Abstract
Hydrokinetic turbines present an opportunity for generating renewable energy sustainably in support of microgrids. This research examines the performance and environmental impact of a 25-kW New Energy vertical axis hydrokinetic river turbine under freewheeling conditions, focusing on flow and turbulence behavior. Field measurements of flow velocity at the Canadian Hydrokinetic Turbine Test Center on the Winnipeg River are measured using an acoustic Doppler current profiler and an acoustic Doppler velocimeter. Measurements are taken at various distances downstream of the turbine, from 1 to 17 turbine diameters, to analyze turbulence intensity, turbulent kinetic energy, and mean velocity profiles. The results indicated that turbulence intensity was highest near the turbine, with peaks at the centerline reaching 84% in the first acoustic Doppler current profiler test and 119% in the second, while acoustic Doppler velocimeter measurements showed 41% and 55%, respectively. As expected, turbulence levels gradually decreased with increasing distance from the turbine and are documented. Additionally, the TKE values exhibited a similar trend, demonstrating significant energy dissipation and flow stabilization further downstream. The mean velocity profiles revealed the maximum velocity deficit near the turbine, which gradually recovered with distance. River in-situ values measured do not compare favorably with scaled turbine water tunnel studies. This comprehensive analysis, comparing acoustic Doppler current profiler and acoustic Doppler velocimeter data, provides valuable insights into the wake dynamics and turbulence characteristics of vertical-axis turbines, which are required for optimizing turbine efficiency and assessing environmental impacts.