Solar Water Pump System Product

Overview

A solar water pump lifts groundwater using nothing but sunlight. A small photovoltaic array feeds a power-electronic controller, which drives a submersible brushless motor and multi-stage pump hanging in a borehole. There are no batteries in the standard configuration — the system pumps when the sun shines and stores energy as water in an elevated tank instead of as charge in cells, which is cheaper and lasts decades. Systems of this type irrigate smallholder farms, water livestock, and supply village drinking water; IEC 62253 covers their rating and testing.

Sizing is a balance of three numbers: total dynamic head (static lift plus pipe friction), daily water demand, and local insolation. A typical livestock installation — 60 m head, 10 m³/day, 5.5 peak sun hours — needs roughly a 1.2 kW motor under a 1.6 kWp PV Array.

Hydraulic end

The Pump End is a stack of 5–12 centrifugal stages inside a 3- or 4-inch stainless Pump Casing. Each stage pairs an impeller with a stationary diffuser: the Impeller Stack adds kinetic energy to the water, and the Diffuser Stack converts that velocity into pressure and feeds the next stage. Head adds stage by stage — about 8–15 m per stage at rated speed — so a 10-stage pump delivers around 100 m of head. Centrifugal stages suit high flow at moderate head; for very deep, low-flow wells, manufacturers substitute a helical-rotor (progressive cavity) end, which holds its flow rate better at reduced speed.

Water enters through the Inlet Screen, which excludes sand coarser than about 2 mm, and leaves through a built-in Check Valve that holds the riser column when the sun drops, preventing back-spin and water hammer. All stages ride on a common Pump Shaft splined to the motor below.

Motor

The Submersible BLDC Motor is the part that distinguishes a solar pump from a grid pump. Grid submersibles use induction motors at fixed speed; a solar pump sees input power swinging from 10% to 100% over a day, so it uses a permanent-magnet BLDC machine that stays above 85% efficiency across a 3:1 speed range. The Rotor Assembly carries Neodymium Magnet poles; three Hall Sensor elements (or sensorless back-EMF estimation) tell the controller the rotor angle for commutation.

The motor can is water-filled: the Motor Shell is flooded with water or food-grade glycol that lubricates the Thrust Bearing and conducts winding heat to the pumped flow passing over the shell. The thrust bearing matters more than it looks — the impeller stack generates hundreds of newtons of downthrust, and the water-lubricated tilting-pad design carries it for years without service. An Oil Seal and the encapsulated Stator Assembly keep well water out of the electrical section.

Power electronics

The MPPT Pump Controller does two jobs at once. Its MPPT stage continuously perturbs the array operating point to hold the panels at their maximum power voltage, which moves with irradiance and temperature; without tracking, a directly coupled motor would drag the array off its power point and waste 20–30% of the available energy. Its inverter stage — six Power MOSFET devices in a three-phase bridge — synthesizes the variable-frequency drive waveform for the motor, with the DC Link Capacitor Bank smoothing the PWM current draw and the Controller Heatsink shedding the 2–4% switching loss.

The controller also enforces the protections. The Well Probe stops the motor if the water table draws down to the pump; the Tank Float Switch idles it when the tank is full; a Pressure Sensor flags a closed valve or burst pipe. Morning starts are automatic: the controller wakes when array voltage rises, waits for enough power to reach minimum pump speed (a centrifugal stage delivers nothing below roughly 60% speed), then ramps up.

Array and wiring

The PV Array is wired as one or two series strings to land inside the controller's MPPT window, typically 80–375 V DC. Modules sit on a galvanized Array Frame tilted near the site latitude; pole mounts keep panels above livestock and dust. The Combiner Box holds string fuses, a surge arrester bonded to the Earth Rod, and a DC disconnect for service.

Downhole, the Drop Cable is taped to the Riser Pipe every three metres and joined to the motor pigtail with a resin-and-heat-shrink Cable Splice Kit rated to full bore depth. The pump hangs from the riser through the Well Seal at the surface, with a Safety Rope as retrieval backup.

Performance and economics

Wire-to-water efficiency — hydraulic output over array DC output — runs 35–55% for good systems, dominated by pump-end losses. Output tracks the sun: a system rated 12 m³/day delivers most of that between 09:00 and 16:00, which suits irrigation and tank-fed supply well. Compared with a diesel pump of equal duty, the solar system costs two to three times more upfront but eliminates fuel and most maintenance; payback in off-grid agriculture commonly lands in two to four years.