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Irrigation - Multiple benefits of energy efficiency?

How to run your irrigation system smoothly and with lower electricity costs

Energy efficiency remains the most affordable and effective way to combat the global warming and energy challenge. In fact, by industry alone investing in energy efficient technology up to 50 percent more added value on top of energy savings is generated. These multiple benefits of energy efficiency, however, are often overlooked when investment decisions are made.

When we are discussing the benefits that variable speed drives (VSDs) give to motors, pumps and fans it’s important to keep in mind that valuable gains can be achieved not only in large industrial operations but also in smaller installations.

As an example, one of our South African customers in the farming industry was struggling with the continuously increasing electricity prices. As the South African economy developed over the past five years or so, growing demand for electricity has meant that rates rose by more than 20% every year.

Since the electricity costs of running motors and pumps in irrigation systems was one of the company’s biggest operating expenses profitability was harshly squeezed.

The customer’s old irrigation system was based on a piping network that included numerous water pumps running at constant speed, with control of the flow rate and destination done by the manual opening and closing of valves in the pipelines. The system worked, but it was certainly not energy efficient.

In addition, the need to manually open and close the valves depending on water demand, combined with the hassle of frequent power outages and voltage dips from the electrical utility, made the whole process very labor intensive. Startups had become almost a full-time job as the labor needed to start one of the farm’s six pumping stations could take one person up to an hour, and sometimes there were as many as three power outages in a day.

Not surprisingly, the farm management began to look for alternatives, and turned to ABB South Africa’s energy efficiency engineers. As a solution, six general purpose drives were installed at the water pumps at one of the farm’s six pumping stations. Working with a system integrator, ABB assisted in the design, installation and commissioning of five VSDs, running irrigation pumps with 45-75kW motors, and the sixth VSD used on the water transfer pump.

With the new VSD units installed, Riecor saw a big drop in electric energy use. Demand from the irrigation system was reduced by 116 kW, equaling an impressive 40% drop in electric consumption at just one pumping station.

In financial terms, the 2,970 hours that irrigation pumps operate per year equates to an annual savings of nearly USD 20,000 in electricity costs. The payback time amounted to a short 7 months, and the farm quickly made a repeat order to install similar drives on a second pumping station.

In addition to significant financial savings on the electricity bill, the farm also got further operational savings in both man-hours and trouble during the startup process. Operators now only need to flick a switch to start, and in the event of power interruptions the system starts up automatically at pre-set times.

The VSDs give a long ramp-up time that allows for a very smooth pipe-filling process, so the previous mechanical stresses on the pump couplings during startup have been completely eliminated. In addition, there are reduced friction losses in the pipes, water hammering has disappeared, and less wear and tear has been seen on the impeller due to the extended ramp-up and ramp-down times.

This is just one example of many about a small operation realizing big savings in electrical consumption and increasing profit margins by utilizing variable speed drives. In addition, what had been a very labor-intensive process became much easier to manage, giving additional savings in labor costs.

In fact, any process that is using pumps and fans driven by motors can achieve important monetary savings and operational benefits with the use of VSDs. You might want to take a good look around your own operations and processes, no matter how big or small, to see where targeted use of variable speed drives can help you get fast financial payback and long-term competitive advantages.

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