Finite Element Analysis of Tidal Turbine Blade Subjected to Impact Loads from Sea Animals

The present work investigates structural response of tidal stream turbine blades subjected to impact loads from sea animals. A full-scale tidal turbine blade model was developed using a finite element modelling software ABAQUS, while a simplified geometry of an adult killer whale (Orcinus orca) was assumed in simulating impact on the blade. The foil profiles along the turbine blade were based on the NACA 63-8XX series, while the geometric and material properties of the sea animal were calibrated with experimental results. The numerical model simulated the dynamic response of the blade, accounting for radial velocities of the blade corresponding to real life scenarios. Different magnitudes and trajectories of the velocity vector of the sea animal were simulated, in order to investigate their influence on the turbine blade’s plastic deformation. Furthermore, multiple impacts were analysed, in order to monitor the accumulation of plastic strain in the material of the blade. Finally, the potential application of stainless steel material in tidal stream turbine blades for impact resistance was evaluated, through comparison of numerical results obtained from models using stainless steel and mild carbon steel materials.

Comparison of unidirectional and bidirectional airfoils in a tidal stream turbine

Tidal stream turbines offer an attractive method for stable renewable energy generation. Due to the periodicity of the tidal stream, a tidal stream turbine can be designed to operate in a bidirectional manner, thereby avoiding a yaw control system. This article compares a unidirectional design with a bidirectional design to estimate the expected power loss for the bidirectional design. First, a blade-element momentum theory approach is used to find optimum pitch angles for the blades and give a low-cost estimate of the power production. Next, fully-resolved computational fluid dynamics simulations are performed to validate the BEMT approach and gain insight into the flow patterns. The two approaches estimate that the power output of the bidirectional design is approximately 15-20 % lower than for the unidirectional design. This suggests that although a bidirectional design will have some power loss compared to a unidirectional design it is an interesting alternative as it can yield the same power output for both the ebb and the tide. The study also serves as a starting point for further optimization of the bidirectional design.

Multi-Point Shape Optimization of a Horizontal Axis Tidal Stream Turbine

A method was developed to perform shape optimization of a tidal stream turbine hydrofoil using a multi-objective genetic algorithm. A bezier curve parameterized the reference hydrofoil profile NACA 63815. Shape optimization of this hydrofoil maximized its lift-to-drag ratio and minimized its pressure coefficient, thereby increasing the turbines power output power and improving its cavitation characteristics. The Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) was employed to perform the shape optimization. A comparative study of two- and three-dimensional optimizations was carried out. The effect of varying the angle of attack on the quality of optimized results was also studied. Predictions based on two-dimensional panel method results were also studied. Predictions based on a two-dimensional panel method and on a computational fluid dynamics code were compared to experimental measurements.

Potential Study of Tidal Stream Turbine Farm at Toyapakeh Strait, Bali

In 2015, Bali Province is mandated by ESDM ministry to become the National Region of Clean Energy, promoting efforts to explore new source of electricity namely tidal stream energy. Previous works have demonstrated that Toyapakeh Strait contains a promising tidal stream resource, with a high stream in a long period. In this study, hydrodynamic modelling and power production analysis is conducted to evaluate this potential with an aim to meet energy demand of Tiga Nusa Cluster Islands. Twenty-one Gen5 KHPS turbines are employed in this study, at an optimized location, 8.72°S, 115.44°E, which contains the highest energy potential. Financial analysis, with 25-year return period of investment and 3.60% interest rate, resulting levelized cost of energy (LCOE) of Rp 6,100.kWh-1. This value is higher than the national and regional selling nominal, in other word the energy cost of tidal stream turbine is relatively high in this location. Nearly 46% of energy cost is spent for turbine fabrication, and from the sensitivity analysis, cutting half the turbine costs may reduce the price by Rp 1,400.kWh-1 while increasing the amount of installed turbine is less significant. Despite of the high prices, the study shows that Toyapakeh Strait holds a promising resource of tidal stream energy.

Multi-Point Shape Optimization of a Horizontal Axis Tidal Stream Turbine

A method was developed to perform shape optimization of a tidal stream turbine hydrofoil using a multi-objective genetic algorithm. A bezier curve parameterized the refrence hydrofoil profoil NACA 63815. Shape optimization of this hydrofoil maximized its lift-to-darg ratio and minimized its pressure coefficient, thereby increasing the turbines power output power and improving its cavitation characteristics. The Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) was employed to perform the shape optimization. A comparative study of two-and three-dimensional optimizations was carried out. The effect of varing the angle of attack on the quality of optimized results was also studied. predictions based on two-dimensional panel method results was also studied. Preditions based on a two-dimensional panel method and on a computational fluid dynamics code were compared to experimental measurments.