Solar Water Pumping Systems
and Applications

Water and the access to a clean supply of water are essential for everyday life, irrigation, health of livestock and may other uses. An estimated 1.2billion people in the world today do not have access to clean water. The pumping of ground water can only be done on a sustainable basis if the water extracted from the well is replenished. Harvesting rainwater may, in some cases, be a better option and a wide variety of pumping methods are available, depending upon local conditions, to extract the water.

The variety of water pumping applications is considerable and they can vary widely, both in their requirements and the conditions under which water must be pumped. the volumes of water required, the capacity of the source to deliver the water, the depth from which the water is pumped, the season and time of the pumping, and most importantly, the amount of solar radiation falling at the point where the water is to be extracted.

Solar water pumping is done all over the world and greatly enhances the quality of life of people's living in rural and remote communities. Solar PV water pumping systems are reliable, and very cost-effective and can replace manual pumps, if used in the right location. A solar water pumping system does not have to use batteries to provide the power as the pump will operate during the day by pumping water into a tank for use at night.

If you're looking for a solar water pumping system it is essential to understand how they work.

Types of Water Pumping System Configurations

In the simplest solar water pumping systems the, the solar panels are connected directly to the a small DC motor that drives the water pump. These simplified systems use CENTRIFUGAL pumps, because of their ability to be matched to the output of the solar panels.

DISPLACEMENT pumps, otherwise known as volumetric pumps, have very different speed-torque characteristics and are not very well suited to being connected directly to solar panels. When such pumps are used, power conditioning or maximum power point tracking is commonly included between the solar panel and the pump, so that the electrical energy can be converted into a more useable form.

Just like the variety of water pumps, there is a huge variety of motor types, used for water pumping systems with each motor having its own advantages and disadvantages, which result in the type of application they can be used for.

If AC motors are used, an inverter must be placed between the solar panels and the motor.

Batteries

If it is absolutely critical that the water pump should operate at a specific time, day or night, then batteries are used. They also have the advantage of being able to use the stored energy for a period of days during poor weather conditions. Having said that, the use of batteries should be avoided if at all possible as they require maintenance and protection from the environment in which the pump is used.

Water pump system configurations

Water pumps can be split into two categories:

1. Dynamic - the water velocity is increased then reduced at the output and thus increasing pressure.

2. Displacement (volumetric) - these include rotary and reciprocal pumps.

This leads to four different types of configurations:

a) Submerged pump and motor - used with centrifugal pumps for medium depth bores. The pumps are automatically primed and easy to maintain.

b) Submerged pump with surface motor - this type of configuration allows easy access to the motor, but requires a mechanical drive down the bore to the pump.

c) Floating pump and motor - this type of pump is ideal for open wells and canals, but is unsuited to borehole pumping.

d) Surface suction pump - ideal for small surface systems, but priming can be an issue of the water level varies.