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 variation
Turbine mount geometry calculated using
the bearing load ratings as the limiting
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 generation are inherently intermittent which
requires excess power to be stored in chemical batteries or supplemented
with combustion generators. Marine currents provide a more constant source
of power, but underwater turbines are costly to maintain.
Teahupoo Turbines has designed a vertical axis turbine that can be extracted
from the water using a remotely operated ballast system which offers:
Diver & ROV free maintenance
Continuous power generation in any flow direction
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
mounting points reinforced with
carbon fiber
Vacuum bags used to ensure
fiberglass conformed during curing
Mating seam was overlapped to
provide rigidity in the hoop
direction
Mounting plates for pump system
and turbine mount embedded
between layers
Excess material was removed with
a grinding stone
Fiberglass filler used to smooth
imperfections
Desired surface finish was reached
using sand paper
Primer and paint applied
Testing & Results
Turbine Testing
Turbine fixtured at wind tunnel exit due to size constraints
Load applied to shaft using friction clamp and measured by a spring
scale attached to a lever arm to calculate torque
Rotational speed was measured using a laser photo tachometer
Dimensional analysis used to relate performance to aquatic
environment
Coefficient of Power and Tip Speed Ratio calculated from results
Ballast Tank Testing
System mounted to test fixture and submerged in dive tank
Ballast Tank pressure increased and monitored until system reached
neutral buoyancy
System is submerged to maximum depth while Ballast Tank is
evacuated in order to surface system
Testing filmed to calculate surfacing velocity using digital metrology
Critical Metrics Units Ideal Theoretical Result
Solidity of Turbine [unitless] 0.20 – 0.25 0.21
Tip Speed Ratio [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
