Solar power is very useful for water supply systems. The most common applications are for household water supplies and agricultural and livestock needs. Of course, using utility-provided water is more economical in most places, but in remote locations, it's simply not available. The pipes and trenches that would be required to get to the desired site are often prohibitively expensive. And in these types of applications, providing utility electrical power is likely also prohibitively expensive.
Solar water pumps can be located anywhere there's available sunshine and a relatively clean water supply. (Dirty water may be filtered, but filters clog up, and the pump flow becomes constricted, so the application quickly becomes maintenance intensive.) The water supply can be a well, creek or river, lake, and so on. (Check on the legal accessibility of your water source before starting your project.)
In a household application, the storage reservoir is located above the house so that when someone opens a tap, gravity provides the water pressure to the faucets.
For livestock applications, the reservoir may be nothing more than a ditch or a cattle trough set on the ground. This system also works for crop irrigation where there's no reservoir at all. The water simply feeds directly into the irrigation pipes. Because the pressure varies quite a bit, broadcasting sprinklers are impractical, but drippers work very well.
Here are the calculations you need to make in order to specify the system size:
Daily water usage, in gallons, both average and maximum: Some livestock applications don't require water in the winter months at all because the animals are in grocery stores, waiting to take center stage at your holiday banquets.
Available sunshine, in average hours per day, and your need for a consistent water supply: If you need water all the time and sunshine is inconsistent, you'll need a larger reservoir, along with larger PV modules and pumps so you can fill the reservoir on sunny days.
Difference in vertical height between the top level of the water source and the output end of the pump hose: For agricultural applications, this distance is usually small, on the order of 10 or 20 feet. For some residential applications, this number can be more than 100 feet, which makes the pump much more expensive. This number is called the pump's head pressure.
Specifications for pumps list a table of wattages versus pump capacities and heads, like this:
| Head Pressure | Wattage | Daily Output in Gallons |
|---|---|---|
| 3.3 ft. | 80 | 1,500 |
| 9.8 ft. | 80 | 1,300 |
| 23 ft. | 80 | 600 |
| 3.3 ft. | 115 | 2,100 |
| 9.8 ft. | 115 | 1,700 |
| 23 ft. | 115 | 650 |