1 Risø National Laboratory for Sustainable Energy, Technical University of Denmark2 Department of Wind Energy, Technical University of Denmark3 unknown
Wind-speed data from four sites in Denmark have been analyzed in order to obtain estimates of the basic wind velocity which is defined as the 50-year wind speed under standard conditions, i.e. ten-minute averages at the height 10 m over a uniform terrainwith the roughness length 0.05 m. The sites are, from west, Skjern (15 years), Kegnæs (7 years), Sprogø (20 years), and Tystofte (15 years). The data are ten minute averages of wind speed, wind direction, temperature and pressure. The last two quantitiesare used to determine the air density ¤#rho#¤ . The data are cleaned for terrain effects by means of a slightly modified WAsP technique where the sector speed-up factors and roughness lengths are linearly smoothed with a direction resolution of one degree.Assuming geostrophic balance, all the wind-velocity data are transformed to friction velocity ¤u_x¤ and direction at standard conditions by means of the geostrophic drag law for neutral stratification. The basic wind velocity in 30o sectors are obtainedthrough ranking of the largest values of the ¤friction velocity pressure¤ 1/2 ¤#rho#¤¤u¤"2_x taken both once every two months and once every year. The main conclusion is that the basic wind velocity is significantly larger at Skjern, close to the west coast ofJutland, than at any of the other sites. Irrespective of direction, the present standard estimates of 50-year wind are 25 ± 1 m/s at Skjern and 22 ± 1m/s at the other three sites. These results are in agreement with those obtained by Jensen and Franck(1970) and Abild (1994) and supports the conclusion that the wind climate at the west coast of Jutland is more extreme than in any other part of the country.
Vindenergi og atmosfæriske processer; Risø-R-1068; Risø-R-1068(EN)