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

Abstract. Corner watering attachments, specifically end guns and corner extensions, attached to center pivot systems are a common means to irrigate 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 pumping plant at a fixed speed which can lead to excessive energy use. Variable frequency drives (VFD) were introduced to adjust pump speed in response to changes in pressure requirements. In this study, three scenarios were analyzed: 1) Scenario 1, end gun attached at end of center pivot lateral, 2) Scenario 2, corner extension attached at end of center pivot lateral, and 3) Scenario 3, corner extension attached to the end of the pivot lateral and an end gun positioned 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, USA 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 energy required obtained through varying pump speed, along with 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 the corner attachment operation, hours of operation, and electricity costs. Scenario 3 resulted in the maximum energy reduction, annual monetary savings, and minimum payback period when compared to other scenarios. This approach allows the investigation of potential savings associated with the installation of a VFD for center pivots equipped with end guns and corner arm extensions.