Retrofit of a settling basin of a small hydropower plant

Abstract The decrease in electricity production of 8% in a combined system formed by two small hydropower plants (SHPP) with capacities 1.220 MW and 1.327 MW has been noticed. The plants have a common side water intake with a three-chamber settling basin. The initial assumption that inefficient sediment removal due to unequal flow distribution among the chambers of the settling basin is responsible for the decrease in electricity production is proven by numerous water flow measurements. The measurements have been performed according to EN ISO 748:2007, and are used for the validation of a CFD model of the weir intake. The model is used as a tool for the evaluation of 12 different technical solutions that are simultaneously used for: 1) equalization of flows between the chambers, and 2) additional support of a reinforced concrete plate over a common inlet zone of the settling basin. The optimal solution consists of 11 equidistant metal pillars equipped with vanes, where 4 of these vanes have additional wings. Compared with the present case characterized by 15.07%, 36.30%, and 48.69%, the optimal solution has the relative flow distribution among the chambers of 32.88%, 33.29%, and 33.82% at the installed flow rate.