Field-testing of model helical-bladed hydrokinetic turbines for small-scale power generation

The vertical-axis helical-bladed hydrokinetic turbine serves as a viable source of renewable power that can extract kinetic energy of the free flowing water to generate electricity. Such helical-bladed turbines are characterized by lesser pulsation of torque and marginally favorable starting capability as compared to straight-bladed turbines. The present study aims at evaluating the performance of NACA 0020 bladed helical turbines of different solidity ratios. In-situ experiments of the developed turbines have been carried out in an open channel where the turbine with solidity ratio (σ) of 0.38 achieves a maximum power coefficient of 0.20 at a tip-speed ratio (TSR) of 1.02 and an inlet water velocity of 0.87 m/s. The effect of σ on the performance of different turbines is investigated at various immersion levels. For all the tested turbines, it has been observed that with the decrease of immersion levels, the power coefficient values decrease along with the optimum TSRs and this change is found to be predominant for the turbine having lowest σ = 0.31. Higher starting ability has been noticed for the helical-bladed turbine with σ = 0.38 in comparison to lower solidity ratio variants.