wind assessment: tackling uncertainty
DESCRIPTION
State of the art methodologies for wind assessment and how to minimiseTRANSCRIPT
Miguel de Vasconcelos Ferreira
Rethinking Energy Worldwide
Assessing the wind potential: tackling uncertainty
about MEGAJOULE
The importance of wind assessment
Sources of uncertainty
Annual variability
2
Assessing the wind potential – tackling uncertainty
Index
Miguel de Vasconcelos Ferreira
Uncertainty implications
Wind flow modelling
Final remarks
About MEGAJOULE
3
About MEGAJOULE
Founded in February 4, 2004 founding partners having more than 10 years
experience in wind energy consultancy
Renewable Energy consultancy with focus in
wind resource assessment
Leading wind energy consultancy in Portugal
On the way for global expansion Projects in Portugal, Spain, France, Italy, Slovakia, Poland,
Romania, Bulgaria, Croatia, Bosnia, Moldova, Ukraine, Greece,
Turkey, Israel, Brazil, Uruguay, USA, Mexico, Angola, Cape
Verde, South Africa, Australia and East Timor
Miguel de Vasconcelos Ferreira 4
Assessing the wind potential – tackling uncertainty
0,2
m
1,5m
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m
1,5m
1,5
m
1m
2m
120°
0,8m
61m
30m
Dat
a Lo
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Dat
a Lo
gger
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m
12m
Layout definition and energy calculation
Wind farm project due diligence
Wind measurement campaigns
Wind resource assessment (bankable)
Wind Energy
Mesoscale Wind Flow Simulation
Warranty verification and power curve
measurement
Site Assessment (IEC)
About MEGAJOULE
Miguel de Vasconcelos Ferreira 5
Assessing the wind potential – tackling uncertainty
Solar Resource Mapping
Layout definition
Solar Farm Due-Diligence
Site Survey and Assessment
Energy Yield calculation
About MEGAJOULE
Solar Energy
Assessing the wind potential – tackling uncertainty
About MEGAJOULE
Miguel de Vasconcelos Ferreira 7
Acciona Energía
ABO Wind
African Development Bank
Astrum Energy
Banco BPI
European Investment Bank
BES Investimento
Caixa BI
Catavento
Continental Wind Partners
EBRD
EDF EN
EDP Renováveis
EFACEC
Eletrosul
ENEOP2
ENERCON
ENERGI E2 (eoN)
ENERGIX
Energiekontor
ENERSIS
FINERGE (Endesa)
Fomentinvest
Fundação Oriente
GALP Power
GDF-Suez
GE Wind Energy
GENERG
GESFINU
GESTAMP
Green Energy Group
IBERWIND
INFRACO
INFUSION
International Power
Jaguar Capital
Jaime Ribeiro & Filhos
MARTIFER Renewables
Neoenergia (Brazil)
Networkx
Norvento
Pacific Hydro
Petrobrás
PROEF
PSW
REpower
RP Global
SEE
SGE
Siemens
SSE Renewables
Suzlon
TP
Tractebel
Ventinveste
Voltalia
ZORLU Enerji
Assessing the wind potential – tackling uncertainty
About MEGAJOULE
Miguel de Vasconcelos Ferreira 8
Assessing the wind potential – tackling uncertainty
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MEGAJOULE SA
Western Europe
North America
Africa
Asia-Pacific
South Africa Turkey North and
Central Europe
South-East
Europe
Adriatic
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MEGAJOULE
Polska MEGAJOULE
Romania
MEGAJOULE
Do Brasil
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Türkie
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Brazil and Latin
America
The importance of
wind assessment beyond the obvious…
9
Being so, slight differences in annual wind speed, not noticeable for a
human being, may result in significant differences in annual energy yield.
Power density varies with the cube of wind speed
Wind characteristics vary along the year, as well as from one year to
another. Failure in taking into account the effects of seasonality and annual
variability may lead to important errors in annual energy production
estimation. Also important is the spatial variability of the wind
characteristics. In complex terrain, like mountainous regions, the wind
characteristics can vary significantly even in a few hundred meters.
Wind variability
The importance of wind assessment
Miguel de Vasconcelos Ferreira 10
Assessing the wind potential – tackling uncertainty
Due to the complexity of the physical phenomena present at wind flow, local
effects, such as orography, roughness or obstacles, lead to important local variations
of the wind regime and, therefore, to the need of using simulation models.
Simulation models, however, carry a significant uncertainty. Among the available
models, different approaches exist, leading to a trade-off between uncertainty and
calculation time (sometimes very large).
