Are We Any Better Informed? Dr Antony Robotham Auckland University - - PowerPoint PPT Presentation

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Vertical Axis Wind Turbines Are We Any Better Informed? Dr Antony Robotham Auckland University of Technology NZWEA 16 Apr 2014 From the mid-1970s,experimental development of vertical axis wind turbines (VAWTs) was underpinned by an

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SLIDE 1

Vertical Axis Wind Turbines

Are We Any Better

Informed?

Dr Antony Robotham

Auckland University of Technology

NZWEA 16 Apr 2014

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SLIDE 2

Introduction – The Early Years

  • From the mid-1970s,experimental development of vertical

axis wind turbines (VAWTs) was underpinned by an incremental improvements of aerodynamic performance prediction methods 

  • The double actuator disk, multiple streamtube

theory(DMST)with corrections for streamtube expansion, dynamic stall, blade tip effects and flow curvature was the state-of-the-art and was easier to implement than the computationally more demanding vortex methods

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SLIDE 3

Introduction – More Recently

  • Commercially, VAWTs have not been as successful as the

three-bladed, pitch controlled horizontal axis turbine became the standard for the industry and progress in VAWT development stagnated 

  • However, a renewed interest in VAWTs has emerged, prompted

by the development of small turbines for use in urban environments and perceived advantages for large offshore turbines

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SLIDE 4

Objective

The objective today is to:

  • Present trade studies of VAWTs using the double actuator

disk, multiple streamtube theory

  • Look at some recent third party findings
  • Present some initial VAWT investigations using a

proprietary CFD software tool that uses a mesh-less approach to fluid dynamics modelling

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SLIDE 5

VAWTS

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SLIDE 6

Observations

  • Renewed interest in VAWTs for urban and offshore

applications

  • New generations of VAWT favour the helical configuration
  • Helical VAWTs are being designed with large height/diameter

ratios

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SLIDE 7

WHY HELICAL VAWTS?

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SLIDE 8

What does VAWT theory tell us ?

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SLIDE 9

VAWT Multiple Streamtube Theory

𝑊

∞

ΩR

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SLIDE 10

VAWT Streamtube

Ω 𝑆 𝛾 𝜘 𝜘 𝑊

∞

𝑊

𝑣

𝑊

𝑏

𝑊

𝑛

𝑊

𝑒

𝑊

𝑥

𝑞𝑏 𝑞𝑏 𝑞𝑏 𝜘 = 0 𝑈ℎ𝑓 𝑡𝑢𝑠𝑓𝑏𝑛𝑢𝑣𝑐𝑓 𝑗𝑡 𝑐𝑝𝑣𝑜𝑒𝑓𝑒 𝑐𝑧 𝑡𝑢𝑠𝑓𝑏𝑛𝑚𝑗𝑜𝑓𝑡 𝑏𝑢 𝝒 𝑏𝑜𝑒 𝝒 + 𝜺𝝒 𝜄 𝜄

after Sharpe & Read (1982)

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SLIDE 11

Upstream Relative Velocity Triangle

𝜌 2 + 𝜘 𝛽𝑣

Ω𝑆 𝑊

𝑣

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SLIDE 12

Upstream Relative Velocity Triangle

𝜌 2 + 𝜘 𝛽𝑣

Ω𝑆

𝑊

𝑣 cos 𝜘

𝑊

𝑣 sin 𝜘

𝜘

𝑊

𝑣

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SLIDE 13

Upstream Relative Velocity Triangle

𝜌 2 + 𝜘

𝑊

𝑣 𝛽𝑣

𝜀𝑂 Ω𝑆 𝜀𝑈

𝑊

𝑣 cos 𝜘

𝑊

𝑣 sin 𝜘

𝜘

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SLIDE 14

Flow Field Through Turbine k = 0.3 .358

after Sharpe & Read (1982)

𝛞° 𝛄° 𝑾𝒗 𝑾∞ 𝛄° 𝑾𝒆 𝑾∞ 180.0 0.821 0.0 0.463 10 172.8 0.824 12.8 0.471 20 165.4 0.832 25.4 0.495 30 157.8 0.845 37.8 0.535 40 149.9 0.863 49.9 0.589 50 141.6 0.885 61.6 0.655 60 132.9 0.911 72.9 0.732 70 123.8 0.939 83.8 0.816 80 114.3 0.969 94.3 0.907 90 104.4 1.000 104.4 1.000

𝜸

𝑾𝒗 𝑾∞ 𝑾𝒆 𝑾∞ 𝑫𝒒𝒏𝒃𝒚 = 𝟏. 𝟔𝟑𝟑 𝑏𝑢 𝒍 = 𝟏. 𝟒𝟔𝟗 𝑥ℎ𝑓𝑠𝑓 𝑙 = 𝑏𝜏 4𝜌 Ω𝑆 𝑊

∞

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SLIDE 15
  • 30
  • 20
  • 10

