Investigation of power generation from river surface runoff with a novel tilted axis hydrokinetic turbine for off-grid sites

In this study, a novel tilted axis hydrokinetic turbine system is presented and tested to generate electricity from surface water streams in off-grid locations. This system consists of a turbine, differential, reducer, and alternator, and resembles a Pelton turbine. It is used in shallow waters near river banks with the free flow velocity. This study reports significant hydrodynamic efficiencies with field tests consistent with theoretical estimates obtained at the design and fabrication stage, for different flow velocities (0.5–3 m/s in 0.5 m/s internal) and blade numbers (7, 9, and 11 blades) on the Namnam Stream in the Muğla province/Turkey. On the same turbine system, 7, 9, and 11 blades can be disassembled in the center of the turbine. In order to facilitate testing at different water flow velocities, the flow velocity is adjusted by excavation operations in the stream bed. The results of the study indicate that as the water speeds increase, the turbine power, speed, and efficiency of all blade turbines also increase. In terms of hydrokinetic energy potential, the water flow velocity and turbine speed are 2 m/s and 3 r/min, respectively. Because of parasitic drag and lift-induced drag, 7- and 11-blade turbines have higher mechanical losses, lower turbine efficiency, and increased cost due to weight. A 9-blade turbine is preferred for such a prototype due to torque, load power (800 W), and efficiency (15.9%) compared to the others. As a result, this study reports that such a prototype can be used in unpowered riverbanks or free surface currents.