CFD-Assisted Power Efficiency Optimization of a Current Turbine

Marine renewable energy is becoming increasingly important amid the global effort to reduce greenhouse gas emissions. Current turbines have the potential of harnessing the energy in ocean currents and tidal streams and adding power to the grid without emissions. The turbine design studied in this paper applies a Flow Acceleration Technology (FAT), which is comprised of a shroud, a diffuser, and a hollow hub. This configuration helps regulate the incident flow and maximize the current kinetic energy passing through the turbine rotor. In order to achieve the highest hydrodynamic power efficiency for the rotor, a parametric study was conducted for the key geometric parameters for the shroud, the diffuser, and the hub. A robust computational fluid dynamics (CFD) model and gridding strategy were established prior to the application of the setup to more than 100 study cases. From the simulation results, it was found that the key to improving power output of the current turbine design is to reduce the obstruction of the turbine structures to the incident flow. Among baseline designs with different numbers of blades, a three-bladed configuration was found to be most energy efficient. Among all three-bladed design variates, smaller thicknesses, smaller maximum cambers, and maximum camber locations shifted downstream of the shroud, the diffuser, and the hub resulted in increased hydrodynamic power outputs of the rotor. The best design variant, included in the present study, accomplished a 15% increase in power output compared to the baseline case. These findings revealed the capability of CFD in optimizing power efficiency for marine renewable energy devices. This parametric study also laid a solid foundation for a more sophisticated blade optimization to be performed in the next phase.