10 20 30 90 180 270 360 1.1 2.1 3.1 4.1 5.1 6.1 7.1 8.1

H-VAWT Characteristics: 𝜷° 𝒘𝒕 𝜸°

𝜷° 𝝁

𝝉 = 𝟏. 𝟒 𝑿𝑺𝒇 = 𝟐𝟑𝟕𝟖𝟕𝟏

𝜸°

RETREATING ROTOR ADVANCING ROTOR

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SLIDE 16
  • 0.1

0.0 0.1 0.2 0.3 0.4 90 180 270 360 1.1 2.1 3.1 4.1 5.1 6.1 7.1 8.1

H-VAWT Characteristics: 𝑫𝒓𝒘𝒕 𝜸°

𝑫𝒓

𝝉 = 𝟏. 𝟒 𝑿𝑺𝒇 = 𝟐𝟑𝟕𝟖𝟕𝟏

𝜸° 𝝁

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SLIDE 17
  • 1.0

0.0 1.0 2.0 3.0 4.0 90 180 270 360 1.1 2.1 3.1 4.1 5.1 6.1 7.1 8.1

H-VAWT Characteristics: 𝑫𝒐𝒘𝒕 𝜸°

𝜸° 𝑫𝒐

𝝉 = 𝟏. 𝟒 𝑿𝑺𝒇 = 𝟐𝟑𝟕𝟖𝟕𝟏

𝝁

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SLIDE 18

How do the different VAWTs compare ?

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SLIDE 19

GEOMETRY VARIATIONS

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SLIDE 20

VAWT Geometry Variations

  • The derivations presented so far assume an H-type VAWT with

straight blades that are parallel to the axis of rotation

  • The Φ-type (Troposkien Darrieus) and V-type VAWTs have

blades with segments that are inclined to the vertical axis

  • The helical (Gorlov) VAWT have blades that are inclined to

the horizontal plane

  • These geometry variations increase the effective area of

the blade in the streamtube but modify the relative wind vectors and orientation of the aerofoil forces

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SLIDE 21

Trade Studies of VAWT Variations

  • The following studies are based upon the rotor geometry of

a typical helical VAWT with 𝑶 = 𝟒 and 𝝉 = 𝟏. 𝟒 operating in a constant windspeed of 𝑾∞ = 𝟐𝟑 𝒏/𝒕

𝑾∞ = 𝟐𝟑 𝒏/𝒕 helical H-type V-type Φ-type Height (mm) 5300 5300 1500 3820 Diameter (mm) 3000 3000 3000 3000 Swept Area (m2) 15.9 15.9 2.24 8.0 Chord (mm) 200 200 200 200 Blade Span (mm) 6161 5300 1980 5017 Angle 𝝎° 30.7°

