Design of a solar PV powered variable frequency drive for a bubbler irrigation system in palm trees fields

Abstract

This work aims to design a standalone solar photovoltaic (SPV) system to operate variable frequency drive (VFD) for palm trees irrigation using bubblers and control the irrigation network. A complete irrigation system is designed and constructed in two fields of date palm trees. A small photovoltaic (PV) system is used to operate the rainbird controller which changed water delivery from one subline to another after a predetermined time. The performance of the developed system is evaluated under different operating factors and its costs are analyzed. Water distribution uniformity and soil moisture at different depths in the root zoon are measured. The frequency of supply voltage is influential in controlling the speed of the induction motor, whereby operating the inverter, the motor speed is constant without any oscillation. Irrigation through the last two laterals in field II indicated that the required maximum hydraulic energy and maximum PV array power was 7.81 kW h/d and 3.74 kWp, respectively at the total dynamic head of 22.75 m. The coefficient of variation of bubblers flow was a small value for a single lateral (3.83 %), while for two laterals it varied from 8 to 12 %. The total dynamic head reached about 22.75 m for the last sublines in field II. The average subsystem efficiency was about 0.41. The annual cost of unit power of PV system was 0.161 $US /kWh without subsidies. The proposed SPV pumping is cost-effective and controlled the motor efficiently without energy backup.