Solar panels for borehole water pumping systems

Introduction to solar panels for borehole pumping

Solar panels are a major component of a solar borehole pumping system. They convert sunlight into electrical energy that powers a compatible borehole pump through a suitable controller or power-conversion system. The amount of water delivered depends on the complete installation, including the solar array, pump, controller, borehole water level, pipework, and delivery head.

Selecting solar panels for a borehole requires more than matching the advertised panel wattage to the pump's motor rating. The designer must consider the pump's electrical input, controller specifications, solar conditions, expected pumping hours, cable losses, and the daily volume of water required.

Pro-Logic Technologies Limited works with Hydrosol Drilling Solution on borehole-related enquiries and water pumping requirements. Property owners, farmers, institutions, and businesses should assess their water demand and borehole conditions before purchasing solar pumping equipment.

How solar panels power a borehole pump

Solar panels contain photovoltaic cells that convert sunlight into direct-current electricity. When sunlight reaches the panels, the cells produce electrical power that can be used by compatible pumping equipment.

In a typical system, the solar array connects to a solar pump controller. The controller regulates the available power and supplies the pump according to its electrical and operating requirements. Depending on the system, the pump may use a dedicated DC motor or an AC motor supplied through a compatible solar drive or inverter.

The pump then lifts water from the borehole through a rising main pipe to a storage tank or delivery point.

Solar output changes throughout the day. Cloud cover, temperature, panel orientation, shading, dust, and seasonal conditions all influence the power available to the pump. A system should therefore be designed around realistic operating conditions rather than assuming constant full power.

Why correct solar panel sizing matters

An undersized solar array may fail to provide sufficient power for the required pumping schedule. The pump may operate for fewer effective hours, deliver less water during weaker sunlight, or struggle to meet the intended daily water demand.

An oversized array can also be problematic if it exceeds the controller's permitted voltage, current, or power limits. More panels do not automatically solve a hydraulic problem such as an undersized pump, excessive delivery head, blocked pipework, or a borehole that cannot sustainably supply the required water volume.

Correct sizing coordinates the solar array, controller, pump, water source, pipework, and storage arrangement. Each component must be suitable for the operating conditions of the complete system.

Establishing the pump's electrical requirements

Before selecting solar panels, obtain the pump and controller specifications. Important details include motor type, rated voltage, operating current, rated electrical input, controller requirements, permissible voltage range, and any manufacturer guidance concerning solar array sizing.

The motor's mechanical output power is not necessarily equal to the electrical power drawn from the array. Electrical and mechanical losses must be considered, along with controller efficiency and the pump's actual operating point.

A pump that delivers water against a high total dynamic head may have a different electrical demand from its operation at a lower head. The designer should use the manufacturer's technical information for the intended duty rather than relying solely on the motor's nominal power rating.

Understanding watts, volts, and amps

Solar panel and pump specifications use several electrical quantities.

Watts (W) describe electrical power. Volts (V) describe electrical potential difference. Amps (A) describe electrical current. The relationship between power, voltage, and current in a simple DC circuit is:

Power (W) = voltage (V) × current (A).

For example, a DC load operating at 100 volts and drawing 10 amps has an electrical input of 1,000 watts.

This relationship is useful for understanding system ratings, but it does not replace the manufacturer's design requirements. A solar pumping system may operate at varying voltage and current, and controller losses, power factor in AC systems, and motor behaviour can affect the actual electrical calculations.

Panel and controller ratings must be checked carefully before making connections.

Understanding solar panel nameplate ratings

A solar panel's rated power is usually specified under standard test conditions. The nameplate may also list voltage at maximum power, current at maximum power, open-circuit voltage, and short-circuit current.

The maximum-power voltage and current describe the panel's output at its rated maximum-power point under the specified test conditions. Open-circuit voltage is the voltage when the panel is not connected to a load, while short-circuit current is measured under a different test condition.