  • Angle 𝝔°
  • 45°

0° - 57° Airfoil Section NACA 0018

𝐝𝐩𝐭𝟑 𝝎 = 𝟏. 𝟖𝟓

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SLIDE 22
  • 0.1

0.0 0.1 0.2 0.3 0.4 0.5

1 2 3 4 5 6 7 8

Gorlov H-VAWT V-VAWT Darrieus

Trade Studies: 𝑫𝒒𝒘𝒕 𝝁

𝑫𝒒 𝝁

𝑿𝑺𝒇 = 𝟐𝟑𝟕𝟖𝟕𝟏 𝝉 = 𝟏. 𝟒

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SLIDE 23
  • 0.05

0.00 0.05 0.10 0.15 0.20 1 2 3 4 5 6 7 8

Gorlov H-VAWT V-VAWT Darrieus

Trade Studies: 𝑫𝒓𝒘𝒕 𝝁

𝑫𝒓 𝝁

𝑿𝑺𝒇 = 𝟐𝟑𝟕𝟖𝟕𝟏 𝝉 = 𝟏. 𝟒

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SLIDE 24
  • 0.10

0.00 0.10 0.20 0.30 0.40 90 180 270 360

Gorlov H-VAWT V-VAWT Darrieus

Trade Studies: 𝑫𝒓𝒘𝒕 𝜸° at Tip Radius

𝑫𝒓 𝜸°

𝑿𝑺𝒇 = 𝟐𝟑𝟕𝟖𝟕𝟏 𝝉 = 𝟏. 𝟒 𝝁 = 𝟒. 𝟕

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SLIDE 25
  • 1.00

0.00 1.00 2.00 90 180 270 360

Gorlov H-VAWT V-VAWT Darrieus

Trade Studies: 𝑫𝒐𝒘𝒕 𝜸° at Tip Radius

𝑫𝒐 𝜸°

𝑿𝑺𝒇 = 𝟐𝟑𝟕𝟖𝟕𝟏 𝝉 = 𝟏. 𝟒 𝝁 = 𝟒. 𝟕

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SLIDE 26

0.0 0.2 0.4 0.6 0.8 1.0 90 180 270 360

Gorlov H-VAWT V-VAWT Darrieus

Trade Studies: 𝑾 𝒘𝒕 𝜸° at Tip Radius

𝑾 𝜸°

𝑿𝑺𝒇 = 𝟐𝟑𝟕𝟖𝟕𝟏 𝝉 = 𝟏. 𝟒 𝝁 = 𝟒. 𝟕

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SLIDE 27
  • 15
  • 10
  • 5

5 10 15 20 90 180 270 360

Gorlov H-VAWT V-VAWT Darrieus

Trade Studies: 𝜷° 𝒘𝒕 𝜸° at Tip Radius

𝜷° 𝜸°

𝑿𝑺𝒇 = 𝟐𝟑𝟕𝟖𝟕𝟏 𝝉 = 𝟏. 𝟒 𝝁 = 𝟒. 𝟕

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SLIDE 28
  • 0.05

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 90 180 270 360

  • 0.05

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 90 180 270 360

  • 0.05

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 90 180 270 360

Spanwise Variation of 𝑫𝒓𝒘𝒕 𝜸° at 𝝁 = 𝟒. 𝟕

𝑫𝒓 𝜸° 𝑫𝒓 𝑫𝒓 𝑫𝒓 𝜸° 𝜸° 𝜸°

Gorlov H-VAWT V-VAWT Darrieus

  • 0.05

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 90 180 270 360

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SLIDE 29
  • 0.10

0.00 0.10 0.20 0.30 0.40 90 180 270 360 1 2 3 Rotor

  • 0.10

0.00 0.10 0.20 0.30 0.40 90 180 270 360 1 2 3 Rotor

  • 0.10

0.00 0.10 0.20 0.30 0.40 90 180 270 360 1 2 3 Rotor

  • 0.10

0.00 0.10 0.20 0.30 0.40 90 180 270 360 1 2 3 Rotor

Blade Variation of 𝑫𝒓𝒘𝒕 𝜸° at 𝝁 = 𝟒. 𝟕

𝑫𝒓 𝜸° 𝑫𝒓 𝑫𝒓 𝑫𝒓 𝜸° 𝜸° 𝜸°

Gorlov H-VAWT V-VAWT Darrieus

𝑿𝑺𝒇 = 𝟐𝟑𝟕𝟖𝟕𝟏 𝝉 = 𝟏. 𝟒 𝝁 = 𝟒. 𝟕

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SLIDE 30
  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0 2.5 90 180 270 360 Fx Fy

  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0 2.5 90 180 270 360 Fx Fy

  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0 2.5 90 180 270 360 Fx Fy

  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0 2.5 90 180 270 360 Fx Fy

Tower Forces 𝑮𝒚𝒘𝒕 𝜸° and 𝑮𝒛𝒘𝒕 𝜸° at 𝝁 = 𝟒. 𝟕

𝜸° 𝑮𝒚 𝑮𝒛 𝜸° 𝜸° 𝜸°

Gorlov H-VAWT V-VAWT Darrieus

𝑮𝒚 𝑮𝒛 𝑮𝒚 𝑮𝒛 𝑮𝒚 𝑮𝒛

𝑿𝑺𝒇 = 𝟐𝟑𝟕𝟖𝟕𝟏 𝝉 = 𝟏. 𝟒 𝝁 = 𝟒. 𝟕

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SLIDE 31

Observations

  • The numerical results reflect the general observations made

about how VAWT geometry influences aerodynamic performance

  • The advantage of the helical VAWT is its favourable cyclic

loading characteristic, which is offset by a small reduction in performance efficiency

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SLIDE 32

AERODYNAMIC PREDICTIONS

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SLIDE 33

Limitations of Streamtube Theory

Whilst the multiple streamtube theory is useful for VAWT trade studies, it is limited by:

  • Quality of available aerofoil data
  • Models of Dynamic Stall
  • Local blade geometry effects
  • Theory breaking down with high solidity rotors (blockage)
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SLIDE 34

Does CFD offer any substantial new insights into turbine behaviour ?

