Using WindSim by means of WindPRO-interface gives the user many advantages:

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1 1 Content: Content: Introduction...1 Using WindSim by means of WindPRO-interface gives the user many advantages:...1 Important Limitations...2 Important Information about Nested Calculation Preparation of the Project in WindPRO Running WindSim pre-processing from WindPRO Running the WindSim PC software...6 Terrain...6 Wind Fields...9 Objects enter after calculation is performed...10 Results Running WindSim for Post-processing from WindPRO...12 Attachment of Data...13 Loading and Processing...15 Grid Results (calculate.rsf file)...16 Node Results...17 WindSim Output Files...18 Compare RSF Files...19 Advanced Graphic presentation of results...19 Report Introduction Please notice that in order to follow this quick guide it is assumed that you are familiar with WindPRO. The quick guide describes how to perform a calculation with WindSim a Norwegian CFD model for wind flow calculations (CFD = computational fluid dynamics). WindPRO/WindSim-interface module and the basics and needed operations in the WindSim PC-software tool are described in this quick guide. It is also possible to make comparisons of wind resource maps calculated with both WindSim and WAsP. Advanced operations of the WindSim model are not described in this guide to get further info on this topic please print the WindSim documentation. Using WindSim by means of WindPRO-interface gives the user many advantages: Fast and easy preparation of input data to WindSim: Access all map handling and terrain description features in WindPRO, i.e. height- and roughness data can be imported from a variety of formats (such as WAsP, dxf or GIS). Naturally, you can manually digitize the data on top of a scanned map. Note, that both roughness lines and digitized roughness areas can be used, so data can easily be shared with WAsP. Prepare wind resource maps from the WindSim result files: When the WindSim calculation has been completed the WindPRO post processing tool can be used to calculate a wind resource map with Weibull distributions in all calculation nodes. The WindSim data is loaded via a user friendly Wizard.

2 2 Perform wind farm wake calculations: Access all WindPRO calculation and report tools for traditional presentation of results, including the option to use WindSim as source for PARK calculations. The wake calculation is based on the wind resource map generated by WindPRO on basis of the WindSim results. Compare the WindSim results with results from WAsP: The post processing has an option to compare your wind resource files with other sources, e.g. ones calculate from WAsP. So you may visually see how the models differ. Visualize your results: Get graphs of speed-ups and/or wind shifts within the calculation area. Use for example the 3d-plotting tool to view speedup data overlaid on the digital elevation model (DEM). Wind distribution data for any position within your calculation area: The WindPRO post processing tool gives you the option of extracting joint wind distributions or Weibull data for arbitrary positions. Second opinion analysis easy made: If you already have performed a WAsP calculation for a site, it is very easy to establish an additional WindSim calculation for getting a second opinion from an advanced flow model. Important Limitations Local obstacles are not handled in the present version of the interface. WindSim contains such features, but these are for the time being only for very advanced users. A comprehensive verification of the WindSim calculation method is not yet available which means that there is no security that a WindSim calculation will provide a more correct result than WAsP calculation. WindSim can definitely handle some flow situations better than WAsP, but as a wind energy calculation consists of averaging many different weather situations and climatic conditions in a proper way to get the actual prediction of the annual energy production (AEP), verification will be a long process. Important Information about Nested Calculation The calculation area has to be extended relatively to the area of interest with at least 2-5 km due to the fact that WindSim, contrary to WAsP, does NOT know the boundaries of the calculation area and therefore it needs some distance to get the parameters stabilised before the area of interest is reached. In most cases a NESTED calculation will be required, meaning a large area such as 20 x 20 km is needed. This can be with a 500 m grid resolution for calculation of the boundary conditions for a second calculation of for example 5 x 5 km, with 100 m grid resolution. The problem is that WindSim is only able to operate with a specific number of nodes if the area is too large, resolution becomes too small. 2. Preparation of the Project in WindPRO In the WindPRO project the following has to be established as a minimum:

