Selection criteria for hydro kinetic turbines and implications

This review examines the criteria for selecting hydrokinetic turbines (HKTs), which generate electricity directly from flowing water without relying on hydraulic head differences. It emphasizes practical deployment, classifies HKTs into axial-flow and cross-flow types, and evaluates their performance under varied hydrodynamic conditions such as rivers and man- made canals. Selection depends on factors including flow velocity, depth, turbulence intensity, site topography, and blockage constraints. The analysis compares lift-based, drag-based, and hybrid rotor designs, highlighting trade-offs among efficiency, self-starting capability, structural complexity, and reliability. Deployment strategies such as rotor submergence depth, clearance ratio, and blockage ratio are discussed for their influence on performance. Optimizing blockage (25%–45%) and clearance (0.5–0.6) can improve efficiency by 30–55%, yielding power densities of 0.5–1.5 kW/m2 for flows above 1 m/s. Axial- flow turbines typically achieve power coefficients (CP) of 0.35–0.48 at tip-speed ratios of 5–7, while cross-flow turbines operate effectively at CP = 0.15–0.30 for low-velocity flows (0.5–1.5 m/s). Diffuser-augmented designs may increase power output by 1.5–3.1 times, reaching efficiencies up to 50% compared to 45% for free-stream turbines. Environmental assessments indicate minimal aquatic disruption (<5% habitat alteration) when clearance ratios are maintained. The review also addresses challenges such as cavitation, wake interference, and turbine-array spacing, and outlines the technology status of commercial HKT systems. Overall, this work provides a structured framework for selecting HKT configurations suited to specific hydrodynamic and socio-environmental conditions.