Wind Energy

164 J.J. Trujillo et al.
The extended Ainslie wake model assumes a radially symmetric wind speed
field around the wake center line. The single wake is modeled with 2D RANS
with eddy viscosity closure. An internal turbulence intensity model, implemented
by Wessel [7], is used for internal wakes calculation.
Jensen model, defines a wake expanding linearly downwind based on mass
conservation. The wake is defined by the expansion angle which is empirically
defined by calibration with measured data. In FLaP this model has been
implemented making use of two different wake angles that are used for single
and multiple wakes, respectively.
29.1.2 Online Wind Farm Model
Extensions to FLaP have been made in order to enable online modeling. Time
series of operational parameters are fed to the model performing different
checks and corrections to the data as explained later.
Power curve data are corrected for actual air density using the recommendation
of the IEC standard [4]. For this purpose data of temperature and
pressure have to be given as input for each time series.
FLaP searches the best ambient wind speed measurement available for
a particular wind direction giving priority to metmast measurements. The
nacelle anemometer, of the active free wind turbine, is used in case of no
availability of a free metmast for the actual wind direction. This is made
assuming that a proper calibration of the nacelle wind speed is available.
During normal operation of a wind farm there are occasions at which one
or more turbines may not operate. This has to be taken into account by the
wind farm model since the wake structure inside the wind farm changes. FLaP
handles this by simulating with a wind farm layout that only contains the wind
turbines that are actually operating at the time for which the simulation is
performed.
29.2 Measurements and Simulation
Time series of 10 min averages of measured data were collected at a wind farm
located near the North Sea coast of Germany. The wind farm is compounded
by thirty four stall regulated turbines with a nominal power of 600 kW in a
distribution shown in Fig. 29.1.
Data were available from metmast and SCADA system extending over
almost one year. The first system delivered data of wind speed at hub height,
wind direction, and air temperature and pressure. The second collected data
of power production, nacelle wind speed and status for each turbine.
Simulation of Bassens wind farm time series was performed with FLaP
using Ainslie and Jensen models independently.