How to choose the right pump for use with a small PV system - advice needed (newbie)

SystemSystem Posts: 2,511 admin
Hello everybody!
This is my 1th post to this forum. I've been reading the last posts and let me congratulate you all for the real interesting and usefull information you share here.

I'd appreciate if someone could advise me in choosing the right solar pump for use with a very small PV system I've just build at an isolated farm (off grid) in the North of Portugal: 50 W PV panel + 16 A charge control. combined with DC-AC inversor + lead accid bat. 180 Ah. Althoug I was able to install this system by myself, I have very little experience in all this... So, here's my questions:

About 30 meters from the house there is what locals call a 'water mine' - a sort of a short tunnel escavated into the granite 2-3 meters under the ground from where the water comes; it forms a sort of pond 2-2,5 meters deep (the water flows very slowly and goes into a set of similar ponds further in the lower parts of the property; they where used for agricultural purposes when the farm was a real farm). The water surface is about 2,5-2,8 meters deep from the ground level.

I'm looking for the right solutions (using PV energy) for 2 situations:

1th - force the circulation of the water in the 'mine' (so it would create less water plants and other organic stuff thanks to simple mechanical oxygenation) by installing a small 12V dc pump. In the future I am planning to install a container with a set of pipes (placed about 3-4 meters above the mine) containing 2 or 3 lawyers of some mineral granulate and plastic stuff as a bio-filter so it would be possible to improve slightly the water quality.

After a long research (in Portugal the market is so small that it's almost impossible to find this sort of things), I managed to order (from Germany - brand: Barvig) a small 12v dc pump (10L/min) which draws only 1,7Ah/h (which is fine since my actual PV system is still a very small one). Still, the pump manufacturer claims that this 12V pump can operate continuously only if feeded by a 9V dc current. So, my 1th question is: does anyone know about some device which would allow to connet to my 12V PV system for convertion 12V DC into 9V DC? The ideal would be that this same device would have as well a built-in timer so I could use the pump for only several hours every day... I noticed that some charge controlers offer these features (Phocos, series PL), but they're for big PV system's... Or maybe there's some other better solution?

2d question - I want as well to provide water into the small house (just for a couple of weeks/year for 3-4 persons). I am considering to purchase a pression pump. In ideal terms, I would choose a model which would allow to collect the water straight from the 'mine' (i.e., from aprox. 30 meters in the horizontal and 2,7-3,00 manom. height from the water level) keeping at the same time enough pressure so I could use a small heater (1,5-2,0 bars).

At the Shurflo site I saw different models which might be appopriate, but I am not sure which model would suites best my purpose: one of the 2088 series or one of the 'Extreme Smart Sensor 5.7' series? This last model offers more pressure and looks ok, although more expensive. Yet, the thecnical notice says that it primes up to 9' (2,7 meters). My question is: does this means that this pump does not operate for a higher manometric height (say, for 3-3,5 meters deep?) or rather this means that for a higher vertical lenght it will operate slower? Maybe there's another brand/model more suitable fo this situation?..

I apologize for this long message... but maybe some other newbies like me will learn something usefull from the possible hints and suggestins from experienced people in this forum...Thanks in advance for the feedback
Joao (Lisbon)
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