3 3 Height contours and roughness lines (minimum surrounding the entire calculation area) digitize extra lines around site if the calculation area is larger than the region covered with lines. Site data object set up for RESGEN/WindSim purpose, with definition of calculation area (you can create two objects, one for the coarse calculation and one for the detailed (nested) calculation). Please note: The selected wind statistics in the site data object are not used in the WindSim calculation. Note also: There has to be known wind measurements within the calculation area either as time series, TAB files or Weibull data (all of these can at post processing be read directly from the WindPRO METEO object). WindSim can only move specific wind measurement data from one spot within the calculation area to any other spot within the calculation area. It has no way to handle wind statistics as input data like WAsP does. Wind measurement data is NOT required for running the WindSim calculation. But it is needed for the post-processing in WindPRO. The pre-processing interface can transfer wind data to WindSim, in case you will like to use the WindSim tool for other investigations besides the options you have from the post processing in WindPRO.

4 4 Figure 1: The data needed to complete a WindSim calculation. Note, that the wind measurement data will only be needed when the WindSim results have been returned for post processing. In this example there are two wind measurement masts. Actually only one measurement mast is needed to do the WindSim calculations, but two masts are needed to test how calculation transforms measurements from one spot to another.

5 5 3. Running WindSim pre-processing from WindPRO Run the calculation module WindSim and choose pre-processing from the main form and the below form appears: The relevant site data object containing the data is selected click OK to start the calculation which is an export of the needed WindSim input files to the specified folder, including a print report option giving the information of the selected data and files. NOTE: up to nodes can be calculated. However we recommend during the test phase to work with far fewer nodes to minimize the calculation and result presentation time. Figure 2: The 3 exported files from WindPRO. The *.gws-file is used in WindSim. Both the *.gws- and *.ini file are used when post-processing data in WindPRO. The *.err is an error log of the preprocessing calculation (most often this is an empty file).

6 6 4. Running the WindSim PC software Create a new project. Locate the exported *.gws file by clicking the browse button. Hereafter, WindSim have access to the exported data from WindPRO. Terrain Figure 3: WindSim terrain screen: Often some manual changes of the settings are needed.

7 7 The first important setting is the height above terrain. This value ought to have a factor 10 to the height difference of the calculated area (recommended in the WindSim chapter). If the highest mountaintop is 1000 m and the lowest valley point is 750 m, the difference is 250 m and the height above terrain should be set to 2500 m. But if it is much higher, there will be problems with the resolution in z-direction, so compromises have to be made. The number of cells in the Z direction is also a compromise. Below a table of reasonable combinations is shown. Later versions with more nodes will of course increase the flexibility. NOTE: If more cells are used than stated in the input field Maximum number of cells, WindSim will automatically reduce the resolution. Therefore, please make sure that this number is set high enough the maximum number of cells is - in the present version (June-04) nodes. X-km Y-km Res-m Z-diff-m Zheight Z-cells Nodes Doing calculations with close to nodes can get very time-consuming as the maximum is almost reached. Therefore we recommend calculating with or less nodes in particular in the testing phase. Click START when parameters are set. Figure 4: When running the terrain-module, the data is read and it can be inspected graphically.

8 8 Figure 5: Note that the roughness is shown with logarithmic scale. E.g. -1 means 10-1 = 0,1 m = approximately a roughness class 2.3. Note also, that in WindSim the roughness HEIGHT is mentioned this is the same as the roughness LENGTH used in the WAsP terminology. Figure 6: The grid resolution for the calculation is shown. In the bottom of the screen it is possible to find the number of cells that will be used in the calculation.

9 9 Wind Fields Figure 7: The Wind Fields screen does normally not need any changes. The exception is when running a nested calculation. In order to post-process the results in WindPRO, the 12 default sectors (30 degrees) have to be used. NESTING - NOTE: If you are running a nested calculation you must point out the calculation previously made. The property Nesting from meso scale must be set to true. Height of boundary layer is a very sensitive parameter, as it differs much in place and time. It is difficult to give general guidelines but it for sure affects the result. This is where the ultimate solution would be to perform several different calculations for different weather types (stability, temperatures etc.) and then weight the results from more calculation results with the time the different weather types are present. But just to know these will require much knowledge/measurements from the site. The Speed above boundary layer is the calculation wind speed that WindSim uses as the topmost boundary condition (such as the wind speed on the top side of the calculation