These values are not interchangeable. In particular, the controller's maximum permissible input voltage must be checked against the array's open-circuit voltage under the expected coldest conditions, not just its normal operating voltage.

Actual power production varies with sunlight, temperature, panel condition, orientation, and other environmental factors. The nameplate rating should be treated as a reference value rather than a guarantee of constant output.

Calculating preliminary solar array capacity

A preliminary estimate of array capacity can help with project planning, but the final design must follow the pump and controller manufacturer's requirements.

Suppose a pumping system requires an average electrical input of 1,000 watts while operating. An array rated at exactly 1,000 watts will not necessarily supply that power continuously because the panels rarely operate at standard test conditions throughout the day.

The designer must consider site solar conditions, panel temperature, shading, cable losses, controller efficiency, and the desired pumping schedule. The final array may require a higher rated capacity, but the appropriate amount depends on the equipment and site-specific calculations.

The controller must also be able to accept the selected array configuration. An array should never be connected solely because its total wattage appears suitable.

Estimating daily water production

Daily water production depends on pump performance, total dynamic head, available solar energy, and the time the pump operates effectively.

A preliminary calculation is:

Daily water volume = average flow rate × effective pumping time.

For example, if a pump delivers 20 litres per minute under the relevant operating conditions for five effective hours, the theoretical daily volume is:

20 litres/minute × 60 minutes/hour × 5 hours = 6,000 litres.

This is an illustrative calculation, not a performance guarantee. Actual output can vary as sunlight changes, the pumping water level changes, or the pump operates at different heads.

The calculated volume must also be compared with the borehole's sustainable yield. A system should not be operated at a rate that causes unacceptable drawdown simply to meet a daily target.

Understanding peak sun hours

Peak sun hours are a way of expressing daily solar energy in terms of equivalent hours at a reference irradiance of 1,000 watts per square metre.

For example, a location receiving a daily solar irradiation equivalent to five peak sun hours has received approximately the same energy as five hours at that reference irradiance. It does not mean the sun shines at maximum intensity for exactly five consecutive hours.

Peak sun hours vary by location, season, weather, panel orientation, and shading. The designer should use suitable solar-resource information for the installation site and consider less favourable periods when reliable daily water production is important.

The effective pumping window also depends on the pump and controller. A system may operate at reduced output during lower irradiance, so its effective pumping performance cannot always be represented by simply multiplying rated flow by daylight hours.

Panel connection in series

Connecting solar panels in series increases the array voltage while keeping the current approximately at the level of one panel string, subject to the panels' electrical characteristics.

Series connections are used where the pump controller requires a particular input voltage. However, the total open-circuit voltage of the string increases with each additional panel.

The designer must calculate the string voltage using the panels' specifications and the expected temperature range. Cold conditions can increase panel open-circuit voltage, potentially exceeding the controller's maximum input rating if the array is incorrectly configured.

All panels in a series string should be compatible and arranged according to the system design. Incorrect connections can cause equipment damage and hazardous voltages.

Panel connection in parallel

Connecting compatible solar panel strings in parallel increases the available current while maintaining approximately the same string voltage.

Parallel connections can be useful where the required array power cannot be achieved with a single string at the desired voltage. The arrangement must comply with the controller's current limits and any applicable requirements for string protection, cable sizing, and isolators.

Parallel-connected strings should be designed using appropriate panels and connection equipment. The designer must consider the total current, cable voltage drop, connector ratings, and protection requirements.

Series and parallel configurations should never be selected by guesswork. The final arrangement must satisfy the controller's electrical limits and the relevant installation requirements.

Matching the solar array to the pump controller

The solar pump controller is the link between the solar array and the pump. It must be compatible with the panel array and the pump motor.

Before installation, check the controller's minimum start-up voltage, operating voltage range, maximum open-circuit voltage, maximum input current, permitted array power, and motor output specifications. These limits vary by model.

