Development of Micro Hydropower Systems in Amazonia Using Multiple Axial-Flow Turbines

Despite significant Brazilian social programs to expand energy access, approximately one million people in rural Amazonia still lack electricity. Moreover, the existing rural electricity grid in the region is inadequate for supporting efficient small-scale production systems due to both the poor quality and high cost of supplied energy. In parallel, traditional wooden bridges in the Amazon have been progressively replaced by more durable concrete structures in recent years. In this context, this study explores the application of very low-head hydropower installations in the Amazon, focusing on integrating axial-flow turbines beneath small concrete bridges. The methodology involves analyzing flow duration curves and key hydraulic parameters upstream and downstream to design a micro-hydropower system comprising two or more units, thereby maximizing annual energy generation. Additionally, the study assesses the applicability of the minimum pressure coefficient criterion to improve the efficiency of very low-head turbines. This design criterion is first validated against an existing experimental study featuring a propeller turbine with a simple curved plate blade. The proposed methodology is then applied to a case study involving a small dam-bridge with a head variation from 1.4 to 2.4 m and a flow rate ranging from 0.23 to 0.92 m3/s. The optimal configuration achieves an energy output of 26.2 MWh/year with an efficiency of up to 86%.