NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Dr. Ye Li

1st NREL MHK Device Modeling Meeting

March 1, 2011

Innovation for Our Energy Future

Development of a Vortex Method for Simulating

Vertical Axis Tidal Current Turbines

2

Outline

• Introduction

• Turbine Modeling Method Li and Calisal, Journal of Offshore Mechanics & Arctic Engineering,

2010,132(3), 1102-1110

Li and Calisal, Renewable Energy, 2010, 35(10), 2325-2334

• Twin-Turbine System Study Li and Calisal, Ocean Engineering,2010 ,37(7),627-637

Li and Calisal, Ocean Engineering,2011, 38(4),550-558

• Conclusions

• Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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Objective and Motivation of the Research

• Why Vertical Axis Turbine?

Omni directional

Power conversion system close to free surface

Environmentally-friendly

Good for shallow water area

Outline

Introduction

Method

System Study

Conclusion

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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• Theory

Time domain potential flow theory, with discrete

Lamb vortices decaying in time based on Reynolds

number with respect to the blade chord

• Assumptions

Shaft and arm effects are not simulated

No bottom and free surface

2D foil properties remain valid for lift and drag for

the proper angle of attack calculated by the induced

velocities

3D effects are simulated by treating a blade as

multi-elements

A Potential Flow Based Discrete Vortex Method Outline

Introduction

Method

Modeling

1-2-3-4

Validation

System Study

Conclusion

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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Turbine Working Principles Outline

Introduction

Method

Modeling

1-2-3-4

Validation

System Study

Conclusion

Future DirectionR iU U U R

21

2L RL C cU

, 34iP l

l

r d lU

r

R BL U 1

2B L RC cU

National Renewable Energy Laboratory Innovation for Our Energy Future

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Blade and WakeOutline

Introduction

Method

Modeling

1-2-3-4

Validation

System Study

Conclusion

Future Direction

, 1, , 1, , ,S i j B i j B i j

, 1, , , , , 1T i j B i j B i j

National Renewable Energy Laboratory Innovation for Our Energy Future

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Wake Vortices

• Nascent Vortex

• Vortex Decay

• Lamb Vortices

2

1 c

r

re

V rr

cr t

0 1dK

j e

, , 1

1

2o

o

V m V mt tt t

U U

, 1 , 1o

V m iP mt tU U U

, 1,

, 1,

1

2

1

2

o oo

o oo

V mtV m t tt t

V mtV m t tt t

xxx

yyy

Outline

Introduction

Method

Modeling

1-2-3-4

Validation

System Study

Conclusion

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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Turbine Design

Parameters Values

Number of blades 3

Blades type NACA 63(4)-021

Solidity 0.435

Turbine height 0.5m

Turbine diameter 0.91m

Tip speed ratio RU

power coefficient 31

2

PPCAU

Solidity NcR

Outline

Introduction

Method

Modeling

1-2-3-4

Validation

1-2-3

System Study

Conclusion

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

9

Towing Tank TestOutline

Introduction

Method

Modeling

1-2-3-4

Validation

1-2-3

System Study

Conclusion

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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ValidationOutline

Introduction

Method

Modeling

1-2-3-4

Validation

1-2-3

System Study

Conclusion

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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Definition of the Twin-turbine SystemOutline

Introduction

Method

System Study

General

1-2

Power

Torque

Noise

Conclusion

Future Direction 2 2T T SP P

2 1 2TP P P

National Renewable Energy Laboratory Innovation for Our Energy Future

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Twin-Turbine TestOutline

Introduction

Method

System Study

General

1-2

Power

Torque

Noise

Conclusion

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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Twin-Turbine Validation

Outline

Introduction

Method

System Study

General

1-2

Power

1-2

Torque

Noise

Conclusion

Future Direction

Side-by-Side Relative distance=3.5

Counter-rotating

14

Power Analysis

Counter-rotating Co-Rotating

Blade Profile NACA0015

TSR=4.75

(Increase 25%)Outline

Introduction

Method

System Study

General

1-2

Power

1-2

Torque

Noise

Conclusion

Future Direction

15

Torque Fluctuation AnalysisOutline

Introduction

Method

System Study

General

1-2

Power

1-2

Torque

1-2

Noise

Conclusion

Future Direction

TSR=4.75

46

peakTF

peak

PSMC dB

f

Torque Fluctuation Coefficient

16

,

,

TF TwinRTF

TF S

CC

C

Definition of the Relative Torque Fluctuation Coefficient:

Relative Torque Fluctuation CoefficientOutline

Introduction

Method

System Study

General

1-2

Power

1-2

Torque

1-2

Noise

Conclusion

Future Direction

Counter-rotating Co-rotating

TSR=4.75

17

Noise Emission

• Noise Sources Mechanical

Hydrodynamics• Shaft

• Blade tip

• Wake Fluctuation

• Cavitation

• Others

• Assumptions The sound generated by the turbine is a plane

sound wave

Ocean is a free acoustic field without reflecting

boundaries and with a homogenous sound velocity

The velocity fluctuation is fully induced by the vortex shedding effect and the induced velocity caused by the rotation of the turbine

I pu

p Zu

Z c

2I cu

Outline

Introduction

Method

System Study

General

1-2

Power

1-2

Torque

1-2

Noise

1-2-3

Conclusion

Future Direction

18

Noise Emission Intensity Analysis (Reduce 10dB)

Outline

Introduction

Method

System Study

General

1-2

Power

1-2

Torque

1-2

Noise

1-2-3

Conclusion

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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Marine Animal Communication Frequency

Names Frequency (Hz)

American eel 75

Atlantic herring 30 -1,200

Bar jack 30

Bigeye mojarra 75-1,000

Bluefish 60-1,200

Coney 75

Cownose ray 150

Pinnipeds 50-60,000

Toothed Whale 10-10,000

Outline

Introduction

Method

System Study

General

1-2

Power

1-2

Torque

1-2

Noise

1-2-3

Conclusion

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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Conclusions-Method

• A potential flow based numerical method for simulating tidal current turbines is developed

The numerical method can simulate the behavior of tidal current turbines with a good accuracy

This method can be used for predicting not only power output but also other turbine characteristics such as torque fluctuation and noise emission

The 2-D model can be used for preliminary assessment

Outline

Introduction

Method

System Study

Conclusion

1-2

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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Conclusions –System Analysis

• An optimal configuration of twin-turbine

system can significantly increase turbine

performance

The power output of a twin-turbine system with an

optimal layout can be 25% higher than the power

output of two turbines far apart

The noise intensity of a twin-turbine system with

an optimal layout can be 10dB lower than the

noise intensity of two turbines far apart

The torque of a twin-turbine system with an

optimal layout fluctuates much less than torque of

two turbines far apart

Outline

Introduction

Method

System Study

Conclusion

1-2

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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Future Direction

• Hydrodynamics

Free surface

Dynamic stall

Added mass and damping coefficient

• Optimization

Blade curvature

Pitch angle

• Others

Cost

Comprehensive

Outline

Introduction

Method

System Study

Conclusion

Future Direction

National Renewable Energy Laboratory Innovation for Our Energy Future

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Acknowledgements

• Colleagues at the University of British Columbia

• Colleagues at the National Renewable Energy

Laboratory

• Funding Agencies:

John Davies Foundation

Dieter Family Foundation

National Renewable Energy Laboratory Innovation for Our Energy Future

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Thank you!

Q&A