Desing and analysis of an overshot water wheel for a grid-connected pico-hydro system

Abstract

The increase in energy demand, accompanied by the concern to reduce environmental impacts, has intensified the research and use of renewable energy sources. In this context, pico-hydro systems have been intensively investigated due to being environmentally sustainable and for their potential in complementing distributed generation systems and microgrids. Within this class of power generation, water wheels are a prominent choice in sites with low heads and flowrates. Although they may seem a rudimentary solution for the present scenario, in the last two decades, they have returned to the interest of the scientific community and can be an effective alternative for generating clean energy in rural and remote areas without access to the conventional power grid. In urban centres with a well-established power grid, water wheels, such as photovoltaic systems, can contribute to meeting the ever-increasing demand for electricity. One of the main challenges for this technology dissemination lies in the fact that the design of the system depends on the characteristics of the place where it will be installed and, usually, it is done in such a way that the water wheel operates in a very narrow speed range. In this context, this work presents the design and mathematical modelling of an overshot water wheel, as well as the application of theoretical models to estimate its efficiency, aiming to identify its behaviour within an operational range. From the results, the design of a grid-connected pico-hydro system was made, based on permanent magnet synchronous generators and conventional photovoltaic micro-inverters, allowing the water wheel to operate at variable speed. Additionally, the integration with the grid using conventional photovoltaic micro-inverters, as presented in this work, can facilitate the dissemination of these systems, as they are a mature and ready-to-use technology.