Some controllers provide maximum power point tracking, which adjusts operation to make effective use of available solar power. The feature can improve energy utilisation under suitable conditions, but it cannot create energy when sunlight is insufficient.

The controller's protection features should also be reviewed. Dry-run protection, overload protection, overtemperature monitoring, and tank-level inputs may be included on some models but absent on others.

Direct-current solar borehole pumps

Dedicated DC borehole pumps can be designed for direct-current solar power systems. Their controller and motor must be matched to the panel array.

Some systems operate at low voltage, while others use higher-voltage DC arrangements. Higher-voltage systems require appropriate electrical isolation, rated equipment, and safe installation procedures.

The pump's rated flow, head range, motor current, cable requirements, and controller compatibility should be confirmed before purchase. A DC pump is not automatically more efficient in every installation; overall performance depends on the complete system and the operating conditions.

AC borehole pumps supplied by solar drives

An AC borehole pump may be operated from a compatible solar pumping inverter or drive. The drive converts the available electrical energy into a suitable output for the motor and may regulate motor speed.

The equipment must be suitable for the motor's voltage, phase configuration, current, frequency, and starting requirements. Some solar drives include dedicated pumping functions and sensor inputs.

A standard inverter should not be assumed to provide all the functions required for solar pumping. The installer must check the manufacturer's documentation and ensure that protection, motor control, and solar input requirements are met.

The design should also account for the consequences of low solar input and any backup supply arrangements.

Panel orientation and tilt

Solar panel orientation and tilt influence the amount of sunlight received. The preferred arrangement depends on the site's latitude, the desired seasonal performance, roof or ground conditions, shading, and the mounting structure.

A poorly oriented array may generate less energy than expected, especially when combined with shading or dirty panels. A site assessment should identify the available space and the likely movement of shadows during the day.

The mounting structure must be secure and designed for local wind conditions. Panels should be installed according to the manufacturer's requirements and local structural and electrical considerations.

Orientation should be selected to support the intended pumping schedule and annual water demand rather than using a universal angle for every site.

Shading and its effect on water pumping

Shading from trees, buildings, walls, water tanks, or other structures can reduce panel output. The effect depends on the type of panel, electrical configuration, bypass-diode design, and extent of shading.

Even partial shading can reduce output from a panel string. In some configurations, the performance of one shaded panel can affect the current available from the entire series string.

Before installing the array, inspect the site at different times of day and consider future changes, such as growing trees or planned buildings. Where practical, place the panels in an area that receives adequate sunlight with minimal shading.

If output declines unexpectedly, inspect the array for new shadows before assuming the pump or controller has failed.

Dust, dirt, and panel cleaning

Dust and dirt can reduce the amount of sunlight reaching the photovoltaic cells. In agricultural and dry environments, accumulation may be significant enough to affect daily pumping performance.

Panels should be inspected periodically and cleaned when needed, following the manufacturer's recommendations. Cleaning methods should avoid abrasive materials and unsuitable chemicals that could damage the panel surface.

Safe access is essential. Panels should not be cleaned while standing on unstable structures or handling electrical equipment without appropriate precautions.

The required cleaning frequency depends on local dust, rainfall, nearby agricultural activity, and the observed effect on system performance. Inspection records can help determine an appropriate maintenance schedule.

Cable sizing between panels and controller

Cables connecting the solar array to the controller must be rated for the voltage, current, environment, and installation method.

Voltage drop reduces the voltage available at the controller and may affect performance. Cable sizing should therefore account for conductor material, cross-sectional area, route length, current, temperature, and allowable voltage drop.

Cables exposed outdoors should be suitable for ultraviolet exposure and the expected environmental conditions. Mechanical protection may be necessary where cables could be damaged by people, animals, vehicles, or farm equipment.

Connectors must be compatible with the cable and panel system. Mismatched connectors and poor terminations can cause resistance, heating, intermittent operation, or fire hazards.

