Solar Irrigation Systems in Ghana: Plan Water, Pumping and Distribution

Begin with the crop and field water budget

List the crops, planted area, growth stages, soil type, planting schedule and irrigation method. Water needs vary by crop, weather, season and stage of growth; a single daily estimate for every month can lead to over-pumping or water stress. Work with an agronomist or irrigation specialist to estimate the farm’s peak daily demand and the acceptable irrigation interval.

For a first-pass calculation, convert the planned irrigation depth into a volume for the cropped area, then account for application efficiency and distribution losses. Keep the method and assumptions documented. Soil-moisture observations and measured field output can refine the plan after commissioning.

Confirm the water source and sustainable yield

Measure water level and recovery at the intended pumping rate. For a borehole, include pumping drawdown and any seasonal variation. For surface water, check intake location, sediment, debris, changing levels and the permissions or community arrangements that apply to the site.

The pump must not extract more than the source can sustainably provide. If demand exceeds source yield, plan crop area, irrigation timing, storage or water conservation measures before selecting a larger pump. Solar power cannot compensate for insufficient water.

Size for the hydraulic job, not a marketing label

Calculate total dynamic head from pumping water level, elevation to the tank or field, drawdown and pipe friction. Match the pump curve to the required flow at this head. Include filters, valves, long pipe runs and elevation changes. A pump advertised with a maximum flow or maximum head will not normally deliver both maximum values at the same time.

Compare the daily volume the pump can deliver during realistic solar hours with peak crop demand. Specify the PV controller, motor, array voltage and current limits as a matched set. Use manufacturer curves and manuals for the exact models proposed.

Choose an irrigation method that fits the crop

Drip irrigation can apply water near the root zone and is often useful for row crops, orchards and controlled plots, but it requires filtration, pressure management and routine emitter maintenance. Sprinklers suit other crops and layouts but generally need adequate pressure and may be affected by wind and evaporation. Open channels and low-pressure systems have their own land, labour and water-loss trade-offs.

Design the pump around the distribution system’s required pressure and flow. Divide the farm into zones when this permits a smaller pump or more controlled delivery. Filters, pressure regulators, gauges and flush points should be accessible and sized for the planned flow.

Use storage and controls to manage variable sunlight

A water tank or reservoir can store pumping output for a scheduled irrigation window. Size it to the farm’s delivery schedule and the expected gap between pumping and use. The storage plan should include an allowance for low-sun days and a clear operating rule when the tank is not full.

Use tank-level controls, low-source-level or dry-run protection, flow monitoring and simple shutoff logic. Add automation only when the farm can maintain it and staff know how to override it safely. Battery storage is an option where needed, but water storage may be a simpler way to shift supply for many pumping applications.

Commission, measure and maintain

At commissioning, record PV voltage and current, pump flow, discharge pressure, water level, operating hours and tank level. Confirm that protection devices, float switches and controller alarms work. A baseline makes it easier to spot a clogged filter, damaged pipe, declining source yield or electrical fault later.

Inspect panels for shade and dirt, clean filters, flush drip lines as required, check for leaks, and monitor pump output over the season. FAO’s sourcebook on solar energy in irrigated agriculture discusses design, operation and maintenance considerations.

A farm design brief

• Crop plan, field area, soil and estimated peak daily irrigation volume.
• Water source, seasonal levels, sustainable yield and water-quality information.
• Pump head, required flow, pipe layout, filters, pressure and irrigation zones.
• PV module configuration, controller and motor model, protections and controls.
• Storage volume, backup plan, commissioning measurements and named maintenance contact.