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Hello, Here is what I read from a company doing meso maps. Is this also applicable to WAsP? We have a lot of sites entirely located in forested region. "Displacement Height: An additional factor to consider is that the selected heights chosen on the wind maps may not always be the height above ground. Where the vegetation is dense, the "effective ground level" is not the base of the vegetation but the middle of the vegetation canopy because the wind flow is displaced upward. The level of zero wind, called the displacement height, is typically about two-thirds the height of the top of the vegetation. In dense forests the height above ground at which the predicted wind speed actually occurs may be as much as 7-15 m (23-50 ft) higher than indicated on the maps. For example, in an area covered by forest with an average canopy height of approximately 18 m (60 ft), the Wind Map's wind speed prediction at the 65 m (213 ft) level would actually apply to a height of 77 m (253 ft) above ground [65 + 2/3(18)]." Thanks again for any help --------. Hello see http://www.bwea.com/planning/trees.html you'll find some really good lectures. GH, Bonus, RES,... and Risoe's point of view about this problem. Enjoy ! --------

Thank a lot for this forum. I know that WAsP is limited to a maximum of 10 changes in roughness in his model. We normally have huge maps that can contain more than 10 changes in roughness in more than one direction. What are the impliction on the AEP if for exemple I have ocean less then 10 km (the distance necessary to stabilize the wind profil after a change in roughness) from the met mast and just after the 10th changes in roughness ? Is WAsP able to "see" the speed-up effect of the ocean? Am I understanding right the change in roughness model? Thanks for you help. -------- WAsP will look at the entire map when analysing the roughness changes. Even if there are more then 10 roughness change lines in one direction, WAsP will not skip the 11th roughness area and beyond. Rather, the program will merge and average some of the smaller roughness bands, in order to get 'the full picture'. You can always insert a roughness rose as a child of a prediction site, and see how WAsP interprets the different roughness areas and transforms these into the rose. Once you have inspected the roughness rose, you should delete it again from the hierarchy, so that WAsP uses the map for roughness input again (unless you really want the rose to determine the calculations). WAsP Team --------

Gentlemen: In the 1953 edition of The Engineer I was intrigued to read of a 100kW wind driven generator deployed in St. Albans in England that made use of the 'Andreau' principle in which the wind-driven propeller blades were hollow. The trailing tips of the blades were provided with openings through which the air was expelled by centrifugal action as the propeller was rotated by the wind. According to the article, air flow was induced up a vertical converging duct to the hub of the propeller. The air was admitted through vents at the lower end of the duct and passed through an air turbine which drove a vertical shaft alternator mounted at the base of the duct. The duct casing formed a support for the propeller and was stayed by twelve guide ropes. I would be most interested to lean what possible advantage such a design might have had back then, and more importantly, why such a design has been abandoned in favour of modern propeller designs. I think the subject might be most interesting for the readers of www.e4engineering. Please email me with any comments to david.wilson@centaur.co.uk Sincerely: Dave Wilson Editor www.e4engineering --------

-------- Dear all, Some of the external consultants I met in the field of wind resource assessments require that the wind measurement mast is at least 2/3 as high as the forecasted hub height. Which means for 80 meters WTG, a minimum height of 54 meters. In terms of costs, this requirement has huge impact. Among the reasons evoked for such a requirement, it is always mentioned that the more the distance between hub and mast heights is great, the more inaccurate the height extrapolation of WAsp will be. Thus, in case of great difference, the uncertainty of Wasp calculations will be increased. I fully understand that point, but I have to find the good compromise between accuracy and costs of measurement campaigns. My questions are : for the specific point of hub height (with regards with hub height), does Risoe has any recommendations, and if yes how were they issued (case study available?). More generally, I guess that the uncertainty on Wasp calculations depends on this difference of height between measures and hub but also on terrain (orography, especially). Do you have any study on this uncertainty induced by Wasp calculations according to the type of terrain, height extrapolation and other sources of error (I do not mention the uncertainties of measurement/calibration/roughness and orography digitization/power curves ... which are independent) ? Thanks a lot in advance -------- Dear Vincent (and all) In last EWEC'03 conference in Madrid, we presented the results of a wind profile comparisons among 3 SODARs, 2 WAsP extrapolations and a 100m-high met tower measurements over flat terrain. One of the conclusions of that project was that, for that limited set of experimental data, WAsP discrepances relative to tower measurements at 100m could range between 10% and 30% (in terms of AEP) depending of the stability parameters used when extrapolating from 30m measures. Best Regards

Dear people of the ForumWAsP, I am an engineer working for a wind company in Spain. We purchased Wasp7 and WindPRo last year. I am using WindPRO habitually and although commonly, for our future wind farms, I use our "own" wind statistics deduced from data gathered by our weather stations, for a certain set of sites in France and Spain I will need to use the Wind Statistics files (lib files) within the EWA-CDrom. I wonder ( and my boss did also ): what degree of uncertainty can reach a production assessment using one of those Wind Statistics (depending on distance of the site, quality of the wind data used for creating those Wind Statistics )? What rule should I consider to estimate the quality/goodness of the result of a calculation ( Wasp or Park calculation ) when using one of those Wind Statistics? I would be grateful to receive any answer from you, Your sincerely, Mario Gómez-Ruber

I am trying WASP for the first time and I have a doubt on wind data sources format. WASP requires wind data measures to be entered as a table (with wind speed and directions) and it returns frecuencies and Weibull distribution parametres. The point is that I do already have a data table with frecuencies associated to wind speed and directions, not the wind measures at all. I would like to know if it is possible to enter this data into WASP in order to get the Weibull distribution parametres and the associated Wind Atlas. --- Yes, you can use the table of frequencies - provided that you can reformat it to the WAsP *.tab file format, see "Technical Reference | WAsP file formats | Observed Wind Climate (*.tab)" in the WAsP help file for a description of the format. Almost any text editor or spreadsheet will do the reformatting.

This should work.... Set Calculator = ReportingAssistant.TypeCaster.CastMemberToCalculatingHierarchyMember(TurbineSite) Calculator.CalculationByType(ectProductionRose).Calculate