Niels Gylling Mortensen

I have reported this to the development team and programmers. Will be fixed in the next version of the Climate Analyst.

The WAsP Best Practices have been updated slightly, the new version is available at http://www.wasp.dk/Support/FAQ.html.

I find, that even in quite complex terrain, the overall selfprediction is usually quite ok, even though sector-wise results may vary quite a bit, because of the large speed-ups and turnings. In such cases, the terrain is also often close to (or past) the limitations of the WAsP flow model and one would expect a higher than usual uncertainty. The amount of data available may also influence the selfprediction. A rescaling procedure based on the selfprediction at the anemometer site will be determined for one point only and the corrections found in this way may not apply to other (turbine) sites (and heights) where the topographical effects are different. So, in most cases, I would not consider or recommend to use corrections based on the selfprediction. If you work in complex (steep) terrain, I would strongly recommend a RIX analysis of your sites, see e.g. http://www.wasp.dk/Support/Literature.html

We usually don't worry about the scale of a WAsP map because the digital map is defined using real-world coordinates. However, when you use a scanned paper map for digitising the height contours or roughness change lines, this map should preferably be at a large scale, say, 1:25,000 or 1:50,000. Such maps are more detailed than smaller scale maps and WAsP needs these details (e.g. elevation details close to the sites) on order to do a reliable modelling.

Our general recommendations for elevation and landuse information (roughness) are given in the help files and summarised in the WAsP Best Practices; the latter document can be downloaded from http://www.wasp.dk/Support/FAQ.html. Both elevation and roughness maps can be made coarser (i.e. fewer contours and fewer points) far away from the sites in order to speed up calculation time. Circular (or other non-square) maps may be used to decrease the number of points and lines in a map. In some cases, the results may not change much when you clip the map (like described above), but this is not generally true! So, it's recommended to stick to the guidelines offered by the modellers in the best practices.

In general, we recommend to add roughness change lines to the WAsP map; roughness roses are used mainly for quality assurance of the roughness information in the map. How to make the roughness map is described in the various help files; check also the WAsP Best Practices at http://www.wasp.dk/Support/FAQ.html.

There's more information about using shuttle data for making WAsP maps at the WAsP web site, see http://www.wasp.dk/Support/FAQ/SRTM.html

Each data set (anemometer) provides one wind atlas and one set of predictions only. If you have two or more anemometers, on one or more masts, each of these can provide one set of predictions. You should compare these predictions and try to understand why they are different (or identical). So, it is not possible to blend several data sets automatically – this is actually a feature rather than a flaw. You can use two or more anemometers on one mast to investigate how well WAsP predicts the vertical wind profile. One might adjust the terrain descriptions or modeling parameters based on this, in order to improve the modelling. Remember though, that flow distortion from the mast etc. could be significant. Top-mounted anemometer is the reference anemometer for this reason.

Yes, the self-prediction should be fairly close, especially the power density. See also my response here http://www.wasptechnical.dk/forum/viewtopic.php?id=250

Hi Petros, No, this is not the usual difference we see in a self-prediction - even for a fairly complex site. Even half the difference would be quite high. The difference in power densities should be smaller though, also in your case. You could mail your workspace to me or to waspsupport@risoe.dk and let us have a quick look at it. We'll treat your workspace and data confidentially, of course.

This error (also) happens, if WAsP does not find an elevation or roughness contour within 20 km of a site. It will come up with a warning like “CZoomingGrid - Unexpected exception in Fortran code raised at …” – or simply refuse to calculate. This distance (calculation radius) is governed by one of the parameters in the projects "Edit project configuration…" menu. If you go to "Edit project configuration… / WAsP wind modeling / Max. interpolation radius in BZ model", you can change this radius to, say, 30000 m. Now your sites might calculate. You can also make an elevation/roughness contour in the area where the problem is, e.g. around the offshore wind farm site. The problem can also happen sometimes with undefined lines in the map.

You should be able to do it from the "Edit | Clip map | Map part" window; if this doesn't work, report it to waspsupport@risoe.dk.

To get elevation maps of almost any region, you can use the SRTM elevation data set. Read more about the data and procedures at http://www.wasp.dk/Support/FAQ/SRTM.html. It's a good idea to check the final contour map against a paper map or other available information.

I will mail you the rsf2grd program directly; it is an old program now, but maybe it may prove useful. Surfer can also read the rsf and wrg formats and convert the data into grids (Grid | Data).

To get elevation maps of Korea, you can use the SRTM elevation data set. Read more about the data and procedures at http://www.wasp.dk/Support/FAQ/SRTM.html.

Unfortunately, this is not possible in the present version. However, it's on our list of things to do for the next version (1.2).

Hi Sinisa, If you use WAsP 8, be sure to run version 8.4.0; get it at http://www.wasp.dk/Download/Software/PreviousInstallations.html

You need to upgrade from WAsP 8 to 10, see the WAsP web site at http://www.wasp.dk/Order/OrderForm.html

We have uploaded a "WAsP best practices and checklist" document on the WAsP web site at http://www.wasp.dk/Support/FAQ.html This list of requirements, best practices and recommendations is not exhaustive, but is meant to provide a brief summary of some important considerations regarding WAsP modelling.

This could be caused by the shape of the wind speed distribution, especially the Weibull k parameter. Distributions with a long tail will have high power density values, but the turbine can only utilise the wind speeds between, say, 4 and 25 m/s (and not the long tail part). It does sound a bit odd though, so maybe you should also check your data again ;-)

I have made some tests now, and I think it might have to do with lines that contain more than about 32k points. I'll have to ask the developer of the Map Editor for more details now.

The OWC Wizard and the Climate Analyst can take any number of data points, and the predictions are based on whatever you input to WAsP. However, WAsP will assume that the wind climate you provide is representative of the annual, long-term climate - so the prediction is given as X MWh/y.

I suspect something else could be wrong; I just loaded a 47 MB DXF file with no problems at all. Map contains 1,139,318 points in 1589 lines. Is your DXF file much larger than this?

There should be some information in the help file of the program, including reference to a paper. The regional wind climate (wind atlas) should change gently (gradually) with distance for this to work well. You don't always know about this, so take care! I often use it in Denmark, but would advise extreme caution in complex (steep) terrain.

20-50 m resolution sounds about right to me. I often start with a large resolution grid and then divide by 2 a couple of times, say: 800, 400, 200, 100, 50, 25. Makes for fast initial views and WAsP will not need to calculate all grid points all the time, just the new ones. Finest resolutions calculate during lunch break or overnight. Remember that there should be lots of map around the resource grid: at least 100 times the calculation height in all directions.