Parametric assessment of a Pelton turbine within a rainwater harvesting system for micro hydro-power generation in urban zones

Abstract

Hydroelectric power is a renewable and sustainable approach in energy production. However, hydro power generation is almost exclusively used at large scale (>10 kW). On a micro scale, it is still being assessed as a viable alternative to produce energy, even though this generation process seems to require lower installation and maintenance costs. The main aim of this work is the performance assessment of a micro hydro power station integrated into a rainwater harvesting system based on the optimal dimensioning of the turbine geometry. This project proposes different hydraulic heads for a sustainable model that uses the potential energy to generate electrical power in urban areas. As case of study, the system was set up for an industrial facility in the Toluca Metropolitan Zone, Mexico. A methodology was developed in order to: a) determine hydraulic setting-up based on the precipitation regime and operational requirements of the generator; b) assess an efficiency indicator under size variation of main geometric elements through Computational Fluid Dynamic (CFD); and c) validate the prototype throughout a 3D model. Due to the nature of the rainwater harvesting system, the type of the turbine selected was a Pelton turbine. Afterwards, hydraulic characteristics were defined, such as initial size of turbine, as well as the number and diameter of conduit pipes, nozzles, valves, and gates. Besides, the fluid behavior (velocity and pressure fields) in the turbine was analyzed by CFD to define a suitable geometry. Numerical modeling of the turbine allowed to estimate expected system efficiency according to the variation of a coefficient based on inlet and outlet velocities w2w1. By means of an electronic circuit, which measured number of revolutions per minute and power generation (voltage and electrical current) of the system, efficiency and energy produced by the system were analyzed under both controlled conditions and real-time rainfall conditions. In general, the hydro power station managed to generate electrical energy using rainwater harvesting system which achieved up to 81.13% of efficiency.