#1 Re: WAsP » Roughness with many windbreaks » 2018-11-06 15:53:35

Dear Vinh Le Thanh,
You are right: the roughness map is important in this case, so I will try to give you a few more hints:
1. The size (radius) of the map should be = 100 times your mast height and then some. So, for an 80 m mast, the radius should be, say, 8000 m + 50% = 12 km. The total map is then approx. 25 km by 25 km with the mast in the centre.

2. The most important roughness change is the coastline, i.e. from water (z_0 = 0 m) to land. If you download and use an SRTM elevation map in the Map Editor, this comes with the coastline already.

3. You need to generalise the land cover (roughness map) in order for the work to be practical. So, there is maybe not so many land cover classes (e.g. from south to north): the sea, marsh areas along the coast, farmland with few houses, farmland with many houses. For wind directions where a lot of the wind comes from, you can try to detail the land cover description and see if it changes the results. But you cannot specify each and every house, of course, but may specify an area of houses along a road.

4. How to digitise is described in this report http://orbit.dtu.dk/en/publications/win … d057).html


Hope this helps,
Niels

#2 Re: Map Editor » TSRTM_IMPORT ERROR » 2018-09-21 16:20:23

Dear Map Editor user,
If you could share the area you are trying to download, I would be happy to try and reproduce the error. You can send the information to waspsupport@dtu.dk or nimo@dtu.dk.
Best regards,
Niels
WAsP Support

#3 Re: WAsP » Estimating AEP Uncertainty when Blade pitch angel info isn't Available » 2018-08-24 16:40:39

Dear Seenu,
Unfortunately, there is no "site (url) that identifies the level of error or deviation at each stage of WAsP’s calculation". There are some results reported in the literature, e.g. the CREYAP exercises and elsewhere; and the entire uncertainty question is the focus if an IEC working group at the moment.
Best regards,
Niels

#4 Re: WAsP » Wind Turbine Generators and Uncertainty » 2018-08-24 16:37:40

Dear Seenu,
I cannot help you with this question, but would have to refer you to the open literature. WindEurope made a series of test some years back that investigated uncertainties in power curves and wind farm modelling (Google 'CREYAP exercises'). Hope this helps...
Best regards,
Niels

#5 Re: WAsP » Differences in Densities affecting the Estimation » 2018-08-24 16:33:43

Dear Seenu,
We have addressed this problem in WAsP 12, which is able to estimate the air density at any turbine height (anywhere on planet earth) and extrapolate the power curve data to this air density. Before WAsP 12, we would have to do this calculation manually or ask the manufacturer of the turbine for data at the given air density.
Best regards,
Niels

#6 Re: Map Editor » Wind Turbine Editor » 2018-08-24 16:30:23

Dear Roella,
The wind turbine editor is not really meant for the design of wind turbine generators, more like a tool for handling power and thrust curves of existing or modelled turbines and providing the data files to WAsP.
Best regards,
Niels

#7 Re: Map Editor » Sheltering and Obstacle - Modelling of a Circular Water Tank » 2018-08-24 16:27:39

Dear D. Bachai,
Yes, WAsP can only handle rectangular boxes for obstacles, so you have to find a 'box size' to represent the circular obstacle. If you experiment a little with this, you will probably find that the 40-m anemometer is not influenced significantly by the obstacle (40 m being way higher than three times the 6-m water tank). The 10-m level will be influenced, but because of the proximity of the water tank, the obstacle model may not give realistic result. Your experimental setup would require a different type of modelling to obtain reliable results -- and even then it would still be difficult...
Best regards,
Niels

#9 Re: Ideas and suggestions » Roughness length for rice fields - small drainage/irrigation channels » 2018-08-24 16:17:12

Dear D. Bachai,
No, I have never heard of a minimum width threshold for water bodies, but one could make a small case study to explore this. However, I am quite sure that small meter-wide channels will not have any significant effect for a sizeable wind mast or wind turbine.
The recommended roughness for water bodies is always 0 m in WAsP. However, in your case I would suggest a low land roughness for your rice fields, see e.g. http://agrometeorologia.it/documenti/Ri … fields.pdf
Best regards,
Niels

#10 Re: WAsP » WAsP heat flux parameters » 2018-08-02 11:18:41

Dear Caglar,
This is a tricky one, since we use the mast measurements to adjust the heat flux parameters for the site (most often only the average or offset value). There is no simple way of relating the WAsP values to what would have been measured at the site, and there is also no simple relation to modelled heat flux values.

