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Direct-Drive Rotary Generator Design by Genetic Algorithm for Ocean Wave Energy Application
Research Conducted: June - September 2009 Presentation: October 5, 2009
Dr. Ted K.A. Brekken, Ph.D.
Assistant Professor
Oregon State University
[email protected]
Christopher Haller
Graduate Research Assistant
Oregon State University
[email protected]
Hai-Yue Han
Graduate Research Assistant
Oregon State University
[email protected]
Dr. Annette von Jouanne, Ph.D. P.E.
Professor
Oregon State University
[email protected]
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Presentation Outline
1. Wave Energy Background
2. Design Considerations
3. Mechanical Layout
4. Time Domain Electromagnetic Analysis
5. Conclusion
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Wave Energy Background
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• 11 foot spar
• 4 foot diameter float
• Designed for water depth
of 135 feet
2007 10kW Seabeav I
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2007 10kW Seabeav I
Preparing for sea trial
in Newport
[5]
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2007 10kW Seabeav I – Sea Trial
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2008 10kW L-10
• 25 feet tall, 11 feet wide
•Direct Drive
Integrated Linear Generator
No pneumatics or hydraulics
• Developed in collaboration
with C.P.T. and the Navy
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2008 10kW L10 – Sea Trial
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OSU Facilities to Advance Wave Power
O.H. Hinsdale Wave Research Lab
(HWRL)
Wallace Energy Systems and Renewables Facility
(WESRF)
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OSU – Key Location for Wave Power Research• 750 KVA Adjustable Power Supply
• Variable Voltage input(0-600Vac), 600A• 3-phase adjustable (while loaded) for
balanced and unbalanced testing• Highest Power University Lab in the
Nation• Enables Multi-Scale energy research
• Four Quadrant Dynamometer • Programmable torque/speed• Dynamic Vector Controls 0-4000 rpm
• Bidirectional Grid Interface • Regeneration back to the utility grid
• Flexible, 300 hp,Motor/Generator test-bed
• 120KVA programmable source• Transient VLrms=680V• Steady State VLrms= 530V• Frequency range: 45Hz to 2KHz
• 10 kW Linear Test Bed• 2 m/s, 10 kN• 1 ms/, 20 kN
Wallace Energy Systems and Renewables Facility (WESRF)
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Why Wave Energy?
[2,3,4]
• Wind Energy → 587 W/m2 with 8 m/s mean
distribution of wind speed
• Solar Energy → 200 W/m2 Year Round Average
• Wave Energy → 30kW/m Year-Round-Average Available
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Why Wave Energy?
Wave Power Density in Kilowatts per Meter [kW/m][1]
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Design Considerations
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Design Considerations
• Low Speed Operation (5 rpm)
• Reciprocating Rotary Design
• High Torque Load
• Caustic Ocean Environment
• Serviceability Complications
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Top Level Design Choices
Machines Considered
• PMAC
• Doubly Fed Induction
• Induction
• Reluctance
• Vernier Hybrid
Characteristics
• Axial / Radial
• Super Conductor
• Crescent Shaped
• Air / Iron Core
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Mechanical Layout
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Single Coil & C-Core Structure
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Three-Phase Coil Configuration
Cross-Sectional Top-Down View
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Single Layer Structure
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Top Level Machine Structure
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Floating Machine Structure
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Time Domain Electromagnetic
Analysis
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Simplified Magnetic Circuit
Calculation Methods
• Magnetic Circuit Analysis
• Magnetic Shear Line to
2nd Quadrant B-H
Operation intercept
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Initial Motor Chromosome
Primary Gene Set
1 Radius of Machine
2 Length of One Side of C-Core
3 Distance Across Air Gap
4 Cross-Sectional Area of Magnets
5 Length of Magnets
6 Thickness of Magnets
7 Wire Turns
8 Wire Gauge
9 Machine Layers
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Initial Genetic Algorithm• Initial population created.
• Population doubled.