10 10 box). This wind speed is assumed to correspond with the geostrophic wind speed. Using 10 m/s seems to be a good choice unless your calculations are for specific purposes, as most wind energy is produced at 8-12 m/s. However, be aware of the fact that the wind speed at the turbine position may be somewhat lower due to the wind shear. When post processing the results, WindPRO assumes that speed-ups (either positive or negative) are a fixed percentage, i.e. when the wind speed at a turbine position is 11 m/s but at the meteorological mast is 10 m/s, then this 10% increase is assumed to be correct for all wind speeds. Direction changes are assumed constant for all wind speeds, i.e. are not changed. The Number of iterations could be relevant to change some times the 300 default is not enough and might be set to 600, but it can also happen that too many iterations makes the calculation drift away from a converged solution. Click START to run the calculation. This kind of calculation is rather time-consuming depending on the number of nodes and the number of iterations and will take between 2 hours to several days. Objects enter after calculation is performed Figure 8: To extract results you need to add an object.

11 11 Here you simply select a WTG, no matter which one or where (default will be in the middle) it is necessary in order to extract the results for post processing in WindPRO. Click START Results Figure 9 At the result screen the output is selected Choose the VelocityVectorXYZ. Choose heights: Here, preferably all measurement heights are to be selected. Also, the expected hub heights for the WTGs ought to be chosen. The chosen heights decide in which heights post processing (calculations) can be made afterwards. However, the postprocessing tool in WindPRO allows linear interpolation in-between heights. Click START and the files will be written. Now, there are a huge amount of files within your WindSim project directory:

12 12 Figure 10 The file structure of the WindSim files (all found in the project \user \client folder) The files needed to complete a WindPRO post processing calculation are: *.gws *.ini *.ws file dtm.log *.vec File with grid data (roughness and height information) File with coordinate system information Is the WindSim project file including the calculation wind speed. A log file found in the dtm folder. This file contains grid resolution data (especially needed if WindSim has changed the initial grid resolution). Vec-files are result files with wind vectors. One vec file is created for each wind speed and wind direction so you will have twelve vec files per calculation height. The vec files are found in the wind field folder. You may load the files into WindPRO using the Wizard described below. 5. Running WindSim for Post-processing from WindPRO Start the module WindSim from WindPRO and choose post- processing in the main tab sheet.

13 13 Attachment of Data Data is attached with a Wizard, from which all needed data is pointed out. If someone else does the WindSim calculation for you, make sure you both have the WindPRO export files and the needed WindSim result and project files (See end of previous chapter). If you do not have all, you might still be able to perform some analyses, if you are an experienced user and able to point out the relevant data manually.

14 14 Figure 11: Data attachment wizard.

15 15 Loading and Processing Figure 12: Data are loaded and many analysis features are then available. Click the Load/Reload button to load data. Air density must be given for energy calculations, since the wind energy is a part of the.rsf file specification. In later PARK calculations based on the *.rsf file, only the Weibull parameters are reused and then air density must then be specified again. Calculation height for calculation of rsf file or calculations at specific nodes can be any. BUT, if outside the lowest or highest WindSim calculation height, the speed up from the nearest height is used. Within the lowest and highest WindSim calculation height the speed up results are spatially interpolated. Typically hub height is of interest, but in a testing/checking phase measurement heights for other measurement masts in the area can be relevant.

