Hydrokinetic energy harvesting in large natural rivers: a multifaceted experimental study.

Rivers are currently an overlooked potential source of local and continuous kinetic energy that can be harnessed using the present in-stream converters technology. An experimental study was carried out in a quasi-field-scale channel at the Saint Anthony Falls Laboratory to investigate the feasibility of hydrokinetic turbine power plant deployments in large morphodynamically active rivers. A staggered array of twelve axial-flow hydrokinetic turbine models was deployed on one side of the channel, under intense sediment transport conditions. The 2D bathymetry evolution was monitored using a high-resolution submersible laser scanning device, revealing both the local erosion at the base of each individual turbine and a cumulative array-scale effect on the averaged topography. The enhanced shear stress resulting from the operating turbine and responsible for the local scour, is also interpreted as a self-defense mechanism which prevents the large approaching dunes from encroaching on the blades. Turbines wake and performance were characterized through the array, revealing similar features already observed in experimental wind farm models. Results indicate that the staggered configuration is beneficial for both wake recovery and power output.