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Dear Lars Levermann, I see that no other user replied to this, so I (the LibInt programmer) add my own thoughts. Rules for using the lib-interpolator? ------------------------------------- The Lib Interpolator is not based on physics and there are no formal criteria for its application. However, I suggest that you consider the following questions: * Are the data from the reference sites measured with similar equipment? * Are measurement periods and sample intervals comparable? * Are the WAsP RIX numbers of the reference sites comparable? * Are the wind atlases of the reference sites comparable? * Are other climates parameters, e.g. temperature, humidity, and height above sea level, comparable? * Finally, are the conditions at the new site expected to be comparable to conditions at the reference sites? Obviously, it is a good thing if you truly can ask YES to all these questions. Unfortunately, we have no guidelines as to how much you could violate the ideal conditions. Do I need to interpolate 3 files or can I use only 2? ----------------------------------------------------- Using 2 files only is equivalent to interpolation along one leg of the normal interpolation triangle. Create a dummy wind atlas for the third corner, choose manual weighting factors and set the factor for the dummy to zero. Maximum distance from turbine sites or/and between the met. stations? --------------------------------------------------------------------- I suppose there is a maximum distance but it is not a universal constant. The relevant questions to consider is whether the sites relates to the same regional wind climate and whether the WAsP RIX numbers are comparable. Use of 3 stations where the site isn't located in the triangle? -------------------------------------------------------------- I do not recommend excessive extrapolation. Try to interpolate between the two closest stations only. Good luck! Morten --------

I can´t save my workspace.. I get error 503 and I cant find what that means in the help. Can you help my out? thank you Marta -------- This turned out to be a problem saving the (zipped) workspace file, but only for one particular folder. If anyone else experiences this problem, then please do email technical support so that we can investigate further. --------

Hi, I'm a WAsP 8 user, I'd like to know if is possible to assess the model uncertainty. I thought to apply: - as vertical extrapolation uncertainty > the power density error associated with the self prediction error. - as horizontal extrapolatio nuncertainty> the value of dRIX between the met mast and each wtg. In particular I'd apply the dRix value multiplied for the coefficeints as reported in "ris-r-995.pdf" paper. But in this case I could quantify only the error in predicted wind speed and not the uncertainty in energy. If there is someone who can give me some suggestions I'd be glad. Andrea -------- Hi Andrea, I am also a WASP 8 user, my opinion is : if you have obtained the errors on the wind speed using the dRIX as mentioned in the document ris-r-995, the next step for you is to make the wind speed correction for each wtg in WAsP in "user correction" in the "turbine site" window, after that you just recalculate the new AEP for the wind farm and get from there the error on the energy prediction when applying the dRix error indicator. hope that it is helping, and waiting to hear more about that from WASP help team or other WASP users. Sam. --------

I have discovered the 'resource grid'. Unfortunately it appears to produce values different from the turbine calculation. I have tried with two different onsite wind measurements (38m & 50m) and two different hub heights (65m & 85m). e.g. the resource grid predicts 6.00m/s @ 65m from the 50m data but the turbine report presents 4.22m/s with AEP of 1.52. Incidentally, I can't get the resource grid to show any AEP data. -------- Dear Anton, this looks mysterious... Please mail your WAsP8 workspace file to WAsPSupport@risoe.dk. -------- Hello, I either cannot get any AEP data from the Resource grid. What can I do? Katja -------- There will never be AEP results if a wind turbine generator is not associated with the resource grid. You can see the other hierarchy members which are associated with a resource grid by clicking the grid in the hierarchy tree and holding the mouse button down. The associated members will be highlighted in blue. If there *is* a WTG associated, and you still don't see any AEP results, then please email waspsupport@risoe.dk with a full description of what you're seeing. If possible, please send the workspace file too. --------

