0
Research Papers

Effect of Wake Flow Nonuniformity on Wind Turbine Performance and Aerodynamics

[+] Author and Article Information
S. Barber

e-mail: sarah.barber@gmx.ch

R.S. Abhari

Laboratory for Energy Conversion,
Department of Mechanical and Process Engineering,
ETH Zurich, Zurich, Switzerland

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 19, 2011; final manuscript received August 1, 2011; published online November 6, 2012. Editor: David Wisler.

J. Turbomach 135(1), 011012 (Nov 06, 2012) (9 pages) Paper No: TURBO-11-1149; doi: 10.1115/1.4006334 History: Received July 19, 2011; Revised August 01, 2011

Dynamically scaled experiments and numerical analyses are performed to study the effects of the wake from an upstream wind turbine on the aerodynamics and performance of a downstream wind turbine. The experiments are carried out in the dynamically scaled wind turbine test facility at ETH Zurich. A five-hole steady-state probe is used to characterize the cross-sectional distribution of velocity at different locations downstream of the wake-generating turbine. The performance of the downstream wind turbine is measured with an in-line torquemeter. The velocity field in the wind turbine wake is found to differ significantly from the velocity field assumed in numerical wake models. The velocity at hub height does not increase monotonically up to the freestream velocity with downstream distance in the wake. Furthermore, the flowfield is found to vary significantly radially and azimuthally. The application of wake models that assume a constant axial velocity profile in the wake based on the measured hub-height velocity can lead to errors in annual energy production predictions of the order of 5% for typical wind farms. The application of wake models that assume an axisymmetric Gaussian velocity profile could lead to prediction errors of the order of 20%. Thus modeling wind turbine wakes more accurately, in particular by accounting for radial variations correctly, could increase the accuracy of annual energy production predictions by 5%–20%.

© 2013 by ASME
Your Session has timed out. Please sign back in to continue.

References

IEC Wind Turbine Generator Systems, Part 1: Wind Turbine Safety and Design, 1998, IEC International Standard 61400-11.
Barthelmie, R., Larsen, G., Pryor, S., Jørgensen, H., Bergström, H., Schlez, W., Rados, K., Lange, B., Vølund, P., Necelmann, S., Mogensen, S., Schepers, G., Hegberg, T., Folkerts, L., and Magnusson, M., 2004, “ENDOW (Efficient Development of Offshore Wind Farms); Modelling Wake and Boundary Layer Interactions,” Wind Energy, 7, pp. 225–245. [CrossRef]
Jensen, N. O., 1983, “A Note on Wind Turbine Interaction,” Risø-M-2411, Risoø National Laboratory, Roskilde, Denmark.
Frandsen, S., Barthelmie, R., Pryor, S., Rathmann, O., Larsen, S., Højstrup, J., and Thøgersen, M., 2004, “Analytical Modeling of Wind Speed Deficit in Large Offshore Wind Farms,” Scientific Proceedings of the European Wind Energy Conference and Exhibition, London, November 22–25, pp. 6–11.
Larsen, G. C., Madsen, H. A., and Sørensen, N. N., 2003, “Mean Wake Deficit in the Near Field,” Proceedings of the European Wind Energy Conference, Madrid, Spain, June 16–19, European Wind Energy Association, CD-ROM.
Schepers, J. G., 2003, “ENDOW: Validation and Improvement of ECN’s Wake Model,” ECN-C-03-034.
Crespo, A., Hernandez, J., Fraga, E., and Andreu, C., 1988, “Experimental Validation of the UPM Computer Code to Calculate Wind Turbine Wakes and Comparison With Other Models,” J. Wind Eng. Ind. Aerodyn., 27, pp. 77–88. [CrossRef]
Barthelmie, R. J., Folkerts, L., Larsen, G. C., Rados, K., Pryor, S. C., Frandsen, S. T., Lange, B., and Schepers, G., 2006, “Comparison of Wake Model Simulations With Offshore Wind Turbine Wake Profiles Measured by SODAR,” J. Atmos. Oceanic Technol., 23, pp. 888–901. [CrossRef]
Kocer, G., Mansour, M., Chokani, N., Abhari, R. S., and Müller, M., 2011 “Full-Scale Wind Turbine Wake Measurements Using an Instrumented UAV,” European Wind Energy Association Conference, Brussels, Belgium, March 14–17.
Mansour, M., Kocer, G., Lenherr, C., Chokani, N., and Abhari, R. S., 2011, “Seven-Sensor Fast-Response Probe for Full-Scale Wind Turbine Flowfield Measurements,” ASME J. Gas Turbines Power, 133(8), p. 081601. [CrossRef]
Jafari, S., Chokani, N., and Abhari, R. S., 2010, “Terrain Effect on Wind Flow: Simulations With an Immersed Boundary Method,” ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition (GT2011), Vancouver, BC, Canada, June 6–10, ASME Paper No. GT2011-46240, pp. 869–878. [CrossRef]
Barber, S., Wang, Y., Jafari, S., Chokani, N., and Abhari, R. S., 2011, “The Impact of Ice Formation on Wind Turbine Performance and Aerodynamics,” J. Solar Energy, 133(1), p. 011007. [CrossRef]
Rae, W. H., Pope, A., and Barlow, J. B., 1999, Low-Speed Wind Tunnel Testing, John Wiley, New York, Chap. 10.
Giguere, P., and Selig, M. S., 1999, “Design of a Tapered and Twisted Blade for the NREL Combined Experiment Rotor,” NREL Technical Report No. SR-500-26173.
Kupferschmied, P., Köppel, P., Roduner, C., and Gyarmathy, G., 2000, “On the Development and Application of the Fast-Response Aerodynamic Probe System in Turbomachines—Part 1: The Measurement System,” ASME J. Turbomach., 122, pp. 505–516. [CrossRef]
Treiber, M., Kupferschmied, P., and Gyarmathy, G., 1998, “Analysis of Error Propagation Arising From Measurements With a Miniature Pneumatic 5-Hole Probe,” Proceedings of the 14th Symposium on Measuring Techniques for Transonic and Supersonic Flows in Cascades and Turbomachines, Limerick, Ireland, September 2–4.
Kochman, E., 2010, “Effect of Shear Profile and Yaw Angle on Wind Turbine Performance,” LEC internal report, ETH Zurich, Switzerland.
Burton, T., Sharpe, D., Jenkins, N., and Bossanyi, E., 2001, Handbook of Wind Energy, John Wiley, New York.
Somers, D. M., 1997, “Design and Experimental Results for the S809 Airfoil,” NREL Technical Report NREL/SR-440-6918.
Butterfield, C. P., Musial, W. P., and Simms, D. A., 1992, “Combined Experiment Phase I Final Report,” NREL Technical Report NREUTP-257-4655.
Barber, S., Chokani, N., and Abhari, R. S., 2011, “Wind Turbine Performance & Aerodynamics in Wakes Within Wind Farms,” Scientific Proceedings of the European Wind Energy Conference, Brussels, Belgium, March 14–17, CD-ROM.
Barthelmie, R. J., Hansen, K., Frandsen, S. T., Rathmann, O., Schepers, J. G., Schlez, W., Phillips, J., Rado, K., Zervos, A., Politis, E. S., and Chaviaropoulos, P. K., 2009, “Modelling and Measuring Flow and Wind Turbine Wakes in Large Wind Farms Offshore,” Wind Energy, 12, pp. 431–444. [CrossRef]
Pattenden, R. J., Turnock, S. R., and Zhang, X., 2005, “Measurements of the Flow Over a Low-Aspect-Ratio Cylinder Mounted on a Ground Plane,” Exp. Fluids, 39, pp. 10–21. [CrossRef]

