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About Solar Water Pumping

Water supply is an integral part of any business, commercial or agricultural - and therefore so are water pumps. Generally, pumps are either powered electrically or with diesel fuel. For farms that need to pump water in remote areas, access to the electric grid is either unreliable or impossible. With standard electrical power out of the question, many resort to using diesel engines.

Diesel power comes with significant drawbacks. It’s expensive to install and maintain, and fuel is only getting more costly. A diesel powered pump running at 20 horsepower costs about 4 USD to fuel for an hour. Diesel engines are less efficient than electrical systems, and they create emissions that are harmful to the environment.

diesel engine

Solar pumping is the clear solution for water pumping in remote areas. It has applications in drinking water, irrigation, and livestock watering. Solar pumps work most when they are needed most. During clear days, and for the long daylight hours of the summer, crops tend to need more water. Under those same conditions, solar PV systems produce more energy. With no emissions or need for fuel, solar pumping systems are the more cost-effective and environmentally friendly solution than pumping with liquid fuels.

solar panel

Pumps that require more than a few kilowatts of energy are most typically powered by 3-phase AC motors. Solar panels provide a DC current, however, so an inverter, or Variable Frequency Drive (VFD), is necessary for conversion. While running, a water pump will need different amounts of power depending on the amount of water available for pumping and the amount of water needed. A VFD changes the frequency and voltage of the AC current to compensate for the motor’s variable workload. Lauritzen’s solar pump controller makes use of an industry standard line of VFDs. It’s coupled together with the SCX solar tracker controller for maximum output throughout the day and uses advanced maximum power point tracking (MPPT) technology to maximize efficiency.

VFD diagram

As an alternative to a battery, water may be stored in tanks for use when the solar PV system is inactive. A rechargeable battery that can power a motor at 20 hp for just a few hours costs thousands of dollars! It is cheaper to store water than energy; gravity will do the pumping when the stored water is needed.

Solar tracking allows a pump to operate for a longer period each day, and work at its maximum potential for longer. The graph below shows the percentage of maximum power yield throughout a summer day of a dual-axis tracking solar PV system as opposed to a stationary system:

percent power throughout day

A solar PV system that tracks the sun receives all the available sunlight all day, so it reaches full power much more quickly than a stationary system and keeps it for much longer. This is especially important for pumping applications. A pump requires a minimum amount of power to operate at all. If a pump requires a third of its maximum power to operate:

pump's active hours

A stationary PV system allows a pump to work for 7.5 hours on a summer day. A tracking system brings that up to 12 hours. Pumps are designed to work most efficiently at a specific power level. A tracking system provides full power for six hours, while a stationary system only reaches that point briefly. A tracking system allows a pump to use its energy much more efficiently than a stationary system does.

Solar power provides a number of clear advantages for water pumping. Solar tracking greatly enhances the productivity and efficiency of a pumping system. Lauritzen’s integrated solar tracker and power inverter for pump engines is the easy, efficient, and cost-effective solution for solar pumping.