Niels Gylling Mortensen

No, I don't think it is a question of WAsP overestimating systematically. It could have to do with the characteristics of the wind climate at your sites. I would suggest that you email a sample wind climate (OWC) or project to waspsupport@risoe.dtu.dk; then we can take a look at it (keeping your data confidential). Best regards, Niels

If the mast and turbines are of the same approximate height, the WAsP modelling will be quite insensitive to the values of the heat flux parameters -- and to the assignment of roughness length values to the different land cover classes. This is exactly why it is recommended to deploy met. masts that are as high as the wind turbine hub height. If the mast and turbines are of very different heights, you can estimate the effect of stability using WAsP.

In WAsP, simply set the height to the desired value. If using a script, you can make a copy of the script and change the values inside the new script (which is a simple ASCII text file). This way you can change the maximum height and also the height step in the calculations. The changed script should be saved in the standard WAsP scripts folder (C:\Program Files (x86)\Wasp\Internal scripts\WAsP or similar) and will then show up in the 'Tools > Utility scripts' menu.

The Climate Analyst can make an observed extreme wind climate for WAsP Engineering as well, which the Wizard can't. For WAsP, the Analyst can make the observed mean wind climate and export it as a TAB or an OWC file. The TAB file should be identical to the Wizards TAB file, but the OWC is a newer XML-based format which can contain much more information about the data and the analysis. This information is carried over to and can be shown in WAsP, which is a big advantage. The user interface and functionality of the two programs are quite different and the Analyst is faster for processing of many data files since protocols/import filters can be pre-defined. The user is less likely to make errors this way, in my experience. Finally, the Wizard is actually retired now and will not be updated or supported anymore, whereas all our effort in the future will go into the Analyst. -- You can read more about the programs in the WAsP and Climate Analyst Help files.

Haven't seen this one before, so we need to know a bit more before we can find out. Do you only experience the error in this workspace? Please mail the contents of "Help > WAsP on this computer..." to waspsupport@risoe.dtu.dk, then we'll try to sort it out for you.

Haven't seen this error for a long time, so are you sure you are running the latest version of the Climate Analyst? Get the latest installation from: WAsP 10: http://www.wasp.dk/Download/Software/WAsP10_Installation.aspx WAsP 9: http://www.wasp.dk/Download/Software/WAsP9_Installation.aspx Uninstall any old version before installing the new one. If problem persists, mail waspsupport@risoe.dtu.dk.

I guess you are thinking about the "roughness value" or "roughness length / height" around a site. This is changing around the site, depending on the land cover. You may be able to specify a single, typical value for sites in very uniform terrain. In the 'Site effects' window, you can see a reference roughness for each sector, but WAsP will not give you an overall (omni-directional) roughness length for any site.

See reply in WAsP forum at http://www.wasptechnical.dk/forum/viewtopic.php?id=479

It's not much information I have, but I can say that it is important to use the latest version of the software - this often solves the problems. According to your licence, you can download: WAsP 10.1 from http://www.wasp.dk/Download/Software/WAsP10_Installation.aspx WAsP 9.1 from http://www.wasp.dk/Download/Software/WAsP9_Installation.aspx WAsP 8.4 from http://www.wasp.dk/Download/Software/WAsP8_Installation.aspx. It might be a good idea to uninstall whatever version you have now and make a clean reinstall. If problem persists, please report back or write email to waspsupport@risoe.dtu.dk. A TAB file can also be opened in a standard text editor (e.g. NotePad). The format of this kind of file is described in the WAsP help system.

WAsP 10: http://www.wasp.dk/Download/Software/WAsP10_Installation.aspx

The OWC Wizard is not supported anymore. Have you tried the Climate Analyst which is the program we use and support now? Be sure to download the latest version from the WAsP web site www.wasp.dk

The stability model is described in the European Wind Atlas, if you can get hold of a copy from a (university) library near you. The model is based on M-O similarity theory, but the procedure is simplified so it only requires input of the mean and RMS values of the on- and off-shore heat fluxes.

I usually apply the same correction percentage to all sectors at a turbine site. So, I 1) find the dRIX (total) for each turbine site, 2) determine the correction for each turbine site, 3) insert this number for all the sectors for each turbine site. This has worked well for me so far, and I haven't been able to improve the predictions by inserting different corrections for different sectors.