Hi everyone! I´m Francisco Hernández from Enercon Site Assessment. I´m really interested in the physical background theory of the European Wind Atlas methodology. So, I write you to know where I can find the cited references in these manual. I have downloaded someones from Risoe web but I´m not able to find another ones anywhere (university libraries included). Maybe there is some web or address where I can order them. Among others I have specially interest in the next ones: Rossby C.-G. and R.B. Montgomery (1935). The layer of frictional influence in wind and ocean currents. Paper in Phy. Oceanogr. Meteor., MIT and Woods Hole Oceanogr. Ins., III no. 3. 101pp. Beyer, H.G., T. Pahlke, W. Schmidt, H.-P. Wadl and U. de Witt (1994). Wake effects in a linear wind farm. J. Wind Eng. Ind. Aerodyn. 51, 303-318 Lettau, H. (1969). Note on aerodynamic roughness-parameter estimation on the basis of roughness-element distribution. J. Appl. Met., 8, 828-832 Frandsen (2004-. -urbulence and turbulence-generated fatigue loading in wind tubines clusters. Perera, M.D. (1981). Shelter behind two-dimensional solid and porous fences. J. Wind Engin. and Industial Aerodyn. 8, 93-104 Charnock, H. (1955). Wind Stress on a surface water. Quart. J. Roy. Meteor. Soc. 81, 639-640. I would be really gratefull to you if you can give me any information. Thank you very much in advance and best regards Francisco Hernández-Fillols --------

Anemometer mast ~500m from proposed turbine site which is rural/industrial. Is a single roughness rose based on the anemometer position adequate or is a second one sited at the turbine required ? Problem with the latter is: 'The roughness rose 'Turbine' cannot be calculated because: the associated map does not contain any roughness information.' No, the map doesn't but the roughness rose does contain values entered manually. -------- Hi Anton, Roughness roses are site-specific. If you associate a roughness rose with a met. station, then it will affect that site only (and will override any roughness information in the associated map). If you experiment, you will find that a rose can only be associated with one site: you can't insert one at the project level. (This is different from obstacle groups, which can be located in a site-independent way.) A turbine site will not be affected by a roughness rose which is a child of an associated met. station. The turbine site will need a rose of its own. You can enter one manually, or you can ask WAsP to generate a rose from the roughness information in a map. If the map doesn't have any, then you can't, of course. If the map does have some roughness information, then there's no real need to generate a rose, unless you want to add more specific detail about the local site environment. What WAsP does not do is to take a rose from one site and generate a rose for another site. HTH. -------- Hello everyone, I understand that the roughness rose (RR) are site specific as explained in your last response to Anton, I was wondering if you can help me to better understand the effect of adding a RR to met mast station in a project. I have added a RR to the met mast station (with some particular rougness details), I used also a map with roughness details as a child of the project. I get a self predicted wind speed at the met mast, and I get a WRG at the met station location, I have been very surprised to see that there is a difference betwee the predicted wind spped (self prediction)at the met station and the wind speed predicted at the single met station WRG. Is that mean that WAsP has used the map roughness details to calculate the wind speed predicted at the met station WRG single point instead of using the Roughness rose I have associated to the met station. could you help me to know if my understanding is right... thank you very much for your excellent forum. Sam. -------- Dear Samuel A wind resource grid will not be affected by a roughness rose which is a child of an associated met. station. In your case the resource grid member will use the associated map. WAsP Team --------

An example is Enercon where Power versus Wind Speed is presented based on 'easy' measurements by the manufacturer or other organisation. But, where do Ct figures come from and why are they required ? More accurately, can Ct be computed from P-U (with some assumptions) ? Practically, the easiest way of 'producing' a new turbine file is to use an old one and enter the new Power numbers per wind speed. What happens when the existing Ct values are left unchanged ? -------- Ct is - per definition - the dimensionless thrust excerted on the turbine rotor by the wind, as explained in the WAsP HELP system. It is used for calculating the turbine-turbine wake effect in wind farms. It cannot - in general - be calculated from the power curve, as it will e.g. depend on the regulating system (based on blade-pitching or stall). However, it will, contrary to the power curve, be practically independent of the air density. Ct should be supplied by the turbine manufacturer together with the power curve. Normally the manufacturers will supply the Ct-curve upon request. --------

Hello, When I have two masts close one to another, I can produce two wind atlases. At which point these two atlases must be similar to consider them representative for the whole region? Is there a limit in m/s in wind speeds between two wind atlases when they can be considered as completely different? Thank you in advance -------- There is no specific limit beyond which two wind atlases cannot be considered to represent a certain area. Normally it is recommended to use windatlas #1 (based on mast #1)to make a prediction for the wind climate at mast #2. If the difference in mean wind speed (omni directional and in the important sectors)is more than, say 5%, then the reason for that should be investigated, e.g. poor instruments, poor calibration of instruments, non-adequate terrain description (e.g. re. roughnes). Fixing identified deficiencies one should be able to the difference down below the 5%. The WAsP Team. --------

