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Power Curve Working Group Overview
Peter StuartSenior Technical Manager
Tuesday 06th October 2014
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Power Curve Working Group Power Curve Working Group MotivationMotivation
What does the PCWG aim to do?
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• The power curve working group (PCWG) formed to answer a specific question:
What power will a wind turbine generate in the full range of atmospheric conditions seen in the ‘real world’?
Wind Speed
Pow
er
Is a power curve based on just wind speed and density the ‘whole truth’?
Power Curve
Turbine Performance in the Real World
• The real world has…
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high wind speed
high turbulence
low wind shear
high wind shear
low wind speed
low turbulence
• and many combinations of the above (on same site at different times)…
• Wind conditions change all the time, and so does turbine performance.
Wind Speed
Tu
rbu
len
ce
in
ten
sit
y
Measured Power Deviation Matrix: Deviation vs TI and Wind Speed
Power Curve Working Group: Who are we?
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RES, VattenfallCrown EstateDong, IberdrolaSSE, RWEEDF, EON, ESBI, Mainstream, Scottish Power
DNV GLNatural PowerAWS True PowerSgurrWind GuardBarloventoAnemos-JacobPrevailing
VestasSenvionGESuzlonSiemensNordex
The power curve working group (PCWG) is a balanced and broad industry group encompassing Developers, Consultants, Manufacturers and Academics/Researches.
NRELDTULLNJIWESCIRCEORE Catapult
Openness is a key principal: Proceedings of all meetings publically available at: http://www.ewea.org/events/workshops/resource-assessment-2013
LeosphereRomowindZephIRVaisala
The group aims to examine ways of improving understanding of wind turbine energy yield in ‘real world’ conditions.
Understanding the Problem Understanding the Problem and Each Otherand Each Other
Statement of the problem
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• The power function of a wind turbine is dependent on wind speed, density, vertical wind shear, vertical wind veer, turbulence intensity, directional variation and inflow angle.
Pow
er
Wind Speed
Density
Wind Shear
Wind Veer
Turbulence
Power Function
Inflow Angle
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Corrections should be applied for ‘real world’ conditions which are different to those for which a power curve is representative. These corrections fall into two categories:
Type A: Adjustments made to reflect changes in the energy available for conversion across the rotor in a ten minute period due to ‘non-standard conditions’.
Type B: Adjustments made to reflect changes in the conversion efficiency due to ‘non-standard conditions’.
Nomenclature: Types of Correction
Available Energy
Turbine Behaviour
Nomenclature: Types of Correction
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• Proxy methods: relate production to a parameter which is broadly associated with changes in performances. Acknowledge that the underlying mechanisms may not be identified, but pursue regardless if methods demonstrably improve predictions. e.g. production loss based on low turbulence intensity.
• Analytical/physical methods: apply methods based on understanding of underlying physics/statistics. May involve use of additional measurements such as LiDAR e.g. Rotor Equivalent Wind Speed and Turbulence Correction defined in 61400-12-1.
Common Understanding in Practice
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Measured Power Deviation Matrix: Deviation vs TI and Wind Speed
Recent PCWG discussion:‘There is a gap between the proxy and analytical methods, in particular in the low wind speed & low turbulence quadrant. Type B effects are suspected as the reason for the difference’
Round Robins: Understanding Round Robins: Understanding the Methods We Already Havethe Methods We Already Have
Round Robin Exercises
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• The PCWG has held a series of round robins aims at improving common understanding of methods define in 61400-12-1:
• Rotor Equivalent Wind Speed
• Turbulence Correction (Turbulence Renormalisation)
• Equivalent Wind Speed Including Veer
• Site Specific Power Curves (coming soon)
• The Round Robins have been invaluable in prompting detailed discussion in how best to apply these methods.
• The final product of the round robins is a publically available ‘consensus analysis’.
Round Robin: Application of REWS Method
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Pretty good agreement!
Round Robin: Application of Turbulence Correction Method
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Not so good agreement!
Round Robins
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• The disagreement in the Turbulence Correction Method demonstrated that people find this method relatively difficult to apply.
Dropbox\PowerCurveWorkingGroup\Consensus Analysis
• To address this issue a consensus implementation of the Turbulence Correction has been developed.
• The consensus analysis uses a pure excel implementation of the turbulence correction method (Excel array formulas)
• A ‘guided tour’ of the consensus analysis was presented at the September 2014 PCWG meeting.
