Energy Efficiency Enhancement in Pressurized Irrigation Networks through Optimal Location of Pumps-as-Turbines: A Case Study in Spain

One of the hardest challenges in irrigation systems is to reduce the use of water resources. The goal “more crop per drop“ has fostered the improvement of hydraulic infrastructure by replacing old open channel networks with pressurized systems (e.g., drip and sprinkler irrigation). This has resulted in reduced water losses, as well as the possibility for farmers to benefit from on-demand water. On the other hand, this improvement in water efficiency has controversially resulted in a large increase in energy consumption, since pressurized systems demand large flows with high pressures. The high energy requirements, along with the investment and operational costs, may compromise the viability of such irrigation systems. Several strategies to save both water and energy resources have, therefore, been proposed in the recent literature. Among these, the exploitation of excess pressure to produce energy by means of energy production devices (EPDs) has been proven to be a very effective strategy. Pumps-as-turbines (PATs) are, by far, preferred over traditional EPDs, such as pico- or micro-turbines, being very cost-effective solutions. In this study, the optimal location of PATs within an irrigation system is investigated with reference to a whole irrigation season. A case study network, the Zújar Canal irrigation district, is considered, for which accurate records of hourly water demands are available due to a diffuse telemetry system over the irrigation area. The aim of the optimization is to search for the best number and location of PATs within the irrigation network in order to maximize the energy production and minimize the investment costs. The hydraulic resolution of the network is coupled with the optimal location problem in one single mathematical model and the optimization procedure is performed via the use of a global optimization solver. The promising results in terms of the hydropower potential prove the effectiveness of the PAT installation within the case study network.