ESRU
Development and In-Sea Testing of a Single Point Mooring Supported Contra-rotating
Marine Turbine (CoRMaT)
Cameron JohnstoneDirector: Energy Systems Research Unit
University of Strathclyde, UKwww.esru.strath.ac.uk
Technology: Next Generation Tidal Turbine• The novel idea behind the contra-rotating turbine concept is to use
two closely spaced dissimilar rotors, moving in opposite directions
• This has several technical and cost advantages over single rotor designs:
– Increases relative shaft output speed– Increases the efficiency of energy capture– Eliminates complex blade pitch control– Reduces turbulent flow downstream of the rotors– Minimises reactive torque, thus promising a single point mooring
possibility– Increases the dynamic stability of the turbine in the tidal flow
• Electrical power take off is possible via direct drive of a contra-rotating generator, or by separate generators
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Concept Development
Hub
0
0.1
0.2
0.3
0.4
0.5
2 4 6 8 10 12
Tip speed ratio
Po
wer
co
eff
icie
nt
nominal plus2deg plus4deg
Poly. (nominal) Poly. (plus2deg) Poly. (plus4deg)
-20
-10
0
10
20
30
40
50
0 20 40 60 80 100
Time (seconds)
Vgen (V)
Pitch (deg)
Roll (deg)
Phase 1: Tank Testing Phase 2: Rotor Testing Phase 3: System Testing
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Phase 1: 1/30th Scale Turbine Tow-Tank Tests
Hub
– Rotor performance:• Torque/ speed characteristics (power out).• Changes in blade pitch angle and rotor spacing.• Interaction between rotors.
– Structural/ mooring system• Dynamic loading due to reactive torque.
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1/30th Scale Turbine Tow Tank Testing
Hub
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1/30th Scale Turbine Performance ( )
0
0.1
0.2
0.3
0.4
0.5
2 4 6 8 10 12
Tip speed ratio
Po
wer
co
eff
icie
nt
nominal plus2deg plus4deg
Poly. (nominal) Poly. (plus2deg) Poly. (plus4deg)
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Phase 2: 1/7th Scale 2.5m Blades – FEM DesignESRU
1/7th Scale CoRMaT alongside MV St Hilda
Miller Fifer 36’
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1/7th Scale CoRMaT Operating
Miller Fifer 36’
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1/7th Scale Turbine Performance
• Results are as predicted - within test series.
Rotor Dynamics Recorded
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Phase 3 Objectives (2008/ 09)
• To take the proven power capture, wake minimisation and torque cancelling properties of CoRMaT and integrate them into a standalone system that:
– Can easily be deployed, maintained, and recovered
– Generates electricity from a direct drive alternator
– Proves the proposed single-point mooring system
• Complete financial appraisal of scaling to a full scale system and development of the commercialisation plan.
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Phase 3 CRT-2 Schematic
Axial Flux Generator
Contra-rotating Blades
Rear Buoyancy
Front Buoyancy
To Tether
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Direct Drive, Open-to-sea Generator• Advantages:
– Ease of construction– Nacelle & casing leaks not an issue– Natural cooling– No complex sealing requirement– No large diameter seal friction
• Disadvantages:– Hydrodynamic effects of rotating
generator parts (negligible)– Marine growth potential
• Axial flux • Permanent magnet Ne-Fe-B• Rectified 3-phase output
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SpineRotors
Ne-Fe-B Magnets
Stator
Prime Mover 1
Shaft Prime Mover 2
Shaft
CoRMaT Test-tank Video ESRU
CoRMaT Mooring
• Single point tether from either a seabed gravity base or anchors:
– ease of installation and retrieval,
– low cost,– available proven
components,– flexible configuration, tuned
for differing depths, tidal climates and seabed composition.
– tracking of tidal diamond
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CoRMaT System Test Locations
1) Kyles of Bute
2) Sound of Islay
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CoRMaT System Test Location 1
Test SiteKyles of Bute
Site chosen as:– sheltered,– 2.6 knot tide,– easy access,– range of
shallow water depths (6 – 10m).
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CoRMaT System Testing
Installed miniCoRMaT system at slack water
Submerged Turbine
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Turbine Performance – Stability KoB
• Stability of device is good – improves under greater loading
-2-1.5
-1-0.5
00.5
11.5
22.5
33.5
0 500 1000 1500 2000 2500 3000 3500
Time (seconds)
Deg
rees
Turb Pitch (deg)
Turb Roll (deg)
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Sound of Islay (Visual Impact!)
Turbine buoy
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Site chosen as:– more
energetic,– 5.2 knot tide,– water depths
(12– 42 m).
FFT Analysis of CoRMaT pitch data showing dominant frequencies at Islay
Pitch Fn F1 F2 F3
Hz 0.597 1.792 3.885 8.167
Source Oversize nacelle
Fundamental rotor 1 speed
Combined rotor speed
Karman vortex
shedding
F2
FnF1 F3
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FFT Analysis of CoRMaT roll data showing dominant frequencies at Islay
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F3
F5 F6F4
F1
Roll F1 F4 F5 F6
Hz 1.859 9.362 35.657 47.742
Source Fundamental rotor 1 speed
5*F1 PMG stator non
uniformities (9*F2)
Blade- blade interactions
(12*F2)
CoRMaT Islay Deployment Video at ‘Slack Water !!!’
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CoRMaT: Next Phase, 2010 - University Spin-out Company- Marine Renewables Development
Deploy (X) x 250 kW turbines
Operate for 1 year and monitor deviceperformance and interactions
Option C chosen due to ‘off-the-shelf’ component availability
Direct drive 2 x 125 kW gen-sets per device
Development and Up-scaling of contra-rotating generator for next phase of deployment (Option D). Now being implemented
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G Gearbox GGearbox
A)
GDiff.
Gearbox
B)
G G
C)
D)G
Power Take-off Options
Conclusion• Contra-rotation can produce zero reactive torque, eliminate
the need for a gearbox and enable direct drive of a contra-rotating generator.
• Low cost single point mooring provides station keeping in different tidal stream conditions, without impacting on device performance.
• Simplified single point mooring system enables quick and easy deployment/ recovery.
• Considerably reduced system, installation and operational costs attained
• All IPR belongs solely to the University of Strathclyde with a sole license agreement to the University spinout company.
• UK (GB2005/161492) and International patents.
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