Modelling Impact of Non-Standard Conditions Axel Albers Deutsche WindGuard Consulting GmbH, Varel, Germany (a.albers@windguard.de)
Content Modelling of effect of enironmental conditions on power cures according to the draft reision of IEC 6400-2-, Ed.2 Implications on power cure warranties and wind resource assessments
Status of Reision of IEC 6400-2- Includes methods for taking care of wind shear, wind eer and turbulence effects on power cures Committee Draft (CD) Edition 2 aailable since September 20 Integration of national comments completed Committee Draft for Voting (CDV) expected at end of 202 Final reision expected in 203 Release of standard expected in 204
Rotor Equialent Wind Speed: for Taking Into Account Wind Shear Effects eq n = i= 3 i Ai A 3 H D α l α u fr [m] [m] [-] [-] [-] 60 60 0.2 0.2 0.997 60 60 0.3 0.2 0.988 00 60 0.3 0.2 0.993 00 20 0.2 0.2 0.996 00 20 0.3 0.2 0.985 40 20 0.3 0.2 0.990 Wind shear effect is described by Shear Correction Factor: f = r eq H
Wind Shear Normalisation: to Get a Hub Height Wind Speed Power Cure for Defined Wind Shear Conditions The same eq can be reached by different combinations of f r s ans H s: = f = eq r H f r,ref H,ref If reference profile is a power law: H D α l α u fr α ref H,ref / H [m] [m] [-] [-] [-] [-] [-] 60 60 0.2 0.2 0.997 0.2.000 60 60 0.3 0.2 0.988 0.2 0.990 00 60 0.3 0.2 0.993 0.2 0.994 00 20 0.2 0.2 0.996 0.2.000 00 20 0.3 0.2 0.985 0.2 0.988 40 20 0.3 0.2 0.990 0.2 0.99 H,ref = = H,ref n n i= i= zi H i H f f r r,ref 3 3αref H A i A 3 A i A 3 H
Extended Rotor Equialent Wind Speed: for Taking Into Account Wind Shear and Wind Veer Effects eq n = i= ( cos( φ )) i i 3 Ai A 3 D α l α u eer f r [m] [-] [-] [ /m] [%] 60 0 0 0.0.000 60 0 0 0.2 0.999 60 0 0 0.4 0.995 20 0 0 0.0.000 20 0 0 0.2 0.995 20 0 0 0.4 0.979 80 0 0 0.0.000 80 0 0 0.2 0.988 80 0 0 0.4 0.954 Combined shear and eer effect is described by: Normalisation to reference shear and eer conditions possible as in case of just normalising shear effects f = r eq H
Turbulence Normalisation Only the effect of data aeraging oer 0-minute period is considered Key assumption: turbine output follows instantaneous changes of wind speed, i.e. turbine always follows a certain power cure P I=0. mean power output oer 0 minutes: ( ) = PI = 0( ) f ( ) f(): wind speed distribution measured oer 0 minutes Zero turbulence power cure P I=0 is determined from measured power cure under consideration of measured turbulence intensity Turbulence Normalisation: Iref ( ) = P ( ) P ( ) P ( ) meas meas meas sim,i meas P sim P + meas 0 sim,i ref meas d Example: I cp max effect on cp max AEP/AEP I=0 ag =6.0m/s AEP/AEP I=0 ag =7.5m/s AEP/AEP I=0 ag =9.0m/s WT with 382 W/m² [%] [-] [%] [-] [-] [-] 0 0.450-2.9 0.998.006.008 5 0.454-2.2 0.999.005.007 0 0.464 0.0.000.000.000 5 0.480 3.6.002 0.993 0.990 20 0.504 8.7.006 0.985 0.977
Treatment of Uncertainties Uncertainty of all corrections is taken into account: - air density correction - wind shear correction - wind eer correction - turbulence correction Only the air density correction is obligatory, but: Added uncertainty if no correction according to - wind shear - wind eer - turbulence intensity
Conflict WT Owner, WT Supplier Owner wants site specific power cure for his economic considerations Supplier has problems to warrant site specific power cure: - site conditions often not well known - supplier cannot be hold liable for possible special atmospheric conditions at power cure erification (takes only to 6 months) - warranty on site specific power cure more difficult to manage than generic power cure
Conflict WT Owner, WT Supplier Owner wants site specific power cure for his economic considerations Supplier has problems to warrant site specific power cure: - site conditions often not well known - supplier cannot be hold liable for possible special atmospheric conditions at power cure erification (takes only to 6 months) - warranty on site specific power cure more difficult to manage than generic power cure
Current Situation PC Warranty Generic PC, often alid only for idealised conditions Economics, Wind Resource Assessment Owner uses generic PC for economic calculations; yield expectations often too high! Often neither owner, nor sales people from suppliers, nor wind resource experts are aware of the problem PC Verification special filtering: sometimes long extension of erification
Immediate Improement PC Warranty Generic PC, often alid only for idealised conditions Economics, Wind Resource Assessment PC adjusted to mean site conditions by Add uncertainties of corrections according to IEC 6400-2-, Ed. 2 (can be high) Minimum: use generic PC and add uncertainties for not correcting PC to site conditions (can be high) PC Verification special filtering: sometimes long extension of erification
Future Improement, Generic PC PC Warranty Generic PC Based on equialent wind speed Alternatie: alid for reference shear and eer profiles Valid for reference turbulence Valid for reference air density Economics, Wind Resource Assessment Use equialent wind speed or adjust PC to mean shear and eer conditions by Adjust PC to mean turbulence and air density conditions by Add uncertainties of corrections according to IEC 6400-2-, Ed. 2 (can be high) PC Verification Use equialent wind speed or adjust PC to reference shear and eer conditions by Adjust PC to reference turbulence and air density conditions by Add uncertainties of corrections according to IEC 6400-2-, Ed. 2 (can be high)
Future Improement, Site Specific PC PC Warranty PC specific for mean site conditions Economics, Wind Resource Assessment Take PC as it is Assess added uncertainty due to distribution of wind shear, wind eer, turbulence and air density conditions in analogy to IEC PC Verification Use equialent wind speed or adjust PC to mean shear and eer conditions by Adjust PC to mean turbulence and air density conditions by Add uncertainties of corrections according to IEC 6400-2-, Ed. 2
If PC Verification Possible Only Based on Hub Height Measurement PC Warranty Economics, Wind Resource Assessment PC Verification See preious slides See preious slides Adjust PC to mean turbulence and air density conditions by Add uncertainties of turbulence and air density corrections according to IEC Add uncertainty for not correcting PC in terms of wind sheer and eer according to IEC 6400-2-, Ed. 2 (can be high)