Figures

Grahic Jump Location
Fig. 1

(a) Normalized axial velocity in the wake for Jensen, Frandsen, and WAsP models; (b) ECN model velocity profile compared to measurements; and (c) ECN model showing development of velocity in the wake compared to measurements [6]

Grahic Jump Location
Fig. 2

ETH Zurich dynamically scaled wind turbine test facility: (a) schematic diagram and (b) tandem turbine arrangement

Grahic Jump Location
Fig. 3

CP versus tip speed ratio curve for the downstream wind turbine in freestream conditions

Grahic Jump Location
Fig. 4

(a) Head geometry of 5H-SSP and (b) aero calibration coefficients

Grahic Jump Location
Fig. 5

Grid for plane measurements

Grahic Jump Location
Fig. 6

Flowchart of the unsteady BEM method

Grahic Jump Location
Fig. 7

Unsteady BEM code predictions compared to NREL PROPID for (a) power versus velocity and (b) power coefficient versus tip speed ratio

Grahic Jump Location
Fig. 8

Normalized power versus axial downstream distance in the wake of the upstream wind turbine for fixed-speed compared to variable-speed downstream wind turbines

Grahic Jump Location
Fig. 9

Normalized velocity versus axial downstream distance in the wake of the upstream wind turbine

Grahic Jump Location
Fig. 10

(a) Normalized axial velocity for a plane 2D downstream and (b) variation with radial position at 0 deg, 30 deg, and 90 deg

Grahic Jump Location
Fig. 11

(a) Normalized axial velocity for a plane 11D downstream and (b) variation with radial position at 0 deg, 30 deg, and 90 deg

Grahic Jump Location
Fig. 12

Normalized radial and azimuthal velocity components at (a) 2D and (b) 11D downstream in the wake

Grahic Jump Location
Fig. 13

Radial and azimuthal velocity components at (a) 2D and (b) 11D downstream in the wake

Grahic Jump Location
Fig. 14

Vorticity components in the axial direction at (a) 2D and (b) 11D downstream in the wake

Grahic Jump Location
Fig. 15

Schematic diagram of time-averaged flow over truncated cylinder [23]

Grahic Jump Location
Fig. 16

Average incidence over rotor for one revolution: 2D compared to 11D

Grahic Jump Location
Fig. 17

Summary of errors in magnitudes of power and annual energy productions predictions due to common wake model assumptions

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In