The information is given in the paper "IMPROVING WAsP PREDICTIONS IN (TOO) COMPLEX TERRAIN", see http://www.wasp.dk/Support/Literature.aspx. It seems the link is broken right now, but I'll try to fix it.

It's difficult to say from your description only, what is going on here. However, I guess from the scale of things that mesoscale effects may be important here, and I doubt whether any parameter changes will help you improve the WAsP predictions. Rather, the change of the wind climate seems to be governed by terrain features that WAsP cannot model adequately - is my guess... PS. Do you use the same map for all the predictions?

Assuming that you use the same map for the two calculations, it follows that the difference is caused by the two different wind atlases used. And, if you predict one anemometer with the other, and vice versa, you will therefore get similar differences. This difference may be caused by a number of things: 1) are you using the same period of data for the two anemometers? 2) are the two anemometers of the same type and age? 3) are the two anemometers calibrated in the same way? 4) are the mast flow distortion effects similar for the two anemometers? If you can say 'yes' to these questions, it seems that WAsP cannot model the vertical wind profile well, given your topographical inputs. So, you could try to adjust these, especially the roughness description, in order to improve the vertical wind profile modelling. Of course, the roughnesses should still be realistic, after you have changed them. You should also check the elevation map (see the WAsP Best Practices), is it detailed enough close to the mast? If this is still not enough, the wind profile can also be tweaked by changing the heat flux values of the project, but you should be careful doing this - and the values should make sense (where in the world is the project?). Of course, the 50-m anemometer will give the most reliable 50-m predictions - all other things being equal. So, you should probably trust this result more than the results from the 30-m anemometer.

Or, you could contact the manufacturer directly for site-specific power and thrust curves.

Atmospheric stability has a lot to do with the M-O length, and you can search the internet for much more information. Yes, you can account for atmospheric stability in WAsP by changing the mean and RMS heat flux values; however, you should only do so after you've considered very carefully the elevation, roughness, shelter, and mast flow distortion. This is discussed elsewhere on the forum, see e.g. http://www.wasptechnical.dk/forum/viewtopic.php?id=314

You write that you use WAsP 9.0. Before anything else, you should probably update to version 9.1, see http://www.wasp.dk/Download/Software/WAsP9_Installation.aspx.

No, doesn't ring a bell... Be sure to use the latest version of WAsP 10.1; you can download it from http://www.wasp.dk/Download/Software/WAsP10_Installation.aspx. Uninstall any and all previous versions of WAsP 10 before installing the latest version. Report to waspsupport@risoe.dtu.dk if problem persists.

Making WAsP maps from SRTM data is described on the WAsP web site at http://www.wasp.dk/Support/FAQ/SRTM.aspx. Saga GIS is one (free) piece of software that will do this. DXF2MAP is not needed anymore since the Map Editor can read most common DXF files now. GRD2MAP functionality is also covered by Saga GIS, I think. Surfer from Golden Software is an extremely useful commercial program that can do all this, and more, too.

You might take a look at this post http://www.wasptechnical.dk/forum/viewtopic.php?id=332 and the link it contains. The short version is: you can use all the data you have, but not in an automated way ;-)

There was some confusion in early versions of WAsP 10 about southern hemisphere coordinates. This issue has been resolved now; so if you install the latest version of WAsP 10 (which you might get at http://www.risoe.dtu.dk/WAsP/Download/Software/WAsP10_Installation.aspx) you should have no problems at all. I would recommend uninstalling any and all old versions of WAsP 10 first, before installing the latest one.

Surfer 10 can make some very pretty maps for you, with lots of control over the map details and layout. In addition, it will also do quite a bit of work for you on the input side of WAsP and WAsP Engineering; such as making elevation grids from irregularly spaced spot heights and height contours from elevation grids. Great value for the money.

In addition to the Surfer *.grd format, you can also export an ArcGIS *.asc grid from the "Spatial view" tab of the resource grid window. If you need more grid formats there's a grid convert utility at http://www.geospatialdesigns.com/gridconvert.htm