Obtain 'k' and 'A' Weibull parameters using WAsP OWC Wizard
If you have a collection of wind data, the frequency distribution of those data will typically fit to what is know as a Weibull distribution. The function of a particular Weibull distribution fitted to your data can fairly accurately explain your wind environment using just two parameters, A and k. These parameters can be used in WAsP's wind turbine assement tool, Turbine Editor, as described on the turbines page.
To generate the 'k' and 'A' parameters to use in WAsP Turbine Editor, you must first have a table of wind speed data. This should preferably be from on-site wind instrumentation. Only two variables are needed, wind speed and direction. The units need to be in m/s and degrees, respectively. The table must be in a plaintext format, such as comma-separated CSV or tab-separated (ie: not in Excel's XLS spreadsheet format).
Once your data file(s) is/are ready, open up OWC Wizard (a shortcut should exist in the WAsP program folder). You should see the following screen:
Click 'Next' and you should see the screen below, which asks you for the height, latitude and longitude of the anemometer you obtained your data from. Unless you have the licensed version of WAsP, these values are not important for anything, though it is useful for reference; just make sure to enter something.
The next screen will ask you to add data.
Click the 'Add' button to bring up the following screen, then click the '...' button to browse for your data and open it.
Now, go to the next screen which will ask you to specify which part of the added data to use. If you have any header rows, make sure to specify the number of these (my table had none, so I have entered '0'). Then specify which column is for direction, and which is for wind speed (in my case it was column 2 for direction, and 3 for speed).
Once you have the proper columns specified, click 'Next' repeatedly until you come to the screen shown below. This is a good place to control for any erroneously high values. If you know that your data table contains such values, you can adjust the upper limit to cut these values out. For example, if I knew my highest correctly recorded wind speed was 29m/s but that there were higher erroneously recorded values, I could set the upper limit to 29m/s to eliminate these errors and maintain the correct values at/below the limit. By clicking the 'Preview' button, you can visually look through your data for anything that "sticks out." In the likely case that your data do not contain very large errors, you can leave the default values as they are and simply click 'Next.'
Keep clicking 'Next' until you reach the following screen. If you have additional data (e.g.: another year), you may add it here. Otherwise, click 'Next' to continue.
At this screen, click the 'Advanced...' button, and in the 'Advanced settings' windows that comes up, change both values from 1 to 0.5 and click 'OK.' Doing this will make your distribution graph look more precise. Click 'Next' and you should be prompted to save your analysis. Save your file anywhere that is convenient and use an intuitive name. You can later open this file up in WAsP at any time.
After you save the file, the final screen for the OWC Wizard will appear as follows. Click the 'Report' button to display the analysis output in your web browser.
When the output displays, a graph should appear somewhere near the top that looks like the following. Here is where the 'k' and 'A' values may be found.
