Introduction to Solar Water Pumping

Solar water pumping systems are a modern but field proven means of pumping water in locations where access to grid power is not available, or where the grid is not reliable. These systems use photovoltaic (PV) cells to convert sunlight into electricity to power DC pumps which can be used to pump groundwater or surface water.

This blog outlines the basics of solar water pumping, discusses potential applications and highlights some advantages and disadvantages of the method.

THE BASICS OF SOLAR WATER PUMPING

A typical system comprises the following elements:

• The water source: This could be a groundwater source, such as a well or borehole. Alternatively it could be a surface water source such as a river or pond.
• The pump: Depending on depth to water, pumps of either the submersible type or suction type can be used. In the most common solar systems the pumps are powered by DC current, which require considerably low operation and maintenance costs than conventional AC pumps and provides greater efficiency.
• The PV array: Arrays are formed from groups of photovoltaic (PV) cells, aligned to give suitable sun exposure at the site location. The PV cells generate DC power when the sun is shining. The PV array is normally mounted on a stand or mount to allow it to be aligned to maximize sun exposure.
• The pump controller: This unit allows the pump to be controlled and regulated and will be connected to the pump and electrical grounding system.
• Optional battery bank: The PV units only generate power when the sun is shining, and so do not work at night and on cloudy days, One solution to provide continuous pumping is to connect banks of batteries to the PV array to store excess power, to be drawn on when there is no sun.
• Optional generator back up: Another option is to provide a petrol or diesel driven AC generator: intelligent control units make the changing between power supplies automatic.
• Other renewable energy sources: Solar PV can also be combined with a wind turbine: taking maximum advantage of the natural energy resources – solar power when the sun is shining and wind power when the wind is blowing.
• Discharge pipework: This pipework carries the water from the pump to the storage tank and to the end use. It is important that the discharge pipework is designed so that the pipe materials, diameter, layout and fittings are arranged to minimize frictions losses in the pipework. This will help maximize the efficiency of the pumping system.
• Water storage tank: A storage tank is a key part of most solar pumping systems, to ensure constant availability of water, 24 hours per day. The tank capacity should be designed store enough water to allow for water demand on rainy or cloudy days (no sun days) when pumping will be limited. The size and dimensions of the storage tank should be determined based on the required number of days storage.

In reality, each solar water pumping system is unique. Getting the most benefit from a system requires research and design before the first PV module and pump is purchased and installed. Each component must be carefully matched, and proper planning is essential – so the final system will be efficient and reliable system and can function for many years to come