Performance of gravitational water vortex energy system

Abstract

An essential part of a mini-hydropower system is the conversion of low-head potential energy into kinetic energy to drive power turbines. One way of converting low-head potential energy is using a gravitational water vortex power plant (GWVPP). However, the eciency at this very low-head is still low. Therefore, this research focused on two fronts: (1) to optimize the vortex pool so as to increase the eciency of transfer of potential energy to kinetic energy by using the natural vortex and articially augmented vortex and, (2) to design a turbine to obtain maximum power from such low kinetic and potential energy. This work dealt with the optimization of the vortex pool to improve energy conversion and hence, generate electricity from a very low operating head of 0.2 m to 0.3 m. For this purpose, a numerical and experimental studies were carried out to investigate the vortex ow characteristics in a gravitational water vortex system in the absence and presence of a water turbine. The commercial Computational Fluid Dynamics (CFD) software ANSYS Fluent was used to investigate the optimum conguration of the vortex pool system. Moreover, an experimental test rig was set up to validate CFD results. The results of the validation demonstrated that ANSYS Fluent can model the system correctly. The Reynolds Stress model showed better results than K ?? " and K ?? ! models in predicting the vortex ow structure. A parametric study was carried out using the software to determine the main parameters aecting the eciency of energy conversion. Two dierent turbines were tested experimentally, revealing that the curved blade turbine was more ecient than the crooked blade turbine by 18%. Finally, six rectangular vanes were used to guide the ow for enhancing system eciency. Hence, a 50% increment in system eciency was recorded. The maximum eciency of the cylindrical pool system with six vanes was about 54%. This system has broad applications in low-head cases such as streams, small rivers, irrigation canals, wastewater, and rainwater harvesting systems. This system can provide rural and remote communities with an economical green source of energy.