Recent advances and performance characteristics of vertical axis hydrokinetic turbines: A review

This review examines recent advances in the design, hydrodynamic optimization, and techno-economic evaluation of vertical-axis hydrokinetic turbines (VAHTs) for small-scale power generation in rivers and channels with fluctuating flow conditions. Emphasis is placed not only on understanding how geometrical parameters, such as solidity, number of blades, helicity, aspect ratio, and hydrofoil selection, but also on how flow parameters such as tip speed ratio (TSR) and Reynolds number influence the power coefficient (Cₚ) and overall energy conversion efficiency. The analysis reveals that Savonius turbines achieve Cₚ values between 0.12 and 0.25 at low TSRs (0.35–1), making them suitable for turbulent flows, whereas Darrieus turbines exhibit higher efficiencies (Cₚ = 0.29–0.40) at TSRs of 1.5–3.5, driven by lift-dominated aerodynamics. Gorlov turbines, featuring helical blades and optimized NACA hydrofoils, further improve performance with Cₚ values up to 0.45 and stable operation across broad TSR ranges. Hybrid Darrieus–Savonius configurations combine the self-starting characteristics of drag-based rotors with the efficiency of lift-based systems, achieving Cₚ ≈ 0.30–0.35 and offering a balanced solution for variable flow conditions. The review further emphasizes that iterative design processes integrating CFD modeling, experimental validation, economic analysis to stablish technical viability, together with predictive maintenance strategies, are essential for optimizing the performance of VAHTs. Overall, the Gorlov turbine and hybrid Darrieus-Savonius rotors stand out as highly effective and reliable options for riverine hydrokinetic energy harvesting, offering compact design, adaptability to turbulent flows, and enhanced performance suitable for sustainable rural electrification and microgeneration applications.