• An excel consensus analysis of the Rotor Equivalent Wind Speed Method is also available in DropBox.
Inner-Outer Range ProposalInner-Outer Range Proposal
Stakeholder Interaction: Inner and Outer Range Concept
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Shear
Tur
bule
nce
Inner Range
Performance = 100% (on average)
Outer Range
Performance < 100% (on average)
• The inner-out range concept has been proposed as a pragmatic framework for offering a ‘two-tier’ performance warranty.
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Stakeholder Interaction: Inner and Outer Range Concept
• AEPReference(u): The reference AEP per wind speed bin. • AEPmeasured(u): The measured AEP per wind speed bin.• F(u): The fraction of data in the outer range per wind speed.• R: (Warranty level in Outer Range) / (Warranty level in Inner Range)
• Proposal document is publically available at: http://www.ewea.org/events/workshops/wp-content/uploads/2014/03/PCWG-Inner-Outer-Range-Proposal-Dec-2013.pdf
• The proposal has already been used contractually by some working group members.
Inner-Outer Range ProposalInner-Outer Range Proposal
• The first release of the (Version 0.5.0) of the PCWG Open Source Analysis tool is now available to download.
• The code is provided without warranty under the terms of the MIT software license (see attached for more details). The tool itself can be downloaded at: https://sourceforge.net/projects/pcwg/files
• The tool has been benchmarked against the Excel Consensus Analysis of the working group Round Robin Exercises.
• The tool is open source and working group members are encouraged to contribute. Those interested can access the project source code on GitHub: https://github.com/peterdougstuart/PCWG
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PCWG Open Source Analysis Tool
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PCWG Tool: Calculation of Power Curve Deviation Matrices
• Example Analysis of combined dataset of 5 turbines of the same type
Deviation before Turb CorrectionDeviation after Turb Correction
Data SharingData Sharing
• The PCWG currently has 5 datasets which have been supplied to the group by its members.
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Data Sharing
• The existing datasets have been invaluable, but much more could be achieved if more data was available.
• If you have any data which you can share please get in touch!
• In particular analysis like the power deviation matrices require a substantial amount of data to generate something meaningful.
• The ideal dataset is a power performance test dataset with both masts and LiDARs.
• Traditional mast based power performance datasets are also highly useful.
What Next & ConclusionsWhat Next & Conclusions
What Next for the PCWG
1. Publication of companion document for Turbulence Correction Consensus Analysis i.e. a guide to applying this method.
2. Site Specific Power Curves Round Robin
3. Publication of document expressing the ideal format for communicating power curve information.
4. New features in Open Source Analysis Tool e.g. site calibration module.
5. Innovative data sharing exercise: find new ways to bring data together
6. Examine correction methods for other parameters e.g. inflow angle
7. Drill into ‘gap’ between proxy and analytical methods (Type B effects).
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Conclusions
• The PCWG has been formed to find practical approaches to deal with the issue of turbine performance in real world conditions.
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• The PCWG has reached a consensus that the power function of a wind turbine is dependent on wind speed, density, vertical wind shear, vertical wind veer, turbulence intensity, directional variation and inflow angle.
• The PCWG is exploring corrections for ‘real-world’ wind conditions and new methods of stake holder interaction in order to give a more realistic expectation of turbine performance.
• Further collaboration between manufacturers, developers and consultants is required to improve communication of power function information and explore corrections for real world conditions.
• This is an issue the industry has the power to solve!
• These corrections will help the wind industry further improve/refine the accuracy of its energy yield predictions and thus improve investor confidence.
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Time
Power Curve Working Group Roadmap
Dec 2012
Definition
Meeting 1
Define what’s the problem we are trying to solve.
Solution / Evolution
Meeting 2
Identify possible solutions
Round Robin 1
Mar 2013
Meeting 3
May 2013
Apr - May 2013
Conclusion
Trial solutions
Feedback on solutions.
Compare experiences & lessons leant.
Identify refined and/or alternative solutions
Jun – Sep 2013
Round Robin 2
Meeting 4
Trial refined solutions
Feedback on refined solutions.
Dec 2013
Is problem is solved?
Jun2014
Publically disseminate presentations and minutes
Should problem be redefined?
Iterate solutions as required…
Final Meeting
Finalise conclusions
Publication of journal paper by working group.
Publication of guideline document.
Current Status
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