Surface Extractable Marine Current Turbine Teahupoo Turbines: Doug Beard, Robert Hilliard, Keaton Rich Advisor: Meredith Metzger Ph.D. Special thanks to: Michael Czabaj Ph.D., Tom Slowik, Absolute Machine LLC FEA modeling used to determine ideal number of blades, wrap angle, and hydrofoil shape. The symmetric foil (NACA-0012) produce the highest mean torque A wrap angle of 180 degrees produced the least torque variaon Turbine mount geometry calculated using the bearing load rangs as the liming constraints. Bearing spacing selected to resolve bending moment from flow forces without exceeding load capacity. Tapered bearing resolves axial load The system mass was calculated from a solid model. An appropriate Ballast Tank volume was selected to balance gravity with buoyancy. Background Offshore wind and solar power generaon are inherently intermient which requires excess power to be stored in chemical baeries or supplemented with combuson generators. Marine currents provide a more constant source of power, but underwater turbines are costly to maintain. Teahupoo Turbines has designed a vercal axis turbine that can be extracted from the water using a remotely operated ballast system which offers: Diver & ROV free maintenance Connuous power generaon in any flow direcon Operates at variable depth Withstands saline environment Minimizes interference with local wildlife and ocean traffic Design Manufacturing Ballast Tank mold and turbine blade plugs were machined from EPS foam Blocks cut to accommodate machining envelope of 2.5 axis mill Turbine blades and Ballast Tank wrapped with fiberglass and mounng points reinforced with carbon fiber Vacuum bags used to ensure fiberglass conformed during curing Mang seam was overlapped to provide rigidity in the hoop direcon Mounng plates for pump system and turbine mount embedded between layers Excess material was removed with a grinding stone Fiberglass filler used to smooth imperfecons Desired surface finish was reached using sand paper Primer and paint applied Tesng & Results Turbine Tesng Turbine fixtured at wind tunnel exit due to size constraints Load applied to shaſt using fricon clamp and measured by a spring scale aached to a lever arm to calculate torque Rotaonal speed was measured using a laser photo tachometer Dimensional analysis used to relate performance to aquac environment Coefficient of Power and Tip Speed Rao calculated from results Ballast Tank Tesng System mounted to test fixture and submerged in dive tank Ballast Tank pressure increased and monitored unl system reached neutral buoyancy System is submerged to maximum depth while Ballast Tank is evacuated in order to surface system Tesng filmed to calculate surfacing velocity using digital metrology Crical Metrics Units Ideal Theorecal Result Solidity of Turbine [unitless] 0.20 – 0.25 0.21 Tip Speed Rao [unitless] 3:1 N/A Coefficient of Power [unitless] 0.2 – 0.4 N/A Buoyancy Force [N] 230 - 260 241 Surfacing Velocity [m/s] 0.2 – 0.3 0.25 Ballast tank internal pressure [psi] 65 - 70 70