Hello, Is it possible to input two diferent meteo stations in Wasp to calculate the wind atlas? Thanks for your help, Best Regards. -------- François, Each wind atlas (aka Regional Wind Climate or *.lib file) data set is derived from one met. station (aka Observed Wind Climate or *.tab file) only. So, with two met. stations you can generate two different wind atlases and use these to get two different Predicted Wind Climates or power productions - which can then be compared. There also exist a possibility to combine (interpolate between) three wind atlases to get the wind atlas for a place in between the three met. stations. This is one of the programs in the WAsP Utility Programs package. The WAsP Team @ Risø -------- Hello, When I have two masts close one to another, I can produce two wind atlases. At which point these two atlases must be similar to consider them representative for the whole region? Is there a limit in m/s in wind speeds between two wind atlases when they can be considered as completely different? Thank you in advance --------

Hello, Thanks for this forum. I'm using Windpro to obtain the digital rugosity maps and the orography maps. So for one project I obtain two ".map" type files. My problem is that in wasp7.2, as far as I know, only one map can be imported. How can I overlap the rugosity and orography maps? Many thanks for your precious help. François -------- by "Rugosity" I mean "Roughness"... :) -------- Actually I select "add clipped", choose the .map to add, enter the boundaries, click "ok" and then a "Invalid floatting point operation" appears. -------- Francois, 1.) Did you check that you are using the latest version of map editor? It is supposed to be the one with the least bugs left in it. 2.) try this: use the wasp map editor to open the roughness map. Activate the "digitize|enable digitizing" option. Add a single "dummy" line containing only height information - 1. e. orografic height 0.0! Save under a new name. Open the height contour map. "File|Add" the roughness map. Remove (!) the dummy line. Save the resulting file under a new name. This worked as a workaround for me. Best regards Christian Berndt -------- Francois, The standard procedure is: 1) Open one of the maps in the Map Editor 2) Add the second map from the file menu It is usually a good idea to use the latest version of any software tool; a pre-release version of the latest Map Editor can be downloaded from http://www.wasp.dk/betadownloads/. The WAsP Team @ Risø -------- Thanks for your help, it worked! -------- Francois, If you still use WAsP 7, be sure to upgrade to WAsP version 7.3. You may download this version from: http://www.wasp.dk/Download/WAsP/PreviousInstallations.html The WAsP Team @ Risø

Hello: I am working with WASP version 7.3. Has this version the CDM, Coastal Discontinuity Model? What versions of WASP have the CDM? On the other hand, Do you know some document where there are studies of a possible validation of buoy measurments against fixed meteorological mast measurements in the same location in the sea or in the coast line? Do you know approximately the measurement´s uncertainty of a buoy approx 2, 5 m. a.s.l. and its extrapolation to 70m, I suppose that it's very high but I don´t know the aprox. value. I know that this study is quite complicated, but does it exist somewhere? I know documents with meteorological validation between several fix offshore met. stations and fix coastline met. stations. (Evaluation of the wind resource estimation program WASP offshore applications), but not with buoys. Finally , what is the best method of measurement with an acceptable relation quality/price for offshore measurements ? Thank you very much in advance by your help and collaboration. Best regards -------- I got to know Lidar or Sodar could be your choices for offshore measuring. It's said Lidar measuring using doppler effect don't need calibration at all. And it could be mounted on buoy with PV-Wind power supply. --------

I'm not able to find the power curve for GE 1.5 MW turbine. Please give me the data file for that or let me know where I can find it. I'm also not able to find it from www.gepower.com. All I need is the wind speeds and corresponding output power at a pariticular air density. I've used the Vestas 44-600kW power curve which was very useful to me. Thanks, Hari -------- Dear Hari, You will have to inquire directly at the manufacturer - this turbine is not included with the WAsP package. Remember to get the power/thrust curves for the site-specific air density. We are working on a download page for wind turbine generators, see http://www.wasp.dk/Download/PowerCurves.html, but this is not yet ready, sorry. The WAsP Team @ Risø --------

I have two different power curves for the same turbine: For the first one, density=1.09 and for the second, density=1.12. Is there any way of working in WAsP for a density of 1.10 or should I change the power curve before entering WAsP? -------- WAsP can handle multiple power curves, where the power and thrust is given for a number of air densities. However, it is not possible (yet) to interpolate (or extrapolate) to other air densities , so you will have to make/get the right power curve before entering it into WAsP. The WAsP Team @ Risø --------