• Random cross breeding between 1st and 2nd population set
• Random mutations w/ fixed-rate / fixed-probability (quantity)
• All genes saturation checked / adjusted.
• Fitness of chromosomes evaluated, sorted from best to worst.
• Worst ½ of chromosomes discarded, repeat back to doubling.
• Best motor tracked throughout process.
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Refined Generator Chromosome
Simplified / Refined Gene Set
1 Magnet Width
2 Magnet Length
3 Magnet Thickness
4 Air Gap Distance
5 Wire Gauge
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Time Domain RefinementSimplified GA Variables
1 Magnet Width
2 Magnet Length
3 Magnet Height
4 Air Gap Distance
5 Wire Gauge
• Maximum allowable turns
in air-gap.
• Steel thickness based upon
allowed flux density.
• Many safety/saturation
checks removed.
• Processing speed 4.3 times
faster than previous model.
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Genetic Algorithm Cost Functions
• -Total Power
• -Total Power, -Efficiency, +Steel Volume
• -Total Power, -Efficiency, + Total Mass, +AWG, +Wire Turns
• -Total Power, Efficiency, +Total Mass, +AWG Size, Wire Turns
Used for final evaluation:
• -Total Power, -Efficiency, +Total Mass, +Magnet Volume
{Negative numbers indicate a “more fit” machine}
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Parametric Sweep of 5 Genes
• Swept 25 steps nested sweep.
• 9,765,625 evaluations.
• 1.5x the run time of the
refined (2nd) design, 2.8x slower
run time of original design (1st).
• Evaluated with GA cost
function for fitness.
• Results different from GA.
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GA vs. Sweep ResultsVariable GA Sweep Units
1 Magnet Width .0020 0.0063 [m]
2 Magnet Length .1157 0.2990 [m]
3 Magnet Height .0254 0.0244 [m]
4 Air Gap Distance
.0034 0.0200 [m]
5 Wire Gauge 20 19 AWG
Characteristics GA Sweep Units
Open EMF (per coil) 0.258 122 [V]
Current (per coil, @ 2.5 [A / mm2]) 1.294 1.632 [A]
Single Layer Total Power 9 1843 [W]
Efficiency (from R. loss) 94 87 [%]
Single Layer Mass 20 811 [kg]
Coil Turns 1 319 qty
Torque (per wheel) 18.5g 4192 [Nm]
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Finite Element Analysis
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Conclusions & Future Work
Conclusions:
• 5 [rpm] generator is feasible.
• Generator possible, but heavy.
• Weight and slow speed lead to issue of cost.
Future Work Direction:
• Examine larger variety of motor topologies.
• Perform more in-depth cost analysis.
• Refinements to manufacturability.
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Bibliography[1] http://www.geni.org/globalenergy/library/renewable-energy-resources/ocean.shtml Global Energy Network Institute
[2] http://blogs.mysanantonio.com/weblogs/clockingin/wind%20turbine.jpg
[3] http://venturebeat.com/wp-content/uploads/2009/07/solar-panel-1.jpg
[4] http://eecs.oregonstate.edu/wesrf/projects/images/Wave%20Energy_Final.ppt
[5] Steven Ernst. Personal interview, 2009. Oregon State University.
[6] Duane C. Hanselman. Brushless Permanent-Magnet Motor Design, 1994.
[7] Magcraft. Permanent magnet selection and design handbook. National Imports,
April 2007.
[8] Ned Mohan. Electric Drives: An Integrative Approach, 2003.
[9] Joseph Prudell. Email, 2009. Oregon State University.
[10]Joseph Prudell. Novel design and implementation of a permanent magnet linear
tubular generator for ocean wave energy conversion, 2007. Thesis for Master of
Science.
[11] P.C. Sen. Principles of Electric Machines and Power Electronics, 1997.
[12] Mueller & McDonald. A Lightweight Low Speed Permanent Magnet Electrical Gen-
erator for Direct-Drive Wind Turbines, 2008.
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Acknowledgement
Thanks to Grainger Center for Electric Machinery and Electromechanics for
supporting this research.