An integrated framework for PAT micro-hydropower: experimental characterization, NSGA-II impeller-volute optimization, and resin MSLA manufacturing

Abstract

Pump-as-Turbine (PAT) technology offers a cost-effective route for micro-hydropower in off-grid Andean communities, but adoption remains limited: manufacturers rarely publish turbine-mode curves, and the available geometries were originally designed for pump operation. This paper presents a framework that combines baseline characterization of a commercial PAT with simultaneous impeller–volute optimization using NSGA-II under an MSLA manufacturability constraint set. An EBARA 3PF 40-125 centrifugal pump was operated in reverse mode on a custom test rig at Escuela Politécnica Nacional. Among four BEP-conversion methods benchmarked against the measured nominal point, the Stepanoff correlation produced the smallest combined error and was adopted as the calibration anchor. The optimization handles eight geometric variables and three objectives: maximize hydraulic efficiency, minimize impeller–volute material volume, and minimize a geometric rotor–stator interaction (RSI) surrogate. A quasi-one-dimensional loss model with eight loss terms enables rapid evaluation without CFD. Within the model, the Pareto front (80 non-dominated solutions) yields modelled efficiency improvements of up to 36.6 percentage points (equivalently, up to 81% higher extracted shaft power) relative to the same loss model evaluated on the commercial baseline geometry, and reveals a model-predicted trade-off with the RSI surrogate. The optimized geometries were exported as watertight STL files compatible with MSLA slicing for hydraulic and pressure-pulsation testing in a companion study.