When I calculated a wind farm by WAsP 8.1, I had the option "Do model the wake effects between sites" selected. Then I created this wind farm report. My question is if the turbine site wind speed and power value presented under Site wind climates in the report are before or after turbine wake loss... -------- The wake model only affects the power predictions. The wind climates (and thus the mean wind speeds) which are included in the report are as calculated without wake effects --------

Hi, In the formula WAsP uses to calculate the effective wind speed deficit in waked loading conditions (found at http://www.wasp.dk/Products/WAsP/WakeEffectModel.html), the term (1-sqrt(1-Ct)), becomes an imaginary number when Ct, the thrust coefficient, becomes higher than 1.0. So since we don't want imaginary numbers, I believe WAsP rounds down to 1 any input Ct values over 1. However, I would note that Ct curves (thrust coefficient per wind speed) for different turbine manufacturers frequently contain Ct values over 1. When WAsP rounds these down to 1, there is some information lost. So my question is: Please explain why it is appropriate for WAsP to round down Ct values over 1 (e.g. does this underestimate the wake losses)?, and my other question is: Can the formula be changed to use values over 1? David Wahl GE Wind Energy -------- The wake model in WAsP is an approximate model according to which Ct cannot exceed 1. I guess it is fair to say that this may lead to sligth underestimation of the wake effects. On the other hand, Ct-values higher than 1 would only occur at very low wind speed, just above cut-in, where the produced power is anyway very low. Thus the impact on the calculated annual energy production is to my judgement negligible. --------

Hello WAsP Team and Users, is there a way to import WindPRO WTG catalogue files into WAsP ? Thanks for suggestions -------- Frank, the WAsP team has not developed an import filter for WindPro WTG catalogue files; I wonder if the WindPro team has developed an export facility to WAsP power curve files? WAsP Team --------

What is the equation of deviation of the wasp predcitions if there're a measured wind speed and a predicted one?? -------- Yoon, you might have to be more specific as to explain what kind of data you would like compare. If "there is" a measured value and "there is" a computed value this information is not sufficient to tell you if there is a computable deviation between them. In general, one should keep in mind that WAsP does not *predict* any sort of data (although stated elsewhere on this site. Yet a prediction would be called "weather forecast"). All results in WAsP only refer to past periods, i. e. measurement periods, long time reference periods and so on. Best regards C. Berndt --------

Which value is correct for the roughness lengh of water in wasp? 0.0m or 0.0002m ?? -------- The roughness of water must be specified as 0 m (zero), in order for WAsP to distinguish between water areas and very smooth land surfaces like snow, sand or bare soil. The wind profiles over water and land are treated differently. The confusion arises because, internally, WAsP uses a fixed value of 0.0002 m for the roughness of a water surface. However, for the reason given above, the user should specify 0 m for water areas in a WAsP roughness map or roughness rose. WAsP Team --------

...the seperate file option would be nice. Yet, I seem unable to retrieve any of the project's members after saving and reloading the workspace. Whatever I do, the project will appear "blank" with all information lost. Any ideas? Has anybody successfully set up and reloaded a project by external reference? Thank you! C. Berndt -------- This functionality seems to work alright, as far as I can tell. What exact sequence are you following? I tried this: Create a new workspace. Add a new project, so that there are two. Insert a map to each project. Save the workspace. On one project, check the 'Maintain as separate file'. Provide a filename for the project. Save and close the workspace. Re-open the workspace. All the members were there. Then I opened a new workspace and inserted that separately maintained project from file. Its map was there, safe and sound. Can you try to follow this sequence of actions, and see what happens, please? If there project's members are lost, then please contact waspsupport and raise this as a bug for investigation. Best wishes, WAsP Team. -------- Dear WAsP, yes, I can reproduce this successfully in a newly created workspace, which is quite encourageing. And no, it does not work for an older workspace that has become rather bulky over the years. I am not going to send this one around the world now. Instead I shall try to rebuild a clean an tidy version of the workspace with external referenced projects, reconsidering the entire structure. Best regards C. Berndt --------

