Direct Drive in Wave Energy Conversion - AWS Full Scale Prototype Case Study Miguel Prado, Henk Polinder

1. 1Challenge the future
Miguel Prado, Henk Polinder
Direct Drive in Wave Energy Conversion
- AWS Full Scale Prototype Case Study

2. 2Challenge the future
Structure
1 Introduction
2 Wave Energy Overview
3 AWS Wave Energy Converter
4 PTO of AWS Pilot Plant
5 Conclusions

3. 3Challenge the future
Wave Energy is not new ...
Source: Christine Miller (www.outsidelands.org/wave-motor.php) and Power Magazine 1911
Holland Wave Motor
California, USA, 1895
US Wave Motor Corporation
New Jersey, USA, 1911

4. 4Challenge the future
Different technologies being developed
Pelamis, Scotland
Wavestar, Denmark OPT, USA
OWC Pico, Portugal
Source: www.wavec.org; www.emec.org.uk

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Wavedragon, Denmark
OEbuoy, Ireland
Wavebob, Ireland
Aquamarine, Scotland
Source: www.wavec.org; www.emec.org.uk
And many more …

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Only a few direct drive applications ...
Source: www.wavec.org; www.emec.org.uk
AWS 2MW, The Netherlands
Oregon Univ. 10kW, USAUppsala Univ. 10kW, Sweden

7. 7Challenge the future
Structure
1 Introduction
2 Wave Energy Overview
2.1 Waves (Fundamentals & World Resource)
2.2 Wave Energy Conversion
3 AWS Wave Energy Converter
4 PTO of AWS Pilot Plant
5 Conclusions

8. 8Challenge the future
Waves, a byproduct of solar energy ...
Source: Hagerman, G., “Wave and Tidal Power: Projects and Prospects”, CEAG, 2005

9. 9Challenge the future
 No net mass transport (particles follow elliptical orbits)
 Skin effect (motion decays exponentially from surface)
 Energy storage (kinetic & gravitational potential)
 Dispersion in frequency (T=6-12s => Vg=5-10m/s)
 Power transmission by pulses (2 x wave frequency)
P
Monochromatic Waves

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time
MAXPP 5.0
P
P
Monochromatic Waves

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Real Seas (Polychromatic)
P
MAXPP 1.0
P
time

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Source: “Wave Energy Utilization in Europe – Current Status and Perspectives”, CRES , 2002 ; Kinsman, B., “Wind Waves”, Prentice Hall, New Jersey, 1965
World Offshore Wave Resource ~2 TW

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~
~Wave
(variable height
and period)
Electricity - Grid
(constant voltage
and frequency)WEC
Wave Energy Conversion

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Wave
(variable height
and period)
Captor PTO (Power Take Off)
2 ... N1
Electricity - Grid
(constant voltage
and frequency)
Wave Energy Conversion

15. 15Challenge the future
Structure
1 Introduction
2 Wave Energy Overview
3 AWS Wave Energy Converter
3.1 Concept
3.2 Pilot Plant
4 PTO of AWS Pilot Plant
5 Conclusions

16. 16Challenge the future
AWS Concept
• Submerged Device (better survivability)
• Variable Volume (higher performance)
• Adjustable Natural Period (higher performance)
• Direct Drive PTO (higher reliability & performance)
• Water Brakes (additional safety)

17. 17Challenge the future
• Captor diameter:9.5m
• Captor stroke: 7m
• Max. PTO Force: 1MN
• Nominal speed: 2.2m/s
• Deployment: easy & reversible
• Test Location: North Portugal (44m)
• Test Period: < 1 year
6 km
~
~
Landstation
15kV
Grid
AWS Pilot Plant

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Pilot Plant Construction (2000-2001)

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Pilot Plant Final Submersion (2004)

20. 20Challenge the future
Structure
1 Introduction
2 Wave Energy Overview
3 AWS Wave Energy Converter
4 PTO of AWS Pilot Plant
4.1 Design
4.2 Construction & Installation
4.3 Offshore Tests Results
5 Conclusions

21. 21Challenge the future
Design Choices (Linear Generator)
• Topology:
 3-phase longitudinal flux PM machine
 Magnets on the translator
 Materials:
 NdFeB magnets
 Copper windings
 Laminated iron (stator core), solid back iron (translator)
• Geometry:
 Flat, double-sided machine (balance of magnetic forces)
 Translator > stator (higher overlap)
 Slots/pole/phase: 1
• Cooling: water cooled
• Power electronics: current source inverter

22. 22Challenge the future
Design Options (Linear Generator)
To p M id B o tto m
T ra n s la to r
S e g m e n t
S ta to r
S e g m e n t
T ra n s la to r P o s itio n

23. 23Challenge the future
Design Options (Converter)
Grid
15kV, 50Hz
AC/ACConverter
Generator
0-6kV,0-21Hz
3kV/3kV/15kV
2x1330kVA
AC/AC Converter
RDC
Generator
0-6kV, 0-21Hz

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Construction (Translator)

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Construction (Stator)

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Installation (Stator)

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Installation (Stator)

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Installation (Translator)

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Installation (Translator)

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Installation (Land Station)

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Offshore Test Results (Resistor Bank)
~
~
15kV
Grid

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Offshore Test Results (Grid Connected)
14:00 14:15 14:30 14:45 15:00 15:15
0
50
100
150
200
250
P
DC
(kW)
14:00 14:15 14:30 14:45 15:00 15:15
0
20
40
60
80
100
120
R
DC
()
~
~
15kV
Grid

33. 33Challenge the future
Structure
1 Introduction
2 Wave Energy Overview
3 AWS Wave Energy Converter
4 PTO of AWS Pilot Plant
5 Conclusions

34. 34Challenge the future
Conclusions / Lessons learnt
• AWS designed, built and tested
• Test results demonstrate the operating principle
• Only test results at low power levels
• Difficulties of submersion operation underestimated
• The principle of AWS is very simple, but all kinds of secondary
systems compromise reliability
• Economic viability is not easy

35. 35Challenge the future
Thank you very much !