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SLIDE 35

Numerical Simulation of Dynamic Stall

Paraschivoiu, I., Saeed, F. & Desobry, V. (2002)

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SLIDE 36

2D CFD Simulation of Dynamic Stall

Ferreira, C.S. (2009)

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SLIDE 37

3D CFD Tip Effects – Iso-Vorticity Surfaces

Ferreira, C.S. (2009)

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SLIDE 38

2D CFD Velocity Field

Deglaire, P. (2010)

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SLIDE 39

Turbulent KE and Relative Velocity

Lanzafame, R., Mauro, S. & Messina, M. (2013)

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SLIDE 40

Flow Velocity & Vortex Shedding

Marsh, P., Ranmuthugala, D., Penesis, I. & Thomas, G.(2013)

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SLIDE 41

VAWT Wakes

Scheurich, F., Fletcher, T.M., & Brown, R.E.(2011)

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SLIDE 42

Meshless CFD Simulations - XFlow

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SLIDE 43

Observations

  • CFD offers substantial new insights into VAWT behaviour

that are well beyond the capabilities of the multiple streamtube theory … but multiple streamtube theory remains a valuable tool for design configuration

  • However, we sadly lack the data to validate numerical

results from either approach

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SLIDE 44

CONCLUDING REMARKS

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SLIDE 45

Conclusions

  • The Vertical Axis Wind Turbine is an under utilised wind

energy technology

  • The Helical VAWT should dispel concerns over long-term

fatigue due to cyclic loading of the structure

  • CFD tools are attractive options for dynamic/transient

flows, moving bodies and complex body surfaces but the simplicity of the multiple streamtube theory makes it useful as a conceptual design tool

  • The challenges remain much the same with a lack of field

and experimental data for validation coupled with a 20+ year lag in commercial development

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SLIDE 46

References

  • Barone, M. & Paquette, J. (2012) “ Vertical-Axis Wind Turbines Revisited: A Sandia Perspective” 2012 Wind Turbine Blade Workshop, 1 June 2012
  • Deglaire, P. (2010) “Analytical Aerodynamic Simulation Tools for Vertical Axis Wmd Turbines” Acta Universitatis Upsaliensis. Digital Comprehensive Summaries of Uppsala

Dissertations from the Faculty of Science and Technology 774. 100 pp. Uppsala. ISBN 978-91-554-7913-8.

  • Ferreira, C.S. (2009) “The near wake of the VAWT: 2D & 3D views of the VAWT aerodynamics” PhD thesis, Technical University of Delft, The Netherlands, October 2009
  • Lanzafame, R., Mauro, S. & Messina, M. (2013) “2D CFD Modeling of H-Darrieus Wind Turbines using a Transition Turbulence Model”, 68th Conf. of the Italian Thermal Machines

Engineering Association, ATI2013 in Energy Procedia 45 ( 2014 ) 131 – 140.

  • Marsh, P., Ranmuthugala, D., Penesis, I. & Thomas, G.(2013) “Performance Predictions of a Straight-bladed Vertical Axis Turbine Using Double-multiple Streamtube and

Computational Fluid Dynamics Models” The Journal of Ocean Technology, Vol. 8, No. 1, 2013

  • Paraschivoiu, I., Saeed, F. & Desobry, V. (2002) “Prediction Capabilities in Vertical-axis Wind Turbine Aerodynamics” The World Wind Energy Conference and Exhibition, Berlin,

Germany, 2-6 July 2002

  • Read, S. & Sharpe, D.J. (1980) “ An Extended Multiple Streamtube Theory for Vertical Axis Wind Turbines”, Proc. 2nd British Wind Energy Association Workshop, Cranfield, UK.
  • Sharpe, D.J. & Read, S. (1982) “ A Critical Analysis of the Extended Multiple Streamtube Theory for the Aerodynamics of a Vertical Axis Wind Turbine”, Proc. Wind & Solar Energy

Technology Conf., Kansas City, USA.

  • Sharpe, D.J. (1984), “Refinements and Developments of the Multiple Stream Tube Theory for the Aerodynamic Performance of Vertical Axis Wind Turbines”, Proc. Sixth BWEA

Wind Energy Conference, Reading, 1984, pp. 148-159

  • Robotham, A.J (1989) “The Aerodynamic Control of the V-type Vertical Axis Wind Turbine”, Phd Thesis, Faculty of Technology, The Open University, Milton Keynes, UK.
  • Scheurich, F., Fletcher, T.M., & Brown, R.E.(2011) “Simulating the aerodynamic performance and wake dynamics of a vertical-axis wind turbine.” Wind Energy, 14 (2). pp. 159-177.

ISSN 1095-4244

  • Sutherland, H.J., Berg, D.E. & Ashwill, T.D. (2012) “ A Retrospective of VAWT Technology” SAND2012-0304, Sandia National Laboratories, New Mexico, January 2012

Thank You!

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SLIDE 47

Dr Antony Robotham Auckland University of Technology tony.robotham@aut.ac.nz