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Update on the PCWGPeter Stuart
December 9, 2014
EWEA Technology Workshop, Malmö
Working Together
• Working together there is a lot we can achieve…
• The Power Curve Working Group (PCWG) aims to bring people together.
An Idealised View of Wind Turbine Behaviour
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• In an ideal world the power output of a wind turbine is dependent on hub
height wind speed and air density
A Real World View of Wind Conditions
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Image from “One year on, A review of Working Group progress to date”,
PCWG Meeting 4th December 2013, Andrew Tindal DNV GL
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5
10
15
20
-0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Shear exponent (lower blade tip to hub height)
Tu
rb
ule
nce i
nte
nsi
ty (
%)
Day: 7:00-19:00
Night: 19:00-7:00
Shear Exponent
Turb
ule
nce Inte
nsi
ty [
%]
A Real World View of Wind Turbine Behaviour
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Image from “Measurements Replace Generic Assumptions” Tomas
Blodau, Head of Wind and Site, Senvion SE, EWEA 2014 Conference,
Barcelona
Wind Speed [m/s]
Turb
ule
nce Inte
nsi
ty [
%]
Colour = % Power Deviation
PCWG: Background
• The PCWG was formed in Dec 2012 to find practical approaches to deal
with the issue of turbine performance in real world conditions.
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• The PCWG explores:
o Corrections for ‘real-world’ wind conditions e.g. high/low turbulence,
high/low shear etc.
o New methods of stake holder interaction in order to give a more
realistic expectation of turbine performance.
• Ultimately the PCWG aims to further refine the accuracy of its energy yield
predictions to improve investor confidence.
• With 130 members the group is open to all. Please visit www.pcwg.org or
email [email protected]
• PCWG aims to provide a platform for broad wind industry collaboration.
Work to Date: Acknowledgement of Issue
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• Formation of consensus view that the power output of a wind turbine is
dependent on wind speed, density, vertical wind shear/veer, turbulence
intensity and inflow angle.
Pow
er
Wind Speed
Density
Wind Shear
Wind Veer
Turbulence
Power Function
• From the above parameters; wind speed, density, vertical wind shear/veer
and turbulence intensity are thought to be of primary importance. Although
inflow also plays an important role.
Inflow
Work to Date: Sensitivity of Power Output to Parameters
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Image from “PCWG Validation Analysis”, Clerc A (RES), PCWG Meeting
Wednesday 4th December 2013
Plot of relative sensitivity of power curve to various input parameters before
and after density correction.
Work to Date: Common Language
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Available Energy
Turbine Behaviour
Type A Correction: 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 Correction: Adjustments made to reflect changes in the
conversion efficiency due to ‘non-standard conditions’.
• Proxy corrections: relate production to a parameter which is broadly
associated with changes in performances. Acknowledge that the underlying
mechanisms may not be identified e.g. production loss based on low
turbulence intensity.
• Analytical corrections: 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 Renormalisation.
Work to Date: Inner/Outer Range Proposal
Public Publication of the Inner/Outer Range Proposal (see www.pcwg.org)
Inner/Outer Range proposal is a schematic concept to assist technical and
contractual discussions relating to turbine performance in real world conditions.
Work to Date: Round Robins and Consensus Analysis
Consensus understanding of the Rotor Equivalent Wind Speed (REWS) and
Turbulence Correction methods from the DRAFT IEC 61400-12-1 standard:
• Round Robin Exercises across three datasets
• Publically available Excel Consensus Analysis
• Publically available Documentation
September 2013 Round Robin
Work to Date: Round Robins and Consensus Analysis
November 2014 Excel Consensus Analysis and Associated Documentation
Work to date: PCWG Open Source Analysis Tool
• Python based open source code project available on GitHub:
https://github.com/peterdougstuart/PCWG
• Code benchmarked against Excel Consensus Analysis from Round Robin
Exercises.
• Code project in early days, but shows early promise. Contributions welcome!
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Work to date: Evaluaton of IEC 61400-12-1 Methods
• Example Analysis of combined dataset of 5 turbines of the same type
Deviation before Turb CorrectionDeviation after Turb Correction
• Rotor Equivalent Wind Speed (REWS) method could not be applied to this
particular dataset due to lack of data.
Wind Speed [m/s]
Turb
ule
nce I
nte
nsi
ty [
%]
• Consensus view that that while helpful, the Rotor Equivalent Wind Speed
(REWS) and Turbulence Correction methods (from the Draft IEC 61400-12-1) do
not fully describe the real world behaviour of turbines.
2015 Roadmap: What Next for the PCWG?
• Publication of 2015 roadmap in December 2014.
• Further Round Robins:
– Site Specific Power Curves
– Power Deviation Matrices
– Rotor Equivalent Wind Speed with Inflow Angle
• Publication of document expressing the ideal format for communicating
power curve information.
• Further development of Open Source Analysis Tool.
• Planned data sharing exercise: find new ways to bring data together
• Drill into ‘gap’ between proxy and analytical methods (Type B effects).
Explore new and novel corrections methods.
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Any Questions?
Data Aggregator (Academic Institution 2)
Proprietary Dataset C
PCWG Analysis Tool
Analysis Definition X
Organization D
Combination Analysis
Proprietary Dataset A
PCWG Analysis Tool
Organization A
Proprietary Dataset B
PCWG Analysis Tool
Organization B
Proprietary Dataset C
PCWG Analysis Tool
Organization C
Data Aggregator (Academic Institution 1)
Combination Analysis
Combined Analysis α
Consistently Analyzed Cleansed Data
Analysis Definition X
Analysis Definition X
Analysis Definition X
How? Part A Data Aggregation
Combined Analysis β
* ‘Cleansed Data’ means that all commercially sensitive information is removed e.g. site, machine, site wind speed etc.
Data Aggregator (Academic Institution 2)
Proprietary Dataset C
Analysis Definition Z
Organization D
Combination Analysis
Proprietary Dataset A
Organization A
Proprietary Dataset B
Organization B
Proprietary Dataset C
Organization C
Data Aggregator (Academic Institution 1)
Combination Analysis
Validation Test β
Consistently Analyzed Cleansed Data
Analysis Definition Y
Analysis Definition Y
Analysis Definition Z
How? Part B Training Independent Test
Validation Test α
Analysis β Analysis α
