Energy Conservation using Variable Frequency Drives for Center Pivot Irrigation: Systems Equipped with Corner Watering Attachments

Corner watering attachments, specifically end guns and corner extensions, attached to center-pivot systems are a common means to irrigate the corners of square fields. The pumping plant is designed to supply water to all sprinklers when the center pivot is irrigating the point of maximum elevation. Most designs include powering the irrigation pump at a fixed speed, which can lead to excessive energy use. Variable-frequency drives (VFDs) were introduced to adjust the pump speed in response to changes in pressure requirements. In this study, three scenarios were analyzed: scenario 1, end gun attached at end of center-pivot lateral; scenario 2, corner extension attached at end of center-pivot lateral; and scenario 3, corner extension attached at end of center-pivot lateral and end gun attached at the end of the corner extension. This study was conducted on 1000 randomly selected center-pivot irrigation systems located in ten counties of Nebraska using GIS-based tools. High-resolution digital elevation maps were used to investigate the impact of flow rate changes and topographical variations on energy requirements. Reductions in the energy required, obtained through varying the pump speed, and annual monetary savings were calculated for each scenario. Average payback periods for VFDs were calculated for each county. The major factors contributing to energy savings and annual returns include large topographical changes, duration of corner attachment operation, hours of operation, and electricity cost. Scenario 3 resulted in the maximum energy reduction, maximum annual monetary savings, and minimum payback period compared to the other scenarios. This approach allows investigation of the potential savings associated with installation of a VFD for center pivots equipped with end guns and corner arm extensions.