Modelling and Planning Operation of Directly Coupled Solar PV Pump Operated Drip Irrigation System

Abstract A dynamic simulation model of a directly coupled solar photovoltaic (SPV) pump operated drip irrigation (DI) system is presented in this study. The model is applied for preparing a plan of DI system operation to meet the irrigation schedule of the Okra crop considered in the case study. The fundamental mathematical expressions of the SPV array, variable frequency drive, submersible pump, and DI system are used to create a general model in the Matlab/Simulink. The hourly solar irradiation, temperature, and groundwater level are input parameters to the model. The SPV power output, pump discharge and pressure head, and emitter discharges are simulated on hourly basis. The simulated values of these parameters for the same time period are compared with the measured values to assess the model’s accuracy. The simulation accuracy of the model is tested using statistical indicators such as model efficiency (ME), coefficient of residual mass (CRM), root mean square error (RMSE), and normalized mean absolute error (NMAE). The higher ME values (close to 1) and lower NMAE and RMSE values indicated that the simulation model outputs are fairly accurate and within acceptable limits. The negative values of CRM indicate the model’s over-prediction tendency. However, the degree of over-prediction is minimal. The results indicated that the developed simulation model is capable of accurately predicting the system parameters. The developed simulation model is applied in a case study to operate different subunit manifolds of DI system installed in an Okra crop field of 1.2 ha. Based on the simulation results an additional area of 0.19 ha Okra crop can be brought under irrigation using the same SPV powered pumping system. A plan of operation of different sub-main manifolds of DI system are prepared using the simulation model for Okra crop. Similarly, the developed model can be applied to any SPV pump integrated DI system to evaluate and prepare the plan of operation of different sub-main manifolds in the field, thereby effective utilization of energy and water, which is the novelty of this study.