Complexity of physical phenomena
The importance of wind assessment
Miguel de Vasconcelos Ferreira 11
Assessing the wind potential – tackling uncertainty
Sources of uncertainty
12
• Annual wind variability
Availability/Quality of long term wind data
Correlation methodologies
• Wind measurements
Quality of the instruments
Adequacy of mast and mounting
Data checking and validation
Minimise data losses
Miguel de Vasconcelos Ferreira 13
Sources of uncertainty
• Spatial wind variability
Met mast siting/Number of met masts
Wind flow models
Terrain characteristics: orography, forest
Assessing the wind potential – tackling uncertainty
The annual wind variability issue
Miguel de Vasconcelos Ferreira 14
Limited access to meteorological stations data
• Lack of long term data
No long term wind energy specific data series
• Lack of quality of long term data
Long operation without anemometer calibration
Location change over time
Measurement height change over time
Inadequate siting of met stations for wind projects purpose
Assessing the wind potential – tackling uncertainty
Miguel de Vasconcelos Ferreira 15
Better control of uncertainty factors that are present in met masts
• Using mesoscale virtual wind data series
Enables to derive a long term data series for the required site
Represents the pattern even when having a systematic deviation
-100%
-50%
0%
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100%
Jan-06 Jul-06 Jan-07 Jul-07 Jan-08 Jul-08 Jan-09 Jul-09 Jan-10
Month
ly W
indIn
dex [%
]
NCEP NCAR (1000 mBar) Jasionka Airport (Poland) Local Mast #1 Local Mast #2 Virtual Wind Index
The annual wind variability issue
Assessing the wind potential – tackling uncertainty
Miguel de Vasconcelos Ferreira 16
The modelling issue - Linear models
Advantages
• Reference tools, industry recognized
• Fast and easy to use
• Use of measurement results as an input
Problems
• Not adequate for complex terrain
• Do not take into account recirculation or turbulence effects
• Do not consider vertical component of wind speed
Assessing the wind potential – tackling uncertainty
Miguel de Vasconcelos Ferreira 17
The modelling issue - CFD models
Advantages:
• Adequate for complex terrain
• Simulate recirculation areas
• Calculate vertical component of wind speed
• Consider stratification effects (temperature)
• Consider time variation phenomena
Problems
• Heavy calculation load and more expertise required
•“Driven” by boundary conditions (using mesoscale virtual data series as an
input can minimise this problem)
Assessing the wind potential – tackling uncertainty
Miguel de Vasconcelos Ferreira 18
When is CFD needed :: Possible criteria
• Obstacles
• Forests
• Higher elevations nearby
• High orographic complexity (RIX > 40%)
• Measured Turbulence Intensity at Met masts > 15%
• Deviations in Cross-predictions between masts > 10%
• Ratio between anemometer height and hub height < 2/3
• Large distances between met masts and turbine positions
• Deviations between predicted and measured wind profiles > 5%
Terrain
Measured data
Measurement
campaign
Linear model
performance
The modelling issue - CFD models
Assessing the wind potential – tackling uncertainty
Miguel de Vasconcelos Ferreira 19
CFD performance
Assessing the wind potential – tackling uncertainty
• Feasible :: speed and cost
• Repeatability & reliability
• Better results
Miguel de Vasconcelos Ferreira 20
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0.9 1.0 1.1 1.2 1.3 1.4
He
igh
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Non-Dimensional Wind Speed
SODAR2 WINDIE WAsP
SODAR1 WINDIE WAsP
CFD performance
Assessing the wind potential – tackling uncertainty
Miguel de Vasconcelos Ferreira 21
Uncertainty minimisation using CFD
Case Study - 35 MW wind farm in complex terrain
i)
First wind assessment using data from one met mast
Uncertainty using traditional linear models = 19.1%
Uncertainty using WINDIE CFD model = 15.4%
ii)
Uncertainty using traditional linear models = 12.7%
Uncertainty using WINDIE CFD model = 11.6%
Decision to install a second met mast and perform new wind assessment
Assessing the wind potential – tackling uncertainty
Miguel de Vasconcelos Ferreira 22
Uncertainty minimisation using CFD
The difference in accuracy between linear models and CFD tends to
decrease when more local measurements are available
A case by case analysis should always be made as some atypical
cases can always occur, leading to different results
Importance of local wind data is still present by permitting the CFD
model to achieve better results
When the local measurements coverage is low, the use of the CFD
can enhance the accuracy by reaching lower uncertainty values
Assessing the wind potential – tackling uncertainty
Uncertainty implications
23
Miguel de Vasconcelos Ferreira 24
Uncertainty implications
Example:
P50 = 79.5 GWh/y
Unc. 10% => P90 = 69 GWh/y (-13%)
Unc. 20% => P90 = 59 GWh/y (-26%)
On a 100€/MWh tariff, it means 1 M€ annual difference!
Assessing the wind potential – tackling uncertainty
Final remarks
25
The costs associated to the use of state of the art wind
assessment methodologies are very low, when compared with
the total investment costs.
Accurate wind assessment adds value to the project, by enabling
uncertainty minimisation, lowering project risk and, therefore,
permitting better financing conditions.
Wind assessment must be carefully planned, since the start, as
sometimes it might not be possible to recover from previous
inaccuracies, penalising the project in its latter stages.
Issues related with wind assessment have impact in every stage
of the project development, from site procurement to wind farm
operation.
Final remarks
Miguel de Vasconcelos Ferreira 26
Assessing the wind potential – tackling uncertainty
Tel: +351 220 915 480
Fax: +351 229 488 166
www.megajoule.pt
Rethinking Energy Worldwide
Thank you for your attention!