Hi, I've read in two conference proceedings ("Exploring the limits of wasp" (Bowen & Mortensen, ewec, Goteborg 1996) and in "Influence of topographical input data on the accuracy of wind flow modelling in complex terrain" (Mortensen & Petersen, ewec, Dublin 1997)) that delta rix factor should be used as a wasp prediction error calibrator. In order to correct wasp predictions, I'd like to know how use it properly. In particular, I was studying a case with two met station with contemporary data over a period of 1 year. The two met station are 30 e 40 meters tall each one, and the 10 minutes cross correlation factor is 0.862, so they are well correlated. Delta rix value is 2.96% and the error between the estimated mean-wind speed and the observed mean-wind speed at the same predicted site is 23%. regards -------- Andrea, sorry for the very late answer to your post... Most likely, the delta_RIX value does not (alone) explain the discrepancy between predicted and observed wind climates in your case. There can be many other explanations for prediction errors and it would take a closer look and some analyses to investigate the reason(s) for the error in your case. Until now, there has been no 'standard' way of applying the RIX analysis for correction of prediction errors. At the 2006-EW-C conference in Athens there will be a paper about this issue, including an updated procedure for making the RIX analysis and a proposal for a correction procedure. The WAsP Team @ Risø --------

Hi, when the wind atlas structure is modified using Project Configuration, the re-calculated AEP changes appreciably ! In my mind, the wind atlas structure, as a wind atlas representation, must not change the results. Is this problem known ? Is that a bug ? Thank you for any help. Philippe. -------- Better late than never, as they say... sorry Philippe, your post was somehow forgotten. Changing the default roughness lengths and default heights in the wind atlas, will affect the predictions, since WAsP needs to interpolate between the default values to obtain the values for the actual site and height. Ideally, this interpolation error should be small; however, it will increase if actual conditions are far from default/standard conditions. You may decrease the uncertainty by choosing default values that are close to and representative of your wind turbine sites (e.g. use the hub height as one of the standard heights in the wind atlas, or insert a standard roughness of, say, 0.001 m if your sites are in the desert or another low-roughness area). This has always been a known issue (and not a bug), but probably an issue that deserves more attention in the future. The WAsP Team @ Risø --------

Hello, I'm Mauro Ricci, an engineering's student of Bologna University. I'm doing a thesis about a eolic park near to the location of Malaga (Spain). My teacher has suggested to me to look for the mathematical equations used by wasp program for calculating output energy produced by the eolic park in order of knowing which parameters are used for it. I'm sure it's very difficult to obtain all this information but I just need the basic equations. If that is not posible .... would you give me some information about something related to it ( links, e-books, equations similar to that used by the program, etc). I'm looking forward to hearing from you. Yours faithfully. Mauro Ricci p.d. Si quereís podeis responderme en español. Gracias -------- Hi, you'll find what you want in Engineering meteorology (E. Plate) fundamentals of meteorology and their application to problems in environmental and civil engineering ISBN: 0444419721 Regards. --------

Dear Forum At each "Turbine site", the "Site effects" table contains the column "Orography/sp[%]". I am not so sure of the meanning of these numbers: -Does a value, f.ex., of 25% for sector 3 (45deg) mean that, at this location and hub-height, wind is 12.5m/s when wind measured at the "Met.station" is 10m/s? -If so, and since the model is linear, is this ratio independent from the input wind at the Met.station? -If so then, is there a way to extract this information by means of a script? Thanks in advance for your attention --------

Dear Sir: I have a question in WindPro, in "Park" calculation results, then there's a "WTG data to file". When perform this and get a readable file contain informations about the sited WTGs. There's a column named "equivalent roughness", and I often get "Not calculated" on position of some WTGs. How it comes? And Is it a sign that there are mistakes in roughness definition, and will it influence the AEP results? Anybody can help me here? Thanks a lot in advance! Regards, Wang Yang China -------- The equivalent roughness is all effects caused by the surrounding put into one value, e.g. terrain, roughness and obstacles. The note 'not calculated' simply means a value below zero! This should change with version 2.4 according to EMD. --------

Dear all, I would like to know which are the requirements to create a Vector Map in order to have an aceptable standard outcome from the orography effect. Thanks in advance for your comments. Rafael -------- This problem is adressed in the following paper: Mortensen, N.G. and E.L. Petersen (1997). Influence of topographical input data on the accuracy of wind flow modelling in complex terrain. Proceedings of the 1997 European Wind Energy Conference, Dublin, Ireland, October 6-9, 317-320. WAsP Team --------