Uncertainty in a post-construction energy yield estimate

Transcription

1 Uncertainty in a post-construction energy yield estimate Sónia Liléo, Johannes Lindvall and Johan Hansson Analysis of Operating Wind Farms, EWEA Technology Workshop, Malmö

2 Contents Methodologies for post-construction assessment of the wake reduced gross production (i.e., gross AEP wake losses) Methodologies for the post-construction assessment of non-full performance losses Dependence on the operational period length Uncertainty assessment 2

3 ProdOptimize Assessment and optimization of the energy production of operational wind farms Research project within the Vindforsk IV programme Mainly financed by the Swedish Energy Council and the branch organization Elforsk. Partly co-financed by: 3

4 Post-construction assessment methods Measured short-term wind series A: Nacelle anemometer wsp B: None C: None D: None E: None Modelled long-term wind series A: WRF ERA-Interim B: WRF ERA-Interim C: WRF ERA-Interim D: WRF ERA-Interim LTC method to calculate farm s long-term wind A: U&N method B: None C: None D: None E: None E: WRF ERA-Interim extrapol. to each wtg position using WAsP Modelled long-term power series A: 10-min LT power series B: 10-min LT power series C1: Weekly LT power series C2: Monthly LT power series D: Monthly wind index E: 1-hour LT power series Used power curve A: Sectorwise PC relates nacelle anem wsp and prod power for each wtg B: Sectorwise PC relates modelled wsp and prod power for each wtg C: Sectorwise PC relates modelled wsp and modelled power (PPV model) D: None E: Official PC for density corrected (1h res) wsp Wake Reduced Gross AEP A: Annual mean value B: Annual mean value C1: Linear reg modelled and actual prod on a weekly basis. Fit applied on remaining series. AEP = 52.18*Weekly mean value. C2: Linear reg modelled and actual prod on a monthly basis; Fit applied on remaining series. AEP = 12 * Monthly mean value D: Linear reg wind index and actual prod on a monthly basis. AEP = 12*Prod normal month E: Wake model run for each time step and for each wtg. Modelled production adjusted to actual production for full performance periods. Obtained mean ratio applied on remaining series. Annual mean value. 4

5 Post-construction assessment methods Used methods A: Measured wsp ; Measured PC B: Modelled wsp; Measured PC C1: Modelled wsp; Modelled PC; Regression weekly basis C2: Modelled wsp; Modelled PC; Regression monthly basis D: Monthly wind index E: WFS 5

6 Method E: Newly developed model Model developed by KVT in partnership with the University of Oslo (UiO) and Statkraft. The project was financed by the Norwegian Research Council (50 %), Statkraft (40 %), and KVT (10 %) Simulates the production of each turbine of a wind farm in the time domain, including density correction and wake modeling in the time domain (1 h resolution) Has been validated against data from the Norwegian wind farms Smøla and Kjøllefjord owned by Statkraft 6

7 Normalized Wake Reduced Gross AEP Comparison of the methods Wind farm 1 First 6 months of operation not included in the calculation Deviation of up to 8 % between the methods based on 2.5 y data Normalized by the average Wake Reduced Gross for max nr of months Nr of operational months after the first 6 months of operation

8 Comparison of the methods Normalized Wake Reduced Gross AEP Wind farm 2 Deviation of up to 2 % between the methods based on 5.5 y operation Deviation of up to 8 % Nr of operational months after the first 6 months of operation

9 Methods presented in IEC/TS Methodologies for the post-construction assessment of non-full performance losses Method 1 Historical power curve relating the nacelle anemometer wind speed and the produced power Method 2 Average production of wind farm Method 3 Average production of most representative neighbour turbines chosen subjectively based on proximity/terrain charactieristices Method 4 Power correlation matrix Method 5 Production of the most representative neighbour turbine chosen objectively based on lowest historical sectorwise deviation Method 6 Wind Farm Simulator, WFS 9

10 Normalized non-full performance losses (%) Comparison of the methods Wind farm 1 Very large deviation between the methods Normalized by the average non-wake losses for max nr of months Nr of operational months after first 6 months of operation

11 Normalized non-full performance losses (%) In case of a non-full perf loss of 6 % Comparison of the methods Wind farm 2 Deviation of 40 % = 2.4 % Deviation of 25 % = 1.5 % Deviation of up to 40 % Deviation of up to 25 % of the estimated loss Nr of operational months after first 6 months of operation

12 Normalized non-full performance losses (%) Comparison of the methods Wind farm 1 Very large deviation between the methods Normalized by the average non-wake losses for max nr of months Nr of operational months after first 6 months of operation

13 Nacelle anemom wsp T2 [m/s] Nacelle anemometer performance Wind farm 1 T1 & T2 full perf T1 not full perf & T2 full perf Wind farm 2 Different accuracy of the nacelle anemometer wsp when turbine is in full perfrmance compared to when it is not in full performance Higher uncertainty in Method 1 for Wind farm 1 than for Wind farm 2 Nacelle anemom wsp T1 [m/s] 13

