Wind farm production estimates

Publication: Research - peer-reviewArticle in proceedings – Annual report year: 2012

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In this paper, the Dynamic Wake Meandering (DWM)
model is applied for simulation of wind farm production. In
addition to the numerical simulations, measured data have
been analyzed in order to provide the basis for a full-scale
verification of the model performance.
The basic idea behind the DWMmodel is to model the in-
stationary wind farm flow characteristics by considering wind
turbine wakes as passive tracers continuously emitted from
the wind farm turbines each with a downstream transport pro-
cess dictated by large scale turbulent eddies (lateral and ver-
tical transportation; i.e. meandering) and Taylor advection.
For the present purpose, the DWM model has been im-
plemented in the aeroelastic code HAWC2 [1], and the per-
formance of the resulting model complex is mainly verified
by comparing simulated and measured loads for the Dutch
off-shore Egmond aan Zee wind farm [2]. This farm consists
of 36 Vestas V90 turbine located outside the coast of the
Netherlands. The simulations in this paper were done with
a modified version of HAWC2 only including aerodynamics
and a rigid rotor in order to reduce the simulation time. With
this code a 10min simulation takes approximately 1 minute
on a 3GHz pc. The turbine controller is fully implemented.
Initially, production estimates of a single turbine under free
and wake conditions, respectively, are compared for (undis-
turbed) mean wind speeds ranging from 3m/s to 25m/s. The
undisturbed situation refers to a wind direction bin defined
as 270◦ ±5◦, whereas the wake situation refers to the wind
direction bin 319◦ ±5◦. In the latter case, the investigated
turbine operated in the wake of 6 upstream turbines, with the
mean wind direction being equal to the orientation of the wind
turbine row.
The production of the entire wind farm has been inves-
tigated for a full polar (i.e. as function of mean inflow wind
direction). This investigation relates to a mean wind speed
bin defined as 8m=s±1m=s. The impact of ambient turbu-
lence intensity and turbine inter spacing on the production of
a wind turbine operating under full wake conditions is investi-
gated. Four different turbine inter spacings, ranging between
3.8 and 10.4 rotor diameters, are analyzed for ambient turbu-
lence intensities varying between 2% and 20%. This analysis
is based on full scale production data from three other wind
farms Wieringermeer [3], Horns Rev [4] and Nysted [5]. A
very satisfactory agreement between experimental data and
predictions is observed.
This paper finally includes additionally an analysis of the
production impact caused by atmospheric stability effects.
For this study, atmospheric stability conditions are defined in
terms of the Monin-Obukhov length. Three different stability
classes, including stable, neutral and unstable atmospheric
stratification, have been investigated.
Original languageEnglish
Title of host publicationProceedings of EWEA 2012 - European Wind Energy Conference & Exhibition
Number of pages8
PublisherEuropean Wind Energy Association (EWEA)
Publication date2012
StatePublished

Conference

ConferenceEWEA 2012 - European Wind Energy Conference & Exhibition
CountryDenmark
CityCopenhagen
Period16/04/1219/04/12
Internet addresshttp://events.ewea.org/annual2012/
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