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02/03/2009

Improved resource assessment assessment for small wind turbines in rural and urban areas http://www.microwindturbine.be. Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel. 02/03/2009. Outline. Introduction

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02/03/2009

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  1. Improved resource assessment assessment for small wind turbines in rural and urban areas http://www.microwindturbine.be Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009

  2. Outline • Introduction • Feasibility study for small wind turbines • Shape of the power curve • Representation of the wind speed distribution • Wind shear • Conclusion Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 2

  3. Introduction • Wind energy in Flanders: • Approximately 200 large wind turbines installed (0,5 - 5 MW) • Roughly 4 times less small wind turbines (< 100 kW) • Small wind turbine market is deadlocked • Performance gap with large wind turbines Technological improvement is necessary • No market Very little investment in research and development Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 3

  4. Outline • Introduction • Feasibility study for small wind turbines • Shape of the power curve • Representation of the wind speed distribution • Wind shear • Conclusion Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 4

  5. Feasibility study for small wind turbines • Are small wind turbines suitable to provide sustainable energy for SME’s in Flanders? • wind speed measurements at lower heights in Flanders • Supplemented by measurements from KMI and KNMI • an exhaustive review of small wind turbines • prediction of the annual energy yield • prediction of the payback time • Using an updated tool developed by Apère Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 5

  6. Feasibility study for small wind turbines • Results of the feasibility study • Payback time for 2 turbines and 18 sites • Results for SME’s with local subsidies Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 6

  7. Feasibility study for small wind turbines • Conclusions • Small wind turbines can be profitable if: • Installed on a proper location and • a good wind turbine is selected • Due to the young market • Wide range on the performance of the turbine (very bad - good) • Identification of key factors that determine the reliability of the resource assessment: • Shape of the power curve • Representation of the wind distribution • Extrapolation of wind speed using wind shear laws Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 7

  8. Outline • Introduction • Feasibility study for small wind turbines • Shape of the power curve • Representation of the wind speed distribution • Wind shear • Conclusion Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 8

  9. Shape of the power curve • Prediction of annual energy yield for different turbines and different measurement stations • Rated power and cut-in wind speed can be misleading factors • Example Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 9

  10. Shape of the power curve • Annual energy yield table: • Turbine 2 produces more power for wind speed interval 5-10 m/s • 62 % of the energy is captured in interval for data set 1 • 54 % of the energy is captured below 5 m/s for data set 2 Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 10

  11. Outline • Introduction • Feasibility study for small wind turbines • Shape of the power curve • Representation of the wind speed distribution • Wind shear • Conclusion Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 11

  12. Representation of the wind distribution • Use of Weibull distribution can give rise to substantial errors • Error on the annual energy production of 13 % • Inability to cope with non-zero probability of very low wind speeds • Skewing of distribution for high wind speeds • To alleviate this problem: • We use the wind speed data from the feasibility study to calculate: • Probability distribution • Power density distribution • Annual energy production (AEP) • This process is repeated for different distribution methods Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 12

  13. Representation of the wind distribution • We compare: • Weibull method with moment estimate of parameters • Weibull method with maximum likelihood estimate of parameters • Maximum entropy principle (MEP) with variation of pre-exponential term • Combination of methods above with hybrid method Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 13

  14. Representation of the wind distribution • The different distributions are used to calculate the power density distributions • For 13 different measurement stations • We compare the methods by calculating RMSE and COD with the wind speed data set • Table shows comparison of Weibull and MEP method Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 14

  15. Representation of the wind distribution • Comparison of the RMSE for 2 measurement station shows: • We improve the accuracy of the power density prediction for 8 of the 13 measurement stations compared to the conventional Weibull method Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 15

  16. Representation of the wind distribution • Using the probability distributions we can estimate the AEP for one particular turbine • We compare this estimate with the estimate using the data histogram • We improve the accuracy of the AEP prediction for 9 of the 13 measurement stations compare to the conventional Weibull method Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 16

  17. Representation of the wind distribution • Accuracy of prediction of power density distribution and AEP differ • MEP r = 4 higher probability for lower wind speeds • Compensated for higher wind • Better prediction of AEP Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009

  18. Outline • Introduction • Feasibility study for small wind turbines • Shape of the power curve • Representation of the wind speed distribution • Wind shear • Conclusion Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 18

  19. Wind shear • Wind shear describes the variation of wind speed with elevation • Different methods in literature to describe the wind shear: • Linear log law: • Log law: • Log law high roughness: • Power law: Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 19

  20. Wind shear • Hub height no always equal to measurement height • 2/3 rule is bankable • Way of extrapolation to higher altitude will have an impact on the prediction of the annual energy yield • Extrapolation from 15 m to 22.5 m Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 20

  21. Wind shear • Typical error in wind speed measurements 0,05 m/s • Extrapolation from 15 m to 22,5 m • For each type of error • For each type of shear law • Table represent the difference • Smallest and largest extrapolated wind speed Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 21

  22. Wind shear • We use CFD to compare different shear laws • Siting study of flat terrain with obstacles • Determination of most suitable location to install windturbine • Validated by field measurements • On the validated location we attract the vertical wind profile • Influence of inlet wind profile is minimal Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 22

  23. Wind shear • Fit of wind shear laws on vertical wind profile • Results Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 23

  24. Outline • Introduction • Feasibility study for small wind turbines • Shape of the power curve • Representation of the wind speed distribution • Wind shear • Conclusion Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 24

  25. Conclusion • Our feasibility showed that small wind turbines are suitable to provide sustainable energy for SME’s if they are well chosen and installed on a good location • Rated power is not a good predictor of AEP in typical conditions for small wind turbines • Using more complex wind speed distributions can improve the accuracy on annual yield prediction • Use of different shear laws to extrapolate wind speed from one height to another can have an impact on the estimation of the AEP Fluid Dynamics and Thermodynamics Research Group : Erasmushogeschool Brussel - Vrije Universiteit Brussel 02/03/2009 25

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