RELIABILITY MODEL FOR DESIGNING SOLAR-POWERED CENTER-PIVOT IRRIGATION SYSTEMS

摘要

Due to the energy-intensive nature of sprinkler irrigation and limited availability of conventional energy resources, viable alternative energy sources are becoming increasingly important. The use of solar photovoltaic (PV) technology in irrigated agriculture is particularly appealing because of the mutual dependence of crop evapotranspiration and potential energy production on incoming solar radiation. However, successful implementation of a PV irrigation system depends on appropriately sizing the PV system components (solar panel array, battery capacity, etc.) under highly variable and site-specific influencing factors, which include the inter-annual variability of the local climate, the crop water requirement, the soil water holding capacity of the field, the irrigation management practice, and the capacity of the irrigation system itself. The objective of this research was to develop a model for assessing the reliability of a PV-powered center-pivot irrigation system. A numerical simulation tool was developed by combining sub-models of the solar power production, battery storage, and irrigation system power requirement, which can be used to evaluate the system performance under variable operating and meteorological conditions. Given the required input variables, the model determines the reliability of the PV system by analyzing the time of irrigation for which the power both produced by the PV array and stored in the batteries is sufficient to fulfill the load demands. The model was validated by comparing the simulated results to field measurements of a small (1.4 ha) solar-powered center-pivot irrigation system installed near Outlook, Saskatchewan, Canada. The utility of the model was demonstrated by simulating the system performance over five years. It was shown that a PV system that has a reliability of greater than 90% is required to avoid moisture stress during dry years for the selected irrigation management strategy. It was further demonstrated how the model may be used to explore different combinations of PV sizing for achieving the desired reliability. This modeling approach is presented as an effective tool to ensure the technical feasibility of a PV irrigation system before the system is built.