Hi
I need to lift water 3m. Will a solar pump work? The volume is about 50 liters/day.
First, what size (w) pump will I need? Secondly, will I be able to do it with solar?
I have seen solar powered fishpond pumps but I don't think they will be able to provide the 'lift'.
You can't calculate directly the wattage you need for a pump to do that, for a bunch of complicated reasons, but in laymans terms it comes down to how the motor is geared to the pump, like the transmision in your car. Faster water has lower pressure. You need to look at the pump curves for each pump that satisfies your requierments.
50L/day = 5.787E-4 L/second
So your pump equation P = -kV^2
P = -k(5.787E-4)^2 + 3m,H2O
So k = just under 9x10^6 seconds^2/meter^5, (9 million). You should be able to take that to a pump expert, and he could sort you out. Or just look at a combined pump curve and select one that has the flowrate at that head.
For the wattage, we can make an educated guess, 50L/day at 3 meters. Ep = mgh = 50*9.81*3 (assuming you are pumping pureish water, SG = 1) = 1471,5 J/day = 17.03mW just for pumping. Efficiency is terrible for small pumps, most energy going to heat. So the pump, if built properly will be maybe something like 2W.
So you are looking for a 2 Watt pump with a k value of around 9 million.
So yeah, a solar pannel can do it easily. But you need to find one with a pumpcurve for what you are looking for (the pump has to be "geared" right to pump high head with low flowrate).