Power Curve Working Group Overview
Peter Stuart
Senior Technical Manager
Tuesday 06th October 2014
1
Power Curve Working Group
Motivation
What does the PCWG aim to do?
• 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’?
Power
Power Curve
Wind Speed
Is a power curve based on just wind speed and density the ‘whole truth’?
3
Turbine Performance in the Real World
• The real world has…
low wind speed
high wind speed
high turbulence
low wind shear
high wind shear
Turbulence intensity
low turbulence
Wind Speed
• and many combinations of the above (on same site at different times)…
Measured Power Deviation Matrix: Deviation vs TI and Wind Speed
• Wind conditions change all the time, and so does turbine performance.
4
Power Curve Working Group: Who are we?
The power curve working group (PCWG) is a balanced and broad industry group
encompassing Developers, Consultants, Manufacturers and Academics/Researches.
RES, Vattenfall
Crown Estate
Dong, Iberdrola
SSE, RWE
EDF, EON, ESBI,
Mainstream,
Scottish Power
DNV GL
Natural Power
AWS True Power
Sgurr
Wind Guard
Barlovento
Anemos-Jacob
Prevailing
Vestas
Senvion
GE
Suzlon
Siemens
Nordex
NREL
DTU
LLNJ
IWES
CIRCE
ORE Catapult
Leosphere
Romowind
ZephIR
Vaisala
The group aims to examine ways of improving understanding of wind
turbine energy yield in ‘real world’ conditions.
Openness is a key principal: Proceedings of all meetings publically available at:
http://www.ewea.org/events/workshops/resource-assessment-2013
5
Understanding the Problem
and Each Other
Statement of the problem
• 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.
Wind Speed
Power Function
Power
Density
Wind Shear
Wind Veer
Turbulence
Inflow Angle
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Nomenclature: Types of Correction
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:
Available Energy
Type A: Adjustments made to reflect changes in the energy available
for conversion across the rotor in a ten minute period due to ‘nonstandard conditions’.
Type B: Adjustments made to reflect changes in the conversion
efficiency due to ‘non-standard conditions’.
Turbine Behaviour
8
Nomenclature: Types of Correction
• 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.
9
Common Understanding in Practice
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’
Measured Power Deviation Matrix: Deviation vs TI and Wind Speed
10
Round Robins: Understanding
the Methods We Already Have
Round Robin Exercises
• 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’.
12
Round Robin: Application of REWS Method
Pretty good agreement!
13
Round Robin: Application of Turbulence Correction Method
Not so good agreement!
14
Round Robins
• The disagreement in the Turbulence Correction Method demonstrated that
people find this method relatively difficult to apply.
• To address this issue a consensus implementation of the Turbulence
Correction has been developed.
Dropbox\PowerCurveWorkingGroup\Consensus Analysis
• 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.
15
Inner-Outer Range Proposal
Stakeholder Interaction: Inner and Outer Range Concept
Outer Range
Turbulence
Performance < 100%
(on average)
Inner Range
Performance = 100%
(on average)
Shear
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Stakeholder Interaction: Inner and Outer Range Concept
• The inner-out range concept has been proposed as a pragmatic
framework for offering a ‘two-tier’ performance warranty.
•
•
•
•
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-OuterRange-Proposal-Dec-2013.pdf
• The proposal has already been used contractually by some working group
members.
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Inner-Outer Range Proposal
PCWG Open Source Analysis Tool
• 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 Tool: Calculation of Power Curve Deviation Matrices
• Example Analysis of combined dataset of 5 turbines of the same type
Deviation
before
Deviation
afterTurb
TurbCorrection
Correction
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Data Sharing
Data Sharing
• The PCWG currently has 5 datasets which have been supplied to the
group by its members.
• The existing datasets have been invaluable, but much more could be
achieved if more data was available.
• In particular analysis like the power deviation matrices require a
substantial amount of data to generate something meaningful.
• If you have any data which you can share please get in touch!
• The ideal dataset is a power performance test dataset with both masts
and LiDARs.
• Traditional mast based power performance datasets are also highly
useful.
23
What 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).
25
Conclusions
• The PCWG has been formed to find practical approaches to deal with the
issue of turbine performance in real world conditions.
• 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.
• These corrections will help the wind industry further improve/refine the accuracy
of its energy yield predictions and thus improve investor confidence.
• 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!
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27
Power Curve Working Group Roadmap
Conclusion
Solution / Evolution
Definition
Meeting 1
Meeting 2
Round
Robin 1
Meeting 3
Define what’s
the problem we
are trying to
solve.
Identify
possible
solutions
Trial
solutions
Feedback on
solutions.
Round
Robin 2
Meeting 4
Trial
refined
solutions
Feedback
on
refined
solutions.
Compare
experiences &
lessons leant.
Current
Status
Is problem
is solved?
Identify
refined
and/or
alternative
solutions
Should
problem be
redefined?
Iterate
solutions as
required…
Final
Meeting
Finalise
conclusions
Publication
of journal
paper by
working
group.
Publication
of guideline
document.
Publically disseminate presentations and minutes
Dec
2012
Mar
2013
Apr - May
2013
May
2013
Jun – Sep
2013
Dec
2013
Time
Jun
2014