Analysis of a Vertical-Axis Spherical Turbine for Energy Harvesting in Urban Water Supply Systems

Fast-growing cities are a challenge for its current energy demand, especially in developing countries. Replacement of micro-turbines instead of dropping pressure valves in urban-water pipelines may assist in supplying energy to the electrical grid. The understanding of turbine design and its operational characteristics can help for efficient energy harvesting in these cities. The aim of this work is to design a cheap and versatile hydrokinetic vertical axis spherical turbine for extracting energy from water pipelines of 800 mm in diameter. The turbine runner is based on a NACA0018 airfoil. Performance prediction is obtained by implementing a double multiple stream tube (DMST) based model. Computational fluid dynamics (CFD) and finite element analysis are used for performance and design improvements. Based on the analysis, the turbine can generate an output power of approximately 1.71 kW with a dropping pressure head of 0.4 m and an internal flow velocity of 2.07 m/s with an efficiency of approximately 42.7%. The proposed method allows determining the available energy of 390 kW in the city of Guayaquil, Ecuador.