaire on January 10, 2006, 11:21 pm
 Not quite. There is no siphoning effect neutralizing
the water being pumped up the incline. After the water
begins to descend on the other side it equalizes the
head pressure back to zero or even lower if the basin
exit is below the pump supply. No pump is required for
a siphon.

This only applies in an open system. In a closed system
only the resistance of the plumbing is a factor. There
will be little head to consider.



drop of water 20 feet


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