DC isolation and surge protection

Solar arrays can produce hazardous DC voltage whenever they receive sufficient sunlight. The installation should include suitable isolation and protection equipment based on the array design and applicable electrical requirements.

DC isolators must be rated for the system's voltage and current. Equipment designed only for AC circuits must not be substituted unless it is explicitly rated for the DC application.

Surge protection may be appropriate where lightning-related transients or switching surges present a risk. Its selection and placement should follow the installation design and relevant standards.

Earthing and bonding arrangements should also be designed for the site and equipment. A qualified installer should assess the need for additional lightning protection rather than relying on improvised solutions.

Earthing and electrical safety

Earthing and bonding can help reduce electrical hazards when designed and installed correctly. The requirements depend on the equipment, electrical arrangement, site conditions, and applicable standards.

Metallic structures, equipment enclosures, and protective conductors should be addressed in the installation design. Earthing must not be improvised or treated as a substitute for suitable isolation and overcurrent protection.

Electrical work should be performed by appropriately qualified personnel. The array should be isolated according to the manufacturer's procedures before maintenance, and suitable instruments should be used to verify conditions before touching conductors.

Solar panels may remain energised in daylight even when an isolator has been switched off. Workers must understand the system's isolation points and follow safe working procedures.

Protecting panels and equipment from the environment

Solar pumping equipment may be exposed to rain, dust, high temperatures, livestock, farm machinery, and unauthorised access. The array, controller, junction boxes, and cables should be positioned and protected for the installation environment.

Enclosures should have suitable environmental ratings. Ventilation and temperature limits should be considered where controllers or drives generate heat.

Cables should be routed to reduce the risk of crushing, abrasion, and accidental disconnection. Mounting hardware should be appropriate for the structure and local weather conditions.

Where livestock or machinery may reach the panels, fencing or physical barriers can help reduce accidental damage, provided the arrangement does not create additional safety hazards or interfere with access for maintenance.

Common solar panel sizing mistakes

A frequent mistake is choosing panels solely by adding their advertised wattages and comparing the result with the pump's motor rating. This overlooks operating voltage, current, controller requirements, temperature effects, and the actual hydraulic duty.

Another mistake is exceeding the controller's maximum open-circuit voltage by connecting too many panels in series. Incorrect parallel connections can also exceed input-current limits.

Ignoring shading, cable losses, panel orientation, and seasonal solar conditions can lead to disappointing water output. Likewise, increasing array size will not fix an incorrectly selected pump or a borehole that cannot sustainably provide the required volume.

A sound design verifies electrical compatibility, expected energy production, pump performance, and the daily water budget before the equipment is purchased.

Troubleshooting low solar pumping output

If the pump delivers less water than expected, the diagnosis should consider both electrical and hydraulic factors.

Potential electrical causes include shading, dirty panels, damaged cables, loose connections, unsuitable array configuration, controller faults, or insufficient solar input. Potential hydraulic causes include a falling pumping water level, blocked pipes, leaks, excessive head, worn pump components, or an unsuitable pump selection.

The technician should compare current operating conditions with commissioning records where available. Measurements of solar input, controller status, electrical values, water flow, pressure, and pumping water level can help isolate the problem.

Replacing the controller or pump without testing may not solve the underlying issue. Electrical testing must be performed safely by qualified personnel using equipment suitable for the circuit.

Improving solar pumping performance

Performance improvements should begin with identifying the main limitation. Cleaning dirty panels or removing avoidable shading may improve output where solar generation is the problem. Correcting cable losses or a controller configuration issue may also help.

If the pump is operating at an unsuitable head, hydraulic changes may be required. These could include reviewing pipe diameter, reducing unnecessary restrictions, adjusting the delivery arrangement, or selecting a pump better suited to the duty.

Where the borehole yield is the limiting factor, increasing panel capacity or installing a larger pump may make the problem worse. The operating rate should remain within the borehole's sustainable capacity.

