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