How to size a solar water pumping system for a farm

Solar pumping removes the fuel bill from irrigation, but only if the system is sized to the borehole and the crop rather than to a catalogue page. Three numbers do most of the work.

1. Total head

Total head is the vertical distance from the water level in the borehole to the discharge point, plus friction losses in the pipework. Use the dynamic water level while pumping, not the static level — this is the single most common sizing error we correct.

2. Daily water requirement

Work from the crop and area, or from livestock and household numbers, to a cubic metres per day figure. The pump then has to deliver that volume within the usable solar window — typically five to six peak sun hours in most of Ethiopia.

3. Array size and controller

Once head and daily volume are fixed, the pump's power requirement follows, and the panel array is sized above it to allow for temperature losses, dust and morning and evening light. A controller with dry-run protection is not optional — it is what keeps the pump alive when the borehole draws down.

• Borehole depth and dynamic water level
• Required daily volume in cubic metres
• Distance and elevation to the tank or field
• Pipe diameter and material
• Tank capacity for storage buffering

Storage instead of batteries

For irrigation and livestock, a raised tank is almost always cheaper and more durable than a battery bank. Pump into storage during the day and draw by gravity at night.

Send us those five figures and we will specify a pump, array and controller and issue a quotation.