Effective grid connection approach for an overshot waterwheel

Interest in very small-scale hydropower generation has increased over the past few years. These pico-hydro systems range from a few watts to several kW. The exploitation of low head sites does not require expensive civil works and is environmentally sustainable. Pico-hydro systems are attractive not only for remote areas where the grid is not available, but also for grid connection. This is especially relevant in existing infrastructures, used for other activities but which can also be used for energy generation. Waterwheels are emerging with enormous potential in this context. Low speeds and variations in head and water flow are a constraint to their connection to the grid. This study shows that they can be effectively connected to the grid using competitive and widely available technology for other renewable sources, such as photovoltaics. This paper presents an innovative approach for an effective grid connection of a pico-hydro system based on an overshot waterwheel. For this purpose, a permanent magnet synchronous generator and a photovoltaic inverter are used. The compatibility between them is analysed in detail and the analysis is valid for other hydro turbines. The 2 m diameter waterwheel has been installed on an existing infrastructure of an aquaculture centre. With a flow rate of about 13 l/s, it injects an average power of 126 W into a microgrid with a global efficiency of 50%.