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Part VIII: Wind, Water, and BiofuelsChapter 12. Small Wind and Micro-Hydro

Solar Water Pumping for Gardens and Livestock

Matching a small PV pump to lift and daily volume, without a battery when you can avoid one.

Difficulty
Intermediate
Cost
$150–800
published

A solar pump moves water while the sun is out. The storage is a tank, not a battery, whenever the tank can hold the cloudy days. That is the whole design: match the lift and the gallons to a panel and a controller, and keep the house wiring out of it.

Lift is total dynamic head. It includes the vertical rise and the friction of the pipe, which gets worse in a long, skinny, or kinked line. The static depth of a well is the optimistic number. A surface pump sucks. In practice that suction lift is a short distance, well under the theoretical thirty-some feet of a perfect vacuum, and warm water and a leaky hose make it shorter. A deep source needs the pump down in the water.

About 0.00315 watt-hours lifts one gallon one foot, before the pump wastes some. Five hundred gallons lifted fifty feet at a pump efficiency of 0.35 is 500 times 50 times 0.00315, divided by 0.35, about 225 watt-hours. A modest panel on a clear day can do that if the controller and the pump were chosen for each other. A huge inverter does not help a direct-current pump.

The stock-tank page is the winter end of livestock water. The links below are other projects. Read them on their own sites.

Difficulty

Level
Intermediate
Time
A day to set a listed pump and a tank, after you know the lift
Skills
Keeping suction lifts short and house panels out of the circuit

Cost estimate

$150–800

A small panel, a pump made for photovoltaic input, and a controller sit in this range when the lift is modest and you already have a tank. A deep-well pump, a long wire run, and a new cistern pass it. The inverter you do not need is a common way to overspend.

Materials

ItemQtyNotes
A pump and controller sold to work from a panel1Match the lift and the gallons. A motor clamped straight to a panel, with no controller it was designed for, can stall and cook.
A tank that holds the cloudy days1The battery. Overflow has to go somewhere harmless. Weight is about 8.3 pounds per gallon plus the tank.
A fuse and wire sized to the run1At the panel or the controller, where the instructions say. Long runs lose voltage. Do not borrow household extension cord as a lifestyle.

Sun, tank, and the days with neither

Direct pumping fills the tank at noon and the animals or the garden draw it down later. Size the tank for the demand through a string of dim days, not for a single sunny hour. If the crop will die without water on the third cloudy day, the tank or a backup is part of the design. A battery and an inverter are the expensive way to fake that tank, and they add the failure modes on the battery page. Use them when you must pump at night and cannot store water. Do not use them because a catalog led with an inverter.

Aim the panel. Shade at the stock tank is shade on the water supply. Winter sun is lower. A flat panel that was fine in June can quit in December, which is when some livestock water matters most.

Panel, pump, and a tankA panel and controller above a well, a tank beside them, and a separate mark that the house panel is not connected.PanelControlTankWellThe tank is the storage.House panel: no
Panel, controller, pump, tank. The house service panel is not in the picture.

What the water is allowed to be

Garden irrigation and livestock water are not a drinking-water system. Do not drink untreated surface water, roof water, or a tank you cannot vouch for. A livestock tank still has to be a tank you would let an animal drink from. Never a drum that held fuel or pesticide. If you tie into a potable line, you need a backflow preventer that a plumber and the local code accept. A hose in a stock tank is how a well gets contaminated when the pressure drops.

Wells are regulated. Pulling a pump, opening a casing, or drilling is often licensed work. This page assumes a water source you are already allowed to use. It does not teach you to make a well.

Composite: the hundred-foot suction hose

Invented, not a real well and not a brand. Someone puts a surface pump on the bank and a long hose down a deep well because the pump was cheap. The water never arrives. Suction cannot lift from that depth, so the motor runs dry, heats, and the garden gets nothing. The fix in the composite is a pump made to live down in the water, or a shallower source, not a bigger inverter on the bank.

  1. Write down gallons and total lift

    Include pipe friction. Use 0.00315 watt-hours per gallon per foot as the water's share, then divide by a realistic pump efficiency.

  2. Store water, not charge, if you can

    A tank covers the night. Add a battery only when the water cannot sit and wait.

  3. Put the pump where the physics allows

    Short suction only. Deep water gets a pump in the water. Match the controller to that pump and that panel.

  4. Fuse it, aim it, and keep it off the house

    Follow the maker's wire and fuse notes. Shade and winter angle are part of the yield. No cord to a house outlet.

Further reading

These links go to outside sources. This book cites them by link and does not copy their words or pictures.

General education, not a permit or a stamped design. Follow the safety note in the guide, read the safety disclaimer, and hire a licensed trade when the work requires one.