TIDAL CURRENT TURBINE DESIGNS FOR THE GULF STREAM NEAR FLORIDA COASTAL BELT
Tidal current energy is regarded as one of the most promising alternative energy resources for its minimal environmental footprint and high-energy density. The device used to harness tidal current energy is the tidal current turbine, which shares similar working principle with wind turbines. The high load factors resulting from the fluid properties and the predictable resource characteristics make marine currents particularly attractive for power generation. There is a paucity of information regarding various key aspects of system design encountered in this relatively new area of research. Not much work has been done to determine the characteristics of turbines running in water for kinetic energy conversion even though relevant work has been carried out on ship's propellers, wind turbines and on hydro turbines. None of these three well established areas of technology completely overlap with this new field so that gaps remain in the state of knowledge. A tidal current turbine rated at 1-3 m/s in water can result in four times as much energy per year/m2 of rotor swept area as similarly rated power wind turbine. Areas with high marine current flows commonly occur in narrow straits, between islands, and around. There are many sites worldwide with current velocities around 2.5 m/s, such as near the UK, Italy, the Philippines, and Japan. In the United States, the Gulf Stream near Florida coastal belt is reasonably swift and continuous current moving close to shore in areas where there is a demand for power. In this study tidal current turbines are designed and optimized for the Gulf Stream for an average tidal current speed of 2 m/s. Tidal current turbines can be classified as either horizontal or vertical axis turbines. In this study several designs from both the classifications are considered and modeled using SolidWorks. Hydrodynamic analysis is performed using SolidWorks Flow simulation software, and then optimization of the designs is performed based on maximizing the starting rotational torque and ultimate power generation capacity. From flow simulations, forces on the tidal current turbine blades and structures are calculated, and used in subsequent stress analysis using SolidWorks Simulation software to confirm structural integrity. First the starting rotational torque is maximized by using lighter rotating parts. However minimization of mass reduces the structural strength of the rotating parts and therefore is limited by the factor of safety to ensure structural integrity. Once a reasonable initial optimization with stationary turbine blades is established, angular acceleration and velocity are calculated with time, rotating region is incorporated using SolidWorks Flow Simulation, and power as a function of time is calculated. Results from this study shows the systematic closed loop optimization of the tidal current turbine design at the average tidal speed of the Gulf Stream near Florida.