Calculation of the energy production of a wind farm including array losses. The park calculation is based on the following modules:


Calculation Method

The wind distribution at each WTG position is calculated /given from one of the 2 modules mentioned above. This means that the wind model can be based on either direct measurements, WAsP model calculations for each WTG location or a wind resource map from WAsP, WAsP-CFD or other sources. The wind distribution is then adjusted for array losses using one of three different models: the PARK model (N.O. Jensen, RISØ), the eddy viscosity model (Ainslie, 1988) or the IWTS II (G. C. Larsen, 1999). This requires information on the ct curves of the WTGs and awake decay constant. Both can be adjusted in the user interface. A displacement height can be withdrawn to the hub height of the turbines affected by the lifting of the wind profile over a forest. Finally the adjusted wind distribution is integrated with the power curve of the WTGs for the energy yield calculation; the power curve being corrected to the air density calculated at each turbine.

Park2Necessary Input Data (Objects)

Wind Turbine (Position and type):

The Power Curve and Ct curve of the WTGs selected can generally be found in the WTG Catalogue – otherwise they can be added manually. There are many advanced features for designing a wind farm layout. To mention some: creation of rows with equal distance, cloning of these for fast parallel rows, use of distance circles around each WTG. Park layout coordinates can also be imported simply from ASCII files or spreadsheets simply by using the “copy/paste” function. A displacement height can be calculated sector wise for the turbines located in or close to forest.

Wind Data:

The wind data are given as output from one of the two modules mentioned previously. Multiple sets of wind data can be used in a park calculation, e.g. measurements for different places in a wind farm area. The park calculation automatically takes the nearest set of wind data. When using WAsP, individual wind data is calculated from one or a combination of wind statistics to each WTG position with just one site data object, which is linked to digitized height contours and roughness lines. Local obstacles are treated individually relative to each WTG position. As an alternative to wind statistics, long term EMD mesoscale data can be used in a PARK , time varying calculation. The energy output is then calculated for the whole time series where the wake decay constant can be defined sector wise and the power curve adjusted for air density, turbulence, shear and veer on each time stamps. The mesoscale data have to be previously calibrated to the local conditions (measurements or production data) making use of the scaler tool. The scaler allows calibrating the data sector wise including a daily and/or monthly correction factor.


PARK is probably the most flexible tool for calculating wind farm production. There is almost no limit to the way data input can be prepared and used in the calculation module. The module ties together the wind model, the wake model and the turbine layout into one operation. WTGs can be entered as both existing and new WTGs and treated separately in the printout, while all are included in the calculation. Even the loss of existing WTGs caused by the new WTGs is calculated automatically in one process if required. There are no limits in using different WTG types or hub heights in same calculation. With the windPRO layer structure, several different layouts can be tested against each other quickly and easily.

The PARK module includes reports with 24-12 tables and duration curves based on time series with wind variations. The resulting time-varying production for each turbine can be used for analyses with the Performance Check module, and gives a new dimension to the analyses of actual vs. calculated production figures. Finally, the PARK model can calculate data for park power curve verification, etc.
The PARK calculation includes a RIX analysis, where the layout calculated is examined for complex terrain problems. Has the alpha parameter of the RIXmethod been calculated in Meteo analyzer, it can be used to correct the AEP directly in PARK. Also included in PARK: a forest model which can calculate the expected sector wise displacement height at each turbine on the basis of the digitized forest.

Calculations report

The report generator includes a number of printouts and analysis options. The following printouts are usually available: Main Printout, Reference WTGs, Energy Production Analysis, Power Curve Analysis, Terrain Analysis, Wind Data Analysis, Park power curve, RIX calculation, Displacement height, Scaler, Wind speeds inside wind farm, Turbulence reports and Maps.

Result to file – all the WTG with coordinates and detailed calculation results can be printed to a text file for further processing in excel etc….

View reports from the PARK module

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