Could you not find some period(s) of data where you could look at the wind profiles?

My general experience is, that the default heat fluxes work quite well in most cases, but not knowing anything about your site this is not very helpful... Anybody else in your region who might have some experience?

Best regards,
Niels

#12 Re: WAsP » Open data file in wasp from windographer » 2018-04-30 10:06:41

Dear Tutitaka,
We cannot help you unless we get to see the file. Maybe you can mail it to waspsupport@dtu.dk so we can have a look?
Best regards,
Niels

#13 Re: WAsP » Is there any easy way to make roughness map ? » 2018-04-23 14:19:09

Dear WAsP user,
The two traditional ways of making roughness maps is 1) by digitising in the Map Editor using a background map image, or 2) by digitising in Google Earth and then edit the lines in the Map Editor. Both methods are described in these course notes http://orbit.dtu.dk/en/publications/win … d057).html (Appendix C).


Map Editor 11 can further vectorise raster land cover data and make them into roughness maps (File > Import > Grid maps). I have used Globcover raster data to make roughness maps this way. In the next Map Editor 12, there will be an additional option to download GlobCover and Corine land cover maps and change them into roughness maps.


Best regards,
Niels
WAsP support

#14 Re: Map Editor » Background Map - Error Message » 2018-04-05 20:24:52

Dear André,
I am not sure what went wrong, but would suggest that you first make the map using the Map Editor (File > Import > SRTM ver.2 database). After that, you can add more roughness areas as described in these notes http://orbit.dtu.dk/en/publications/win … d057).html. Look in Appendix D for more information.

Best regards,
Niels

#15 Re: WAsP » General Questions » 2018-02-28 10:56:37

Dear ysga,
Here are a some brief comments to your post:


Adding a met. station: we recommend you use the Climate Analyst instead. Remember the geographical coordinates of the anemometer, and export in the *.omwc format for best results.


Map for WAsP: once you have the SRTM elevation contour and land/sea roughness map, you can add more roughness areas using Google Earth or a scanned paper map. Procedures are described in these course notes: http://orbit.dtu.dk/en/publications/win … d057).html


Obstacle group: model most cities and towns as roughness areas. The obstacle model is only used for situations where the mast is closer than 50 obstacle heights and lower than 3 obstacle heights in relation to the obstacle. So this is a fairly local effect.


Wind turbine: you can have information on turbines from the manufacturer or the internet. Also, there are some turbine power and thrust curves in the WAsP library. WAsP cannot calculate these specifications, you must know them from somewhere else.


My best piece of advice for now is to study the course notes mentioned above carefully; they contain quite a bit of information and links to other sources.


Good luck with your thesis!


Best regards,
Niels
WAsP support

#16 Re: WAsP » resource grid error » 2018-02-28 10:38:56

Dear Rachel,
Not quite sure what it could be; is it possible that you mail me the workspace (or just the map) to waspsupport@dtu.dk, then I will take a quick look.
Best regards,
Niels
WAsP support

#17 Re: WAsP » WAsP in Tropics (Unstable Atmoshper?) » 2018-02-26 12:47:58

Dear Fierrinho,
There seems to be two schools of thought / practices:
1) Shearing up the observed wind climate to hub height at the mast site and then do the flow modelling – which then describes the horizontal change of the wind climate over the terrain. In this case, you assume that the measured shear is representative for the entire wind profile, and the heat flux value will have little influence on the results (as long as the prediction height is the same).
2) Doing the flow modelling directly between the anemometer and the hub height, which then includes both vertical and horizontal extrapolations. For this, one would need an estimate of the heat flux at the site. The choice of heat flux can be validated at the mast site.

