Mini-hydro: a design approach in case of torrential rivers

The problem of designing small run-of-river hydropower plants is very critical for the cost effectiveness of the investment. In order to maximize the economic benefits, an accurate feasibility study must be effected considering the hydrogeological characteristics of the rivers. In this paper a different design approach regarding mini and micro-hydro plants is presented. Specifically, the proposed methodology wants to be a helpful tool to avoid sizing errors that can occur by applying the conventional calculation methods not suitable for torrential rivers. Starting from the analysis of the flow duration curve, the developed method provides an initial value for the turbine nominal flow rate and, considering the actual daily flow rate usable by the turbine, allows to find the optimal size. The method has been developed on the basis of particular rivers, having different runoff regimes, chosen as cases study; for these rivers it has permitted to optimize the plant and find the shorter investment payback time.