Optimization-Based Methodology for Selection of Pump-as-Turbine in Water Distribution Networks: Effects of Different Objectives and Machine Operation Limits on Best Efficiency Point

Abstract

In recent years, many researchers have recognized pressure reducing valves (PRVs) as potential microhydropower (MHP) sites, aiming to improve the efficiency of water networks. Pump-as-turbines (PATs) have been pointed out as the most suitable technology because of their favorable cost. Most of the methodologies available in the literature for selection of a PAT to replace a PRV follow a traditional approach that is based on scaling aprototype data using affinity curves, thus restricting the solution space only to these curves. The optimization-based methodology presented in this paper uses the classical hydraulic regulation scheme with the Nedler–Mead simplex direct search algorithm to search for the optimal solution within space that is constrained only by the boundaries of available centrifugal PATs on the market. The methodology also defines the PAT’s operation limits based on the PAT’s relative mechanical power. Improvements gained by using the novel methodology have been demonstrated on real-world case studies from Ireland and Italy that were previously used in the literature. The results of the considered sites also suggest that the maximal global plant’s efficiency is around 80% of the maximal efficiency of the theoretically optimal PAT. The paper also examines effects of different objective functions and different PATs’ operation limits on the selection of the optimal PAT.