Optimization of pumps working as turbines under economic criteria in water irrigation networks to improve sustainability: Case study

Hydraulic is a renewable source of energy with a promising future. Its growth is expected in the next years, in which a considerable part of this energy can be obtained due to the energetic recovery in pressure water systems for irrigation or potable water distribution (Emec et al. 2015). Contrary to hydraulic power stations, the main goal of these systems is not energy generation (which means that they are multipurpose systems) but energy recovery, allowing to reduce operating costs or even to obtain benefits from the energy sale. It is necessary to adjust the pressure in irrigation or potable water distribution systems for consumption. For this purpose pressure reducing valves are often used. If these valves are replaced with pumps working as turbines (PATs) not only pressure regulation can be achieved, but also a recovery of energy can be obtained, that otherwise would not be exploited. In this research, an existent energy recovery optimization methodology based on the installation of PATs is applied to an irrigation network located in a town in Valencia local region. Through this methodology, it is possible to find out the installed power and recovered energy in this particular irrigation network according to the number of PATs to be installed. With this information, a viability analysis is performed in order to select the best combination. Then, the methodology searches in a PATs catalogue the machines that optimize the energetic recovery. Finally, the profitability of the real case is evaluated and it is decided to install two groups of PATs, which allow a total energy recovery near 40 MWh/year. This energy can be even increased when variable conditions are considered for the management of the installed machines, under economic criteria for optimization. To do so, simulated annealing is introduced in order to select the final machines performance. Flow, head and power will be known for the selected PATs, even when variable speed of the machines is considered.