Energy and water management for drip-irrigation of tomatoes in a semi- arid district

In this research, an autonomous off-grid system for irrigation in semi- arid areas is presented and discussed. In these areas precise irrigation is essential: as they are characterized by availability of solar radiation, solar irrigation (supported by photovoltaic panels and batteries) is considered here. The correct operation of these installations is a necessity to ensure the correct crop irrigation and to extend the components lifetimes (batteries in particular). These objectives can be ensured by a management system that correctly handles energy and water requirements. In this research, the energy and water management for a photovoltaic water pumping installation used for irrigating tomatoes is developed by integrating fuzzy logic inside the control system. This management system first evaluates the water volume needed by tomatoes during the vegetative cycle considering a detailed model for the tomatoes evapotranspiration and irrigation frequency, following the site and crops characteristics. Based on this and the energy availability a control algorithm decides the switching of the relays which connect the main plant components (panels, batteries and water pumps). The control algorithm fulfills the objectives by considering criteria related to the water volume needed to irrigate the crops, to the safe operation of the batteries and the continuous operating of the pump. The algorithm is tested in two cases study: during normal operation and during faults related with water losses. The obtained results confirm that the irrigation demand is fulfilled, and autonomy is ensured during the vegetative season with a reduced use of the batteries.