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Stefan Blagojevic

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Posts posted by Stefan Blagojevic

    Very far site prediction

    in WAsP CFD

    Posted

    Dear Shin,

    WAsP can in some cases be utilized for masts at distant locations, but it is essential to follow the WAsP similarity principle, which states that the meteorological mast area and the proposed site should closely resemble each other. More information on the similarity principle is available here:
    https://orbit.dtu.dk/files/106096865/THE_SIMILARITY_PRINCIPLE.pdf

    The use of WAsP CFD is advised for semi-complex or complex terrains, where the traditional linear model has limitations as it often excludes non-linear effects that are crucial for accurate wind simulation in such complex areas. The site's distance from the meteorological mast is not the primary factor for using WAsP CFD.

    Best regards,
    Stefan

    .WRG files as source of data for energy yield

    in WAsP

    Posted

    Hi Sergio,

    WRG files are WAsP outputs, and WAsP is unable to open WRG file formats directly. When WAsP is used to calculate a resource grid, you can export the results to files of this format to use in downstream programs. Importing WRG files to WAsP is not its intended use.

    Best regards,
    Stefan

    WAsP-CFD Resolution Height lines

    in WAsP CFD

    Posted

    Hi Lucas,

    The appropriate height contour equidistance to use in CFD simulations can vary depending on the specific requirements of the simulation and the characteristics of the wind flow being modeled. In general, the height contour equidistance should be small enough to capture the important details of the flow, but large enough to ensure computational efficiency.

    I think there is a gain by having high-resolution elevation maps, but you have to be careful, particularly for high-resolution CFD models.
    If the maps have strange elevation spikes, the CFD model will pick up on these and affect the simulations badly.
    So, you could end up wanting to spatially filter your high-resolution data and then lose the high-resolution benefits anyway.

    But for proper high-resolution height contour maps, the limit is basically a matter of computational efficiency. I think that is why "less than 10 m" is mentioned, as this is a typical value considered high enough for standard cases without being too demanding.

    Best regards,
    Stefan
    WAsP Team

    Wasp Error

    in WAsP

    Posted

    Hi Mustafa,

    This error has been fixed in our latest WAsP Suite installer. You can download it here:
    https://www.wasp.dk/download/wasp12-suite-installer

    It works for both WAsP 12 and earlier versions. If you have an earlier version of WAsP, simply install the newest WAsP 12 version using the link above, but keep your old installation of your earlier version of WAsP.

    You can read more about this error in our news article here:
    https://www.wasp.dk/news/nyhed?id=c9c97a25-9a4c-4d99-9d0f-d2a3df277413

    Best regards,
    Stefan

    Obtaining Wind Data

    in Climate Analyst

    Posted

    Hi Lidia,

    This can be done using Python with the xarray and Pandas packages. 

    To create a text file using the xarray package in Python, you can use the open_dataset() function to open the NetCDF file, and then use the to_dataframe() function to convert the data to a Pandas DataFrame. You can then use the drop() function from Pandas to remove the columns that you do not want to include in the output text file, and then use the to_csv() function to write the resulting DataFrame to a text file.

    Here is an example of how you can do this: 

    import xarray as xr
import pandas as pd

# Open the NetCDF file using xarray
ds = xr.open_dataset('input.nc')

# Convert the data to a Pandas DataFrame
df = ds.to_dataframe()

# Remove the "height" and "crs" columns from the DataFrame
df = df.drop(columns=['height', 'crs'])

# Write the DataFrame to a text file in the preferred format for WAsP Climate Analyst
df.to_csv('output.txt', sep='\t', index=False)
     

    Note that this makes a tab-separated file with "sep='\t'. This can be changed to your preferred delimiter.

    In this example, we are using the drop() function from Pandas to remove the "height" and "crs" columns from the DataFrame. We are then using the to_csv() function to write the resulting DataFrame to a text file with a tab-separated value (TSV) format, which is the format that is required by the WAsP Climate Analyst tool.
     

    For more information and examples of using the xarray and Pandas packages to convert NetCDF data to text files, you can refer to the xarray and Pandas documentation:
    http://xarray.pydata.org/en/stable/generated/xarray.Dataset.to_dataframe.html
    https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.to_csv.html

    Missing CRS in WAsP

    in WAsP

    Posted

    The actual WAsP model runs purely in a metric system and doesn't care about the geographical location of the sites. It's only relevant in a few places:

    1) Preparing KML for Google Earth visualisation

    2) Pulling down GWCs automatically from the GWA data set server

    3) Warning about location mismatch between OWC and met. station

    4) Pulling down barometric reference data automatically for air density calculations.

    So, the results will not be much affected by a slight shift in location caused by a wrong coordinate system, but generally the whole program will not behave quite right. That's why we now require a CRS for each vector map.

    Missing CRS in WAsP

    in WAsP

    Posted

    Hi Antoine,

    If the coordinate system does not match in WAsP, there will be an offset which will impact the results. We recommend to stick to a single CRS and use it throughout the project.
    I know that QGIS has Lambert-93, where you could transform the projections.

    Best regards,
    Stefan

    Sizing wind farm

    in Windfarm Assessment Tool

    Posted

    If you have measurements from a met. mast, the data is imported in WAsP Climate Analyst.
    With a new project open, you can right-click your site and click "Import dataset to site."
    From here you need to create an Observed Wind Climate (OWC) to import into WAsP.

    Which map do you not have access to? You could create your own vector maps in WAsP Map Editor.

     

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