A performance review should use measurements and system records rather than assumptions about which component is responsible.

Monitoring solar panel and pump performance

Regular monitoring helps distinguish normal solar variation from a developing fault. Useful records may include daily water volume, pumping hours, controller alarms, water levels, and any available electrical readings.

If a system produces significantly less water under comparable conditions than it did after commissioning, the change should be investigated. Weather differences should be considered before concluding that equipment performance has deteriorated.

Some controllers support remote monitoring or data logging. Where such features are available, they can help identify operating patterns, recurring faults, and periods of low solar input.

Monitoring does not eliminate the need for physical inspection. Panels, cables, connectors, mounting structures, pipes, and controls still require appropriate maintenance.

Solar panels for residential borehole systems

Residential solar borehole systems should be designed around household water consumption, storage capacity, pumping head, and expected water availability.

A storage tank can allow water to be pumped during daylight and used later. The tank's size should reflect daily demand and the consequences of interruptions rather than being selected arbitrarily.

If water must be supplied under pressure to multiple floors, the design should distinguish between the borehole pump's task of lifting water and the building's requirement for distribution pressure. A separate booster pump may be needed.

The solar array, controller, pump, and protection equipment must be suitable for the actual operating requirements. A residential system should also include practical arrangements for inspection and maintenance.

Solar panels for farm irrigation

Farm irrigation systems may require large daily water volumes, particularly during dry periods. The design should calculate crop water demand, irrigation flow, pumping hours, borehole yield, and the pressure requirements of the irrigation equipment.

A tank or reservoir can provide flexibility by allowing water to be pumped when sunlight is available and used according to the irrigation schedule. However, the storage capacity must be appropriate for the daily water budget and the expected variability of solar energy.

The solar array should be sized to support the pump at the intended operating point. Pipework, filtration, valves, and distribution equipment must also be designed to deliver water efficiently.

Where irrigation requires a specific pressure, the pump's performance curve should be checked at the combined lift, friction, and delivery-pressure head.

Planning the solar pumping project budget

The total project cost may include panels, mounting structures, the pump, controller, cables, isolation and protection equipment, rising main pipes, storage tanks, sensors, installation labour, testing, and transport.

The cost depends on the required daily water volume, total dynamic head, borehole characteristics, equipment specifications, site access, and the complexity of the installation.

Comparing projects by panel wattage alone can be misleading. Two systems with similar arrays may use different pumps, controllers, storage arrangements, or hydraulic designs.

A detailed quotation should identify the equipment included, the intended operating duty, installation requirements, and any work that remains outside the scope. This helps the customer compare proposals on a like-for-like basis.

Preparing for a solar borehole installation quotation

Before requesting a quotation, prepare the available borehole records, pumping-test results, water demand estimate, tank height, delivery distance, and details of any existing pump or controller.

If the borehole water levels or sustainable yield are unknown, additional assessment may be necessary. The installer should identify which values are measured, which are estimated, and which require verification.

The solar array and pump should be specified together. This avoids purchasing panels that are electrically incompatible with the controller or a pump that cannot meet the required flow at the actual head.

A clear scope of work should also state whether the proposal includes tank controls, rising main pipes, electrical protection, commissioning, and operator guidance.

Solar panels for borehole water pumping enquiries

Pro-Logic Technologies Limited works with Hydrosol Drilling Solution on borehole-related enquiries and water pumping requirements. Customers planning a solar pumping installation should establish the borehole yield, required daily water volume, total dynamic head, pump specifications, and solar resource before selecting the array.

The aim is to match the solar panels, controller, pump, cables, protection equipment, and storage arrangement into a compatible system.

Contact: 0723763173

Website: https://prologictecnologies.co.ke

Correct solar array sizing, electrical compatibility, safe installation, and routine maintenance are essential to reliable borehole water pumping. A properly designed system should be based on measured site conditions and the operating limits of the selected equipment.