Oral Presentation

Asa Sproul

MSEE Defense

April 3rd, 2015

Advisory Committee:

Duane C. Hanselman, Associate Professor of Electrical and Computer Engineering, Advisor

Bruce E. Segee, Professor of Electrical and Computer Engineering

Nathan D. Weise , Assistant Professor of Electrical and Computer Engineering at Marquette University

• Introduction

• Theory

• Testing

• Discussion

• Conclusion

Content

April 3rd, 2015 Asa Sproul 2


• Ocean wave energy is highly underutilized

• 15-20x more available energy/m2 than wind or solar

• Estimated 8000-80,000 TWh/yr available throughout ocean

• Economical viability for capture not yet achieved


Background

• WEC: Wave Energy Converter

• Mechanical structures absorb wave power

• Power capturing structure coupled with generator

• Maximum capture through mechanical resonance

• Can operate in various water depths


What is a WEC?

• LIMPET:

• Pelamis:


Technology Under Development

• Wave Dragon:

• PowerBuoy:


Technology Under Development con’t

• No universal design converged upon

• Find viable control method of novel prototype

• Maximize mechanical efficiency

• Provide groundwork for large-scale device


Research Purpose


• 𝐹 = 𝑚𝑥 + 𝑅𝑥 + 𝑆𝑥

• Can be compared with power

absorbing structure of WEC

• Provides basis for control

• 𝐹 = 𝐹𝑤𝑎𝑣𝑒


Linearized Wave Equation

• 𝐹𝑔𝑒𝑛 = 𝑚𝑔𝑒𝑛𝑥 + 𝑅𝑔𝑒𝑛𝑥 + 𝑆𝑔𝑒𝑛𝑥

• 𝐹𝑔𝑒𝑛 ∝ 𝑇𝑔𝑒𝑛 ∝ 𝐼𝑔𝑒𝑛

• Current controller may be used

• Controller input based on acceleration, speed, and position


Assisted Movement


Simplified Control Diagram


RTI F2

• Typically expressed as available power per meter crest length

• 𝑃𝑤𝑎𝑣𝑒,𝑚𝑐𝑙 =1

8𝜌𝑔𝐻2𝑐𝑔

• Equation takes 3 forms

1. Shallow

2. Intermediate

3. Deep

• Equation form depends on water depth and wavelength


Wave Power

𝜌 = mass density of liquid

𝑔 = acceleration due to gravity

𝐻 = peak-to-trough wave height

𝑐𝑔 = wave’s group velocity

• Means of measuring efficiency and economic viability

• Defined as “The width of the wavefront (assuming uni-

directional waves) that contain the same amount of power as

that absorbed by the WEC.” Price et al., 2009

• 𝐶𝑊 = 𝑃𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑

𝑃𝑤𝑎𝑣𝑒,𝑚𝑐𝑙


Capture Width


• 120’ long, 12’ wide, 8’ deep

• Programmable wave maker

• Wave Staff


UNH Chase Laboratory Wave Tank

• Mounted frame

• Vessel facing

wave maker

• Wave attenuator

at far end


Device Setup

• Motor/generator

• Brushed DC

• Coupled with gearbox

• Controlled from control

platform


Power Take Off

• CUSP Educational Lab Inverter

• MATLAB, Simulink, dSPACE


Hardware and Software

• Determine optimal control technique

• Validate wave front parallel configuration

• Operate device as intended for structural considerations

• Analyze system losses

• Provide groundwork for ongoing development


Objectives

• Wave height and wave period

• Control methods

– Damping control

– Damping + inertial control

• Added mass

• Plate angle

• Frictional correction


Test Variables

• 𝑃1 = 𝐼𝑉

• 𝑃2 = 𝑃1 + 𝐼2𝑅

• 𝑃3 = 𝑃2 + 𝐵𝜔2

• 𝑃4 = 𝑃3 + 𝑇𝑠𝑡𝑖𝑐

• 𝑃5 =𝑃4

0.93


Capture Widths and System Losses

𝐶𝑊1−5 =𝑃1−5

𝑃𝑤𝑎𝑣𝑒,𝑚𝑐𝑙


Capture Widths and System Losses con’t

≈ 0.38

Not enough torque


• Stationary frame will be floating at full scale

• Capture width needs further improvement

• Prototype should be optimized to panchromatic conditions

• Other control strategies should be tested


Things to Consider

• Direct drive would eliminate frictional losses due to gearbox

• Generator optimized for low speed

• Generator optimized for high torque

• Brushless DC would provide better efficiency than brushed


Power Take Off Improvements


Trending

• Prototype to full scale parameter estimates

• Froude scale factor = 11


Froude Scaling

Parameter Prototype Full Scale

Generator 250W 1MW

Structure Width 1m 11m

PTO Peak Torque 1.35Nm 19.7kNm

PTO Peak Speed 42.3rad/s 12.8rad/s

Optimal Wave Period 2s 6.6s


• RTI F2 tested

• Efficiency maximized through control

• Linear wave theory basis of control theory

• Sufficient test data captured for analysis and

improvements


Overview

• RTI working on next set of prototypes

• RTI F2S and RTI F2DS

• Utilize swingarm and dual swingarm configurations

• Better economic feasibility

• Stronger structures


Future Models

• Nathan Weise

• Duane Hanselman

• Bruce Segee

• John Rohrer

• Sean Lewis

• Matt Rowell

• Matt Hall

• Lance Doiron

• Arjun Prabu

• Adam Nickerson

• Lonnie Labonte

• Sara Lemik


Special Thanks


• J. Vining and A. Muetze, “Economic factors and incentives for ocean wave energy conversion,” IEEE Trans. Ind. Appl., vol. 45, pp. 547–

554, March 2009. Slide 4

• http://upload.wikimedia.org/wikipedia/en/thumb/2/26/Maine_Black_Bears_Logo.svg/1280px-Maine_Black_Bears_Logo.svg.png Black

Bear image on section headers

• N. Ahmed and M. Mueller, “Impact of airflow impingment on heat transfer from induction generators in oscillating water columns,” in Proc.

International Conference on Power Electronics, Machines and Drives (PEMD), pp. 1–6, March 2012. LIMPET picture

• N. Muller, S. Kouro, J. Glaria, and M. Malinowski, “Medium-voltage power converter interface for wave dragon wave energy conversion

system,” in Proc. IEEE Energy Conversion Congress and Exposition (ECCE), pp. 352–358, Sept 2013. Wave Dragon picture

• R. Yemm, D. Pizer, C. Retzler, and R. Henderson, “Pelamis: experience from concept to connection,” Philosophical Transactions of the

Royal Society A: Mathematical, Physical and Engineering Sciences, vol. 370, no. 1959, pp. 365–380, 2012. Pelamis picture

• A. F. de O. Falco, “Wave energy utilization: A review of the technologies,” Renewable and Sustainable Energy Reviews, vol. 14, no. 3, pp.

899 – 918, 2010. Power Buoy picture

• J. Falnes, Ocean Waves and Oscillating Systems. Cambridge University Press, 2002. Mass Spring Damper picture


References

http://upload.wikimedia.org/wikipedia/en/thumb/2/26/Maine_Black_Bears_Logo.svg/1280px-Maine_Black_Bears_Logo.svg.png




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