TECH CORNER
To make solar pumping even more efficient, solar pump drives have been developed. These maximize the useful power of the sun from dawn until dusk. In fact, various features in modern drives enable more than 98% of the available PV power to be used for pumping.
For example, maximum power point tracking adjusts the pump motor’s speed according to sunlight conditions to ensure maximum power output from the pump. This is because insolation varies both gradually during the day and instantaneously due to cloud cover.
Selecting a drive with a wide input voltage range means the drive can still operate even when the voltage supplied by the solar panels drops off. This effectively means that the pump can start very early in the day and stop very late in the evening. It also means the whole system is less affected by variations in sunlight.
A modern solar pump drive can also be controlled remotely so that the pump can start and stop without any manual intervention. It can be programmed for specific start and stop times, with MPPT handling variations in flow during the day. For example, with level sensors fitted to tanks, the system can be programmed to start and stop pumping to avoid overfilling or underfilling the tank without any human input. Drives can also deliver useful data like calculated, total, daily and hourly flows.
Drives also boost the reliability of the solar pump. Dry run protection, for example, can use an in-pump sensor to see when the inlet water flow is running low or simply detect minimum load current which can also signal when there is no water in the system so it can cease pumping and ensure components don’t overheat from dry running. Pump cleaning settings mean the drive quickly operates the pump in forward and reverse to push out any unwanted material that might cause blockages.
If more power is required than is available from the PV panels, then solar pump drives can draw additional power from a generator or a grid connection.
An agricultural business in Herencia, Spain, had a problem with the irrigation system on its pistachio plantations. In a country where production is increasing exponentially, with the potential to reach 25,000 tons of pistachios every year within the decade, faults and inefficiencies lose money incredibly quickly.
This crop’s irrigation needs aren’t especially high and are normally carried out by water pumped directly from the subsoil with submerged pumps. This particular business had a solar installation with photovoltaic cells, a solar frequency converter and a submerged pump with a nominal power of 7.5 kW.
irrigationtoday.org
However, the system was experiencing a lot of downtime and, when it was working, the pump could only run during hours when solar irradiation was highest.
With advice from the installer, the company installed a new solar pump drive with features like MPPT to maximize output and performance from solar power and a proportional integral derivative control function to achieve the desired water pressure at the output in the irrigation system.
The result was a huge improvement in the solar pump system’s performance. System availability increased by 100%, and the company saw a doubling of the usable hours of solar irradiation compared to the previous year.
Solar pumping is an ideal irrigation solution for remote regions. By making use of the sun, a solar pump saves energy, reduces costs and doesn’t rely on a grid connection.
By pairing solar pumps with high-performance drives, efficiency is increased even further, making it a solution that could become even more important in the coming years as vast areas of land become hotter and drier than ever.
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HAVE A PIVOT? MAKE
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www. DragonLine . net 100 S. Main St • Ulysses, KS • (844) 424-3724
Summer 2024 | Irrigation TODAY 29
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