Best regards,
Niels

#18 Re: Map Editor » Georeference/projection of .map file format (GDAL/OGR) » 2017-12-28 17:51:00

Dear Alex,
Hmm, I don't know exactly what format and rules are applied in the first line of the map file. I will forward your questions to the programmer of the feature.

Best regards,
Niels
WAsP Support

#19 Re: Climate Analyst » Automation error » 2017-12-03 21:41:05

Dear Ismail,
Could you mail a sample data file to waspsupport@dtu.dk, then I will take a look at it and report back.
Best regards,
Niels
WAsP Support

#20 Re: WAsP » Gross AEP by Month » 2017-11-27 10:51:28

Dear Carriv9,
Other users have asked for this functionality, i.e. being able to distribute the yearly production over the months in a typical year, or even other periods. We are looking into this, and with our new subscription-based licence and fast-track development initiatives we hope to be able to make a simple tool available soon (2018). As a WAsP user, you will get information about this in a newsletter or on www.wasp.dk.
Best regards,
Niels

#21 Re: WAsP » Wind Speed measurment question » 2017-08-28 10:45:54

kedx3mmn wrote:

MET data of Malaysia (from NOAA) is measured at 10m. There is no other free data available for us to do the calculation. In that case, if I do calculations with the 10m data, would my calculations become totally invalid?

No, the software will certainly extrapolate these measurements for you, but the uncertainty will be higher than if you used a taller mast.

Other free data: you can always use the Global Wind Atlas as well, but this also carries a fairly high uncertainty in predictions of single wind turbines and farms, see this presentation: http://orbit.dtu.dk/en/publications/glo … 7ff8).html.

Best regards,
Niels

#22 Re: WAsP » Required information needed to run wind assessment in Wasp 11 » 2017-08-28 10:36:28

Duncan wrote:

SRTM is orographic (elevation) only. There is no roughness information from that radar survey of the world.

True, but information on land and water surfaces has been added to the SRTM database. So, if you construct an elevation map from SRTM data using the Map Editor, the map will contain roughness change lines at the coastlines, lakes, large rivers etc. Roughness of the water areas will be 0 m (zero m), and roughness of the land areas is specified by the user. You can then add more land cover classes to this map using the Map Editor, or Google Earth.

Best regards,
Niels

#23 Re: WAsP » Required information needed to run wind assessment in Wasp 11 » 2017-08-28 10:27:41

Dear gtaklis,
It is difficult to provide any advice for this combination of software; WAsP 8.4 has not been supported for about 10 years now.
Best regards,
Niels

#24 Re: WAsP » WAsP in Tropics (Unstable Atmoshper?) » 2017-04-19 13:45:55

Dear Irving,
As you write, I have some experience in hotter climates, where it is sometimes required to tweak the heat flux values to get a better fit of the WAsP modelling to the measured profile. However, you have to be careful... many things have to be checked/done first:
- mast spec's (position, height of instruments, boom orientation, etc.)
- wind measurements (calibration, data quality, missing data, etc.)
- elevation map (size, resolution, detail, quality, etc.)
- roughness map (size, resolution, roughness values, etc.)
- any nearby obstacles or significant mast flow distortion
- adjustment of GWC heights to project spec's


If these basics are ok, it may be in order to tweak the heat flux values. However, it should be done based on a wind profile analysis as described in the report. This is because the WAsP heat fluxes are not exactly the same as the heat fluxes you can measure / estimate in nature (though they are strongly related).


In South Africa, I have used heat flux offset values from -50 to +20 W/m^2, see the Wind Atlas for South Africa (http://orbit.dtu.dk/en/publications/win … f8c7).html). Note though, that this atlas is still being developed. - You will find that the variation on the unstable side is much smaller than on the stable side.


Remember, that the WAsP analysis is for entire years, so even if you think the climate / atmosphere is 'unstable', in many cases it is not so on average over the year. We are working on improving the models so they can use measured or modelled heat fluxes in the future.


Best regards,
Niels

#25 Re: WAsP » Faster way of placing turbines » 2017-03-27 12:00:13

Dear all,
We do have a simple MS Excel tool that will help you make different types of layouts. I will make it available on the web site www.wasp.dk asap. -- Niels, WAsP support

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