16 16 Joint wind distribution decides which wind measurement data that will be used together with the WindSim speed up data to give the wind distribution at any point in the calculation height. The Save Weibull and save TAB option is just export tools for getting the data from the METEO object into file formats for viewing/processing with other tools. Note: Only meteorological masts within your calculation area are shown. Grid Results (calculate.rsf file) This is the most important part of the post processing of WindSim results in WindPRO. With an *.rsf wind resource file it is possible to perform a traditional PARK calculation from the WindPRO module PARK and thus get a final result based on WindSim data processing instead of WAsP. But important are also the features for comparing WindSim and WAsP wind resource maps, which gives useful information on the differences by using the two different models. Figure 13: The Weibull fit algorithm can be chosen for calculation of the rsf file based on the WindSim speed up results and the measured data in the Meteo object. The Weibull fit algorithm is used for generating the Weibull data at each node in the rsf file. All calculations are based on the Table data from the WindPRO meteo object at the specified measurement mast and height. The table data are with the WindSim speed up calculation result moved to each node in the rsf file by generating a new set up table data (TAB-file). This TAB file at each node is then Weibull fitted and the Weibull parameters are stored in the rsf file. WindPRO traditionally estimates the Weibull fit based on discreet values, i.e. the binned probabilities for each direction and discrete wind speeds (1,2,3 m/s). More important values (higher wind speeds) are weighted more in the best fit. Another improved method for this purpose - is a fitting method based on continuous distribution - which in general gives better Weibull fits. Please consult the WindPRO online help for further documentation. The calculation will take some time, typically around minutes, depending on the speed of your computer.

17 17 Node Results With this feature you can plot or save results as speed up or direction change for a specific node. Figure 14: Check the box in the lower left of the graph to show as polar plot (only for 1 wind speed) Figure 15: Clicking the property button access a toolbox used to edit the graphs in all kinds of ways. Try for example to go on to the tab sheet Series, then Marks and finally Style. Check the "Visible" check box and you remove the labels. On the Chart tab sheet, under Axis, the left and bottom axis increment can also be changed creating a new version of the graph shown to the right.

18 18 WindSim Output Files Click the show buttons. It takes some time to load all the WindSim node results, but then a graphic view for the entire calculation area are presented. Figure 16: 3D Graphic, here the speed up results from a specific direction, where both the wire grid z- value and the colour are used for showing the speedup. See in next paragraph how you can userdefine this graphic for many more informative views.

19 19 Compare RSF Files Select the calculated rsf file from WindSim (on the previous tab sheet of the post processing) and a similar WAsP calculation (should be for the same height). Max. distance between nodes will cancel all points, that do not exist in both.rsf files within a specified distance. Otherwise the nearest nodes are always compared. Met mast position is for defining the point, where the graphs comparing parameters versus distance shown in the right column below will be generated. This could be any other point of interest. Advanced Graphic presentation of results For the 3D graphic presentation, the following parameters can be shown.

20 20 Figure 17: My(WindSim) is the mean wind speed (My) calculated by WindSim. This can be compared to the wind speed calculated for the same node by WAsP. The other parameters are E (Energy), A (Weibull Scale), k (Weibull shape) and height (altitude). Note the "Edit chart setting" menu (a floating menu) If you uncheck the Link Graph and colouring, you can for example show height of terrain as the basis (Wire grid), while the colourings are the speed-ups.

21 Figure 18: Relative WindSim/WAsP calculated wind speed given by colours while the wire grid shows the terrain altitude (z-value). It is in this view remarkable that at the hilltop, WindSim calculates higher, while on the side of the mountain, WindSim calculates lower wind speeds than WAsP. At the bottom of the graph, where the measurement mast is positioned, both models agree pretty well the only difference here is the difference in shear, while the measurement mast are 10 m high and the two resource maps are calculated for 50 m height.

22 22 Figure 19: The distribution of the ratio between WindSim and WAsP in any calculation point can be shown for the different parameters. Here the mean wind speed is seen to be typically 0-4% higher in the WindSim calculation, at an average of 1,5% higher, but with many nodes with much less calculated wind speed. 1,15 1,1 1,05 1 0,95 Source data Running mean Mean + 1 x STD Mean - 1 x STD Mean + 2 x STD Mean - 2 x STD 0,9 0,85 0,8 0, Figure 20: Finally, the ratio of WindSim/WAsP for a number of parameters can be plotted versus distance from the measurement mast. In this example the calculated mean wind speed is shown for 50 m.agl. based on 10 m measurement height. Close to the mast WindSim predicts around 3% higher speed, which mean that it assume higher shear than WAsP. At 7 km distance, at the mountain, there are differences up to +15% - 30% for the WindSim relative to the WAsP calculation. Report At present, the report from a WindSim post processing only holds information on how it can be used etc.