14 Normalized non-full performance losses (%) Comparison of the methods Wind farm 1 Deviation of up to 40 % of the estimated loss Not reliable Nr of operational months after first 6 months of operation

15 Conclusions Methodologies for post-construction assessment of the wake reduced gross production A MeasWind MeasPC B ModWind Meas PC C ModWind ModPC D Mod WindIndex E WFS Short operational period Long oper. period but large amount of non-full performance periods Non-consistent nacelle anemometer wind speed More recommended - Less recommended Choose the most adequate method for each case 15

16 Conclusions Methodologies for post-construction assessment of non-full performance losses 1 Hist PC 2 Average WF prod 3 Average Repres WTGs 4 PCM 5 Most Repres WTG 6 WFS Large amount of non-full performance periods Change in nacelle anemometer calibration during the oper period Different accuracy of the nacelle wind speed for full and non-full performance periods Large variation in mean wsp between wtg positions Methods presented in IEC/TS More promising 16

17 Conclusions Total uncertainty in the post-construction AEP First 6 months not included Uncertainty Wind farm 1 Wind farm 2 Based on 2.5 y oper Based on 2.5 y Based on 5.5 y Input data 1 2 % 1 2 % 1 2 % Method for the estimate of Wake Reduced Gross AEP Estimate of non-full perf losses future turbine performance will be equal to past performance future wind climate will be equal to past wind climate 8 % 8 % 2 % 2.4 % 2.4 % 1.5 % 2-3 % 2-3 % 2-3 % 4 % 4 % 4 %

18 Conclusions Total uncertainty in the post-construction AEP First 6 months not included Uncertainty Wind farm 1 Wind farm 2 Based on 2.5 y Based on 2.5 y Based on 5.5 y Input data 1 2 % 1 2 % 1 2 % Method for the estimate of Wake Reduced Gross AEP Estimate of non-full perf losses future turbine performance will be equal to past performance future wind climate will be equal to past wind climate 8 % 8 % 2 % 2.4 % 2.4 % 1.5 % 2-3 % 2-3 % 2-3 % 4 % 4 % 4 % Total % % %

19 Conclusions Total uncertainty in the post-construction AEP First 6 months not included For non-full perf loss of 6 % Uncertainty Wind farm 1 Wind farm 2 Based on 2.5 y Based on 2.5 y Based on 5.5 y Input data 1 2 % 1 2 % 1 2 % Method for the estimate of Wake Reduced Gross AEP Estimate of non-full perf losses future turbine performance will be equal to past performance future wind climate will be equal to past wind climate 8 % 8 % 2 % 2.4 % 2.4 % 1.5 % 2-3 % 2-3 % 2-3 % 4 % 4 % 4 % Total % % %

20 Conclusions Total uncertainty in the post-construction AEP First 6 months not included For non-full perf loss of 6 % Uncertainty Wind farm 1 Wind farm 2 Based on 2.5 y Based on 2.5 y Based on 5.5 y Input data 1 2 % 1 2 % 1 2 % Method for the estimate of Wake Reduced Gross AEP Estimate of non-full perf losses future turbine performance will be equal to past performance future wind climate will be equal to past wind climate 8 % 8 % 2 % 2.4 % 2.4 % 1.5 % 2-3 % 2-3 % 2-3 % 4 % 4 % 4 % Total % % %

21 Conclusions Total uncertainty in the post-construction AEP First 6 months not included For non-full perf loss of 6 % Assuming 2 % unc in wsp Uncertainty Wind farm 1 Wind farm 2 Based on 2.5 y Based on 2.5 y Based on 5.5 y Input data 1 2 % 1 2 % 1 2 % Method for the estimate of Wake Reduced Gross AEP Estimate of non-full perf losses future turbine performance will be equal to past performance future wind climate will be equal to past wind climate 8 % 8 % 2 % 2.4 % 2.4 % 1.5 % 2-3 % 2-3 % 2-3 % 4 % 4 % 4 % Total % % %

22 Conclusions Total uncertainty in the post-construction AEP First 6 months not included For non-full perf loss of 6 % Assuming 2 % unc in wsp Uncertainty Wind farm 1 Wind farm 2 Based on 2.5 y Based on 2.5 y Based on 5.5 y Input data 1 2 % 1 2 % 1 2 % Method for the estimate of Wake Reduced Gross AEP Estimate of non-full perf losses future turbine performance will be equal to past performance future wind climate will be equal to past wind climate 8 % 8 % 2 % 2.4 % 2.4 % 1.5 % 2-3 % 2-3 % 2-3 % 4 % 4 % 4 % Total Uncertainty % % %

23 Thank you! Telf: All the results will be published in a publicly available report in April